rustfmt

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CONTRIBUTING.md

@@ -13,6 +13,14 @@ else (videos, Discord and other community material) lives elsewhere.
 suggest something. A pull request for a roadmap item carries its `roadmap:<id>` label; ideas go to the suggestion
 queue (the hub, or `/suggest` on Discord) rather than to issues, which are for bugs.
 
+**Mod-related pull requests go to [arismoko/horizon](https://github.com/arismoko/horizon)**, the fork that carries the
+mod API and reviews and merges that work. That covers the mod API, native hooks and events for mods, native mods,
+content mods (`.hmod`), mixins, wasm mods, `cargo horizon-mod`, `horizon-mods`, mod builds and the registry, and
+their docs ([mods](docs/mods.md), [native mods](docs/native-mods.md)). Open the pull request there from your usual
+branch. Mod-related pull requests opened here are closed with a pointer to it. Engine extension points that Horizon's
+own crates register (the [layer split](docs/layers.md)), resource and shader pack formats, and gameplay fixes stay
+here.
+
 ## Build it
 
 - **Prerequisites:** Rust (stable), Python 3.10+, JDK 25, and on Linux the ALSA and udev headers

Cargo.lock

@@ -1418,6 +1418,7 @@ dependencies = [
 name = "horizon-chat-filter"
 version = "0.1.0"
 dependencies = [
+ "horizon-server-files",
  "serde",
  "serde_json",
  "toml",
@@ -1528,7 +1529,6 @@ dependencies = [
  "horizon-client-render",
  "horizon-command",
  "horizon-core",
- "horizon-friends",
  "horizon-hdr",
  "horizon-hooks",
  "horizon-items",
@@ -1592,7 +1592,6 @@ dependencies = [
  "horizon-optifine",
  "horizon-polytone",
  "horizon-protocol",
- "horizon-render-pipeline",
  "horizon-shader-api",
  "horizon-shaders",
  "horizon-system",
@@ -1651,6 +1650,15 @@ dependencies = [
  "ureq",
 ]
 
+[[package]]
+name = "horizon-discord"
+version = "0.1.0"
+dependencies = [
+ "horizon-platform",
+ "log",
+ "serde_json",
+]
+
 [[package]]
 name = "horizon-dualsense"
 version = "0.1.0"
@@ -1668,6 +1676,7 @@ dependencies = [
  "getrandom 0.3.4",
  "hkdf",
  "horizon-addresses",
+ "horizon-platform",
  "if-addrs",
  "serde",
  "serde_json",
@@ -1793,13 +1802,25 @@ dependencies = [
 name = "horizon-official"
 version = "0.1.0"
 dependencies = [
+ "horizon-discord",
+ "horizon-friends",
  "horizon-game",
  "horizon-heartbeat",
+ "horizon-official-servers",
  "horizon-platform",
  "log",
  "winresource",
 ]
 
+[[package]]
+name = "horizon-official-servers"
+version = "0.1.0"
+dependencies = [
+ "horizon-addresses",
+ "horizon-platform",
+ "log",
+]
+
 [[package]]
 name = "horizon-optifine"
 version = "0.1.0"
@@ -1891,10 +1912,6 @@ dependencies = [
  "ring",
 ]
 
-[[package]]
-name = "horizon-render-pipeline"
-version = "0.1.0"
-
 [[package]]
 name = "horizon-server"
 version = "0.1.0"
@@ -1957,7 +1974,6 @@ version = "0.1.0"
 dependencies = [
  "half",
  "horizon-core",
- "horizon-render-pipeline",
  "naga",
  "png",
  "zip",

Cargo.toml

@@ -34,6 +34,8 @@ members = [
     "crates/horizon-game",
     "crates/horizon-official",
     "crates/horizon-heartbeat",
+    "crates/horizon-discord",
+    "crates/horizon-official-servers",
     "crates/horizon-bench",
     "crates/horizon-friends",
     "crates/horizon-relay",
@@ -43,7 +45,6 @@ members = [
     "crates/cargo-horizon-mod",
     "crates/horizon-port-pack",
     "crates/horizon-shaders",
-    "crates/horizon-render-pipeline",
     "crates/horizon-optifine",
     "crates/horizon-polytone",
     "crates/horizon-shader-api",

crates/horizon-addresses/src/lib.rs

@@ -15,6 +15,10 @@ pub const OFFICIAL_SERVER: &str = "play.playhorizon.dev";
 /// `official_server_previous` in `launcher/links.json`).
 pub const OFFICIAL_SERVER_PREVIOUS: &[&str] = &["horizon.bunchy7s.dev"];
 
+/// Afri-Network, a partner server the game added once below the official server (#9299) until
+/// the partnership ended: kept so the game can take back out the entry it added.
+pub const WITHDRAWN_PARTNER_SERVER: &str = "afri-network.co.za";
+
 /// [`OFFICIAL_SERVER`] with the port its SRV record gives, for askers that don't look SRV up
 /// (the telemetry server's status checks).
 pub const OFFICIAL_SERVER_STATUS: &str = "play.playhorizon.dev:24454";

crates/horizon-chat-filter/Cargo.toml

@@ -7,6 +7,8 @@ rust-version.workspace = true
 description = "The dedicated server's chat filter: its [chat_filter] settings, the slur list's matcher and the mutes, with no game state (docs/chat-filter.md)"
 
 [dependencies]
+# The moderation durations, shared with `/tempban`.
+horizon-server-files = { path = "../horizon-server-files" }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 toml = "1.1"

crates/horizon-chat-filter/src/lib.rs

@@ -10,6 +10,9 @@ use std::path::{Path, PathBuf};
 
 mod normalise;
 
+pub use horizon_server_files::duration::{
+    DurationUnit, duration_parts, duration_text, now_millis, parse_duration,
+};
 pub use normalise::{Run, Text};
 
 /// The list built into the game, used when `words_file` is empty.
@@ -474,61 +477,6 @@ pub fn append_log(path: &Path, line: &str) -> std::io::Result<()> {
     writeln!(f, "{line}")
 }
 
-/// `/tempmute`'s duration in milliseconds: a positive whole number and a unit, `s`, `m`, `h`, `d` or
-/// `w` (`10m`, `2h`, `1d`).
-pub fn parse_duration(text: &str) -> Option<i64> {
-    let unit = match text.chars().last()? {
-        's' => 1_000,
-        'm' => MINUTE,
-        'h' => 60 * MINUTE,
-        'd' => 24 * 60 * MINUTE,
-        'w' => 7 * 24 * 60 * MINUTE,
-        _ => return None,
-    };
-    let count: i64 = text[..text.len() - 1].parse().ok()?;
-    (count > 0).then(|| count.checked_mul(unit)).flatten()
-}
-
-/// The unit used when presenting a moderation duration to a player.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum DurationUnit {
-    Minute,
-    Hour,
-    Day,
-}
-
-/// A duration's rounded count and unit, shared by logs and translated replies.
-pub fn duration_parts(millis: i64) -> (i64, DurationUnit) {
-    let (unit, kind) = if millis <= 60 * MINUTE {
-        (MINUTE, DurationUnit::Minute)
-    } else if millis <= 48 * 60 * MINUTE {
-        (60 * MINUTE, DurationUnit::Hour)
-    } else {
-        (24 * 60 * MINUTE, DurationUnit::Day)
-    };
-    (
-        millis.div_euclid(unit) + i64::from(millis.rem_euclid(unit) > 0),
-        kind,
-    )
-}
-
-/// `millis` for logs, rounded up: minutes up to an hour, hours up to two days, then days.
-pub fn duration_text(millis: i64) -> String {
-    let (count, unit) = duration_parts(millis);
-    let unit = match unit {
-        DurationUnit::Minute => "minute",
-        DurationUnit::Hour => "hour",
-        DurationUnit::Day => "day",
-    };
-    format!("{count} {unit}{}", if count == 1 { "" } else { "s" })
-}
-
-pub fn now_millis() -> i64 {
-    std::time::SystemTime::now()
-        .duration_since(std::time::UNIX_EPOCH)
-        .map_or(0, |d| d.as_millis() as i64)
-}
-
 /// `YYYY-MM-DDTHH:MM:SSZ` for epoch milliseconds.
 pub fn utc(millis: i64) -> String {
     let secs = millis.div_euclid(1000);

crates/horizon-client-input/src/window.rs

@@ -670,6 +670,39 @@ pub fn with_horizon_icon(
     attributes
 }
 
+/// The screen a window is on: its size in physical pixels, its refresh rate where the OS gives
+/// it, and its scale. For `horizon-ctl status` and the performance statistics' `system.display`.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Display {
+    pub width: u32,
+    pub height: u32,
+    pub refresh_hz: Option<u32>,
+    pub scale: f64,
+}
+
+/// The screen `window` is on, else the primary one, else the only one: right after the window
+/// is made, Wayland doesn't say yet which screen it is on.
+pub fn monitor(window: &winit::window::Window) -> Option<winit::monitor::MonitorHandle> {
+    let only = || {
+        let mut all = window.available_monitors();
+        all.next().filter(|_| all.next().is_none())
+    };
+    window
+        .current_monitor()
+        .or_else(|| window.primary_monitor())
+        .or_else(only)
+}
+
+/// [`monitor`]'s size, refresh rate and scale.
+pub fn display(window: &winit::window::Window) -> Option<Display> {
+    monitor(window).map(|m| Display {
+        width: m.size().width,
+        height: m.size().height,
+        refresh_hz: m.refresh_rate_millihertz().map(|r| r.div_ceil(1000)),
+        scale: m.scale_factor(),
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/horizon-client-lib/Cargo.toml

@@ -42,8 +42,6 @@ horizon-chat-filter = { path = "../horizon-chat-filter" }
 horizon-shaders = { path = "../horizon-shaders" }
 # Horizon's own shader packs: the format, the stages and the check (docs/shaders.md).
 horizon-shader-api = { path = "../horizon-shader-api" }
-# Play with Friends: invite codes and their tunnel; the `friends` feature.
-horizon-friends = { path = "../horizon-friends", optional = true }
 # The narrator (GameNarrator): text-to-speech of chat, system messages and screens.
 horizon-narrator = { path = "../horizon-narrator" }
 # Horizon mods: sandboxed WebAssembly components, off unless installed and turned on (docs/mods.md).
@@ -111,16 +109,12 @@ objc2-foundation = { version = "0.3", default-features = false, features = ["std
 wgpu = { version = "30.0.1", default-features = false, features = ["gles"] }
 
 [features]
-default = ["audio", "controllers", "discord", "friends"]
+default = ["audio", "controllers"]
 # Sound output. Without it (and `controllers`) the program links neither libasound nor libudev on
 # Linux: the server build (`--no-default-features`, released as horizon-engine; docs/server.md).
 audio = ["horizon-client-render/audio"]
 # Controllers: gilrs, and the DualSense's own output. Without it only `horizon-ctl pad`'s virtual pad.
 controllers = ["dep:gilrs", "horizon-client-input/controllers"]
-# "Playing Horizon" on the player's Discord profile (`discord_presence`).
-discord = []
-# Play with Friends, joining side (`net.rs`): without it no invite code joins.
-friends = ["dep:horizon-friends"]
 # Records the call sites of mob random draws (`mob_ai_probe` traces).
 rng-trace = ["horizon-core/rng-trace"]
 # Compatibility with earlier experiment commands: main already uses mimalloc.

crates/horizon-client-render/Cargo.toml

@@ -26,7 +26,6 @@ horizon-narrator = { path = "../horizon-narrator" }
 horizon-optifine = { path = "../horizon-optifine" }
 horizon-polytone = { path = "../horizon-polytone" }
 horizon-protocol = { path = "../horizon-protocol" }
-horizon-render-pipeline = { path = "../horizon-render-pipeline" }
 horizon-shader-api = { path = "../horizon-shader-api" }
 horizon-shaders = { path = "../horizon-shaders" }
 horizon-system = { path = "../horizon-system" }

crates/horizon-client-render/src/extras.rs

@@ -2,7 +2,7 @@
 //! settings, kept in `horizon-extras.txt` next to `options.txt` so that file
 //! stays exactly vanilla's, and the logic behind them. Every extra is off by
 //! default; see `docs/extras.md`. Horizon's own switches outside the Extras page
-//! (No AI, Agent Control, Discord Rich Presence) are kept here too.
+//! (No AI, Agent Control) are kept here too.
 use std::{collections::VecDeque, fs, path::Path};
 
 pub const FILE: &str = "horizon-extras.txt";
@@ -145,8 +145,6 @@ pub struct Extras {
     /// F3+R and F3+E start/stop a repro recording and write its bundle (off by
     /// default: a recording copies the world).
     pub repro_keys: bool,
-    /// "Playing Horizon" on the player's Discord profile (`discord_presence`; on by default).
-    pub discord_presence: bool,
     /// Another controller can join P1's world (`splitscreen`, off by default).
     pub splitscreen: bool,
     /// Two players in one window: 0 auto (side by side when wider than tall), 1 side by side,
@@ -233,7 +231,6 @@ impl Default for Extras {
             no_ai: false,
             agent_control: false,
             repro_keys: false,
-            discord_presence: true,
             splitscreen: false,
             splitscreen_two: 0,
             splitscreen_three: 0,
@@ -338,7 +335,6 @@ impl Extras {
                 horizon_core::no_ai::KEY => e.no_ai = flag(e.no_ai),
                 "agentControl" => e.agent_control = flag(e.agent_control),
                 "reproKeys" => e.repro_keys = flag(e.repro_keys),
-                "discordPresence" => e.discord_presence = flag(e.discord_presence),
                 "splitscreen" => e.splitscreen = flag(e.splitscreen),
                 "splitscreenTwo" => e.splitscreen_two = value.parse().unwrap_or(0).min(2),
                 "splitscreenThree" => e.splitscreen_three = value.parse().unwrap_or(0).min(2),
@@ -376,7 +372,7 @@ impl Extras {
     }
     pub fn serialize(&self) -> String {
         let mut text = format!(
-            "packBrowser:{}\npregen:{}\nfullbright:{}\ndynamicLights:{}\nzoom:{}\nzoomKey:{}\nzoomLevel:{}\nzoomSmooth:{}\nzoomSensitivity:{}\nlodZoomDetail:{}\nfps:{}\nfpsCorner:{}\nfpsLows:{}\nkeystrokes:{}\nkeystrokesCorner:{}\nkeystrokesCps:{}\nmovedToMods:{}\nminimap:{}\nminimapCorner:{}\nminimapSize:{}\nminimapShape:{}\nminimapZoom:{}\nminimapRotate:{}\nautoReconnect:{}\nuiSoundReserve:{}\nownNameTag:{}\nhideBlockParticles:{}\nmouseTweaks:{}\nmouseTweaksWheel:{}\nsort:{}\nsortKey:{}\nchatAnimation:{}\nchatIndicator:{}\n{}:{}\nagentControl:{}\nreproKeys:{}\ndiscordPresence:{}\nsplitscreen:{}\nsplitscreenTwo:{}\nsplitscreenThree:{}\nsplitscreenNames:{}\nwheelCyclesListSettings:{}\nmusicOff:{}\nmusicPage:{}\ncosmeticsMine:{}\n{}cosmeticsHideFx:{}\ncosmeticsSolo:{}\n{}:{}\n{}:{}\n{}:{}\n",
+            "packBrowser:{}\npregen:{}\nfullbright:{}\ndynamicLights:{}\nzoom:{}\nzoomKey:{}\nzoomLevel:{}\nzoomSmooth:{}\nzoomSensitivity:{}\nlodZoomDetail:{}\nfps:{}\nfpsCorner:{}\nfpsLows:{}\nkeystrokes:{}\nkeystrokesCorner:{}\nkeystrokesCps:{}\nmovedToMods:{}\nminimap:{}\nminimapCorner:{}\nminimapSize:{}\nminimapShape:{}\nminimapZoom:{}\nminimapRotate:{}\nautoReconnect:{}\nuiSoundReserve:{}\nownNameTag:{}\nhideBlockParticles:{}\nmouseTweaks:{}\nmouseTweaksWheel:{}\nsort:{}\nsortKey:{}\nchatAnimation:{}\nchatIndicator:{}\n{}:{}\nagentControl:{}\nreproKeys:{}\nsplitscreen:{}\nsplitscreenTwo:{}\nsplitscreenThree:{}\nsplitscreenNames:{}\nwheelCyclesListSettings:{}\nmusicOff:{}\nmusicPage:{}\ncosmeticsMine:{}\n{}cosmeticsHideFx:{}\ncosmeticsSolo:{}\n{}:{}\n{}:{}\n{}:{}\n",
             bool_text(self.pack_browser),
             bool_text(self.pregen),
             bool_text(self.fullbright),
@@ -418,7 +414,6 @@ impl Extras {
             bool_text(self.no_ai),
             bool_text(self.agent_control),
             bool_text(self.repro_keys),
-            bool_text(self.discord_presence),
             bool_text(self.splitscreen),
             self.splitscreen_two,
             self.splitscreen_three,
@@ -613,8 +608,6 @@ pub enum Item {
     /// Not on the Extras page: Horizon Settings shows No AI, its AI Agent page Agent Control.
     NoAi,
     AgentControl,
-    /// On the Horizon Settings page.
-    DiscordPresence,
     /// On the AI Agent page, next to Agent Control: the F3 recording shortcuts.
     ReproKeys,
     /// On the Splitscreen settings page.
@@ -691,7 +684,6 @@ impl Item {
             Item::NoAi => "horizon.extras.no_ai",
             Item::AgentControl => "horizon.extras.agent_control",
             Item::ReproKeys => "horizon.extras.repro_keys",
-            Item::DiscordPresence => "horizon.extras.discord_presence",
             Item::Splitscreen => "horizon.extras.splitscreen",
             Item::ChatAnimation => "horizon.extras.chat_animation",
             Item::ChatIndicator => "horizon.extras.chat_indicator",
@@ -724,7 +716,6 @@ impl Item {
             Item::NoAi => "horizon.extras.no_ai.tooltip",
             Item::AgentControl => "horizon.extras.agent_control.tooltip",
             Item::ReproKeys => "horizon.extras.repro_keys.tooltip",
-            Item::DiscordPresence => "horizon.extras.discord_presence.tooltip",
             Item::Splitscreen => "horizon.extras.splitscreen.tooltip",
             Item::ChatAnimation => "horizon.extras.chat_animation.tooltip",
             Item::ChatIndicator => "horizon.extras.chat_indicator.tooltip",
@@ -768,7 +759,6 @@ impl Item {
             Item::NoAi => "No AI",
             Item::AgentControl => "Agent Control",
             Item::ReproKeys => "Recording shortcuts",
-            Item::DiscordPresence => "Discord Rich Presence",
             Item::Splitscreen => "Splitscreen",
             Item::WheelCyclesSettings => "Scroll wheel changes settings",
             Item::PackBrowser => "Resource pack browser",
@@ -792,10 +782,9 @@ impl Item {
             ChatIndicator => ChatAnimation,
             Pvp(o) => return o.parent().map(Pvp),
             Fullbright | DynamicLights | OwnNameTag | HideBlockParticles | MouseTweaks | Sort
-            | AutoReconnect | NoAi | AgentControl | ReproKeys | DiscordPresence | Splitscreen
-            | ChatAnimation | WheelCyclesSettings | MusicPage | PackBrowser | CosmeticsMine
-            | CosmeticsOthers | CosmeticsHideFx | CosmeticsSolo | HorizonMarks | HorizonMe
-            | Pregen => {
+            | AutoReconnect | NoAi | AgentControl | ReproKeys | Splitscreen | ChatAnimation
+            | WheelCyclesSettings | MusicPage | PackBrowser | CosmeticsMine | CosmeticsOthers
+            | CosmeticsHideFx | CosmeticsSolo | HorizonMarks | HorizonMe | Pregen => {
                 return None;
             }
         })
@@ -844,9 +833,6 @@ impl Item {
             Item::NoAi => {
                 "Hides and turns off every AI feature: agent control, horizon-ctl and the MCP servers. The launcher's switch too."
             }
-            Item::DiscordPresence => {
-                "Shows Playing Horizon on your Discord profile while Discord runs: menus, single player or multiplayer, the dimension and the time played. Never a world's name or a server's address."
-            }
             Item::Splitscreen => {
                 "In a world, another controller can join as a new player: press A when it asks, then pick a profile and where to play."
             }
@@ -927,7 +913,6 @@ impl Item {
             Item::NoAi => e.no_ai,
             Item::AgentControl => e.agent_control,
             Item::ReproKeys => e.repro_keys,
-            Item::DiscordPresence => e.discord_presence,
             Item::Splitscreen => e.splitscreen,
             Item::WheelCyclesSettings => e.wheel_cycles_settings,
             Item::PackBrowser => e.pack_browser,
@@ -986,7 +971,6 @@ impl Item {
             Item::NoAi => e.no_ai = !e.no_ai,
             Item::AgentControl => e.agent_control = !e.agent_control,
             Item::ReproKeys => e.repro_keys = !e.repro_keys,
-            Item::DiscordPresence => e.discord_presence = !e.discord_presence,
             Item::Splitscreen => e.splitscreen = !e.splitscreen,
             Item::WheelCyclesSettings => e.wheel_cycles_settings = !e.wheel_cycles_settings,
             Item::PackBrowser => e.pack_browser = !e.pack_browser,
@@ -1104,7 +1088,7 @@ mod tests {
         assert!(!d.mouse_tweaks && !d.sort && !d.own_name_tag && !d.ui_sound_reserve);
         assert!(!d.hide_block_particles && !d.pregen);
         assert!(!d.music_page && d.music_off.is_empty());
-        assert!(d.discord_presence && !d.wheel_cycles_settings);
+        assert!(!d.wheel_cycles_settings);
         assert_eq!(Extras::parse(""), d);
         assert_eq!(Extras::parse(&d.serialize()), d);
         let mut e = d.clone();
@@ -1143,7 +1127,6 @@ mod tests {
         e.sort_key = "key.keyboard.r".into();
         e.chat_animation = true;
         e.chat_indicator = false;
-        e.discord_presence = false;
         assert!(!e.splitscreen);
         Item::Splitscreen.cycle(&mut e, false);
         assert_eq!(Item::Splitscreen.switch(&e), Some(true));

crates/horizon-client-render/src/extras_ui.rs

@@ -1,5 +1,6 @@
 //! The Horizon Extras page, on the settings shell (`settings_shell`): which rows it has and what
-//! pressing them does. Each one's value and what it does stay in `extras::Item`.
+//! pressing them does. Each one's value and what it does stay in `extras::Item`; the sections crates
+//! add (`horizon_hooks::pages::Place::Extras`) keep theirs.
 use crate::{
     extras::{self, Item},
     lang,
@@ -7,6 +8,7 @@ use crate::{
     settings::Settings,
     settings_shell::{self as shell, Binding, Group, Output, Row, Screen, Sheet, Value},
 };
+use horizon_hooks::pages::{self as added, Act, Label};
 
 const TITLE: &str = "horizon.pages.extras";
 const ABOUT: &str = "horizon.pages.extras.tooltip";
@@ -31,6 +33,121 @@ pub(crate) enum ExtraRow {
     /// It isn't installed: where to get it. A note, not a button: Options > Mods already has the
     /// one way into the Mods page (`every_setting_and_page_is_reached_from_one_place`).
     ZoomInstall,
+    /// Row `.1` of the section registered page `.0` adds (`Place::Extras`).
+    Added(usize, usize),
+}
+
+#[cfg(test)]
+thread_local! {
+    /// A test's own pages, instead of the game's registered ones: each test runs on its thread.
+    static TEST_PAGES: std::cell::Cell<Option<&'static [&'static dyn added::Page]>> =
+        const { std::cell::Cell::new(None) };
+}
+
+/// The pages crates registered, all places.
+fn pages() -> &'static [&'static dyn added::Page] {
+    #[cfg(test)]
+    if let Some(pages) = TEST_PAGES.get() {
+        return pages;
+    }
+    added::engine::all()
+}
+
+/// The sections of this page, by their index among the registered pages.
+fn sections() -> impl Iterator<Item = (usize, &'static dyn added::Page)> {
+    let pages = pages().iter().copied().enumerate();
+    pages.filter(|(_, page)| page.place() == added::Place::Extras)
+}
+
+fn label_text(label: Label) -> String {
+    match label {
+        Label::Key(key) => lang::get(key),
+        Label::Value(text) => text,
+    }
+}
+
+/// The page's group named `name`, made at the end if it has none.
+fn group_named<'a>(
+    groups: &'a mut Vec<Group<ExtraRow>>,
+    name: &'static str,
+) -> &'a mut Group<ExtraRow> {
+    let at = groups.iter().position(|group| group.name == name);
+    let at = at.unwrap_or_else(|| {
+        groups.push(Group {
+            name,
+            rows: Vec::new(),
+        });
+        groups.len() - 1
+    });
+    &mut groups[at]
+}
+
+/// The sections' rows, in the groups their titles and headings name.
+fn add_sections(groups: &mut Vec<Group<ExtraRow>>) {
+    for (page, section) in sections() {
+        let mut rows = Vec::new();
+        section.rows(&mut rows);
+        let mut name = section.title();
+        for (r, row) in rows.into_iter().enumerate() {
+            let id = ExtraRow::Added(page, r);
+            let row = match row {
+                added::Row::Heading(key) => {
+                    name = key;
+                    continue;
+                }
+                added::Row::Note(text) => Row::new(id, text, Value::Note).live(false),
+                added::Row::Toggle { label, on } => {
+                    Row::new(id, lang::get(label), Value::Switch(on))
+                }
+                added::Row::Cycle { label, value } => {
+                    Row::new(id, lang::get(label), Value::Choice(label_text(value)))
+                }
+                added::Row::Slider { label, value, text } => {
+                    let position = value.clamp(0.0, 1.0);
+                    let text = label_text(text);
+                    let value = Value::Slider {
+                        position,
+                        steps: None,
+                        text,
+                    };
+                    Row::new(id, lang::get(label), value)
+                }
+                added::Row::Button { label } => Row::new(id, lang::get(label), Value::Press),
+                added::Row::Key { label, key } => {
+                    let key = crate::keybinds::display_name(&key).plain();
+                    Row::new(id, lang::get(label), Value::Read(key))
+                }
+                // A row kind newer than this engine.
+                _ => continue,
+            };
+            let row = match section.tooltip(r) {
+                Some(about) => row.about(label_text(about)),
+                None => row,
+            };
+            group_named(groups, name).rows.push(row);
+        }
+    }
+}
+
+/// Row `r` of registered page `page` was acted on: the options screen saves when it closes.
+fn act(page: usize, r: usize, act: Act) -> Vec<Output> {
+    let Some(section) = pages().get(page) else {
+        return Vec::new();
+    };
+    section.act(r, act);
+    vec![Output::Event(Event::Changed)]
+}
+
+/// Whether row `r` of registered page `page` steps (a switch or a cycle).
+fn steps(page: usize, r: usize) -> bool {
+    let mut rows = Vec::new();
+    if let Some(section) = pages().get(page) {
+        section.rows(&mut rows);
+    }
+    matches!(
+        rows.get(r),
+        Some(added::Row::Toggle { .. } | added::Row::Cycle { .. })
+    )
 }
 
 fn item_row(item: Item, s: &Settings) -> Row<ExtraRow> {
@@ -85,9 +202,14 @@ impl Screen for ExtrasScreen {
     fn note_lines(&self) -> usize {
         NOTE_LINES
     }
-    /// The rows read the extras, the mods and whether cosmetics are offered.
+    /// The rows read the extras, the mods, whether cosmetics are offered and the sections' rows.
     fn stamp(&self, s: &Settings) -> u64 {
-        shell::stamp_of(&(&s.extras, &s.mods, horizon_cosmetics::enabled()))
+        let mut added = Vec::new();
+        for (_, section) in sections() {
+            section.rows(&mut added);
+        }
+        let cosmetics = horizon_cosmetics::enabled();
+        shell::stamp_of(&(&s.extras, &s.mods, cosmetics, added))
     }
     fn sheets(&self, s: &Settings) -> Vec<Sheet<(), ExtraRow>> {
         let mut groups = vec![Group {
@@ -107,6 +229,7 @@ impl Screen for ExtrasScreen {
                 }
             }
         }
+        add_sections(&mut groups);
         vec![Sheet::new((), lang::get(TITLE), lang::get(ABOUT), groups)]
     }
     fn press(&mut self, s: &mut Settings, row: ExtraRow, back: bool) -> Vec<Output> {
@@ -125,16 +248,29 @@ impl Screen for ExtrasScreen {
                 Output::Event(Event::NativeSettings(i)),
             ],
             ExtraRow::ZoomInstall => Vec::new(),
+            ExtraRow::Added(page, r) => {
+                act(page, r, if back { Act::PressBack } else { Act::Press })
+            }
+        }
+    }
+    fn slide(&mut self, _s: &mut Settings, row: ExtraRow, position: f32) {
+        if let ExtraRow::Added(page, r) = row {
+            act(page, r, Act::Slide(position));
         }
     }
     /// With the wheel extra on, the wheel over an item changes it, without a click; the mod's rows
     /// let the list scroll.
     fn wheel_step(&mut self, s: &mut Settings, row: ExtraRow, back: bool) -> Option<Vec<Output>> {
-        let ExtraRow::Item(item) = row else {
-            return None;
-        };
-        item.cycle(&mut s.extras, back);
-        Some(vec![Output::Event(Event::Changed)])
+        match row {
+            ExtraRow::Item(item) => {
+                item.cycle(&mut s.extras, back);
+                Some(vec![Output::Event(Event::Changed)])
+            }
+            ExtraRow::Added(page, r) if steps(page, r) => {
+                Some(act(page, r, if back { Act::PressBack } else { Act::Press }))
+            }
+            _ => None,
+        }
     }
 }
 
@@ -292,4 +428,148 @@ mod tests {
         shell.key(&mut s, K::ArrowDown, None, false, size);
         assert_eq!(shell.focused_row(), Some(first));
     }
+
+    /// A section with a switch in the page's Multiplayer group, then a heading of its own with a
+    /// number that steps either way, a note and a volume.
+    struct Section {
+        on: std::sync::Mutex<bool>,
+        step: std::sync::Mutex<i32>,
+        volume: std::sync::Mutex<f32>,
+    }
+    impl added::Page for Section {
+        fn id(&self) -> &'static str {
+            "test.section"
+        }
+        fn title(&self) -> &'static str {
+            "horizon.extras.header.multiplayer"
+        }
+        fn place(&self) -> added::Place {
+            added::Place::Extras
+        }
+        fn rows(&self, rows: &mut Vec<added::Row>) {
+            rows.push(added::Row::Toggle {
+                label: "test.section.switch",
+                on: *self.on.lock().unwrap(),
+            });
+            rows.push(added::Row::Heading("test.section.heading"));
+            rows.push(added::Row::Cycle {
+                label: "test.section.step",
+                value: Label::Value(self.step.lock().unwrap().to_string()),
+            });
+            rows.push(added::Row::Note("a note".into()));
+            rows.push(added::Row::Slider {
+                label: "test.section.volume",
+                value: *self.volume.lock().unwrap(),
+                text: Label::Value(String::new()),
+            });
+        }
+        fn act(&self, row: usize, act: Act) {
+            match (row, act) {
+                (0, Act::Press | Act::PressBack) => {
+                    let mut on = self.on.lock().unwrap();
+                    *on = !*on;
+                }
+                (2, Act::Press) => *self.step.lock().unwrap() += 1,
+                (2, Act::PressBack) => *self.step.lock().unwrap() -= 1,
+                (4, Act::Slide(v)) => *self.volume.lock().unwrap() = v,
+                _ => {}
+            }
+        }
+    }
+
+    /// A page for Horizon Settings: never on Extras.
+    struct Elsewhere;
+    impl added::Page for Elsewhere {
+        fn id(&self) -> &'static str {
+            "test.elsewhere"
+        }
+        fn title(&self) -> &'static str {
+            "test.elsewhere"
+        }
+        fn place(&self) -> added::Place {
+            added::Place::HorizonSettings
+        }
+        fn rows(&self, rows: &mut Vec<added::Row>) {
+            rows.push(added::Row::Button {
+                label: "test.elsewhere.button",
+            });
+        }
+        fn act(&self, _: usize, _: Act) {}
+    }
+
+    fn with_section() -> &'static Section {
+        let section: &'static Section = Box::leak(Box::new(Section {
+            on: false.into(),
+            step: 0.into(),
+            volume: 0.5.into(),
+        }));
+        let pages: &'static [&'static dyn added::Page] = Box::leak(Box::new([
+            &Elsewhere as &dyn added::Page,
+            section as &dyn added::Page,
+        ]));
+        TEST_PAGES.set(Some(pages));
+        section
+    }
+
+    /// The section's first row joins the page's own Multiplayer group, after its rows; its heading
+    /// starts a group after the page's; a page for elsewhere adds nothing.
+    #[test]
+    fn a_section_joins_the_group_its_title_names_and_heads_its_own() {
+        with_section();
+        let s = Settings::default();
+        let sheets = ExtrasScreen.sheets(&s);
+        let groups = &sheets[0].groups;
+        let ids = |name: &str| -> Vec<ExtraRow> {
+            let group = groups.iter().find(|g| g.name == name).unwrap();
+            group.rows.iter().map(|r| r.id).collect()
+        };
+        let multiplayer = ids("horizon.extras.header.multiplayer");
+        assert_eq!(multiplayer.last(), Some(&ExtraRow::Added(1, 0)));
+        assert_eq!(groups.last().unwrap().name, "test.section.heading");
+        let own = [
+            ExtraRow::Added(1, 2),
+            ExtraRow::Added(1, 3),
+            ExtraRow::Added(1, 4),
+        ];
+        assert_eq!(ids("test.section.heading"), own);
+        let all = rows_of(&s);
+        assert!(!all.iter().any(|r| matches!(r.id, ExtraRow::Added(0, _))));
+    }
+
+    /// A click flips the switch, a Shift click steps the number back, the wheel steps it, and the
+    /// note takes no click; the rows show what the section holds after each.
+    #[test]
+    fn a_sections_rows_act_on_it() {
+        let section = with_section();
+        let mut s = Settings::default();
+        let mut shell = Shell::<ExtrasScreen>::default();
+        let switch = ExtraRow::Added(1, 0);
+        let at = shell.point_at(&s, SIZE, switch);
+        assert!(
+            !shell
+                .click(&mut s, at, SIZE, false, false, false)
+                .is_empty()
+        );
+        assert!(*section.on.lock().unwrap());
+        let value = |s: &Settings, id| rows_of(s).into_iter().find(|r| r.id == id).unwrap().value;
+        assert_eq!(value(&s, switch), Value::Switch(true));
+        let step = ExtraRow::Added(1, 2);
+        let mut screen = ExtrasScreen;
+        screen.press(&mut s, step, true);
+        assert_eq!(value(&s, step), Value::Choice("-1".into()));
+        assert!(screen.wheel_step(&mut s, step, false).is_some());
+        assert_eq!(*section.step.lock().unwrap(), 0);
+        assert_eq!(
+            screen.wheel_step(&mut s, ExtraRow::Added(1, 3), false),
+            None
+        );
+        let note = shell.point_at(&s, SIZE, ExtraRow::Added(1, 3));
+        assert!(
+            shell
+                .click(&mut s, note, SIZE, false, false, false)
+                .is_empty()
+        );
+        screen.slide(&mut s, ExtraRow::Added(1, 4), 0.25);
+        assert_eq!(*section.volume.lock().unwrap(), 0.25);
+    }
 }

crates/horizon-client-render/src/gfx.rs

@@ -239,6 +239,7 @@ mod reuse;
 mod stars;
 mod surface_setup;
 use surface_setup::{AdapterChoice, AdapterFailure, open_adapter, pick_adapter, set_up_surface};
+mod off_page;
 pub mod submit;
 mod sunrise_fan;
 mod timing;
@@ -250,6 +251,7 @@ mod wgsl_prefix;
 mod world_post;
 pub mod world_primitives;
 mod world_warp;
+use off_page::move_off_page;
 
 /// A section's instance: its camera-relative origin and, in `w`, the step of
 /// its fixed-point UVs (`terrain.wgsl`'s `terrain_uv`).
@@ -726,62 +728,6 @@ impl Part {
         }
     }
 }
-/// `Renderer::compact_arena`'s and `shrink_translucent`'s moves: what the meshes
-/// hold on `page` of `arena` (`part`) goes to its other pages in video memory,
-/// until the next range would pass `budget` bytes (it keeps what is left; the
-/// first range moves whatever its size, so none keeps the page closed), the
-/// copies into `encoder`, the ranges' flat draw ids (`flat`) and, in the
-/// section arena, GPU culling's records (`records`) along. False when the other
-/// pages have no room left.
-fn move_off_page<'a>(
-    arena: &mut arena::Arena,
-    encoder: &mut wgpu::CommandEncoder,
-    mut flat: Option<(&mut flat::Flat, &wgpu::Device, &mut upload::Uploads)>,
-    mut records: Option<&mut gpu_culling::Records>,
-    meshes: impl Iterator<Item = &'a mut SectionGpu>,
-    page: u32,
-    part: Part,
-    budget: &mut u64,
-) -> bool {
-    debug_assert!(
-        records.is_none() || matches!(part, Part::Section { .. }),
-        "records follow the section arena's ranges"
-    );
-    let mut moved = false;
-    for s in meshes {
-        // Nothing of a mesh here: split, one without solid quads (its (0, 0) is no
-        // range of page 0); in the other arenas, one without translucent quads.
-        let Some((_, start, vertices)) = part.of(s).filter(|r| r.0 == page) else {
-            continue;
-        };
-        let bytes = vertices * arena.stride();
-        if moved && bytes > *budget {
-            break;
-        }
-        let Some(to) = arena.alloc_moved(vertices) else {
-            return false;
-        };
-        arena.copy(encoder, (page, start), to, vertices);
-        arena.release(page, start, vertices);
-        if let (Some((flat, device, uploads)), Some(id)) = (&mut flat, s.flat_id) {
-            let key = match part {
-                Part::Translucent => to.0 + flat::TRANSLUCENT_KEYS,
-                _ => to.0,
-            };
-            flat.place(device, encoder, uploads, id, key, to.1, vertices);
-        }
-        part.set(s, to);
-        // Its solid quads start the range in either layout.
-        if let (Part::Section { .. }, Some(records), Some(id)) =
-            (part, records.as_deref_mut(), s.gpu_id)
-        {
-            records.relocate(id, to.0, u64::from(s.solid_base()));
-        }
-        *budget = budget.saturating_sub(bytes);
-        moved = true;
-    }
-    true
-}
 /// Starts moving a page of a large arena far larger than its ranges in use
 /// (`Arena::oversized`) into a new page of the size they get (`Arena::open_page`),
 /// for `Renderer::shrink_translucent`: the page closes and `move_off_page` empties
@@ -10116,7 +10062,11 @@ impl Renderer {
         let pack_reads_world = pack_post || native_post;
         laps.lap("r_uploads");
         // Phase 2 of occlusion culling draws over the depth, and a shader pack or TAA reads it.
+        // Post effects (a resource pack's chains, `use_depth_buffer`) read the world's depth
+        // after the world pass, as `GameRenderer.render` hands them the main target's.
+        let post_reads_depth = !frame.title && !frame.post_effects.effects.is_empty();
         let keep_depth = pack_reads_world
+            || post_reads_depth
             || (taa && self.world_post.taa)
             || oit_on
             || native_render::render_needs().world_depth
@@ -15718,11 +15668,11 @@ mod shadow_caster_tests {
     #[test]
     fn the_shadow_pass_draws_terrain_outside_the_pack_s_planes() {
         let kept = |near: Option<f32>, far: Option<f32>, y: f64, min: [f32; 3], depth: bool| {
-            let shadow = horizon_render_pipeline::Shadow {
+            let shadow = horizon_shaders::Shadow {
                 distance: 128.0,
                 near,
                 far,
-                ..horizon_render_pipeline::Shadow::default()
+                ..horizon_shaders::Shadow::default()
             };
             let camera = DVec3::new(13.5, y + 1.62, -13.5);
             let view = pack_post::ShadowView {

crates/horizon-client-render/src/gfx/native_post.rs

@@ -338,7 +338,7 @@ pub struct NativeFrame {
     reflection_sampler: wgpu::Sampler,
     /// The shadow map the stages read, and the camera that draws it when the pack asks for one.
     pub shadow_map: super::native_shadow::ShadowMap,
-    shadow_camera: Option<horizon_render_pipeline::Shadow>,
+    shadow_camera: Option<horizon_shaders::Shadow>,
     /// Whether the pack's material reads `reflection` (`NativePack::new`): else no mirror
     /// is drawn and `has_reflection` stays 0.
     pub reflects: bool,
@@ -1497,7 +1497,7 @@ pub fn frame_inputs(
     size: [u32; 2],
     seconds: f32,
     index: u32,
-    shadow: Option<&horizon_render_pipeline::Shadow>,
+    shadow: Option<&horizon_shaders::Shadow>,
 ) -> FrameInputs {
     let aspect = size[0] as f32 / size[1].max(1) as f32;
     let view = crate::camera::view_matrix(frame.yaw, frame.pitch);

crates/horizon-client-render/src/gfx/native_shadow.rs

@@ -6,8 +6,8 @@
 //! draw lists (`ShadowView`) serve both; the map's texels are distorted toward the camera as the
 //! prelude's `shadow_position` undoes.
 
-use horizon_render_pipeline::Shadow;
 use horizon_shader_api::{Api, Frame as FrameInputs, manifest::Shadow as Settings, stages::GROUP};
+use horizon_shaders::Shadow;
 
 use super::native_material::TerrainShape;
 use super::wgsl_prefix::{TERRAIN, prefixed, section};

crates/horizon-client-render/src/gfx/off_page.rs

@@ -0,0 +1,59 @@
+//! `move_off_page`, moved out of `gfx.rs` unchanged.
+use super::*;
+
+/// `Renderer::compact_arena`'s and `shrink_translucent`'s moves: what the meshes
+/// hold on `page` of `arena` (`part`) goes to its other pages in video memory,
+/// until the next range would pass `budget` bytes (it keeps what is left; the
+/// first range moves whatever its size, so none keeps the page closed), the
+/// copies into `encoder`, the ranges' flat draw ids (`flat`) and, in the
+/// section arena, GPU culling's records (`records`) along. False when the other
+/// pages have no room left.
+pub(super) fn move_off_page<'a>(
+    arena: &mut arena::Arena,
+    encoder: &mut wgpu::CommandEncoder,
+    mut flat: Option<(&mut flat::Flat, &wgpu::Device, &mut upload::Uploads)>,
+    mut records: Option<&mut gpu_culling::Records>,
+    meshes: impl Iterator<Item = &'a mut SectionGpu>,
+    page: u32,
+    part: Part,
+    budget: &mut u64,
+) -> bool {
+    debug_assert!(
+        records.is_none() || matches!(part, Part::Section { .. }),
+        "records follow the section arena's ranges"
+    );
+    let mut moved = false;
+    for s in meshes {
+        // Nothing of a mesh here: split, one without solid quads (its (0, 0) is no
+        // range of page 0); in the other arenas, one without translucent quads.
+        let Some((_, start, vertices)) = part.of(s).filter(|r| r.0 == page) else {
+            continue;
+        };
+        let bytes = vertices * arena.stride();
+        if moved && bytes > *budget {
+            break;
+        }
+        let Some(to) = arena.alloc_moved(vertices) else {
+            return false;
+        };
+        arena.copy(encoder, (page, start), to, vertices);
+        arena.release(page, start, vertices);
+        if let (Some((flat, device, uploads)), Some(id)) = (&mut flat, s.flat_id) {
+            let key = match part {
+                Part::Translucent => to.0 + flat::TRANSLUCENT_KEYS,
+                _ => to.0,
+            };
+            flat.place(device, encoder, uploads, id, key, to.1, vertices);
+        }
+        part.set(s, to);
+        // Its solid quads start the range in either layout.
+        if let (Part::Section { .. }, Some(records), Some(id)) =
+            (part, records.as_deref_mut(), s.gpu_id)
+        {
+            records.relocate(id, to.0, u64::from(s.solid_base()));
+        }
+        *budget = budget.saturating_sub(bytes);
+        moved = true;
+    }
+    true
+}

crates/horizon-client-render/src/gfx/pack_images.rs

@@ -4,8 +4,7 @@
 
 use std::collections::BTreeMap;
 
-use horizon_render_pipeline::{Format, Kind};
-use horizon_shaders::{BufferObject, CustomImage};
+use horizon_shaders::{BufferObject, CustomImage, Format, Kind};
 
 pub(super) struct PackImage {
     pub(super) def: CustomImage,

crates/horizon-client-render/src/gfx/pack_post.rs

@@ -18,8 +18,7 @@
 use std::collections::HashMap;
 
 use glam::{DMat4, DVec3};
-use horizon_render_pipeline::{BUFFERS, Format, Kind, SHADOW_COLORS};
-use horizon_shaders::{Group, Post};
+use horizon_shaders::{BUFFERS, Format, Group, Kind, Post, SHADOW_COLORS};
 use smallvec::SmallVec;
 
 use super::pack_draw::DrawUniforms;
@@ -893,7 +892,7 @@ fn depth_linear(interface: &horizon_shaders::Interface, linear: u8) -> [f32; 4]
 }
 
 fn source(name: &str, shadow_space: bool, shadow_pass: bool, watershadow: bool) -> Source {
-    let shadow_color = horizon_render_pipeline::shadow_color(name);
+    let shadow_color = horizon_shaders::shadow_color(name);
     let shadow_depth = match name {
         "shadowtex0" | "watershadow" | "shadowtex0HW" => Some(0),
         "shadowtex1" | "shadowtex1HW" => Some(1),
@@ -912,7 +911,7 @@ fn source(name: &str, shadow_space: bool, shadow_pass: bool, watershadow: bool)
             };
         }
     }
-    if shadow_space && horizon_render_pipeline::buffer_index(name).is_some() {
+    if shadow_space && horizon_shaders::buffer_index(name).is_some() {
         // colortex buffers are not this pass's.
         return Source::Dummy;
     }
@@ -926,7 +925,7 @@ fn source(name: &str, shadow_space: bool, shadow_pass: bool, watershadow: bool)
         "normals" => Source::Normals,
         "specular" => Source::Specular,
         horizon_shaders::WATER_MASK => Source::WaterMask,
-        n => horizon_render_pipeline::buffer_index(n).map_or(Source::Dummy, Source::Color),
+        n => horizon_shaders::buffer_index(n).map_or(Source::Dummy, Source::Color),
     }
 }
 
@@ -1583,7 +1582,7 @@ fn bindings(
             !unbound
                 && (t.stage != pack_textures::stage(group)
                     || released.0 != t.stage
-                    || horizon_render_pipeline::buffer_index(&t.name)
+                    || horizon_shaders::buffer_index(&t.name)
                         .is_none_or(|b| released.1 & 1 << b == 0))
         });
         let image = pack
@@ -2433,7 +2432,7 @@ impl PackPost {
         let shadow_config = post.config.shadow.clone();
         let noise_size = post.config.noise_resolution.unwrap_or(256);
         let half_lives = post.config.half_lives;
-        for (name, ticks) in horizon_render_pipeline::HALF_LIVES.iter().zip(half_lives) {
+        for (name, ticks) in horizon_shaders::HALF_LIVES.iter().zip(half_lives) {
             if let Some(t) = ticks {
                 notes.push(format!("`{name}` is {t} ticks"));
             }

crates/horizon-client-render/src/gfx/pack_post/packed.rs

@@ -10,7 +10,7 @@
 //! a fit to one driver's values, not a rule Iris states. `RGBA4` and `RGBA2` read back the `RGBA8`
 //! bytes in the same probe, as Horizon's 8-bit buffers already do.
 
-use horizon_render_pipeline::{Format, Kind};
+use horizon_shaders::{Format, Kind};
 use naga::{BinaryOperator, Expression, Literal, MathFunction, Statement, VectorSize};
 
 /// The bits each channel keeps in a buffer of format `f`, for the formats that keep fewer than

crates/horizon-client-render/src/gfx/pack_shadow.rs

@@ -3,7 +3,7 @@
 //! with two sides that `shadowcomp` programs flip as composite programs flip colortex (6.1.6).
 //! Square, `shadowMapResolution` pixels.
 
-use horizon_render_pipeline::SHADOW_COLORS;
+use horizon_shaders::SHADOW_COLORS;
 
 type Ops<T> = wgpu::Operations<T>;
 type Color = wgpu::Color;
@@ -97,11 +97,7 @@ pub(super) fn stand_in(device: &wgpu::Device) -> wgpu::TextureView {
 }
 
 impl ShadowTargets {
-    pub fn reset_history(
-        &mut self,
-        device: &wgpu::Device,
-        shadow: &horizon_render_pipeline::Shadow,
-    ) {
+    pub fn reset_history(&mut self, device: &wgpu::Device, shadow: &horizon_shaders::Shadow) {
         let mut colors = 0;
         let mut doubled = 0;
         let formats = std::array::from_fn(|n| match &self.color[n] {
@@ -129,7 +125,7 @@ impl ShadowTargets {
     /// resolution is kept within the device's limit.
     pub fn new(
         device: &wgpu::Device,
-        shadow: &horizon_render_pipeline::Shadow,
+        shadow: &horizon_shaders::Shadow,
         formats: [wgpu::TextureFormat; SHADOW_COLORS],
         colors: u16,
         doubled: u16,

crates/horizon-client-render/src/gfx/pack_textures.rs

@@ -1,8 +1,7 @@
 //! A shader pack's custom textures (`texture.<stage>.<name>`, `texture.noise`) on the GPU, and
 //! which of them a program's sampler reads.
 
-use horizon_render_pipeline::Kind;
-use horizon_shaders::{CustomTexture, Group, Texels, Texture, TextureDim, TextureSource};
+use horizon_shaders::{CustomTexture, Group, Kind, Texels, Texture, TextureDim, TextureSource};
 
 /// What a custom texture is once uploaded: an image of ours, or one the game already has.
 pub(super) enum Image {
@@ -119,12 +118,12 @@ pub(super) fn find(textures: &[PackTexture], group: Group, ty: &str, name: &str)
     } else {
         wgpu::TextureViewDimension::D2
     };
-    let buffer = horizon_render_pipeline::buffer_index(name);
+    let buffer = horizon_shaders::buffer_index(name);
     let staged = textures.iter().position(|t| {
         t.stage == stage(group)
             && t.dimension == dimension
             && (t.name == name
-                || buffer.is_some() && horizon_render_pipeline::buffer_index(&t.name) == buffer)
+                || buffer.is_some() && horizon_shaders::buffer_index(&t.name) == buffer)
     });
     staged.or_else(|| {
         textures.iter().position(|t| {

crates/horizon-client-render/src/gfx/pack_uniforms.rs

@@ -28,7 +28,7 @@
 //! [-w, w], and the depth buffers packs read hold GL window depth.
 
 use glam::{DMat4, DVec3, Mat4, Vec3, Vec4};
-use horizon_render_pipeline::Shadow;
+use horizon_shaders::Shadow;
 
 use super::Frame;
 
@@ -440,7 +440,7 @@ pub struct FrameUniforms {
     center_depth: Option<f32>,
     /// The pack's shadow settings (7.1).
     pub shadow: Shadow,
-    /// The pack's smoothing half-lives in ticks (`horizon_render_pipeline::HALF_LIVES`).
+    /// The pack's smoothing half-lives in ticks (`horizon_shaders::HALF_LIVES`).
     pub half_lives: [Option<f32>; 4],
 }
 

crates/horizon-client-render/src/options_ui.rs

@@ -339,6 +339,7 @@ impl Opt {
             Opt::SharePresence => "options.sharePresence",
             Opt::DirectionalAudio => "options.directionalAudio",
             Opt::MusicToast => "options.musicToast",
+            Opt::Page(page, row) => pages::slider_caption(page, row),
         }
     }
     pub(crate) fn kind(self, s: &Settings) -> Kind {
@@ -402,6 +403,7 @@ impl Opt {
             Opt::PadLookDeadzone => unit(s.controller.look_deadzone, 0.0, 0.5),
             Opt::PadTriggerThreshold => unit(s.controller.trigger_threshold, 0.1, 0.9),
             Opt::SprintWindow => unit(s.sprint_window as f32, 0.0, 10.0),
+            Opt::Page(page, row) => pages::slider_kind(page, row),
             _ => Kind::Cycle,
         }
     }
@@ -878,6 +880,7 @@ impl Opt {
                 gamepad::TextKeyboard::Horizon => "horizon.options.keyboard.horizon",
                 gamepad::TextKeyboard::Steam => "horizon.options.keyboard.steam",
             }),
+            Opt::Page(page, row) => pages::slider_text(page, row),
             _ => Text::empty(),
         }
     }
@@ -952,6 +955,7 @@ impl Opt {
             Opt::PadLookDeadzone => s.controller.look_deadzone = step(0.0, 50.0) / 100.0,
             Opt::PadTriggerThreshold => s.controller.trigger_threshold = step(10.0, 90.0) / 100.0,
             Opt::SprintWindow => s.sprint_window = step(0.0, 10.0) as i32,
+            Opt::Page(page, row) => pages::slide(page, row, v),
             _ => {}
         }
         if self.affects_preset() {
@@ -1331,6 +1335,8 @@ pub enum Page {
     ModProject,
     /// A native mod's settings page: its index in `mods.installed`.
     NativeMod(usize),
+    /// A page a crate registered (`horizon_hooks::pages`): its index in `OptionsUi::pages`.
+    Added(usize),
     /// Horizon's shader packs, either kind (`shader_pack_list`).
     ShaderPacks,
     /// The picked pack's options: the shader screen (`shader_ui`) at the pack's main screen.
@@ -1390,6 +1396,8 @@ enum Act {
     /// A native mod's key (mod, key) waits for a key; a button of its page.
     NativeKey(usize, usize),
     NativeButton(usize, usize),
+    /// A registered page's row: (page, row).
+    PageRow(usize, usize),
     OpenModFolder,
     /// Browse mods: the page of listing `.0` of `mod_browser`.
     ModProject(usize),
@@ -1617,7 +1625,8 @@ pub struct OptionsUi {
     /// Key Binds: the mapping waiting for a key ([`NATIVE_KEY`]: a native
     /// mod's, `selected_native_key`).
     pub selected_key: Option<&'static str>,
-    /// The native mod's key waiting: (mod, key) in `mods.installed`.
+    /// The native mod's key waiting: (mod, key) in `mods.installed`, or a registered page's
+    /// (page, row) ([`pages::PAGE_KEY`]).
     selected_native_key: Option<(usize, usize)>,
     /// Bindings: the action waiting for a pad button.
     pub selected_pad_action: Option<&'static str>,
@@ -1861,25 +1870,6 @@ fn wide_extras(s: &Settings, width: impl Fn(&str) -> f32) -> Vec<crate::extras::
         })
         .collect()
 }
-/// What a button opening one of Horizon's pages says on hover.
-fn horizon_page_tooltip(page: Page) -> Option<&'static str> {
-    Some(match page {
-        Page::Horizon => "horizon.pages.settings.tooltip",
-        Page::Studio => "horizon.pages.studio.tooltip",
-        Page::Graphics => "horizon.pages.graphics.tooltip",
-        Page::GraphicsAdvanced => "horizon.pages.graphics_advanced.tooltip",
-        Page::Controller => "horizon.pages.controller.tooltip",
-        Page::Extras => "horizon.pages.extras.tooltip",
-        Page::Pvp => "horizon.pages.pvp.tooltip",
-        Page::Agent => "horizon.pages.agent.tooltip",
-        Page::SplitProfiles => "horizon.pages.split_profiles.tooltip",
-        Page::ShaderPacks => "horizon.pages.shader_packs.tooltip",
-        Page::Mods => "horizon.pages.mods.tooltip",
-        Page::SplitSetup => "horizon.pages.split_setup.tooltip",
-        Page::Music => "horizon.pages.music.tooltip",
-        _ => return None,
-    })
-}
 /// Rows of an OptionsList: (big?, options) or a header.
 enum Row {
     Big(Opt),
@@ -1899,14 +1889,17 @@ fn tooltip_text(s: &Settings, wd: &Widget) -> Option<Text> {
             return None;
         };
         let key = opt.tooltip_key(s);
-        return lang::has(&key).then(|| tr(&key));
+        let Opt::Page(page, row) = opt else {
+            return lang::has(&key).then(|| tr(&key));
+        };
+        return pages::tooltip(*page, *row);
     };
     let mut tip = None;
     if let Act::Extra(item) = act {
         tip = Some(Text::literal(item.description_text()));
     }
     if let Act::Push(page) = act
-        && let Some(text) = horizon_page_tooltip(*page)
+        && let Some(text) = pages::horizon_page_tooltip(*page)
     {
         tip = Some(tr(text));
     }
@@ -1926,6 +1919,7 @@ fn tooltip_text(s: &Settings, wd: &Widget) -> Option<Text> {
     }
     match act {
         Act::Cycle(opt) if !opt.available() => Some(tr("horizon.options.unavailable")),
+        Act::PageRow(page, row) => pages::tooltip(*page, *row),
         Act::ToggleMod(i) => match s.mods.installed.get(*i) {
             Some(installed) => {
                 let description = installed
@@ -2367,6 +2361,7 @@ impl OptionsUi {
             Page::ModBrowser => "horizon.mods.browse.title",
             Page::ModProject => "horizon.mods.browse.project",
             Page::NativeMod(_) => "Mod Settings",
+            Page::Added(i) => pages::title(i),
             Page::ShaderPacks => "horizon.pages.shader_packs",
             Page::ShaderOptions => "horizon.pages.shader_options",
             Page::PackOptions => "horizon.pack.options.title",
@@ -2647,47 +2642,7 @@ impl OptionsUi {
                 flush(&mut rows, &mut section);
                 rows
             }
-            Page::Horizon => {
-                // Two to a row, as vanilla's OptionsList.addSmall lays out
-                // buttons; each opens one of Horizon's settings pages. Each page has
-                // one way in: graphics and shader packs are Video Settings' (the graphics
-                // screen), the controller is Controls', mods are the Options screen's.
-                let open =
-                    |key: &str, page: Page| button(0.0, 0.0, 150.0, tr(key), Act::Push(page));
-                vec![
-                    Row::Buttons(
-                        open("horizon.pages.open.extras", Page::Extras),
-                        Some(open("horizon.pages.open.pvp", Page::Pvp)),
-                    ),
-                    Row::Buttons(
-                        open(
-                            "horizon.pages.open.split_setup",
-                            if self.split_guest {
-                                Page::SplitProfiles
-                            } else {
-                                Page::SplitSetup
-                            },
-                        ),
-                        Some(open("horizon.pages.open.studio", Page::Studio)),
-                    ),
-                    // No AI hides the AI Agent page and everything AI.
-                    Row::Buttons(
-                        self.extra_button(s, crate::extras::Item::DiscordPresence),
-                        Some(if s.extras.no_ai {
-                            self.extra_button(s, crate::extras::Item::NoAi)
-                        } else {
-                            open("horizon.pages.open.agent", Page::Agent)
-                        }),
-                    ),
-                ]
-                .into_iter()
-                .chain(
-                    (!s.extras.no_ai).then(|| {
-                        Row::Buttons(self.extra_button(s, crate::extras::Item::NoAi), None)
-                    }),
-                )
-                .collect()
-            }
+            Page::Horizon => self.horizon_rows(s),
             Page::Agent => {
                 let mut rows = vec![Row::Buttons(
                     self.extra_button(s, crate::extras::Item::AgentControl),
@@ -2970,6 +2925,7 @@ impl OptionsUi {
             Page::ModBrowser => self.mod_browser_rows(),
             Page::ModProject => self.mod_project_rows(s),
             Page::NativeMod(i) => self.native_rows(s, i),
+            Page::Added(i) => self.added_rows(i),
             _ => {
                 let _ = s;
                 Vec::new()
@@ -4238,6 +4194,7 @@ impl OptionsUi {
                         }
                         Act::NativeKey(i, k) => self.wait_native_key(i, k),
                         Act::NativeButton(i, b) => events.push(Event::NativeButton(i, b)),
+                        Act::PageRow(p, r) => events.extend(self.page_act(p, r, self.shift)),
                         Act::OpenModFolder => events.push(Event::OpenModFolder),
                         Act::ModProject(i) => {
                             if let Some(listing) = self.mod_browser.listings.get(i) {
@@ -4741,8 +4698,8 @@ impl OptionsUi {
         let Some(name) = self.selected_key.take() else {
             return Vec::new();
         };
-        if name == NATIVE_KEY {
-            return self.bind_native_key(s, value);
+        if name == NATIVE_KEY || name == pages::PAGE_KEY {
+            return self.bind_native_key(s, name, value);
         }
         if !s.extras.set_key(name, value.clone()) {
             s.keys.set(name, &value);
@@ -5126,6 +5083,7 @@ impl OptionsUi {
                         }
                         Act::NativeKey(i, k) => self.wait_native_key(i, k),
                         Act::NativeButton(i, b) => events.push(Event::NativeButton(i, b)),
+                        Act::PageRow(p, r) => events.extend(self.page_act(p, r, shift)),
                         Act::OpenModFolder => events.push(Event::OpenModFolder),
                         Act::ModProject(i) => {
                             if let Some(listing) = self.mod_browser.listings.get(i) {

crates/horizon-client-render/src/options_ui_pages.rs

@@ -1,8 +1,224 @@
 //! The pages crates add to the options screens: a native mod's settings page (its keys and
-//! buttons). Kept out of options_ui.rs, which may not grow (tools/check_file_size.py).
+//! buttons), and the pages crates above the engine register (`horizon_hooks::pages`, docs/layers.md
+//! "Platform registries") with their entries on Horizon Settings. Kept out of options_ui.rs, which
+//! may not grow (tools/check_file_size.py).
 use super::*;
+use horizon_hooks::pages as added;
+
+/// `selected_key` while a registered page's key waits (`selected_native_key`: page, row).
+pub(super) const PAGE_KEY: &str = "horizon.pageKey";
+
+#[cfg(test)]
+thread_local! {
+    /// A test's own pages, instead of the game's registered ones: each test runs on its thread.
+    static TEST_PAGES: std::cell::Cell<Option<&'static [&'static dyn added::Page]>> =
+        const { std::cell::Cell::new(None) };
+}
+
+/// The pages crates registered.
+fn registered() -> &'static [&'static dyn added::Page] {
+    #[cfg(test)]
+    if let Some(pages) = TEST_PAGES.get() {
+        return pages;
+    }
+    added::engine::all()
+}
+
+/// A registered page's title (a translation key).
+pub(super) fn title(page: usize) -> &'static str {
+    registered().get(page).map_or("", |p| p.title())
+}
+
+/// Row `r` of a registered page, as it is now.
+fn row(page: usize, r: usize) -> Option<added::Row> {
+    let mut rows = Vec::new();
+    registered().get(page)?.rows(&mut rows);
+    rows.into_iter().nth(r)
+}
+
+/// A registered page's slider ([`Opt::Page`]): its caption (a translation key).
+pub(super) fn slider_caption(page: usize, r: usize) -> &'static str {
+    match row(page, r) {
+        Some(added::Row::Slider { label, .. }) => label,
+        _ => "",
+    }
+}
+
+/// A registered page's slider: its position.
+pub(super) fn slider_kind(page: usize, r: usize) -> Kind {
+    match row(page, r) {
+        Some(added::Row::Slider { value, .. }) => Kind::Slider(value.clamp(0.0, 1.0)),
+        _ => Kind::Cycle,
+    }
+}
+
+/// A registered page's slider: the value its message shows after the caption.
+pub(super) fn slider_text(page: usize, r: usize) -> Text {
+    match row(page, r) {
+        Some(added::Row::Slider { text, .. }) => label_text(text),
+        _ => Text::empty(),
+    }
+}
+
+/// A registered page's slider moved.
+pub(super) fn slide(page: usize, r: usize, value: f32) {
+    if let Some(registered) = registered().get(page) {
+        registered.act(r, added::Act::Slide(value));
+    }
+}
+
+/// What a registered page's row says on hover.
+pub(super) fn tooltip(page: usize, r: usize) -> Option<Text> {
+    registered().get(page)?.tooltip(r).map(label_text)
+}
+
+/// What a button opening one of Horizon's pages says on hover.
+pub(super) fn horizon_page_tooltip(page: Page) -> Option<&'static str> {
+    Some(match page {
+        Page::Horizon => "horizon.pages.settings.tooltip",
+        Page::Studio => "horizon.pages.studio.tooltip",
+        Page::Graphics => "horizon.pages.graphics.tooltip",
+        Page::GraphicsAdvanced => "horizon.pages.graphics_advanced.tooltip",
+        Page::Controller => "horizon.pages.controller.tooltip",
+        Page::Extras => "horizon.pages.extras.tooltip",
+        Page::Pvp => "horizon.pages.pvp.tooltip",
+        Page::Agent => "horizon.pages.agent.tooltip",
+        Page::SplitProfiles => "horizon.pages.split_profiles.tooltip",
+        Page::ShaderPacks => "horizon.pages.shader_packs.tooltip",
+        Page::Mods => "horizon.pages.mods.tooltip",
+        Page::SplitSetup => "horizon.pages.split_setup.tooltip",
+        Page::Music => "horizon.pages.music.tooltip",
+        _ => return None,
+    })
+}
+
+fn label_text(label: added::Label) -> Text {
+    match label {
+        added::Label::Key(key) => tr(key),
+        added::Label::Value(value) => Text::literal(value),
+    }
+}
 
 impl OptionsUi {
+    /// Horizon Settings: its pages, then the pages crates registered for it.
+    pub(super) fn horizon_rows(&self, s: &Settings) -> Vec<Row> {
+        // Two to a row, as vanilla's OptionsList.addSmall lays out
+        // buttons; each opens one of Horizon's settings pages. Each page has
+        // one way in: graphics and shader packs are Video Settings' (the graphics
+        // screen), the controller is Controls', mods are the Options screen's.
+        let open = |key: &str, page: Page| button(0.0, 0.0, 150.0, tr(key), Act::Push(page));
+        let mut rows: Vec<Row> = vec![
+            Row::Buttons(
+                open("horizon.pages.open.extras", Page::Extras),
+                Some(open("horizon.pages.open.pvp", Page::Pvp)),
+            ),
+            Row::Buttons(
+                open(
+                    "horizon.pages.open.split_setup",
+                    if self.split_guest {
+                        Page::SplitProfiles
+                    } else {
+                        Page::SplitSetup
+                    },
+                ),
+                Some(open("horizon.pages.open.studio", Page::Studio)),
+            ),
+            // No AI hides the AI Agent page and everything AI.
+            if s.extras.no_ai {
+                Row::Buttons(self.extra_button(s, crate::extras::Item::NoAi), None)
+            } else {
+                Row::Buttons(
+                    open("horizon.pages.open.agent", Page::Agent),
+                    Some(self.extra_button(s, crate::extras::Item::NoAi)),
+                )
+            },
+        ];
+        self.added_entries(&mut rows);
+        rows
+    }
+
+    /// The entries of the pages registered for Horizon Settings, two to a row like the engine's.
+    fn added_entries(&self, rows: &mut Vec<Row>) {
+        let mut entries = registered()
+            .iter()
+            .enumerate()
+            .filter(|(_, page)| page.place() == added::Place::HorizonSettings)
+            .map(|(i, page)| button(0.0, 0.0, 150.0, tr(page.title()), Act::Push(Page::Added(i))));
+        while let Some(first) = entries.next() {
+            rows.push(Row::Buttons(first, entries.next()));
+        }
+    }
+
+    /// A registered page's rows, asked of it each time the page is drawn.
+    pub(super) fn added_rows(&self, page: usize) -> Vec<Row> {
+        let Some(registered) = registered().get(page) else {
+            return Vec::new();
+        };
+        let mut rows = Vec::new();
+        registered.rows(&mut rows);
+        rows.into_iter()
+            .enumerate()
+            .map(|(r, row)| self.added_row(page, r, row))
+            .collect()
+    }
+
+    fn added_row(&self, page: usize, r: usize, row: added::Row) -> Row {
+        let act = Act::PageRow(page, r);
+        let wide = |label: Text| Row::Buttons(button(0.0, 0.0, 310.0, label, act.clone()), None);
+        match row {
+            added::Row::Heading(key) => Row::Heading(key.to_owned()),
+            added::Row::Note(text) => Row::Note(text),
+            added::Row::Toggle { label, on } => wide(generic(label, on_off(on))),
+            added::Row::Cycle { label, value } => wide(generic(label, label_text(value))),
+            added::Row::Slider { .. } => Row::Big(Opt::Page(page, r)),
+            added::Row::Button { label } => wide(tr(label)),
+            added::Row::Key { label, key } => {
+                let mut message = keybinds::display_name(&key);
+                if self.selected_key == Some(PAGE_KEY)
+                    && self.selected_native_key == Some((page, r))
+                {
+                    message = Text::literal("> ")
+                        .append(message.with_color(text::WHITE))
+                        .append(" <")
+                        .with_color(text::YELLOW);
+                }
+                let caption = button(0.0, 0.0, 150.0, tr(label), Act::None);
+                let change = button(0.0, 0.0, 150.0, message, act);
+                Row::Buttons(inactive(caption), Some(change))
+            }
+            // A row kind newer than this engine: shown empty.
+            _ => Row::Note(String::new()),
+        }
+    }
+
+    /// A registered page's row was pressed: a key row waits for a key, any other row hears it.
+    pub(super) fn page_act(&mut self, page: usize, r: usize, shift: bool) -> Vec<Event> {
+        let Some(registered) = registered().get(page) else {
+            return Vec::new();
+        };
+        let mut rows = Vec::new();
+        registered.rows(&mut rows);
+        match rows.get(r) {
+            Some(added::Row::Key { .. }) => {
+                self.selected_key = Some(PAGE_KEY);
+                self.selected_native_key = Some((page, r));
+                Vec::new()
+            }
+            Some(_) => {
+                registered.act(
+                    r,
+                    if shift {
+                        added::Act::PressBack
+                    } else {
+                        added::Act::Press
+                    },
+                );
+                vec![Event::Changed]
+            }
+            None => Vec::new(),
+        }
+    }
+
     /// A native mod's page: its name, its keys as Key Binds rows (the
     /// player's choice, else the default), then its buttons.
     pub(super) fn native_rows(&self, s: &Settings, i: usize) -> Vec<Row> {
@@ -46,9 +262,21 @@ impl OptionsUi {
         self.selected_native_key = Some((i, k));
     }
 
-    /// The key pressed for the native mod's key that waited for one.
-    pub(super) fn bind_native_key(&mut self, s: &mut Settings, value: String) -> Vec<Event> {
+    /// The key pressed for the native mod's key, or the registered page's ([`PAGE_KEY`]), that
+    /// waited for one.
+    pub(super) fn bind_native_key(
+        &mut self,
+        s: &mut Settings,
+        name: &str,
+        value: String,
+    ) -> Vec<Event> {
         let (i, k) = self.selected_native_key.take().unwrap_or_default();
+        if name == PAGE_KEY {
+            if let Some(page) = registered().get(i) {
+                page.act(k, added::Act::Bind(value));
+            }
+            return vec![Event::Changed];
+        }
         let Some(m) = s.mods.installed.get(i) else {
             return Vec::new();
         };
@@ -60,3 +288,171 @@ impl OptionsUi {
         vec![Event::Changed]
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::Mutex;
+
+    /// A page with a heading, a switch, a number that steps either way, a key and a volume.
+    struct Sample {
+        on: Mutex<bool>,
+        step: Mutex<i32>,
+        key: Mutex<String>,
+        volume: Mutex<f32>,
+    }
+
+    impl added::Page for Sample {
+        fn id(&self) -> &'static str {
+            "test.sample"
+        }
+        fn title(&self) -> &'static str {
+            "test.sample.title"
+        }
+        fn place(&self) -> added::Place {
+            added::Place::HorizonSettings
+        }
+        fn rows(&self, rows: &mut Vec<added::Row>) {
+            rows.push(added::Row::Heading("test.sample.heading"));
+            rows.push(added::Row::Toggle {
+                label: "test.sample.switch",
+                on: *self.on.lock().unwrap(),
+            });
+            rows.push(added::Row::Cycle {
+                label: "test.sample.step",
+                value: added::Label::Value(self.step.lock().unwrap().to_string()),
+            });
+            rows.push(added::Row::Key {
+                label: "test.sample.key",
+                key: self.key.lock().unwrap().clone(),
+            });
+            let volume = *self.volume.lock().unwrap();
+            rows.push(added::Row::Slider {
+                label: "test.sample.volume",
+                value: volume,
+                text: added::Label::Value(format!("{}%", (volume * 100.0).round())),
+            });
+        }
+        fn act(&self, row: usize, act: added::Act) {
+            match (row, act) {
+                (1, added::Act::Press) => {
+                    let mut on = self.on.lock().unwrap();
+                    *on = !*on;
+                }
+                (2, added::Act::Press) => *self.step.lock().unwrap() += 1,
+                (2, added::Act::PressBack) => *self.step.lock().unwrap() -= 1,
+                (3, added::Act::Bind(key)) => *self.key.lock().unwrap() = key,
+                (4, added::Act::Slide(v)) => *self.volume.lock().unwrap() = v,
+                other => panic!("row and act the page doesn't expect: {other:?}"),
+            }
+        }
+        fn tooltip(&self, row: usize) -> Option<added::Label> {
+            (row == 1).then_some(added::Label::Key("test.sample.switch.tooltip"))
+        }
+    }
+
+    static SAMPLE: Sample = Sample {
+        on: Mutex::new(false),
+        step: Mutex::new(0),
+        key: Mutex::new(String::new()),
+        volume: Mutex::new(0.0),
+    };
+    static PAGES: [&dyn added::Page; 1] = [&SAMPLE];
+
+    /// Clicks the active button that does `act`, with Shift held or not.
+    fn press(ui: &mut OptionsUi, s: &mut Settings, act: Act, shift: bool) -> Vec<Event> {
+        let size = (480.0, 240.0);
+        let (widgets, ..) = ui.layout(s, size.0, size.1);
+        let (x, y) = widgets
+            .iter()
+            .find_map(|w| match &w.kind {
+                WKind::Button {
+                    act: a,
+                    active: true,
+                    ..
+                } if *a == act => Some((w.x + 1.0, w.y + 1.0)),
+                _ => None,
+            })
+            .unwrap_or_else(|| panic!("no button does {act:?}"));
+        ui.shift = shift;
+        let atlas = super::super::tests::atlas();
+        ui.click(s, &atlas, x, y, size, [480, 240], false, false)
+    }
+
+    #[test]
+    fn a_registered_page_opens_from_horizon_settings_and_hears_its_rows() {
+        let mut s = Settings::default();
+        TEST_PAGES.set(Some(&PAGES));
+        let mut ui = OptionsUi::default();
+        ui.show(Page::Horizon);
+        press(&mut ui, &mut s, Act::Push(Page::Added(0)), false);
+        assert_eq!(ui.page(), Page::Added(0));
+        // Rows: the heading (0), the switch (1), the step (2), the key (3).
+        let events = press(&mut ui, &mut s, Act::PageRow(0, 1), false);
+        assert_eq!(
+            events.last(),
+            Some(&Event::Changed),
+            "the settings get saved"
+        );
+        assert!(*SAMPLE.on.lock().unwrap());
+        press(&mut ui, &mut s, Act::PageRow(0, 2), false);
+        press(&mut ui, &mut s, Act::PageRow(0, 2), true);
+        press(&mut ui, &mut s, Act::PageRow(0, 2), true);
+        assert_eq!(*SAMPLE.step.lock().unwrap(), -1, "Shift steps back");
+        // A key row waits for the next key, as on Key Binds, and the page gets its name.
+        press(&mut ui, &mut s, Act::PageRow(0, 3), false);
+        let atlas = super::super::tests::atlas();
+        let events = ui.key(&mut s, &atlas, winit::keyboard::KeyCode::KeyZ, None);
+        assert_eq!(events, [Event::Changed]);
+        assert_eq!(*SAMPLE.key.lock().unwrap(), "key.keyboard.z");
+        assert_eq!(ui.selected_key, None);
+        // The volume is one of the screen's own sliders: dragged to its middle, then let go.
+        let size = (480.0, 240.0);
+        let (widgets, ..) = ui.layout(&s, size.0, size.1);
+        let slider = widgets
+            .iter()
+            .find(|w| {
+                matches!(
+                    w.kind,
+                    WKind::Slider {
+                        opt: Opt::Page(0, 4),
+                        ..
+                    }
+                )
+            })
+            .expect("the volume's slider");
+        let (x, y) = (slider.x + slider.w / 2.0, slider.y + 1.0);
+        ui.click(&mut s, &atlas, x, y, size, [480, 240], false, false);
+        let volume = *SAMPLE.volume.lock().unwrap();
+        assert!((0.45..0.55).contains(&volume), "{volume}");
+        assert!(ui.release().contains(&Event::Changed));
+        // The slider shows the page's value once let go.
+        let (widgets, ..) = ui.layout(&s, size.0, size.1);
+        let shown = widgets.iter().find_map(|w| match w.kind {
+            WKind::Slider {
+                opt: Opt::Page(0, 4),
+                value,
+                ..
+            } => Some(value),
+            _ => None,
+        });
+        assert_eq!(shown, Some(volume));
+        // The page's tooltip for its switch.
+        let switch = widgets
+            .iter()
+            .find(|w| {
+                matches!(
+                    &w.kind,
+                    WKind::Button {
+                        act: Act::PageRow(0, 1),
+                        ..
+                    }
+                )
+            })
+            .expect("the switch");
+        assert_eq!(
+            tooltip_text(&s, switch).map(|t| t.plain()),
+            Some(tr("test.sample.switch.tooltip").plain())
+        );
+    }
+}

crates/horizon-client-render/src/particles.rs

@@ -31,6 +31,7 @@ mod native;
 pub mod polytone;
 mod polytone_gpu;
 mod polytone_model;
+mod spawn;
 pub use native::{ParticleController, ParticleUpdate};
 
 /// `ParticleOptions` with the parameters of the option classes used here.
@@ -2026,73 +2027,6 @@ impl ParticleEngine {
             (eye[0] - pos[0]).powi(2) + (eye[1] - pos[1]).powi(2) + (eye[2] - pos[2]).powi(2) <= 9.0
         })
     }
-    /// `ClientPacketListener.handleParticleEvent` for `ServerLevel.sendParticles`.
-    pub fn send_particles(
-        &mut self,
-        options: &ParticleOptions,
-        at: [f64; 3],
-        spread: [f64; 3],
-        speed: f64,
-        count: u32,
-    ) {
-        if count == 0 {
-            let v = [speed * spread[0], speed * spread[1], speed * spread[2]];
-            self.add(options, at, v);
-            return;
-        }
-        for _ in 0..count {
-            let r = &mut self.random;
-            let p = [
-                at[0] + r.next_gaussian() * spread[0],
-                at[1] + r.next_gaussian() * spread[1],
-                at[2] + r.next_gaussian() * spread[2],
-            ];
-            let v = [
-                r.next_gaussian() * speed,
-                r.next_gaussian() * speed,
-                r.next_gaussian() * speed,
-            ];
-            self.add(options, p, v);
-        }
-    }
-    /// `ParticleEngine.createParticle`: always spawned, but `ParticleEngine.add`
-    /// drops a spore blossom air particle once `ParticleLimit.SPORE_BLOSSOM` is full.
-    pub fn create(&mut self, options: &ParticleOptions, p: [f64; 3], v: [f64; 3]) {
-        if let Some(requests) = &mut self.created_requests {
-            requests.push((options.clone(), p, v));
-            return;
-        }
-        let seed = self.seeds.next_long();
-        if let Some(mut particle) = self.make(options, p, v, seed) {
-            *self.made.entry(options.ty.name()).or_default() += 1;
-            // Resource packs' Polytone particle modifiers (#11486), once as it spawns.
-            if let Some(registry) = &self.polytone
-                && registry.modifies_particles()
-            {
-                let id = match &options.mod_particle {
-                    Some(name) => name.clone(),
-                    None => format!("minecraft:{}", options.ty.name()),
-                };
-                polytone::modify(registry, &id, options.source.as_deref(), &mut particle);
-            }
-            // The provider has drawn, so rejecting here keeps vanilla's RNG order.
-            // shortcut: counts live plus queued particles by scanning instead of
-            // vanilla's counted map; use a counter if spore spawning shows in profiles.
-            if particle.ty == ParticleType::SporeBlossomAir
-                && self.particles.len() + self.pending.len() >= SPORE_BLOSSOM_LIMIT
-                && self
-                    .particles
-                    .iter()
-                    .chain(self.pending.iter())
-                    .filter(|q| q.ty == ParticleType::SporeBlossomAir)
-                    .count()
-                    >= SPORE_BLOSSOM_LIMIT
-            {
-                return;
-            }
-            self.pending.push(particle);
-        }
-    }
     /// How many particles of each type were made so far.
     pub fn made(&self) -> &std::collections::BTreeMap<&'static str, u64> {
         &self.made

crates/horizon-client-render/src/particles/spawn.rs

@@ -0,0 +1,73 @@
+//! Where particles come into the engine: a server's particle packet and a single particle made
+//! where the game asks for one.
+use super::*;
+
+impl ParticleEngine {
+    /// `ClientPacketListener.handleParticleEvent` for `ServerLevel.sendParticles`.
+    pub fn send_particles(
+        &mut self,
+        options: &ParticleOptions,
+        at: [f64; 3],
+        spread: [f64; 3],
+        speed: f64,
+        count: u32,
+    ) {
+        if count == 0 {
+            let v = [speed * spread[0], speed * spread[1], speed * spread[2]];
+            self.add(options, at, v);
+            return;
+        }
+        for _ in 0..count {
+            let r = &mut self.random;
+            let p = [
+                at[0] + r.next_gaussian() * spread[0],
+                at[1] + r.next_gaussian() * spread[1],
+                at[2] + r.next_gaussian() * spread[2],
+            ];
+            let v = [
+                r.next_gaussian() * speed,
+                r.next_gaussian() * speed,
+                r.next_gaussian() * speed,
+            ];
+            self.add(options, p, v);
+        }
+    }
+    /// `ParticleEngine.createParticle`: always spawned, but `ParticleEngine.add`
+    /// drops a spore blossom air particle once `ParticleLimit.SPORE_BLOSSOM` is full.
+    pub fn create(&mut self, options: &ParticleOptions, p: [f64; 3], v: [f64; 3]) {
+        if let Some(requests) = &mut self.created_requests {
+            requests.push((options.clone(), p, v));
+            return;
+        }
+        let seed = self.seeds.next_long();
+        if let Some(mut particle) = self.make(options, p, v, seed) {
+            *self.made.entry(options.ty.name()).or_default() += 1;
+            // Resource packs' Polytone particle modifiers (#11486), once as it spawns.
+            if let Some(registry) = &self.polytone
+                && registry.modifies_particles()
+            {
+                let id = match &options.mod_particle {
+                    Some(name) => name.clone(),
+                    None => format!("minecraft:{}", options.ty.name()),
+                };
+                polytone::modify(registry, &id, options.source.as_deref(), &mut particle);
+            }
+            // The provider has drawn, so rejecting here keeps vanilla's RNG order.
+            // shortcut: counts live plus queued particles by scanning instead of
+            // vanilla's counted map; use a counter if spore spawning shows in profiles.
+            if particle.ty == ParticleType::SporeBlossomAir
+                && self.particles.len() + self.pending.len() >= SPORE_BLOSSOM_LIMIT
+                && self
+                    .particles
+                    .iter()
+                    .chain(self.pending.iter())
+                    .filter(|q| q.ty == ParticleType::SporeBlossomAir)
+                    .count()
+                    >= SPORE_BLOSSOM_LIMIT
+            {
+                return;
+            }
+            self.pending.push(particle);
+        }
+    }
+}

crates/horizon-client-render/src/settings.rs

@@ -864,6 +864,8 @@ pub enum Opt {
     PadGameplayGuide,
     /// `options.modelPart.*`: one skin layer (index into `options_file::MODEL_PARTS`).
     ModelPart(usize),
+    /// A slider of a page a crate registered (`horizon_hooks::pages`): (page, row).
+    Page(usize, usize),
     /// 3D skin layers: the player's outer layer as extruded slabs.
     SkinLayers3d,
     MainHand,

crates/horizon-client/Cargo.toml

@@ -119,15 +119,13 @@ audio = ["horizon-client-render/audio", "horizon-client-lib/audio"]
 controllers = ["horizon-client-lib/controllers", "dep:gilrs", "dep:horizon-dualsense", "horizon-client-input/controllers"]
 # Horizon's own extras over the vanilla game, for a fork that wants them out (docs/forking.md):
 # cosmetics and emotes, the "Horizon player" presence, the official server added to
-# the server list, the Horizon Settings and Mods pages, Discord and Play with Friends. Players always get them; there is no switch. `grep -rn horizon-extras crates/` lists
+# the server list, the Horizon Settings and Mods pages and Play with Friends. Players always get them; there is no switch. `grep -rn horizon-extras crates/` lists
 # every place it gates. Without it (`--no-default-features --features audio,controllers`) the
 # client is best effort: CI builds only the default.
-horizon-extras = ["discord", "friends"]
-# Online extras a server or a port can leave out; the server build has none of them. "Playing Horizon"
-# on Discord (game/discord.rs).
-discord = ["horizon-client-lib/discord"]
-# Play with Friends: sharing a world behind an invite code (game/friends.rs) and joining one.
-friends = ["horizon-client-lib/friends", "dep:horizon-friends"]
+horizon-extras = ["friends"]
+# Play with Friends: sharing a world behind an invite code (game/friends.rs). Joining one is
+# horizon-friends' `game` side, which horizon-official registers (`horizon_hooks::tunnel`).
+friends = ["dep:horizon-friends"]
 # Records the call sites of mob random draws (`mob_ai_probe` traces).
 rng-trace = ["horizon-core/rng-trace", "horizon-client-lib/rng-trace"]
 # Rust's allocations go to the system heap instead of mimalloc, where heap profilers that replace

crates/horizon-client/src/client_lib.rs

@@ -58,8 +58,6 @@ pub mod debug_overlay;
 pub mod debugworld;
 pub mod dialog;
 pub mod dialog_screen;
-#[cfg(feature = "discord")]
-pub mod discord_presence;
 pub mod end_crystal;
 pub mod end_gateway;
 pub mod entities;
@@ -70,7 +68,6 @@ pub mod falling_block;
 pub mod fire_render;
 pub mod first_person;
 pub mod flatgen;
-pub mod friends_screen;
 pub mod furnace;
 pub mod game_mode_switcher;
 pub mod game_rules_screen;

crates/horizon-client/src/entities.rs

@@ -84,7 +84,7 @@ fn slime_at(world: &World, facts: &BlockFacts, position: BlockPos) -> bool {
 mod fluids;
 mod item_fall;
 mod item_no_physics;
-pub use fluids::{fluid_flow, update_entity_fluids, water_clip};
+pub use fluids::{fall_reset_hit, fluid_flow, update_entity_fluids, water_clip};
 
 #[cfg(test)]
 mod drop_motion_tests {

crates/horizon-client/src/entities/fluids.rs

@@ -45,6 +45,30 @@ pub fn fluid_flow(world: &World, fluids: &FluidResources, pos: [i32; 3]) -> [f64
     let flow = flow_at(&mut scene, state, at).unwrap_or(Vec3::ZERO);
     [flow.x, flow.y, flow.z]
 }
+/// `Entity.move`'s fall-reset ray along a move from `from`, up to 8 blocks:
+/// `ClipContext.Fluid.WATER` (the water's shape) and
+/// `ClipContext.Block.FALLDAMAGE_RESETTING` (a block `tagged` says is a reset
+/// block clips as a full block). Both shapes are queried for every visited
+/// block, the water's first (its first query fixes the shared cached shape);
+/// either one hitting ends the ray.
+pub fn fall_reset_hit(
+    world: &World,
+    fluids: &FluidResources,
+    tagged: impl Fn(BlockPos) -> bool,
+    from: Vec3,
+    moved: Vec3,
+) -> bool {
+    let to = from.add_vector(moved.normalize().scale(moved.length().min(8.0)));
+    let hit = horizon_core::geometry::traverse_blocks(from, to, 1_000_000, |p| {
+        let water = water_clip(world, fluids, from, to, p);
+        let reset = tagged(p)
+            && horizon_core::geometry::VoxelShape::block()
+                .clip(from, to, p)
+                .is_some();
+        (water || reset).then_some(())
+    });
+    matches!(hit, Ok(Some(())))
+}
 /// `ClipContext.Fluid.WATER` in a fall-reset ray through `p`: the water's
 /// shape from the shared `FlowingFluid.shapes` cache (the first query of a
 /// fluid state fixes its height), as the player's own ray reads it.

crates/horizon-client/src/entity_nbt.rs

@@ -233,7 +233,7 @@ fn is_animal(id: &str) -> bool {
 use crate::mobs::persistent_anger;
 /// The single player's UUID (`offline_uuid("Player")`): the entity the
 /// neutral mobs are angry at.
-fn player_uuid() -> [i32; 4] {
+pub(crate) fn player_uuid() -> [i32; 4] {
     let u = horizon_protocol::crypto::offline_uuid("Player");
     [
         (u >> 96) as u32 as i32,
@@ -1297,7 +1297,7 @@ pub fn mob_to_nbt(
             crate::mobs::nautilus::to_nbt(m, map);
         }
         "minecraft:sulfur_cube" => crate::mobs::sulfur_cube::to_nbt(m, map),
-        "minecraft:bee" => crate::mobs::bee::to_nbt(m, map),
+        "minecraft:bee" => crate::mobs::bee::to_nbt(m, map, &mut uuid_of),
         "minecraft:sniffer" => crate::mobs::sniffer::to_nbt(m, map),
         "minecraft:wither" => {
             map.insert("Invul".into(), Tag::Int(m.extra.counter));

crates/horizon-client/src/extras_hud.rs

@@ -1,9 +1,11 @@
 //! HUD boxes in the corners: the minimap's place and mods' panels, small
-//! boxes in GUI pixels stacked per corner (`docs/extras.md`).
+//! boxes in GUI pixels stacked per corner (`docs/extras.md`), and the layers crates above the
+//! engine register (`horizon_hooks::hud`).
 use crate::{
     extras::Corner,
     hud::{HudAtlas, HudBatch, Rect, rgba},
 };
+use horizon_hooks::hud;
 
 /// The gap between an overlay and the screen edge or the next overlay.
 const MARGIN: f32 = 2.0;
@@ -125,6 +127,68 @@ pub fn draw_lines(
     }
 }
 
+/// Draws the HUD layers crates registered, after the extras' and mods' boxes, which they stack
+/// with. `shown`: whether each corner of `Corner::ALL` shows (the debug screen covers some).
+pub fn draw_layers(
+    layers: &[&dyn hud::Layer],
+    batch: &mut HudBatch,
+    atlas: &HudAtlas,
+    corners: &mut Corners,
+    shown: [bool; 4],
+) {
+    let mut canvas = Canvas {
+        batch,
+        atlas,
+        corners,
+        shown,
+    };
+    for layer in layers {
+        layer.draw(&mut canvas);
+    }
+}
+
+struct Canvas<'a> {
+    batch: &'a mut HudBatch,
+    atlas: &'a HudAtlas,
+    corners: &'a mut Corners,
+    shown: [bool; 4],
+}
+
+/// `0xAARRGGBB` as the batch's colour.
+fn argb_color(argb: u32) -> u32 {
+    let [a, r, g, b] = argb.to_be_bytes();
+    rgba(r, g, b, a)
+}
+
+impl hud::Canvas for Canvas<'_> {
+    fn size(&self) -> (f32, f32) {
+        (self.batch.width, self.batch.height)
+    }
+    fn tr(&self, key: &str) -> String {
+        crate::lang::get(key)
+    }
+    fn text_width(&self, text: &str) -> f32 {
+        HudBatch::text_width(self.atlas, text)
+    }
+    fn text(&mut self, x: f32, y: f32, text: &str, argb: u32, shadow: bool) {
+        self.batch
+            .text(self.atlas, text, x, y, argb_color(argb), shadow);
+    }
+    fn fill(&mut self, x: f32, y: f32, w: f32, h: f32, argb: u32) {
+        self.batch.fill(self.atlas, x, y, w, h, argb_color(argb));
+    }
+    fn place(&mut self, corner: hud::Corner, w: f32, h: f32) -> Option<(f32, f32)> {
+        let corner = match corner {
+            hud::Corner::TopLeft => Corner::TopLeft,
+            hud::Corner::TopRight => Corner::TopRight,
+            hud::Corner::BottomLeft => Corner::BottomLeft,
+            hud::Corner::BottomRight => Corner::BottomRight,
+        };
+        let i = Corner::ALL.iter().position(|c| *c == corner)?;
+        self.shown[i].then(|| self.corners.place(corner, w, h))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -140,4 +204,58 @@ mod tests {
         assert_eq!(c.place(Corner::BottomRight, 50.0, 10.0), (348.0, 274.0));
         assert_eq!(c.place(Corner::BottomLeft, 10.0, 10.0), (2.0, 288.0));
     }
+
+    /// Draws a box of one line in a corner and keeps where it went.
+    struct Panel {
+        corner: hud::Corner,
+        at: std::sync::Mutex<Vec<Option<(f32, f32)>>>,
+    }
+
+    impl hud::Layer for Panel {
+        fn draw(&self, canvas: &mut dyn hud::Canvas) {
+            let w = canvas.text_width("12 CPS") + 4.0;
+            let at = canvas.place(self.corner, w, 12.0);
+            if let Some((x, y)) = at {
+                canvas.fill(x, y, w, 12.0, 0x7800_0000);
+                canvas.text(x + 2.0, y + 2.0, "12 CPS", 0xFFFF_FFFF, true);
+            }
+            self.at.lock().unwrap().push(at);
+        }
+    }
+
+    #[test]
+    fn layers_stack_with_the_extras_and_skip_hidden_corners() {
+        let atlas =
+            HudAtlas::build(std::path::Path::new("/nonexistent/horizon-test-assets")).unwrap();
+        let mut batch = HudBatch::new([800, 600]);
+        let (width, height) = (batch.width, batch.height);
+        let mut corners = Corners::new(width, height, 0.0);
+        // The minimap already took the top right.
+        corners.place(Corner::TopRight, 64.0, 64.0);
+        let right = Panel {
+            corner: hud::Corner::TopRight,
+            at: Default::default(),
+        };
+        let left = Panel {
+            corner: hud::Corner::TopLeft,
+            at: Default::default(),
+        };
+        let layers: [&dyn hud::Layer; 2] = [&right, &left];
+        let empty = batch.vertices.len();
+        draw_layers(
+            &layers,
+            &mut batch,
+            &atlas,
+            &mut corners,
+            [false, true, true, true],
+        );
+        let (_, y) = right.at.lock().unwrap()[0].expect("the top right shows");
+        assert_eq!(y, 2.0 + 64.0 + 2.0, "under the minimap");
+        assert_eq!(
+            *left.at.lock().unwrap(),
+            [None],
+            "the debug screen covers the top left"
+        );
+        assert!(batch.vertices.len() > empty, "the shown box is drawn");
+    }
 }

crates/horizon-client/src/game.rs

@@ -49,6 +49,7 @@ fn pack_files(world_tables: &Option<WorldTables>) -> horizon_world::loot::PackOv
     }
 }
 
+mod activity;
 mod advancements;
 mod advancements_screen;
 mod agent;
@@ -128,8 +129,6 @@ mod decorated_pot;
 mod dedicated;
 mod deflect;
 mod dialogs;
-#[cfg(feature = "discord")]
-mod discord;
 mod dispense_fixture;
 mod dispenser;
 mod dragon;
@@ -650,7 +649,7 @@ enum Screen {
     /// WorldOptionsScreen (game/lan_screen.rs).
     WorldOptions,
     /// Play with Friends, from the pause menu's Friends button
-    /// (`friends_screen`, game/friends.rs).
+    /// (game/friends.rs, game/friends/screen.rs).
     Friends,
     /// `SocialInteractionsScreen` (`social_screen`, game/social.rs).
     Social,
@@ -5490,34 +5489,6 @@ impl Game<'_> {
         );
         cancel
     }
-    /// The ticks the frame shows (animated textures, the HUD, a shader pack's clock): the
-    /// client's, or under `HORIZON_STILL` (`FixedStep::still`) the world's game time, which
-    /// moves only while the world runs.
-    pub(super) fn visual_ticks(&self) -> u64 {
-        if self.clock.still() {
-            self.world.game_time.max(0) as u64
-        } else {
-            self.ticks
-        }
-    }
-    /// The clock of the animated textures: `Minecraft.runTick` ticks the `TextureManager`
-    /// only while the level runs normally. Under `HORIZON_STILL` it is the world's ticks.
-    pub(super) fn texture_clock(&self) -> u64 {
-        if self.clock.still() {
-            self.visual_ticks()
-        } else {
-            self.texture_ticks
-        }
-    }
-    /// `Util.getMillis` for what the frame shows (the world border's scroll, the hearts' blink,
-    /// the glint's under the switch): under `HORIZON_STILL`, the world's ticks in milliseconds.
-    pub(super) fn visual_millis(&self) -> i64 {
-        if self.clock.still() {
-            self.visual_ticks() as i64 * 50
-        } else {
-            self.started.elapsed().as_millis() as i64
-        }
-    }
     /// `PresenceHandler.getPresenceStatus`: what an all-sharing player is doing, for
     /// the friends service's `updatePresence`.
     fn presence_status(&self) -> horizon_client::social::PresenceStatus {
@@ -6503,18 +6474,6 @@ impl Game<'_> {
             self.draw_tooltip_lines(batch, &lines, self.cursor.0, self.cursor.1);
         }
     }
-    /// `AbstractContainerScreen` keeps `isQuickCrafting` and the drag it
-    /// belongs to on the screen. Horizon keeps both on `Game` (`inv_clicks`,
-    /// `inv_drag`, `last_inv_click`), so they are dropped when the pointer
-    /// changes hands: a screen that opens or closes starts with its own
-    /// state, and a press whose release never reached the screen -- the
-    /// pointer left the window, or the screen closed first -- would
-    /// otherwise leave every later press on every later screen swallowed.
-    pub(super) fn reset_inventory_clicks(&mut self) {
-        self.inv_clicks.cancel_drag();
-        self.inv_drag = None;
-        self.last_inv_click = None;
-    }
     pub(super) fn close_container(&mut self) {
         // `Gui.setScreen` clears the old screen's focus before it goes: the
         // key that closed the container (Tab bound to the inventory) has
@@ -6558,20 +6517,6 @@ impl Game<'_> {
         }
         self.close_ender_chest();
     }
-    /// A sound a menu click made the player play (a bundle's insert or
-    /// remove): `Entity.playSound` at the player.
-    pub(super) fn player_menu_sound(&mut self, sound: &str) {
-        let Some(p) = self.player.as_ref() else {
-            return;
-        };
-        let at = [p.position.x, p.position.y, p.position.z];
-        let (volume, pitch) = if sound == horizon_client::bundle::INSERT_FAIL {
-            (1.0, 1.0)
-        } else {
-            (0.8, 0.8 + self.world.random.next_float() * 0.4)
-        };
-        self.audio.play(sound, Some(at), volume, pitch);
-    }
     /// `Camera.setRotation`: the camera's orientation, turned round in
     /// third-person front view.
     pub(super) fn camera_orientation(&self) -> glam::Quat {
@@ -11458,8 +11403,7 @@ impl Game<'_> {
                     self.heal_hold_latches();
                     // For the hooks above the engine (the "I'm playing" ping): said when it changes.
                     horizon_hooks::engine::published(self.is_published());
-                    #[cfg(feature = "discord")]
-                    self.update_discord_presence();
+                    self.report_activity();
                     let steps = self.clock.advance(elapsed);
                     for _ in 0..steps {
                         let started = Instant::now();
@@ -12719,17 +12663,8 @@ pub fn run_with() -> Result<()> {
     // horizon-ctl drives: those start in a source checkout and wrote the list there.
     if !options.offscreen && !synchronous_startup(&options) {
         let version = horizon_client::telemetry::version();
-        horizon_hooks::engine::started(&horizon_hooks::Started::new(&version));
-        let player_dir = horizon_client::logging::player_dir();
-        // horizon-extras: the official server is Horizon's (docs/forking.md).
-        if cfg!(feature = "horizon-extras")
-            && let Err(e) = horizon_client::multiplayer::add_official_server(&player_dir)
-        {
-            log::warn!("could not add the official server to servers.dat: {e}");
-        }
-        if let Err(e) = horizon_client::multiplayer::withdraw_partner_servers(&player_dir) {
-            log::warn!("could not take the withdrawn partner server out of servers.dat: {e}");
-        }
+        let game_dir = horizon_client::logging::player_dir();
+        horizon_hooks::engine::started(&horizon_hooks::Started::new(&version, &game_dir));
     }
     mods::register_components(&vanilla_root)?;
     mods::register_standalone_models();
@@ -12757,15 +12692,8 @@ pub fn run_with() -> Result<()> {
     if options.execution_role.is_client() {
         narrator::start(&early_settings);
     }
-    // "Playing Horizon" on Discord: never for a server; an automated run only talks to a test's fake Discord.
-    #[cfg(feature = "discord")]
-    if options.dedicated.is_none() {
-        let automated = options.benchmark.is_some()
-            || options.offscreen
-            || options.frames.is_some()
-            || options.world_frames.is_some();
-        horizon_client::discord_presence::start(early_settings.extras.discord_presence, automated);
-    }
+    // A game window's hooks (Discord's presence): never for a server.
+    activity::client_started(&options);
     // Snapshots of derived tables live in the game folder, never beside the
     // shared resources.
     Behaviours::set_cache_dir(std::env::current_dir()?.join(".horizon-cache"));

crates/horizon-client/src/game/activity.rs

@@ -0,0 +1,68 @@
+//! What the player is doing, for the hooks above the engine (`Hooks::activity`: the Horizon
+//! layer's Discord presence shows it).
+use super::*;
+use horizon_client::command::args::GameMode;
+use horizon_hooks::{Activity, Client, Dimension, Play};
+
+/// At startup, for a game window (never a dedicated server's): the player's first activity, then
+/// `Hooks::client_started`.
+pub(super) fn client_started(options: &Options) {
+    if options.dedicated.is_some() {
+        return;
+    }
+    let automated = options.benchmark.is_some()
+        || options.offscreen
+        || options.frames.is_some()
+        || options.world_frames.is_some();
+    horizon_hooks::engine::activity(Activity::Menus);
+    horizon_hooks::engine::client_started(&Client::new(automated));
+}
+
+impl Game<'_> {
+    /// Each frame: only a change reaches the hooks.
+    pub(super) fn report_activity(&self) {
+        // One status per computer: P1's, not a splitscreen player's.
+        if self.options.split_guest {
+            return;
+        }
+        horizon_hooks::engine::activity(self.activity());
+    }
+    fn activity(&self) -> Activity {
+        if self.title.is_some() {
+            return Activity::Menus;
+        }
+        let max = horizon_client::lan::MAX_PLAYERS;
+        let play = if let Some(host) = &self.lan {
+            Play::Hosting {
+                players: 1 + host.hub.guests.len(),
+                max,
+            }
+        } else if let Some(server) = &self.integrated {
+            match (server.published(), &self.remote) {
+                (Some(_), Some(remote)) => Play::Hosting {
+                    players: remote.player_count(),
+                    max,
+                },
+                _ => Play::Singleplayer,
+            }
+        } else if self.remote.is_some() {
+            Play::Multiplayer
+        } else {
+            Play::Singleplayer
+        };
+        Activity::World {
+            play,
+            dimension: match self.dim {
+                Dim::Overworld => Dimension::Overworld,
+                Dim::Nether => Dimension::Nether,
+                Dim::End => Dimension::End,
+            },
+            mode: match self.mode {
+                GameMode::Survival => horizon_hooks::GameMode::Survival,
+                GameMode::Creative => horizon_hooks::GameMode::Creative,
+                GameMode::Adventure => horizon_hooks::GameMode::Adventure,
+                GameMode::Spectator => horizon_hooks::GameMode::Spectator,
+            },
+        }
+    }
+}

crates/horizon-client/src/game/boats.rs

@@ -686,23 +686,15 @@ impl Game<'_> {
         if fall == 0.0 || length < 1.0 {
             return fall;
         }
-        let to = from.add_vector(moved.normalize().scale(moved.length().min(8.0)));
         let reset = &self.res.motion().fall_reset;
-        let fluids = &self.res.motion().fluids;
-        let hit = horizon_core::geometry::traverse_blocks(from, to, 1_000_000, |p| {
-            // A tagged block clips as a full block, not its collider.
-            let name = &self.res.facts().get(self.world.block(p.x, p.y, p.z)).name;
-            if reset.contains(&**name) && VoxelShape::block().clip(from, to, p).is_some() {
-                return Some(());
-            }
-            // The water's shape, through the shared fluid shape cache.
-            horizon_client::entities::water_clip(&self.world, fluids, from, to, p).then_some(())
-        });
-        if matches!(hit, Ok(Some(()))) {
-            0.0
-        } else {
-            fall
-        }
+        let hit = horizon_client::entities::fall_reset_hit(
+            &self.world,
+            &self.res.motion().fluids,
+            |p| reset.contains(&*self.res.facts().get(self.world.block(p.x, p.y, p.z)).name),
+            from,
+            moved,
+        );
+        if hit { 0.0 } else { fall }
     }
     /// `AbstractBoat.checkFallDamage` after a move that went `moved_y` (with
     /// `b` already where it landed): on the ground the fall resets; a move

crates/horizon-client/src/game/books.rs

@@ -70,6 +70,23 @@ pub(super) enum BookScreen {
         lectern: Option<(i32, i32, i32)>,
     },
 }
+impl BookScreen {
+    /// `BookSignScreen`'s constructor: its title box opens with the title
+    /// kept from the last time, which Cancel stored (`titleValue`).
+    fn begin_signing(&mut self) {
+        if let Self::Edit {
+            signing,
+            title,
+            title_edit,
+            ..
+        } = self
+        {
+            *signing = true;
+            title_edit.set_value(title.as_str());
+            title_edit.reset_blink();
+        }
+    }
+}
 /// The pages a book screen reads: a written book's components (so their
 /// click events stay), else a writable book's text.
 fn view_pages(data: Option<&StackData>) -> Vec<Text> {
@@ -988,7 +1005,7 @@ impl Game<'_> {
                     title,
                     ..
                 }) if !title.trim().is_empty() => self.save_book(true),
-                Some(BookScreen::Edit { signing, .. }) => *signing = true,
+                Some(book @ BookScreen::Edit { .. }) => book.begin_signing(),
                 _ => return Err("not a book and quill".into()),
             },
             Some("done") => match self.book.as_mut() {
@@ -1190,8 +1207,8 @@ impl Game<'_> {
                     self.turn_page(false);
                 } else if inside(w / 2.0 - 100.0, 196.0, 98.0, 20.0) {
                     click(self);
-                    if let Some(BookScreen::Edit { signing, .. }) = self.book.as_mut() {
-                        *signing = true;
+                    if let Some(book) = self.book.as_mut() {
+                        book.begin_signing();
                     }
                 } else if inside(w / 2.0 + 2.0, 196.0, 98.0, 20.0) {
                     click(self);
@@ -1809,3 +1826,46 @@ mod lectern_reach_tests {
         );
     }
 }
+
+#[cfg(test)]
+mod sign_tests {
+    use super::{BookScreen, book_page_box, book_title_box};
+
+    /// `BookSignScreen`'s constructor sets its title box to `titleValue`, what
+    /// Cancel kept; reopening the sign screen shows the title typed before,
+    /// not an empty box beside a stale `title`.
+    #[test]
+    fn the_sign_screen_opens_with_the_title_it_kept() {
+        let mut book = BookScreen::Edit {
+            slot: 0,
+            pages: vec!["page".into()],
+            page: 0,
+            signing: false,
+            title: "My Book".into(),
+            title_edit: book_title_box(),
+            page_edit: book_page_box(),
+        };
+        assert_eq!(book_title_value(&book), "");
+        book.begin_signing();
+        let BookScreen::Edit {
+            signing,
+            title,
+            title_edit,
+            ..
+        } = &book
+        else {
+            panic!("the book stays open");
+        };
+        assert!(signing);
+        assert_eq!(title.as_str(), "My Book");
+        assert_eq!(title_edit.value, "My Book");
+        assert_eq!(title_edit.cursor, 7);
+    }
+
+    fn book_title_value(book: &BookScreen) -> String {
+        match book {
+            BookScreen::Edit { title_edit, .. } => title_edit.value.clone(),
+            BookScreen::View { .. } => String::new(),
+        }
+    }
+}

crates/horizon-client/src/game/chat_filter.rs

@@ -42,8 +42,8 @@ impl Reply {
     }
 
     pub(super) fn duration(millis: i64) -> Text {
-        use horizon_chat_filter::DurationUnit;
-        let (count, unit) = horizon_chat_filter::duration_parts(millis);
+        use horizon_server_files::duration::{DurationUnit, duration_parts};
+        let (count, unit) = duration_parts(millis);
         let key = match (unit, count == 1) {
             (DurationUnit::Minute, true) => "horizon.moderation.duration.minute",
             (DurationUnit::Minute, false) => "horizon.moderation.duration.minutes",
@@ -93,7 +93,7 @@ pub(super) const MUTE_USAGES: [&str; 4] = [
 fn mute_time(words: &[&str]) -> (Option<i64>, usize) {
     match words
         .get(2)
-        .and_then(|w| horizon_chat_filter::parse_duration(w))
+        .and_then(|w| horizon_server_files::duration::parse_duration(w))
     {
         Some(ms) => (Some(ms), 3),
         None => (None, 2),
@@ -133,7 +133,7 @@ impl Game<'_> {
         count: u32,
         action: Action,
     ) {
-        let now = horizon_chat_filter::now_millis();
+        let now = horizon_server_files::duration::now_millis();
         let summary = format!(
             "[chat-filter] Refused {name}'s {} (hit {count}: {})",
             place.name(),
@@ -281,7 +281,7 @@ impl Game<'_> {
         let reason = |from: usize| (words.len() > from).then(|| words[from..].join(" "));
         match words {
             ["mutelist"] => {
-                let now = horizon_chat_filter::now_millis();
+                let now = horizon_server_files::duration::now_millis();
                 let mutes = host.hub.mutes();
                 if mutes.is_empty() {
                     return vec![Reply::translated("horizon.moderation.mutelist.empty", &[])];
@@ -319,13 +319,15 @@ impl Game<'_> {
                 let (time, from) = mute_time(words);
                 vec![self.mute(host, name, time, reason(from), by)]
             }
-            ["tempmute", name, time, ..] => match horizon_chat_filter::parse_duration(time) {
-                Some(ms) => vec![self.mute(host, name, Some(ms), reason(3), by)],
-                None => vec![Reply::translated(
-                    "horizon.moderation.invalid_duration",
-                    &[Text::literal(*time)],
-                )],
-            },
+            ["tempmute", name, time, ..] => {
+                match horizon_server_files::duration::parse_duration(time) {
+                    Some(ms) => vec![self.mute(host, name, Some(ms), reason(3), by)],
+                    None => vec![Reply::translated(
+                        "horizon.moderation.invalid_duration",
+                        &[Text::literal(*time)],
+                    )],
+                }
+            }
             ["mute", ..] => vec![Reply::translated("horizon.moderation.usage.mute", &[])],
             ["tempmute", ..] => vec![Reply::translated("horizon.moderation.usage.tempmute", &[])],
             ["unmute", ..] => vec![Reply::translated("horizon.moderation.usage.unmute", &[])],
@@ -353,10 +355,10 @@ impl Game<'_> {
         let Some((uuid, name)) = user else {
             return Reply::no_player();
         };
-        let until = time.map(|ms| horizon_chat_filter::now_millis() + ms);
+        let until = time.map(|ms| horizon_server_files::duration::now_millis() + ms);
         let what = time.map_or_else(
             || "until unmuted".into(),
-            |ms| format!("for {}", horizon_chat_filter::duration_text(ms)),
+            |ms| format!("for {}", horizon_server_files::duration::duration_text(ms)),
         );
         let why = reason
             .as_deref()

crates/horizon-client/src/game/control.rs

@@ -1567,11 +1567,11 @@ impl Game<'_> {
             "streaming": self.streaming.stages().into_iter().map(|(k, v)| (k.to_string(), v.into())).collect::<serde_json::Map<_, _>>(),
             "dirty_light": self.world.dirty_light.len(),
             "renderer": renderer,
-            "display": self.window.as_deref().and_then(horizon_client::telemetry::monitor).map(|m| json!({
-                "width": m.size().width,
-                "height": m.size().height,
-                "scale": m.scale_factor(),
-                "refresh_hz": m.refresh_rate_millihertz().map(|r| r.div_ceil(1000)),
+            "display": self.window.as_deref().and_then(horizon_client::window::display).map(|d| json!({
+                "width": d.width,
+                "height": d.height,
+                "scale": d.scale,
+                "refresh_hz": d.refresh_hz,
             })),
             "uptime_seconds": self.started.elapsed().as_secs_f64(),
             "server": self.remote_status(),

crates/horizon-client/src/game/core_tests.rs

@@ -623,3 +623,6 @@ fn stack_drop_requires_ctrl_even_with_sprint_latched() {
         }
     }
 }
+
+#[path = "play_ping_tests.rs"]
+mod play_ping_tests;

crates/horizon-client/src/game/creatures.rs

@@ -2,8 +2,10 @@
 //! chunk-generation spawning (`NaturalSpawner`), mob events (attacks,
 //! breeding, conversions, drops), projectiles, player interactions
 //! (feeding, shearing, milking, spawn eggs, throwing) and rendering.
+mod mob_geometry;
 mod projectile_world;
 mod pufferfish_player;
+mod spawn_eggs;
 
 use super::{
     Dim, Game, Hand, InteractTarget, entity_culling::EntityCullDecision,
@@ -7450,171 +7452,6 @@ impl Game<'_> {
         }
         Ok(true)
     }
-    /// `Mob.checkAndHandleImportantInteractions` with a spawn egg of mob
-    /// `index`'s own kind (`SpawnEggItem.spawnOffspringFromSpawnEgg`): a baby
-    /// at the mob's feet, taking the parent's variant as `getBreedOffspring`
-    /// does, and one egg used. False (PASS) when the mob has no baby form.
-    fn spawn_egg_offspring(&mut self, index: usize) -> bool {
-        let Some(stack) = self.held().cloned() else {
-            return false;
-        };
-        let parent = &self.mobs[index];
-        if !parent.alive()
-            || !horizon_client::mobs::finalize::spawn_egg_is_for(&stack.item, &parent.kind.id)
-            || !horizon_client::mobs::species::can_be_a_baby(parent.species())
-            // WanderingTrader.getBreedOffspring returns null: no offspring, the
-            // click carries on to trading.
-            || parent.species() == Species::WanderingTrader
-        {
-            return false;
-        }
-        let (kind, at) = (
-            parent.kind.id.clone(),
-            [parent.position.x, parent.position.y, parent.position.z],
-        );
-        let (species, variant, color) =
-            (parent.species(), parent.extra.variant, parent.extra.color);
-        let target = self.mob_entity(&self.mobs[index]);
-        // SpawnEggItem.spawnOffspringFromSpawnEgg: `type.create(level, SPAWN_ITEM_USE)`
-        // creates the baby without finalizeSpawn, and `snapTo(pos, 0, 0)` faces
-        // it south without a level-random draw.
-        let Some(id) =
-            self.spawn_mob_internal(&kind, at, false, false, false, false, SpawnYaw::Fixed(0.0))
-        else {
-            return false;
-        };
-        if let Some(child) = self.mobs.iter_mut().find(|m| m.id == id) {
-            horizon_client::mobs::finalize::spawn_egg_offspring(child, species, variant, color);
-        }
-        // `Mob.checkAndHandleImportantInteractions` then calls
-        // `onOffspringSpawnedFromEgg`: `Fox`'s makes the baby trust the player
-        // who used the egg (a fox egg used on a block trusts nobody).
-        if species == Species::Fox {
-            let spawner = self.acting_player_uuid();
-            if let Some(child) = self.mobs.iter_mut().find(|m| m.id == id) {
-                horizon_client::mobs::fox::add_trusted_entity(child, spawner);
-            }
-        }
-        self.trigger_item_entity("minecraft:player_interacted_with_entity", &stack, &target);
-        self.consume_held();
-        true
-    }
-    /// `SpawnEggItem.use`: the SOURCE_ONLY ray must hit a liquid block.
-    pub(super) fn spawn_egg_fluid_hit(&self) -> Option<super::Hit> {
-        let hit = self.bucket_hit()?;
-        matches!(
-            &*self.block_name(hit.pos),
-            "minecraft:water" | "minecraft:lava"
-        )
-        .then_some(hit)
-    }
-    /// Shared peaceful-mode eligibility for spawn eggs.
-    pub(super) fn spawn_egg_allowed(&self, item: &str) -> bool {
-        let kind = item.trim_end_matches("_spawn_egg");
-        self.ui.difficulty != 0
-            || self
-                .res
-                .mob_types()
-                .get(kind)
-                .is_none_or(|t| horizon_client::mobs::spawn_rules::allowed_in_peaceful(t.species))
-    }
-    /// `SpawnEggItem.useOn` for a block, or `use` for a fluid source.
-    fn use_spawn_egg(&mut self, stack: &ItemStack) -> Result<bool> {
-        let fluid = matches!(self.guest_use, Some(super::GuestUse::Item(_)));
-        let Some(hit) = (if fluid {
-            self.spawn_egg_fluid_hit()
-        } else {
-            self.pick()
-        }) else {
-            return Ok(false);
-        };
-        let kind = stack.item.trim_end_matches("_spawn_egg").to_owned();
-        if !self.spawn_egg_allowed(&stack.item) {
-            self.use_failed = true;
-            return Ok(true);
-        }
-        if fluid
-            && !self.may_build()
-            && !self.can_place_on_in_adventure([
-                hit.pos[0] - hit.face[0],
-                hit.pos[1] - hit.face[1],
-                hit.pos[2] - hit.face[2],
-            ])
-        {
-            self.use_failed = true;
-            return Ok(true);
-        }
-        // SpawnEggItem.useOn on a spawner sets its mob (and an op's egg data).
-        let (spawner_id, data) = horizon_client::block_entity_item::spawn_egg_on_spawner(
-            stack,
-            self.acting_player_is_op(),
-        );
-        if let Some(done) = self.use_spawn_egg_on_spawner(hit.pos, &spawner_id, data.as_ref()) {
-            if done {
-                self.swing_arm();
-                self.award_stat("used", &stack.item, 1);
-                self.consume_held();
-            }
-            return Ok(true);
-        }
-        // useOn: a clicked block without a collision shape (vines, grass)
-        // takes the mob itself, any other the one on the clicked face.
-        let p = if fluid || self.collision_empty(hit.pos) {
-            hit.pos
-        } else {
-            [
-                hit.pos[0] + hit.face[0],
-                hit.pos[1] + hit.face[1],
-                hit.pos[2] + hit.face[2],
-            ]
-        };
-        let at = [
-            f64::from(p[0]) + 0.5,
-            f64::from(p[1]),
-            f64::from(p[2]) + 0.5,
-        ];
-        // SpawnEggItem.spawnMob: `EntityType.spawn`.
-        let Some(id) = self.spawn_mob_spawned(&kind, at, SpawnYaw::Created) else {
-            return Ok(false);
-        };
-        // SpawnEggItem.spawnMob: `EntityType.create` finalizes the mob, then
-        // `PostSpawnProcessor` puts the egg's components on it.
-        if let Some(m) = self.mobs.iter_mut().find(|m| m.id == id) {
-            horizon_client::entity_nbt::apply_item_components(m, stack);
-        }
-        self.apply_spawn_egg_entity_data(id, stack);
-        self.post_block_game_event("minecraft:entity_place", p, Some(Who::Player), None);
-        self.award_stat("used", &stack.item, 1);
-        self.swing_arm();
-        if !self.creative
-            && let Some(s) = self.held_mut().as_mut()
-        {
-            s.count -= 1;
-            if s.count == 0 {
-                *self.held_mut() = None;
-            }
-        }
-        Ok(true)
-    }
-    /// `EntityType.updateCustomEntityTag`: the egg's `minecraft:entity_data` on
-    /// the mob it spawned, once the guards let it through, as
-    /// `TypedEntityData.loadInto`: the mob's own compound, the data merged over
-    /// it, loaded back into the same mob (`/data merge entity`'s loader).
-    pub(super) fn apply_spawn_egg_entity_data(&mut self, id: u32, stack: &ItemStack) {
-        let Some(i) = self.mobs.iter().position(|m| m.id == id) else {
-            return;
-        };
-        let kind = self.mobs[i].kind.id.clone();
-        let op = self.acting_player_is_op();
-        let Some(data) = horizon_client::block_entity_item::spawn_egg_entity_data(stack, &kind, op)
-        else {
-            return;
-        };
-        let own = self.mob_tree_nbt(i);
-        let tag = horizon_client::data_cmd::merged(&own, data);
-        // Nothing to report: the mob's own compound always loads back.
-        let _ = self.apply_entity_nbt(super::commands::Target::Mob(id), tag);
-    }
     /// A beam target's centre (half its height), interpolated.
     fn beam_target(&self, who: Option<Who>, alpha: f64) -> Option<glam::DVec3> {
         match who? {
@@ -7785,624 +7622,6 @@ impl Game<'_> {
             }
         }
     }
-
-    pub(super) fn mob_geometry(&self, camera: glam::DVec3, alpha: f64, out: &mut Vec<Vertex>) {
-        // The coarse mob bounds pay off only in dense async scenes; otherwise,
-        // keep the existing exact mesh-culling path.
-        if self.settings.horizon.entity_culling == EntityCullingMode::Asynchronous
-            && self
-                .async_occlusion_culler
-                .as_ref()
-                .is_some_and(|culler| culler.camera_is_stationary())
-            && self.settings.horizon.entity_culling_precheck != 0
-            && self.mobs.len() >= self.settings.horizon.entity_culling_precheck as usize
-            && !self.pack_shadow_casters.0
-            && horizon_client::mod_api::mods().is_empty()
-        {
-            self.mob_geometry_inner::<true>(camera, alpha, out);
-        } else {
-            self.mob_geometry_inner::<false>(camera, alpha, out);
-        }
-    }
-
-    fn mob_geometry_inner<const PRECHECK: bool>(
-        &self,
-        camera: glam::DVec3,
-        alpha: f64,
-        out: &mut Vec<Vertex>,
-    ) {
-        let atlas = &self.gui.atlas;
-        let lookup = |name: &str| atlas.sprites.get(name).map(|r| [r.u0, r.v0, r.u1, r.v1]);
-        let scale = self.view_scale();
-        self.rendered_mobs.set(0);
-        let skinning = self.skinning();
-        // What custom entity model animations read of the frame.
-        horizon_client::mobs::cem_anim::set_frame(horizon_client::mobs::cem_anim::Frame {
-            time: self.world.game_time as f64 + alpha,
-            day_time: self.world.day_time as f64 + alpha,
-            dimension: match self.dim {
-                Dim::Overworld => 0.0,
-                Dim::Nether => -1.0,
-                Dim::End => 1.0,
-            },
-            player: self.player.as_ref().map_or(camera.to_array(), |p| {
-                [p.position.x, p.position.y, p.position.z]
-            }),
-            player_rot: [self.pitch, self.yaw],
-            paused: self.pause,
-            first_person: self.camera_type.first_person(),
-            third_person_reversed: self.camera_type
-                == super::perspective::CameraType::ThirdPersonFront,
-            ..Default::default()
-        });
-        for mob in &self.mobs {
-            // LevelRenderer: the entity the view looks out of is not drawn
-            // in first person.
-            if self.hides_as_camera(mob.id) {
-                continue;
-            }
-            let is_player = &*mob.kind.id == "minecraft:player";
-            let d = glam::DVec3::new(mob.position.x, mob.position.y, mob.position.z) - camera;
-            // Entity.shouldRenderAtSqrDistance: 64 times the bounding box's
-            // mean edge, scaled by the view scale. RemotePlayer's box counts
-            // ten times.
-            let (w, h, _) = mob.dims();
-            let edge = (w + h + w) / 3.0 * if is_player { 10.0 } else { 1.0 };
-            let range = edge * 64.0 * scale;
-            if d.length_squared() >= range * range {
-                continue;
-            }
-            let beam = horizon_client::mobs::guardian::beam(mob, alpha as f32);
-            // EntityRenderer.shouldRender: the renderer's interpolated culling box,
-            // grown by 0.5 (GuardianRenderer also draws while its beam is out).
-            if let Some(view) = &self.view_frustum
-                && beam.is_none()
-            {
-                let (lo, hi) = super::entity_culling::cull_box(mob, alpha);
-                let (lo, hi) = (
-                    (lo - camera - glam::DVec3::splat(0.5)).as_vec3(),
-                    (hi - camera + glam::DVec3::splat(0.5)).as_vec3(),
-                );
-                if !view.intersects(lo, hi) {
-                    continue;
-                }
-            }
-            let outline = self.mob_outline(mob);
-            // Entity.DATA_SHARED_FLAGS_ID invisible: only the name tag draws (and
-            // the outline of a glowing mob, LivingEntityRenderer.getRenderType).
-            // A player keeps its armour, elytra and held items
-            // (`LivingEntityRenderer.submit` skips only the body).
-            let layers_only = mob.invisible && outline.is_none() && is_player;
-            if mob.invisible && outline.is_none() && !layers_only {
-                continue;
-            }
-            let culling = if PRECHECK
-                && outline.is_none()
-                && !is_player
-                && mob.kind.id.starts_with("minecraft:")
-                && [
-                    &mob.extra.head,
-                    &mob.extra.chest,
-                    &mob.extra.legs,
-                    &mob.extra.feet,
-                    &mob.extra.main_hand,
-                    &mob.extra.off_hand,
-                ]
-                .iter()
-                .all(|item| item.is_none())
-                && beam.is_none()
-            {
-                self.entity_cull_decision(mob, alpha)
-            } else {
-                EntityCullDecision::CheckVertices
-            };
-            if culling.hides_entity() {
-                continue;
-            }
-            let entity_start = out.len();
-            self.mark_motion(entity_start, (1 << 32) | u64::from(mob.id));
-            self.mark_entity(entity_start, &mob.kind.id);
-            self.rendered_mobs.set(self.rendered_mobs.get() + 1);
-            // `EntityRenderer.getPackedLightCoords`: the block the mob's light
-            // probe (its eye) is in, at the position this frame draws rather
-            // than this tick's.
-            let probe = mob.light_probe(alpha);
-            let light = self.world.light(probe[0], probe[1], probe[2]);
-            let mut packed = (u32::from(light >> 4) * 16) | ((u32::from(light & 15) * 16) << 8);
-            // EntityRenderer.getBlockLightLevel: a burning mob has 15 block
-            // light, and so do the Allay, Blaze, Magma Cube, Vex and Wither
-            // renderers' overrides; the sky light stays the level's.
-            if mob.fire_ticks > 0
-                || matches!(
-                    mob.species(),
-                    Species::Allay
-                        | Species::Blaze
-                        | Species::MagmaCube
-                        | Species::Vex
-                        | Species::Wither
-                )
-            {
-                packed = (packed & 0xFF) | ((15 * 16) << 8);
-            }
-            // GlowSquidRenderer.getBlockLightLevel: the body brightens as the
-            // dark ticks run out (the block light is the second byte).
-            if mob.species() == Species::GlowSquid {
-                let lit = (packed >> 12) & 15;
-                let block = horizon_client::mobs::aquatic::glow_squid_block_light(mob, lit);
-                packed = (packed & 0xFF) | ((block * 16) << 8);
-            }
-            // A native mod's own model in place of the vanilla one
-            // (`native_mob_submit`), before any of the vanilla model's parts
-            // (a sulfur cube's swallowed block) are drawn.
-            // A player's own hook (`native_player_submit`) is asked for the
-            // other players in view.
-            let who = is_player
-                .then(|| self.remote_player_name(mob.id))
-                .flatten()
-                .map(|name| NativePlayerRender { name, local: false });
-            let modded = if layers_only {
-                false
-            } else if let Some(who) = who {
-                self.mod_player_geometry(mob, who, alpha as f32, camera, packed, out)
-            } else {
-                !is_player && self.mod_mob_geometry(mob, alpha as f32, camera, packed, out)
-            };
-            if modded {
-                if let Some(rgb) = outline {
-                    self.mark_outline(&out[entity_start..], rgb);
-                    if mob.invisible {
-                        out.truncate(entity_start);
-                        continue;
-                    }
-                }
-                if outline.is_none() {
-                    self.cull_entity_vertices(out, entity_start);
-                }
-                continue;
-            }
-            if mob.species() == Species::SulfurCube
-                && !horizon_client::mobs::trader::is_invisible(mob)
-            {
-                self.sulfur_cube_body_geometry(
-                    mob,
-                    alpha as f32,
-                    horizon_client::mobs::render::base_transform(mob, alpha as f32, camera),
-                    packed,
-                    out,
-                );
-            }
-            // Other players on a server: PlayerRenderer's HumanoidArmorLayer.
-            let armor = if is_player {
-                self.worn_armor_layers(mob)
-            } else {
-                Vec::new()
-            };
-            let body = out.len();
-            // The GPU path: an ordinary mob, no layers the CPU path changes after drawing them
-            // (a player's, the HDR tiers below, the sulfur cube's shell). A glowing mob's
-            // silhouette is posed too (`SkinFrame::outline_since`), unless it is invisible:
-            // then only the outline draws.
-            let silhouette_on_gpu = outline.is_none() || !mob.invisible;
-            let posable = skinning
-                && !is_player
-                && !layers_only
-                && silhouette_on_gpu
-                && armor.is_empty()
-                && !matches!(
-                    mob.species(),
-                    Species::Blaze | Species::MagmaCube | Species::GlowSquid | Species::SulfurCube
-                );
-            let mut skinned = None;
-            if posable {
-                let mut models = self.skin_models.borrow_mut();
-                let mut frame = self.skin_frame.borrow_mut();
-                let mark = frame.mark();
-                let mut skin = horizon_client::mobs::skin::Skin::new(&mut models, &mut frame);
-                horizon_client::mobs::render::render_skinned(
-                    mob,
-                    alpha as f32,
-                    camera,
-                    &lookup,
-                    packed,
-                    self.res.mob_data(),
-                    out,
-                    &mut skin,
-                );
-                skinned = Some((mark, skin.bounds));
-            } else {
-                let render = if layers_only {
-                    horizon_client::mobs::render::render_layers
-                } else {
-                    horizon_client::mobs::render::render_with
-                };
-                render(
-                    mob,
-                    alpha as f32,
-                    camera,
-                    &lookup,
-                    packed,
-                    self.res.mob_data(),
-                    &armor,
-                    out,
-                );
-            }
-            // HDR output: mobs that are light shine by their kind, as blocks do (entity.wgsl
-            // fs_hdr_mark); a tier's window lifts only their bright texels.
-            if let Some(tier) = match mob.species() {
-                Species::Blaze => Some(horizon_client::mesher::BRIGHT),
-                Species::MagmaCube | Species::GlowSquid => Some(horizon_client::mesher::LOW),
-                _ => None,
-            } {
-                for v in &mut out[body..] {
-                    v.layer |= u32::from(tier) << 16;
-                }
-            }
-            // AvatarRenderer.shouldRenderLayers: a spectator draws no layers.
-            let layers = horizon_client::mobs::render::layers_shown(mob);
-            if is_player && layers {
-                // PlayerRenderer's CapeLayer, WingsLayer, ParrotOnShoulderLayer
-                // and SpinAttackEffectLayer. Only the cape hides with the body;
-                // the others have no `isInvisible` check.
-                let chest = mob.extra.chest.as_deref();
-                if !layers_only {
-                    self.player_cape_geometry(mob, chest, camera, alpha as f32, packed, out);
-                }
-                if let Some((_, name)) = self
-                    .remote_player_names()
-                    .into_iter()
-                    .find(|(id, _)| *id == mob.id)
-                {
-                    self.player_ears_geometry(mob, &name, camera, alpha as f32, packed, out);
-                }
-                self.player_elytra_geometry(mob, chest, camera, alpha as f32, packed, out);
-                self.shoulder_parrots_geometry(mob, camera, alpha as f32, packed, out);
-                self.spin_attack_geometry(mob, camera, alpha as f32, packed, out);
-                self.stuck_in_body_geometry(mob, mob.id as i32, camera, alpha as f32, packed, out);
-            }
-            // Cosmetics (game/cosmetics.rs), posed on the GPU with the mob's own jobs: culled
-            // with it.
-            if !layers_only
-                && super::cosmetics::enabled()
-                && (is_player || &*mob.kind.id == "minecraft:mannequin")
-            {
-                let mark = self.skin_frame.borrow().mark();
-                let base = horizon_client::mobs::render::base_transform(mob, alpha as f32, camera);
-                let gpu = skinning;
-                if let Some((lo, hi)) = self.cosmetics_geometry(
-                    mob,
-                    false,
-                    base,
-                    Some(camera),
-                    alpha as f32,
-                    packed,
-                    gpu,
-                    out,
-                ) {
-                    skinned = Some(match skinned {
-                        Some((first, Some((l, h)))) => (first, Some((l.min(lo), h.max(hi)))),
-                        Some((first, None)) => (first, Some((lo, hi))),
-                        None => (mark, Some((lo, hi))),
-                    });
-                }
-            }
-            // CustomHeadLayer (a pumpkin, skull or head item) included.
-            if layers {
-                // Held items join the GPU path's draws, their silhouette too.
-                let skin = (skinning && silhouette_on_gpu).then_some(&mut skinned);
-                self.mob_block_geometry(mob, camera, alpha, packed, skin, out);
-                // `native_mob_layer`: a native mod's layer, over the vanilla ones.
-                self.mod_mob_layer_geometry(mob, who, alpha as f32, camera, packed, out);
-            }
-            if let Some(rgb) = outline {
-                self.mark_outline(&out[entity_start..], rgb);
-                if let Some(((first, _, _), _)) = skinned {
-                    let color = horizon_client::mobs::render::abgr(rgb);
-                    self.skin_frame.borrow_mut().outline_since(first, color);
-                }
-                if mob.invisible {
-                    out.truncate(entity_start);
-                    continue;
-                }
-            }
-            // Glowing outlines and a guardian's beam remain visible independently
-            // of whether the body is hidden behind terrain.
-            if outline.is_none() && culling.checks_vertices() && beam.is_none() {
-                // What the GPU draws of the mob counts by its bounds' corners.
-                self.cull_skinned(out, entity_start, skinned);
-            }
-            // GuardianRenderer: the laser to the locked target.
-            if let Some((time, scale)) = beam
-                && let Some(target) = self.beam_target(mob.ai.target, alpha)
-                && let Some(uv) = lookup("entity/guardian/guardian_beam")
-            {
-                let a = alpha;
-                let eye = glam::DVec3::new(
-                    mob.previous.x + (mob.position.x - mob.previous.x) * a,
-                    mob.previous.y + (mob.position.y - mob.previous.y) * a + mob.eye_height(),
-                    mob.previous.z + (mob.position.z - mob.previous.z) * a,
-                ) - camera;
-                horizon_client::mobs::guardian::beam_geometry(
-                    eye.as_vec3(),
-                    (target - camera).as_vec3(),
-                    time,
-                    scale,
-                    uv,
-                    out,
-                );
-            }
-        }
-        // What follows isn't a tracked mob: close the last one's span.
-        self.mark_motion(out.len(), 0);
-        self.elder_apparition_geometry(alpha, out);
-        self.spawner_geometry(camera, alpha, out);
-        // Projectiles: the baked vanilla arrow model, the rest as item billboards.
-        let (right, up) = thrown_item_axes(self.camera_type, self.yaw, self.pitch);
-        let live = self.creatures.projectiles.iter().map(|a| {
-            let at = [
-                a.previous.x + (a.position.x - a.previous.x) * alpha,
-                a.previous.y + (a.position.y - a.previous.y) * alpha,
-                a.previous.z + (a.position.z - a.previous.z) * alpha,
-            ];
-            (a, at)
-        });
-        // ItemPickupParticle: a picked-up arrow flying to its collector.
-        let taken = self.pickups.live.iter().filter_map(|p| match &p.taken {
-            super::pickups::Taken::Arrow(a) => Some((&**a, super::pickups::position(p, alpha))),
-            _ => None,
-        });
-        // A glowing projectile's outline: what it drew up to the next one.
-        let mut glowing = None;
-        for (a, at) in live.chain(taken) {
-            if let Some((start, rgb)) = glowing.take() {
-                self.mark_outline(&out[start..], rgb);
-            }
-            if a.id != 0
-                && let Some(rgb) = self.thing_outline(a.id, a.kind.id())
-            {
-                glowing = Some((out.len(), rgb));
-            }
-            let p = glam::DVec3::from_array(at) - camera;
-            let c = p.as_vec3();
-            // EntityRenderer.getPackedLightCoords: the block its light probe
-            // (the eye) is in, at the position this frame draws rather than
-            // this tick's, and not the one under its feet.
-            let light = self.world.light(
-                at[0].floor() as i32,
-                a.light_probe_y(alpha).floor() as i32,
-                at[2].floor() as i32,
-            );
-            let mut packed = (u32::from(light >> 4) * 16) | ((u32::from(light & 15) * 16) << 8);
-            // EntityRenderer.getBlockLightLevel: a shulker bullet and anything
-            // on fire are drawn at 15 block light (the fireball renderers'
-            // own override); the sky light stays the level's.
-            if let Some(block) = a.block_light_override() {
-                packed = (packed & 0xFF) | (u32::from(block) * 16) << 8;
-            }
-            if a.is_arrow() {
-                let Some(model) = self.arrow_model.as_ref() else {
-                    continue;
-                };
-                // SpectralArrowRenderer, and TippableArrowRenderer's `getColor() > 0`.
-                let texture = if a.is_spectral_arrow() {
-                    "entity/projectiles/arrow_spectral"
-                } else if a.arrow.as_ref().is_some_and(|s| s.effect_color > 0) {
-                    "entity/projectiles/arrow_tipped"
-                } else {
-                    "entity/projectiles/arrow"
-                };
-                let Some(r) = atlas.sprites.get(texture).copied() else {
-                    continue;
-                };
-                // ArrowRenderer: `Mth.lerp(partialTick, state.yRotO, state.yRot)`
-                // and the same for the pitch, so a turning arrow is drawn
-                // between the two ticks it turned over.
-                let alpha32 = alpha as f32;
-                let yaw = a.previous_yaw + alpha32 * (a.yaw - a.previous_yaw);
-                let pitch = a.previous_pitch + alpha32 * (a.pitch - a.previous_pitch);
-                let m = glam::Mat4::from_translation(c)
-                    * glam::Mat4::from_rotation_y((yaw - 90.0).to_radians())
-                    * glam::Mat4::from_rotation_z(pitch.to_radians());
-                // ArrowRenderer: `state.shake = shakeTime - partialTicks`; ArrowModel.setupAnim
-                // rolls the root while the shake timer runs.
-                let shake = a
-                    .arrow
-                    .as_ref()
-                    .map_or(0.0, |s| s.shake as f32 - alpha as f32);
-                let roll = if shake > 0.0 {
-                    -(shake * 3.0).msin() * shake * (std::f32::consts::PI / 180.0)
-                } else {
-                    0.0
-                };
-                let pose_for = |part: &horizon_client::mobs::Part| {
-                    let mut pose = part.pose;
-                    if std::ptr::eq(part, model) {
-                        pose[5] += roll;
-                    }
-                    pose
-                };
-                horizon_client::mobs::render_model(
-                    model,
-                    m,
-                    &pose_for,
-                    [r.u0, r.v0, r.u1, r.v1],
-                    packed,
-                    0,
-                    out,
-                );
-                if a.arrow.as_ref().is_some_and(|s| s.on_fire()) {
-                    flame_geometry(atlas, c, 0.5, 0.5, self.yaw, light, out);
-                }
-                continue;
-            }
-            // ThrownTridentRenderer.
-            if matches!(a.kind, ProjectileKind::Trident) {
-                let Some(model) = self.trident_model.as_ref() else {
-                    continue;
-                };
-                let Some(r) = atlas.sprites.get("entity/trident/trident").copied() else {
-                    continue;
-                };
-                let m = glam::Mat4::from_translation(c)
-                    * glam::Mat4::from_rotation_y((a.yaw - 90.0).to_radians())
-                    * glam::Mat4::from_rotation_z((a.pitch + 90.0).to_radians());
-                let poses = horizon_client::mobs::anim::Poses::new(model);
-                horizon_client::mobs::render::draw(
-                    model,
-                    m,
-                    &poses,
-                    [r.u0, r.v0, r.u1, r.v1],
-                    0xFFFF_FFFF,
-                    packed,
-                    0,
-                    out,
-                );
-                continue;
-            }
-            // WindChargeRenderer.
-            if matches!(
-                a.kind,
-                ProjectileKind::WindCharge | ProjectileKind::BreezeWindCharge
-            ) {
-                self.wind_charge_geometry(a, c, packed, alpha as f32, out);
-                continue;
-            }
-            // ShulkerBulletRenderer: the tumbling bullet model, then a larger
-            // translucent copy of it (colour 0x26FFFFFF); always 15 block light.
-            if matches!(a.kind, ProjectileKind::ShulkerBullet { .. }) {
-                let model = &self.entity_models.shulker_bullet;
-                if let (Some(model), Some(r)) =
-                    (model, atlas.sprites.get("entity/shulker/spark").copied())
-                {
-                    use horizon_core::geometry::trig;
-                    let tc = a.age as f32 + alpha as f32;
-                    let mut poses = horizon_client::mobs::anim::Poses::new(model);
-                    poses.yrot("main", a.yaw.to_radians());
-                    poses.xrot("main", a.pitch.to_radians());
-                    let light = (packed & 0xFF) | ((15 * 16) << 8);
-                    let base = glam::Mat4::from_translation(c)
-                        * glam::Mat4::from_translation(glam::Vec3::new(0.0, 0.15, 0.0))
-                        * glam::Mat4::from_rotation_y(
-                            (trig::sin(f64::from(tc * 0.1)) * 180.0).to_radians(),
-                        )
-                        * glam::Mat4::from_rotation_x(
-                            (trig::cos(f64::from(tc * 0.1)) * 180.0).to_radians(),
-                        )
-                        * glam::Mat4::from_rotation_z(
-                            (trig::sin(f64::from(tc * 0.15)) * 360.0).to_radians(),
-                        )
-                        * glam::Mat4::from_scale(glam::Vec3::new(-0.5, -0.5, 0.5));
-                    let uv = [r.u0, r.v0, r.u1, r.v1];
-                    horizon_client::mobs::render::draw(
-                        model,
-                        base,
-                        &poses,
-                        uv,
-                        0xFFFF_FFFF,
-                        light,
-                        0,
-                        out,
-                    );
-                    // The translucent shell blends over the opaque core
-                    // (`RenderTypes.entityTranslucent`).
-                    let shell = out.len();
-                    horizon_client::mobs::render::draw(
-                        model,
-                        base * glam::Mat4::from_scale(glam::Vec3::splat(1.5)),
-                        &poses,
-                        uv,
-                        0x26FF_FFFF,
-                        light,
-                        0,
-                        out,
-                    );
-                    horizon_client::gfx::mark_oit(&mut out[shell..]);
-                }
-                continue;
-            }
-            // WitherSkullRenderer: the skull model facing its flight.
-            if let Some(dangerous) = super::wither::skull_kind(a) {
-                let model = &self.entity_models.wither_skull;
-                let tex = if dangerous {
-                    "entity/wither/wither_invulnerable"
-                } else {
-                    "entity/wither/wither"
-                };
-                if let (Some(model), Some(r)) = (model, atlas.sprites.get(tex).copied()) {
-                    let mut poses = horizon_client::mobs::anim::Poses::new(model);
-                    poses.yrot("head", a.yaw.to_radians());
-                    poses.xrot("head", a.pitch.to_radians());
-                    let base = glam::Mat4::from_translation(c)
-                        * glam::Mat4::from_scale(glam::Vec3::new(-1.0, -1.0, 1.0));
-                    horizon_client::mobs::render::draw(
-                        model,
-                        base,
-                        &poses,
-                        [r.u0, r.v0, r.u1, r.v1],
-                        0xFFFF_FFFF,
-                        packed,
-                        0,
-                        out,
-                    );
-                }
-                continue;
-            }
-            if let Some(stack) = a.drawn_item() {
-                let owner = super::item_draw::owner_at(at, 0.0, a.kind.id());
-                let state = self.resolve_item(&stack, DisplayContext::Ground, Some(&owner), 0);
-                let pose = glam::Mat4::from_translation(c)
-                    * glam::Mat4::from_quat(self.camera_orientation());
-                self.submit_item_world(&state, pose, packed, out);
-                continue;
-            }
-            // `Entity.displayFireAnimation`: a thrown item that flew through a
-            // fire block burns (`ThrowableProjectile.tick`'s
-            // `applyEffectsFromBlocks`), and ThrownItemRenderer draws the flame
-            // over its box as any other entity renderer does.
-            if a.on_fire() {
-                let size = a.kind.size() as f32;
-                flame_geometry(atlas, c, size, size, self.yaw, light, out);
-            }
-            // `ThrownItemRenderer` for a fireball: the item `Fireball.getItem`
-            // returns (a fire charge until `setItem` gave it another), its model
-            // at the renderer's scale for the kind. `packed` is already 15, the
-            // renderer's full bright.
-            if let Some(stack) = a.item.as_ref() {
-                let owner = super::item_draw::owner_at(at, 0.0, a.kind.id());
-                let state = self.resolve_item(stack, DisplayContext::Ground, Some(&owner), 0);
-                let pose = glam::Mat4::from_translation(c)
-                    * glam::Mat4::from_quat(self.camera_orientation())
-                    * glam::Mat4::from_scale(glam::Vec3::splat(a.sprite_scale()));
-                self.submit_item_world(&state, pose, packed, out);
-                continue;
-            }
-            let Some(name) = a.item_sprite() else {
-                continue;
-            };
-            let Some(r) = atlas.sprites.get(name).copied() else {
-                continue;
-            };
-            let lift = is_item_billboard(&a.kind);
-            let quad = thrown_item_quad(c, right, up, a.sprite_scale(), lift);
-            for (v, uv) in quad
-                .iter()
-                .zip([[r.u0, r.v1], [r.u1, r.v1], [r.u1, r.v0], [r.u0, r.v0]])
-            {
-                out.push(Vertex {
-                    normal: [0; 4],
-                    pos: v.to_array(),
-                    uv,
-                    layer: 0,
-                    color: 0xFFFF_FFFF,
-                    light: packed,
-
-                    glint_uv: [0.0, 0.0],
-                });
-            }
-        }
-        if let Some((start, rgb)) = glowing {
-            self.mark_outline(&out[start..], rgb);
-        }
-    }
 }
 /// `ThrownItemRenderer.submit` turns the item by `CameraRenderState.orientation`
 /// (`Camera.setRotation`): the billboard's right and up axes are the camera's.

crates/horizon-client/src/game/creatures/mob_geometry.rs

@@ -0,0 +1,629 @@
+//! Drawing the mobs, players and projectiles the client sees, each frame (`mob_geometry`).
+use super::*;
+
+impl Game<'_> {
+    pub(in crate::game) fn mob_geometry(
+        &self,
+        camera: glam::DVec3,
+        alpha: f64,
+        out: &mut Vec<Vertex>,
+    ) {
+        // The coarse mob bounds pay off only in dense async scenes; otherwise,
+        // keep the existing exact mesh-culling path.
+        if self.settings.horizon.entity_culling == EntityCullingMode::Asynchronous
+            && self
+                .async_occlusion_culler
+                .as_ref()
+                .is_some_and(|culler| culler.camera_is_stationary())
+            && self.settings.horizon.entity_culling_precheck != 0
+            && self.mobs.len() >= self.settings.horizon.entity_culling_precheck as usize
+            && !self.pack_shadow_casters.0
+            && horizon_client::mod_api::mods().is_empty()
+        {
+            self.mob_geometry_inner::<true>(camera, alpha, out);
+        } else {
+            self.mob_geometry_inner::<false>(camera, alpha, out);
+        }
+    }
+
+    fn mob_geometry_inner<const PRECHECK: bool>(
+        &self,
+        camera: glam::DVec3,
+        alpha: f64,
+        out: &mut Vec<Vertex>,
+    ) {
+        let atlas = &self.gui.atlas;
+        let lookup = |name: &str| atlas.sprites.get(name).map(|r| [r.u0, r.v0, r.u1, r.v1]);
+        let scale = self.view_scale();
+        self.rendered_mobs.set(0);
+        let skinning = self.skinning();
+        // What custom entity model animations read of the frame.
+        horizon_client::mobs::cem_anim::set_frame(horizon_client::mobs::cem_anim::Frame {
+            time: self.world.game_time as f64 + alpha,
+            day_time: self.world.day_time as f64 + alpha,
+            dimension: match self.dim {
+                Dim::Overworld => 0.0,
+                Dim::Nether => -1.0,
+                Dim::End => 1.0,
+            },
+            player: self.player.as_ref().map_or(camera.to_array(), |p| {
+                [p.position.x, p.position.y, p.position.z]
+            }),
+            player_rot: [self.pitch, self.yaw],
+            paused: self.pause,
+            first_person: self.camera_type.first_person(),
+            third_person_reversed: self.camera_type
+                == super::super::perspective::CameraType::ThirdPersonFront,
+            ..Default::default()
+        });
+        for mob in &self.mobs {
+            // LevelRenderer: the entity the view looks out of is not drawn
+            // in first person.
+            if self.hides_as_camera(mob.id) {
+                continue;
+            }
+            let is_player = &*mob.kind.id == "minecraft:player";
+            let d = glam::DVec3::new(mob.position.x, mob.position.y, mob.position.z) - camera;
+            // Entity.shouldRenderAtSqrDistance: 64 times the bounding box's
+            // mean edge, scaled by the view scale. RemotePlayer's box counts
+            // ten times.
+            let (w, h, _) = mob.dims();
+            let edge = (w + h + w) / 3.0 * if is_player { 10.0 } else { 1.0 };
+            let range = edge * 64.0 * scale;
+            if d.length_squared() >= range * range {
+                continue;
+            }
+            let beam = horizon_client::mobs::guardian::beam(mob, alpha as f32);
+            // EntityRenderer.shouldRender: the renderer's interpolated culling box,
+            // grown by 0.5 (GuardianRenderer also draws while its beam is out).
+            if let Some(view) = &self.view_frustum
+                && beam.is_none()
+            {
+                let (lo, hi) = super::super::entity_culling::cull_box(mob, alpha);
+                let (lo, hi) = (
+                    (lo - camera - glam::DVec3::splat(0.5)).as_vec3(),
+                    (hi - camera + glam::DVec3::splat(0.5)).as_vec3(),
+                );
+                if !view.intersects(lo, hi) {
+                    continue;
+                }
+            }
+            let outline = self.mob_outline(mob);
+            // Entity.DATA_SHARED_FLAGS_ID invisible: only the name tag draws (and
+            // the outline of a glowing mob, LivingEntityRenderer.getRenderType).
+            // A player keeps its armour, elytra and held items
+            // (`LivingEntityRenderer.submit` skips only the body).
+            let layers_only = mob.invisible && outline.is_none() && is_player;
+            if mob.invisible && outline.is_none() && !layers_only {
+                continue;
+            }
+            let culling = if PRECHECK
+                && outline.is_none()
+                && !is_player
+                && mob.kind.id.starts_with("minecraft:")
+                && [
+                    &mob.extra.head,
+                    &mob.extra.chest,
+                    &mob.extra.legs,
+                    &mob.extra.feet,
+                    &mob.extra.main_hand,
+                    &mob.extra.off_hand,
+                ]
+                .iter()
+                .all(|item| item.is_none())
+                && beam.is_none()
+            {
+                self.entity_cull_decision(mob, alpha)
+            } else {
+                EntityCullDecision::CheckVertices
+            };
+            if culling.hides_entity() {
+                continue;
+            }
+            let entity_start = out.len();
+            self.mark_motion(entity_start, (1 << 32) | u64::from(mob.id));
+            self.mark_entity(entity_start, &mob.kind.id);
+            self.rendered_mobs.set(self.rendered_mobs.get() + 1);
+            // `EntityRenderer.getPackedLightCoords`: the block the mob's light
+            // probe (its eye) is in, at the position this frame draws rather
+            // than this tick's.
+            let probe = mob.light_probe(alpha);
+            let light = self.world.light(probe[0], probe[1], probe[2]);
+            let mut packed = (u32::from(light >> 4) * 16) | ((u32::from(light & 15) * 16) << 8);
+            // EntityRenderer.getBlockLightLevel: a burning mob has 15 block
+            // light, and so do the Allay, Blaze, Magma Cube, Vex and Wither
+            // renderers' overrides; the sky light stays the level's.
+            if mob.fire_ticks > 0
+                || matches!(
+                    mob.species(),
+                    Species::Allay
+                        | Species::Blaze
+                        | Species::MagmaCube
+                        | Species::Vex
+                        | Species::Wither
+                )
+            {
+                packed = (packed & 0xFF) | ((15 * 16) << 8);
+            }
+            // GlowSquidRenderer.getBlockLightLevel: the body brightens as the
+            // dark ticks run out (the block light is the second byte).
+            if mob.species() == Species::GlowSquid {
+                let lit = (packed >> 12) & 15;
+                let block = horizon_client::mobs::aquatic::glow_squid_block_light(mob, lit);
+                packed = (packed & 0xFF) | ((block * 16) << 8);
+            }
+            // A native mod's own model in place of the vanilla one
+            // (`native_mob_submit`), before any of the vanilla model's parts
+            // (a sulfur cube's swallowed block) are drawn.
+            // A player's own hook (`native_player_submit`) is asked for the
+            // other players in view.
+            let who = is_player
+                .then(|| self.remote_player_name(mob.id))
+                .flatten()
+                .map(|name| NativePlayerRender { name, local: false });
+            let modded = if layers_only {
+                false
+            } else if let Some(who) = who {
+                self.mod_player_geometry(mob, who, alpha as f32, camera, packed, out)
+            } else {
+                !is_player && self.mod_mob_geometry(mob, alpha as f32, camera, packed, out)
+            };
+            if modded {
+                if let Some(rgb) = outline {
+                    self.mark_outline(&out[entity_start..], rgb);
+                    if mob.invisible {
+                        out.truncate(entity_start);
+                        continue;
+                    }
+                }
+                if outline.is_none() {
+                    self.cull_entity_vertices(out, entity_start);
+                }
+                continue;
+            }
+            if mob.species() == Species::SulfurCube
+                && !horizon_client::mobs::trader::is_invisible(mob)
+            {
+                self.sulfur_cube_body_geometry(
+                    mob,
+                    alpha as f32,
+                    horizon_client::mobs::render::base_transform(mob, alpha as f32, camera),
+                    packed,
+                    out,
+                );
+            }
+            // Other players on a server: PlayerRenderer's HumanoidArmorLayer.
+            let armor = if is_player {
+                self.worn_armor_layers(mob)
+            } else {
+                Vec::new()
+            };
+            let body = out.len();
+            // The GPU path: an ordinary mob, no layers the CPU path changes after drawing them
+            // (a player's, the HDR tiers below, the sulfur cube's shell). A glowing mob's
+            // silhouette is posed too (`SkinFrame::outline_since`), unless it is invisible:
+            // then only the outline draws.
+            let silhouette_on_gpu = outline.is_none() || !mob.invisible;
+            let posable = skinning
+                && !is_player
+                && !layers_only
+                && silhouette_on_gpu
+                && armor.is_empty()
+                && !matches!(
+                    mob.species(),
+                    Species::Blaze | Species::MagmaCube | Species::GlowSquid | Species::SulfurCube
+                );
+            let mut skinned = None;
+            if posable {
+                let mut models = self.skin_models.borrow_mut();
+                let mut frame = self.skin_frame.borrow_mut();
+                let mark = frame.mark();
+                let mut skin = horizon_client::mobs::skin::Skin::new(&mut models, &mut frame);
+                horizon_client::mobs::render::render_skinned(
+                    mob,
+                    alpha as f32,
+                    camera,
+                    &lookup,
+                    packed,
+                    self.res.mob_data(),
+                    out,
+                    &mut skin,
+                );
+                skinned = Some((mark, skin.bounds));
+            } else {
+                let render = if layers_only {
+                    horizon_client::mobs::render::render_layers
+                } else {
+                    horizon_client::mobs::render::render_with
+                };
+                render(
+                    mob,
+                    alpha as f32,
+                    camera,
+                    &lookup,
+                    packed,
+                    self.res.mob_data(),
+                    &armor,
+                    out,
+                );
+            }
+            // HDR output: mobs that are light shine by their kind, as blocks do (entity.wgsl
+            // fs_hdr_mark); a tier's window lifts only their bright texels.
+            if let Some(tier) = match mob.species() {
+                Species::Blaze => Some(horizon_client::mesher::BRIGHT),
+                Species::MagmaCube | Species::GlowSquid => Some(horizon_client::mesher::LOW),
+                _ => None,
+            } {
+                for v in &mut out[body..] {
+                    v.layer |= u32::from(tier) << 16;
+                }
+            }
+            // AvatarRenderer.shouldRenderLayers: a spectator draws no layers.
+            let layers = horizon_client::mobs::render::layers_shown(mob);
+            if is_player && layers {
+                // PlayerRenderer's CapeLayer, WingsLayer, ParrotOnShoulderLayer
+                // and SpinAttackEffectLayer. Only the cape hides with the body;
+                // the others have no `isInvisible` check.
+                let chest = mob.extra.chest.as_deref();
+                if !layers_only {
+                    self.player_cape_geometry(mob, chest, camera, alpha as f32, packed, out);
+                }
+                if let Some((_, name)) = self
+                    .remote_player_names()
+                    .into_iter()
+                    .find(|(id, _)| *id == mob.id)
+                {
+                    self.player_ears_geometry(mob, &name, camera, alpha as f32, packed, out);
+                }
+                self.player_elytra_geometry(mob, chest, camera, alpha as f32, packed, out);
+                self.shoulder_parrots_geometry(mob, camera, alpha as f32, packed, out);
+                self.spin_attack_geometry(mob, camera, alpha as f32, packed, out);
+                self.stuck_in_body_geometry(mob, mob.id as i32, camera, alpha as f32, packed, out);
+            }
+            // Cosmetics (game/cosmetics.rs), posed on the GPU with the mob's own jobs: culled
+            // with it.
+            if !layers_only
+                && super::super::cosmetics::enabled()
+                && (is_player || &*mob.kind.id == "minecraft:mannequin")
+            {
+                let mark = self.skin_frame.borrow().mark();
+                let base = horizon_client::mobs::render::base_transform(mob, alpha as f32, camera);
+                let gpu = skinning;
+                if let Some((lo, hi)) = self.cosmetics_geometry(
+                    mob,
+                    false,
+                    base,
+                    Some(camera),
+                    alpha as f32,
+                    packed,
+                    gpu,
+                    out,
+                ) {
+                    skinned = Some(match skinned {
+                        Some((first, Some((l, h)))) => (first, Some((l.min(lo), h.max(hi)))),
+                        Some((first, None)) => (first, Some((lo, hi))),
+                        None => (mark, Some((lo, hi))),
+                    });
+                }
+            }
+            // CustomHeadLayer (a pumpkin, skull or head item) included.
+            if layers {
+                // Held items join the GPU path's draws, their silhouette too.
+                let skin = (skinning && silhouette_on_gpu).then_some(&mut skinned);
+                self.mob_block_geometry(mob, camera, alpha, packed, skin, out);
+                // `native_mob_layer`: a native mod's layer, over the vanilla ones.
+                self.mod_mob_layer_geometry(mob, who, alpha as f32, camera, packed, out);
+            }
+            if let Some(rgb) = outline {
+                self.mark_outline(&out[entity_start..], rgb);
+                if let Some(((first, _, _), _)) = skinned {
+                    let color = horizon_client::mobs::render::abgr(rgb);
+                    self.skin_frame.borrow_mut().outline_since(first, color);
+                }
+                if mob.invisible {
+                    out.truncate(entity_start);
+                    continue;
+                }
+            }
+            // Glowing outlines and a guardian's beam remain visible independently
+            // of whether the body is hidden behind terrain.
+            if outline.is_none() && culling.checks_vertices() && beam.is_none() {
+                // What the GPU draws of the mob counts by its bounds' corners.
+                self.cull_skinned(out, entity_start, skinned);
+            }
+            // GuardianRenderer: the laser to the locked target.
+            if let Some((time, scale)) = beam
+                && let Some(target) = self.beam_target(mob.ai.target, alpha)
+                && let Some(uv) = lookup("entity/guardian/guardian_beam")
+            {
+                let a = alpha;
+                let eye = glam::DVec3::new(
+                    mob.previous.x + (mob.position.x - mob.previous.x) * a,
+                    mob.previous.y + (mob.position.y - mob.previous.y) * a + mob.eye_height(),
+                    mob.previous.z + (mob.position.z - mob.previous.z) * a,
+                ) - camera;
+                horizon_client::mobs::guardian::beam_geometry(
+                    eye.as_vec3(),
+                    (target - camera).as_vec3(),
+                    time,
+                    scale,
+                    uv,
+                    out,
+                );
+            }
+        }
+        // What follows isn't a tracked mob: close the last one's span.
+        self.mark_motion(out.len(), 0);
+        self.elder_apparition_geometry(alpha, out);
+        self.spawner_geometry(camera, alpha, out);
+        // Projectiles: the baked vanilla arrow model, the rest as item billboards.
+        let (right, up) = thrown_item_axes(self.camera_type, self.yaw, self.pitch);
+        let live = self.creatures.projectiles.iter().map(|a| {
+            let at = [
+                a.previous.x + (a.position.x - a.previous.x) * alpha,
+                a.previous.y + (a.position.y - a.previous.y) * alpha,
+                a.previous.z + (a.position.z - a.previous.z) * alpha,
+            ];
+            (a, at)
+        });
+        // ItemPickupParticle: a picked-up arrow flying to its collector.
+        let taken = self.pickups.live.iter().filter_map(|p| match &p.taken {
+            super::super::pickups::Taken::Arrow(a) => {
+                Some((&**a, super::super::pickups::position(p, alpha)))
+            }
+            _ => None,
+        });
+        // A glowing projectile's outline: what it drew up to the next one.
+        let mut glowing = None;
+        for (a, at) in live.chain(taken) {
+            if let Some((start, rgb)) = glowing.take() {
+                self.mark_outline(&out[start..], rgb);
+            }
+            if a.id != 0
+                && let Some(rgb) = self.thing_outline(a.id, a.kind.id())
+            {
+                glowing = Some((out.len(), rgb));
+            }
+            let p = glam::DVec3::from_array(at) - camera;
+            let c = p.as_vec3();
+            // EntityRenderer.getPackedLightCoords: the block its light probe
+            // (the eye) is in, at the position this frame draws rather than
+            // this tick's, and not the one under its feet.
+            let light = self.world.light(
+                at[0].floor() as i32,
+                a.light_probe_y(alpha).floor() as i32,
+                at[2].floor() as i32,
+            );
+            let mut packed = (u32::from(light >> 4) * 16) | ((u32::from(light & 15) * 16) << 8);
+            // EntityRenderer.getBlockLightLevel: a shulker bullet and anything
+            // on fire are drawn at 15 block light (the fireball renderers'
+            // own override); the sky light stays the level's.
+            if let Some(block) = a.block_light_override() {
+                packed = (packed & 0xFF) | (u32::from(block) * 16) << 8;
+            }
+            if a.is_arrow() {
+                let Some(model) = self.arrow_model.as_ref() else {
+                    continue;
+                };
+                // SpectralArrowRenderer, and TippableArrowRenderer's `getColor() > 0`.
+                let texture = if a.is_spectral_arrow() {
+                    "entity/projectiles/arrow_spectral"
+                } else if a.arrow.as_ref().is_some_and(|s| s.effect_color > 0) {
+                    "entity/projectiles/arrow_tipped"
+                } else {
+                    "entity/projectiles/arrow"
+                };
+                let Some(r) = atlas.sprites.get(texture).copied() else {
+                    continue;
+                };
+                // ArrowRenderer: `Mth.lerp(partialTick, state.yRotO, state.yRot)`
+                // and the same for the pitch, so a turning arrow is drawn
+                // between the two ticks it turned over.
+                let alpha32 = alpha as f32;
+                let yaw = a.previous_yaw + alpha32 * (a.yaw - a.previous_yaw);
+                let pitch = a.previous_pitch + alpha32 * (a.pitch - a.previous_pitch);
+                let m = glam::Mat4::from_translation(c)
+                    * glam::Mat4::from_rotation_y((yaw - 90.0).to_radians())
+                    * glam::Mat4::from_rotation_z(pitch.to_radians());
+                // ArrowRenderer: `state.shake = shakeTime - partialTicks`; ArrowModel.setupAnim
+                // rolls the root while the shake timer runs.
+                let shake = a
+                    .arrow
+                    .as_ref()
+                    .map_or(0.0, |s| s.shake as f32 - alpha as f32);
+                let roll = if shake > 0.0 {
+                    -(shake * 3.0).msin() * shake * (std::f32::consts::PI / 180.0)
+                } else {
+                    0.0
+                };
+                let pose_for = |part: &horizon_client::mobs::Part| {
+                    let mut pose = part.pose;
+                    if std::ptr::eq(part, model) {
+                        pose[5] += roll;
+                    }
+                    pose
+                };
+                horizon_client::mobs::render_model(
+                    model,
+                    m,
+                    &pose_for,
+                    [r.u0, r.v0, r.u1, r.v1],
+                    packed,
+                    0,
+                    out,
+                );
+                if a.arrow.as_ref().is_some_and(|s| s.on_fire()) {
+                    flame_geometry(atlas, c, 0.5, 0.5, self.yaw, light, out);
+                }
+                continue;
+            }
+            // ThrownTridentRenderer.
+            if matches!(a.kind, ProjectileKind::Trident) {
+                let Some(model) = self.trident_model.as_ref() else {
+                    continue;
+                };
+                let Some(r) = atlas.sprites.get("entity/trident/trident").copied() else {
+                    continue;
+                };
+                let m = glam::Mat4::from_translation(c)
+                    * glam::Mat4::from_rotation_y((a.yaw - 90.0).to_radians())
+                    * glam::Mat4::from_rotation_z((a.pitch + 90.0).to_radians());
+                let poses = horizon_client::mobs::anim::Poses::new(model);
+                horizon_client::mobs::render::draw(
+                    model,
+                    m,
+                    &poses,
+                    [r.u0, r.v0, r.u1, r.v1],
+                    0xFFFF_FFFF,
+                    packed,
+                    0,
+                    out,
+                );
+                continue;
+            }
+            // WindChargeRenderer.
+            if matches!(
+                a.kind,
+                ProjectileKind::WindCharge | ProjectileKind::BreezeWindCharge
+            ) {
+                self.wind_charge_geometry(a, c, packed, alpha as f32, out);
+                continue;
+            }
+            // ShulkerBulletRenderer: the tumbling bullet model, then a larger
+            // translucent copy of it (colour 0x26FFFFFF); always 15 block light.
+            if matches!(a.kind, ProjectileKind::ShulkerBullet { .. }) {
+                let model = &self.entity_models.shulker_bullet;
+                if let (Some(model), Some(r)) =
+                    (model, atlas.sprites.get("entity/shulker/spark").copied())
+                {
+                    use horizon_core::geometry::trig;
+                    let tc = a.age as f32 + alpha as f32;
+                    let mut poses = horizon_client::mobs::anim::Poses::new(model);
+                    poses.yrot("main", a.yaw.to_radians());
+                    poses.xrot("main", a.pitch.to_radians());
+                    let light = (packed & 0xFF) | ((15 * 16) << 8);
+                    let base = glam::Mat4::from_translation(c)
+                        * glam::Mat4::from_translation(glam::Vec3::new(0.0, 0.15, 0.0))
+                        * glam::Mat4::from_rotation_y(
+                            (trig::sin(f64::from(tc * 0.1)) * 180.0).to_radians(),
+                        )
+                        * glam::Mat4::from_rotation_x(
+                            (trig::cos(f64::from(tc * 0.1)) * 180.0).to_radians(),
+                        )
+                        * glam::Mat4::from_rotation_z(
+                            (trig::sin(f64::from(tc * 0.15)) * 360.0).to_radians(),
+                        )
+                        * glam::Mat4::from_scale(glam::Vec3::new(-0.5, -0.5, 0.5));
+                    let uv = [r.u0, r.v0, r.u1, r.v1];
+                    horizon_client::mobs::render::draw(
+                        model,
+                        base,
+                        &poses,
+                        uv,
+                        0xFFFF_FFFF,
+                        light,
+                        0,
+                        out,
+                    );
+                    // The translucent shell blends over the opaque core
+                    // (`RenderTypes.entityTranslucent`).
+                    let shell = out.len();
+                    horizon_client::mobs::render::draw(
+                        model,
+                        base * glam::Mat4::from_scale(glam::Vec3::splat(1.5)),
+                        &poses,
+                        uv,
+                        0x26FF_FFFF,
+                        light,
+                        0,
+                        out,
+                    );
+                    horizon_client::gfx::mark_oit(&mut out[shell..]);
+                }
+                continue;
+            }
+            // WitherSkullRenderer: the skull model facing its flight.
+            if let Some(dangerous) = super::super::wither::skull_kind(a) {
+                let model = &self.entity_models.wither_skull;
+                let tex = if dangerous {
+                    "entity/wither/wither_invulnerable"
+                } else {
+                    "entity/wither/wither"
+                };
+                if let (Some(model), Some(r)) = (model, atlas.sprites.get(tex).copied()) {
+                    let mut poses = horizon_client::mobs::anim::Poses::new(model);
+                    poses.yrot("head", a.yaw.to_radians());
+                    poses.xrot("head", a.pitch.to_radians());
+                    let base = glam::Mat4::from_translation(c)
+                        * glam::Mat4::from_scale(glam::Vec3::new(-1.0, -1.0, 1.0));
+                    horizon_client::mobs::render::draw(
+                        model,
+                        base,
+                        &poses,
+                        [r.u0, r.v0, r.u1, r.v1],
+                        0xFFFF_FFFF,
+                        packed,
+                        0,
+                        out,
+                    );
+                }
+                continue;
+            }
+            if let Some(stack) = a.drawn_item() {
+                let owner = super::super::item_draw::owner_at(at, 0.0, a.kind.id());
+                let state = self.resolve_item(&stack, DisplayContext::Ground, Some(&owner), 0);
+                let pose = glam::Mat4::from_translation(c)
+                    * glam::Mat4::from_quat(self.camera_orientation());
+                self.submit_item_world(&state, pose, packed, out);
+                continue;
+            }
+            // `Entity.displayFireAnimation`: a thrown item that flew through a
+            // fire block burns (`ThrowableProjectile.tick`'s
+            // `applyEffectsFromBlocks`), and ThrownItemRenderer draws the flame
+            // over its box as any other entity renderer does.
+            if a.on_fire() {
+                let size = a.kind.size() as f32;
+                flame_geometry(atlas, c, size, size, self.yaw, light, out);
+            }
+            // `ThrownItemRenderer` for a fireball: the item `Fireball.getItem`
+            // returns (a fire charge until `setItem` gave it another), its model
+            // at the renderer's scale for the kind. `packed` is already 15, the
+            // renderer's full bright.
+            if let Some(stack) = a.item.as_ref() {
+                let owner = super::super::item_draw::owner_at(at, 0.0, a.kind.id());
+                let state = self.resolve_item(stack, DisplayContext::Ground, Some(&owner), 0);
+                let pose = glam::Mat4::from_translation(c)
+                    * glam::Mat4::from_quat(self.camera_orientation())
+                    * glam::Mat4::from_scale(glam::Vec3::splat(a.sprite_scale()));
+                self.submit_item_world(&state, pose, packed, out);
+                continue;
+            }
+            let Some(name) = a.item_sprite() else {
+                continue;
+            };
+            let Some(r) = atlas.sprites.get(name).copied() else {
+                continue;
+            };
+            let lift = is_item_billboard(&a.kind);
+            let quad = thrown_item_quad(c, right, up, a.sprite_scale(), lift);
+            for (v, uv) in quad
+                .iter()
+                .zip([[r.u0, r.v1], [r.u1, r.v1], [r.u1, r.v0], [r.u0, r.v0]])
+            {
+                out.push(Vertex {
+                    normal: [0; 4],
+                    pos: v.to_array(),
+                    uv,
+                    layer: 0,
+                    color: 0xFFFF_FFFF,
+                    light: packed,
+
+                    glint_uv: [0.0, 0.0],
+                });
+            }
+        }
+        if let Some((start, rgb)) = glowing {
+            self.mark_outline(&out[start..], rgb);
+        }
+    }
+}

crates/horizon-client/src/game/creatures/spawn_eggs.rs

@@ -0,0 +1,171 @@
+//! Spawn eggs: a baby from an egg used on its own kind, an egg used on a block or a fluid, and the
+//! egg's entity data on the mob it spawned.
+use super::*;
+
+impl Game<'_> {
+    /// `Mob.checkAndHandleImportantInteractions` with a spawn egg of mob
+    /// `index`'s own kind (`SpawnEggItem.spawnOffspringFromSpawnEgg`): a baby
+    /// at the mob's feet, taking the parent's variant as `getBreedOffspring`
+    /// does, and one egg used. False (PASS) when the mob has no baby form.
+    pub(super) fn spawn_egg_offspring(&mut self, index: usize) -> bool {
+        let Some(stack) = self.held().cloned() else {
+            return false;
+        };
+        let parent = &self.mobs[index];
+        if !parent.alive()
+            || !horizon_client::mobs::finalize::spawn_egg_is_for(&stack.item, &parent.kind.id)
+            || !horizon_client::mobs::species::can_be_a_baby(parent.species())
+            // WanderingTrader.getBreedOffspring returns null: no offspring, the
+            // click carries on to trading.
+            || parent.species() == Species::WanderingTrader
+        {
+            return false;
+        }
+        let (kind, at) = (
+            parent.kind.id.clone(),
+            [parent.position.x, parent.position.y, parent.position.z],
+        );
+        let (species, variant, color) =
+            (parent.species(), parent.extra.variant, parent.extra.color);
+        let target = self.mob_entity(&self.mobs[index]);
+        // SpawnEggItem.spawnOffspringFromSpawnEgg: `type.create(level, SPAWN_ITEM_USE)`
+        // creates the baby without finalizeSpawn, and `snapTo(pos, 0, 0)` faces
+        // it south without a level-random draw.
+        let Some(id) =
+            self.spawn_mob_internal(&kind, at, false, false, false, false, SpawnYaw::Fixed(0.0))
+        else {
+            return false;
+        };
+        if let Some(child) = self.mobs.iter_mut().find(|m| m.id == id) {
+            horizon_client::mobs::finalize::spawn_egg_offspring(child, species, variant, color);
+        }
+        // `Mob.checkAndHandleImportantInteractions` then calls
+        // `onOffspringSpawnedFromEgg`: `Fox`'s makes the baby trust the player
+        // who used the egg (a fox egg used on a block trusts nobody).
+        if species == Species::Fox {
+            let spawner = self.acting_player_uuid();
+            if let Some(child) = self.mobs.iter_mut().find(|m| m.id == id) {
+                horizon_client::mobs::fox::add_trusted_entity(child, spawner);
+            }
+        }
+        self.trigger_item_entity("minecraft:player_interacted_with_entity", &stack, &target);
+        self.consume_held();
+        true
+    }
+    /// `SpawnEggItem.use`: the SOURCE_ONLY ray must hit a liquid block.
+    pub(in crate::game) fn spawn_egg_fluid_hit(&self) -> Option<super::super::Hit> {
+        let hit = self.bucket_hit()?;
+        matches!(
+            &*self.block_name(hit.pos),
+            "minecraft:water" | "minecraft:lava"
+        )
+        .then_some(hit)
+    }
+    /// Shared peaceful-mode eligibility for spawn eggs.
+    pub(in crate::game) fn spawn_egg_allowed(&self, item: &str) -> bool {
+        let kind = item.trim_end_matches("_spawn_egg");
+        self.ui.difficulty != 0
+            || self
+                .res
+                .mob_types()
+                .get(kind)
+                .is_none_or(|t| horizon_client::mobs::spawn_rules::allowed_in_peaceful(t.species))
+    }
+    /// `SpawnEggItem.useOn` for a block, or `use` for a fluid source.
+    pub(super) fn use_spawn_egg(&mut self, stack: &ItemStack) -> Result<bool> {
+        let fluid = matches!(self.guest_use, Some(super::super::GuestUse::Item(_)));
+        let Some(hit) = (if fluid {
+            self.spawn_egg_fluid_hit()
+        } else {
+            self.pick()
+        }) else {
+            return Ok(false);
+        };
+        let kind = stack.item.trim_end_matches("_spawn_egg").to_owned();
+        if !self.spawn_egg_allowed(&stack.item) {
+            self.use_failed = true;
+            return Ok(true);
+        }
+        if fluid
+            && !self.may_build()
+            && !self.can_place_on_in_adventure([
+                hit.pos[0] - hit.face[0],
+                hit.pos[1] - hit.face[1],
+                hit.pos[2] - hit.face[2],
+            ])
+        {
+            self.use_failed = true;
+            return Ok(true);
+        }
+        // SpawnEggItem.useOn on a spawner sets its mob (and an op's egg data).
+        let (spawner_id, data) = horizon_client::block_entity_item::spawn_egg_on_spawner(
+            stack,
+            self.acting_player_is_op(),
+        );
+        if let Some(done) = self.use_spawn_egg_on_spawner(hit.pos, &spawner_id, data.as_ref()) {
+            if done {
+                self.swing_arm();
+                self.award_stat("used", &stack.item, 1);
+                self.consume_held();
+            }
+            return Ok(true);
+        }
+        // useOn: a clicked block without a collision shape (vines, grass)
+        // takes the mob itself, any other the one on the clicked face.
+        let p = if fluid || self.collision_empty(hit.pos) {
+            hit.pos
+        } else {
+            [
+                hit.pos[0] + hit.face[0],
+                hit.pos[1] + hit.face[1],
+                hit.pos[2] + hit.face[2],
+            ]
+        };
+        let at = [
+            f64::from(p[0]) + 0.5,
+            f64::from(p[1]),
+            f64::from(p[2]) + 0.5,
+        ];
+        // SpawnEggItem.spawnMob: `EntityType.spawn`.
+        let Some(id) = self.spawn_mob_spawned(&kind, at, SpawnYaw::Created) else {
+            return Ok(false);
+        };
+        // SpawnEggItem.spawnMob: `EntityType.create` finalizes the mob, then
+        // `PostSpawnProcessor` puts the egg's components on it.
+        if let Some(m) = self.mobs.iter_mut().find(|m| m.id == id) {
+            horizon_client::entity_nbt::apply_item_components(m, stack);
+        }
+        self.apply_spawn_egg_entity_data(id, stack);
+        self.post_block_game_event("minecraft:entity_place", p, Some(Who::Player), None);
+        self.award_stat("used", &stack.item, 1);
+        self.swing_arm();
+        if !self.creative
+            && let Some(s) = self.held_mut().as_mut()
+        {
+            s.count -= 1;
+            if s.count == 0 {
+                *self.held_mut() = None;
+            }
+        }
+        Ok(true)
+    }
+    /// `EntityType.updateCustomEntityTag`: the egg's `minecraft:entity_data` on
+    /// the mob it spawned, once the guards let it through, as
+    /// `TypedEntityData.loadInto`: the mob's own compound, the data merged over
+    /// it, loaded back into the same mob (`/data merge entity`'s loader).
+    pub(in crate::game) fn apply_spawn_egg_entity_data(&mut self, id: u32, stack: &ItemStack) {
+        let Some(i) = self.mobs.iter().position(|m| m.id == id) else {
+            return;
+        };
+        let kind = self.mobs[i].kind.id.clone();
+        let op = self.acting_player_is_op();
+        let Some(data) = horizon_client::block_entity_item::spawn_egg_entity_data(stack, &kind, op)
+        else {
+            return;
+        };
+        let own = self.mob_tree_nbt(i);
+        let tag = horizon_client::data_cmd::merged(&own, data);
+        // Nothing to report: the mob's own compound always loads back.
+        let _ = self.apply_entity_nbt(super::super::commands::Target::Mob(id), tag);
+    }
+}

crates/horizon-client/src/game/dedicated.rs

@@ -2671,7 +2671,7 @@ mod tests {
     #[test]
     fn a_temporarily_banned_player_is_refused_with_the_end_until_it_has_passed() {
         use super::{BanEntry, BanList, Lists, NameAndId};
-        use horizon_chat_filter::now_millis;
+        use horizon_server_files::duration::now_millis;
         let dir = std::env::temp_dir().join(format!("horizon-can-login-{}", std::process::id()));
         fs::create_dir_all(&dir).unwrap();
         let mut lists = Lists {

crates/horizon-client/src/game/discord.rs

@@ -1,49 +0,0 @@
-//! What the player is doing, for Discord Rich Presence (`horizon_client::discord_presence`).
-use super::*;
-use horizon_client::discord_presence::{self as presence, Dimension, Play, Status};
-
-impl Game<'_> {
-    /// Each frame: only a change reaches the presence thread.
-    pub(super) fn update_discord_presence(&self) {
-        // One Discord status per computer: P1's, not a splitscreen player's.
-        if self.options.split_guest {
-            return;
-        }
-        presence::set(self.discord_status());
-    }
-    fn discord_status(&self) -> Status {
-        if !self.settings.extras.discord_presence {
-            return Status::Off;
-        }
-        if self.title.is_some() {
-            return Status::Menus;
-        }
-        let play = if let Some(host) = &self.lan {
-            Play::Hosting {
-                players: 1 + host.hub.guests.len(),
-                max: horizon_client::lan::MAX_PLAYERS,
-            }
-        } else if let Some(server) = &self.integrated {
-            match (server.published(), &self.remote) {
-                (Some(_), Some(remote)) => Play::Hosting {
-                    players: remote.player_count(),
-                    max: horizon_client::lan::MAX_PLAYERS,
-                },
-                _ => Play::Singleplayer,
-            }
-        } else if self.remote.is_some() {
-            Play::Multiplayer
-        } else {
-            Play::Singleplayer
-        };
-        Status::World {
-            play,
-            dimension: match self.dim {
-                Dim::Overworld => Dimension::Overworld,
-                Dim::Nether => Dimension::Nether,
-                Dim::End => Dimension::End,
-            },
-            mode: self.mode,
-        }
-    }
-}

crates/horizon-client/src/game/extras.rs

@@ -273,6 +273,12 @@ impl Game<'_> {
         }
         self.draw_pvp_hud(batch, &mut corners);
         self.native_hud(batch, &mut corners);
+        // The layers crates registered (`horizon_hooks::hud`): none, no canvas.
+        let layers = horizon_hooks::hud::engine::all();
+        if !layers.is_empty() {
+            let shown = Corner::ALL.map(|corner| self.native_corner_shown(corner));
+            extras_hud::draw_layers(layers, batch, &self.gui.atlas, &mut corners, shown);
+        }
     }
     /// The height the status effect icons take at the top right
     /// (`Hud.extractEffects`: beneficial at y 1, harmful at y 26).

crates/horizon-client/src/game/friends.rs

@@ -1,23 +1,23 @@
 //! Play with friends, host side: "Start Sharing" on the Play with Friends
-//! screen (`friends_screen`, the pause menu's Friends button) opens the world to LAN if
+//! screen (`screen`, the pause menu's Friends button) opens the world to LAN if
 //! it isn't (with Open to LAN's defaults) and shares that port behind an
 //! invite code (horizon-friends). The code holds this computer's addresses
 //! and the key, so friends join with no server of ours; a relay the player
 //! configured adds a short code and a fallback. The integrated server is the
 //! LAN one, unchanged: tunnelled guests are LAN guests that connect from the
-//! loopback address.
+//! loopback address. The joining side is horizon-friends' (`game`), registered by
+//! horizon-official.
 use super::{Game, lan::LanSettings};
-use horizon_client::{
-    Result,
-    friends_screen::{self, Action, FriendsView},
-    hud::HudBatch,
-    lang,
-    text::Text,
-};
+use horizon_client::{Result, hud::HudBatch, lang, text::Text};
 use horizon_friends::{Host, HostConfig, HostEvent, PathMode, host::DEFAULT_PORT, reach, stun};
 use horizon_protocol::{GAME_VERSION, PROTOCOL_VERSION};
 use std::time::{Duration, Instant};
 
+mod screen;
+
+use screen::{self as friends_screen, Action, FriendsView};
+pub use screen::{TITLE, title};
+
 pub(super) struct Sharing {
     host: Host,
     /// Sharing opened the world to LAN, so stopping closes it again.
@@ -240,6 +240,11 @@ impl Game<'_> {
         }
     }
 
+    /// Whether the pause menu offers Play with Friends (a singleplayer world).
+    pub(super) fn friends_shown(&self) -> bool {
+        self.friends_view().shown
+    }
+
     /// What Play with Friends shows.
     pub(super) fn friends_view(&self) -> FriendsView {
         let guests = match &self.lan {

crates/horizon-client/src/game/friends/screen.rs

@@ -1,9 +1,9 @@
 //! Play with Friends: Horizon's own sharing of the open world behind an
-//! invite code (`game/friends.rs`). The pause menu's Friends button, the icon
+//! invite code (`game/friends.rs`), with the rest of Play with Friends' game glue. The pause menu's Friends button, the icon
 //! vanilla's PauseScreen already has, opens it. It is drawn the way a mod adds
 //! a screen to vanilla: the menu background, a centred title and text,
 //! vanilla's buttons and Done in the footer.
-use crate::{
+use horizon_client::{
     hud::{HudAtlas, HudBatch, rgba},
     multiplayer::wrap,
     text::Text,
@@ -14,7 +14,7 @@ use crate::{
 pub const TITLE: &str = "Play with Friends";
 /// A string of this screen: the language table's, or the English text.
 fn tr(key: &str, english: &str) -> String {
-    crate::lang::get_or(key, english)
+    horizon_client::lang::get_or(key, english)
 }
 /// The title in the current language.
 pub fn title() -> String {
@@ -245,8 +245,8 @@ pub fn draw(
     for b in buttons {
         let hover = b.active && ui::hovered(cursor, b.x, b.y, b.w, 20.0);
         if matches!(b.action, Action::Done) {
-            crate::widgets::declare_action(
-                crate::widgets::Action::Done,
+            horizon_client::widgets::declare_action(
+                horizon_client::widgets::Action::Done,
                 [b.x, b.y, b.w, 20.0],
                 b.active,
             );

crates/horizon-client/src/game/friends_off.rs

@@ -1,11 +1,17 @@
 //! Play with Friends left out of the build (the `friends` feature off, as in the server build):
-//! no world is shared, the pause menu has no Friends button (`FriendsView::shown` is false, as on
+//! no world is shared, the pause menu has no Friends button (`friends_shown` is false, as on
 //! another server) and `horizon-ctl friends` says it isn't there. game/friends.rs is the real one.
 use super::{Game, Screen};
-use horizon_client::{Result, friends_screen::FriendsView, hud::HudBatch};
+use horizon_client::{Result, hud::HudBatch};
 
 pub const HELP: &[&str] = &[];
 
+/// The pause menu's Friends icon is vanilla's, drawn inactive: its name for the widget tree.
+pub const TITLE: &str = "Play with Friends";
+pub fn title() -> String {
+    horizon_client::lang::get_or("horizon.friends.title", TITLE)
+}
+
 impl Game<'_> {
     pub(super) fn friends_lan_closed(&mut self) {}
 
@@ -18,8 +24,8 @@ impl Game<'_> {
 
     pub(super) fn friends_screen_click(&mut self) {}
 
-    pub(super) fn friends_view(&self) -> FriendsView {
-        FriendsView::default()
+    pub(super) fn friends_shown(&self) -> bool {
+        false
     }
 
     /// `horizon-ctl friends ...`.

crates/horizon-client/src/game/loading_screen.rs

@@ -34,8 +34,6 @@ pub(super) fn run_event_loop(mut game: Game<'_>) -> Result<()> {
     narrator::stop();
     leave_fullscreen_after(&result, &mut game.settings);
     result?;
-    #[cfg(feature = "discord")]
-    horizon_client::discord_presence::stop();
     write_report(&game)?;
     if let Some(e) = game.error.take() {
         return Err(e);

crates/horizon-client/src/game/menu_clicks.rs

@@ -899,4 +899,32 @@ impl Game<'_> {
             f.input_clicked(world_recipes!(self), before);
         }
     }
+
+    /// `AbstractContainerScreen` keeps `isQuickCrafting` and the drag it
+    /// belongs to on the screen. Horizon keeps both on `Game` (`inv_clicks`,
+    /// `inv_drag`, `last_inv_click`), so they are dropped when the pointer
+    /// changes hands: a screen that opens or closes starts with its own
+    /// state, and a press whose release never reached the screen -- the
+    /// pointer left the window, or the screen closed first -- would
+    /// otherwise leave every later press on every later screen swallowed.
+    pub(super) fn reset_inventory_clicks(&mut self) {
+        self.inv_clicks.cancel_drag();
+        self.inv_drag = None;
+        self.last_inv_click = None;
+    }
+
+    /// A sound a menu click made the player play (a bundle's insert or
+    /// remove): `Entity.playSound` at the player.
+    pub(super) fn player_menu_sound(&mut self, sound: &str) {
+        let Some(p) = self.player.as_ref() else {
+            return;
+        };
+        let at = [p.position.x, p.position.y, p.position.z];
+        let (volume, pitch) = if sound == horizon_client::bundle::INSERT_FAIL {
+            (1.0, 1.0)
+        } else {
+            (0.8, 0.8 + self.world.random.next_float() * 0.4)
+        };
+        self.audio.play(sound, Some(at), volume, pitch);
+    }
 }

crates/horizon-client/src/game/minecarts.rs

@@ -28,6 +28,10 @@ use horizon_core::{
 };
 use horizon_world::registry::BlockStateId;
 use std::{collections::HashMap, sync::Arc};
+mod index;
+mod nbt;
+pub(super) use index::CartIndex;
+use index::cart_at;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub(super) enum CartKind {
@@ -187,102 +191,6 @@ pub(super) const TNT_PRIME_EVENT: i8 = 70;
 mod display;
 use display::{cart_render_bounds, display_offset, shown_unless_air};
 pub(super) use display::{default_display_offset, forget_unreadable_display};
-/// The carts' and mobs' boxes for one tick's cart pushes (`push_from_cart`,
-/// `pickup_from_cart`), so a cart reads its neighbours instead of every cart and
-/// every mob of the level. Both answer in slot order, as the scans did.
-///
-/// The cart grid follows each ticked cart ([`CartIndex::moved`]); it is
-/// rebuilt once the list's length changed (a cart gone or added), and dropped
-/// after a command, which can move or replace any cart
-/// ([`CartIndex::forget_carts`]). The mob grid holds until the mob
-/// list's next write ([`ListStamp`]). A native mod's hook can move either kind
-/// unseen, so with mods loaded both scans stay.
-#[derive(Default)]
-pub(super) struct CartIndex {
-    carts: Option<(SeenGrid, Vec<u32>)>,
-    /// The grid, and the carts a mob rides.
-    mobs: Option<(ListStamp, SeenGrid, FxHashSet<u32>)>,
-    near: Vec<u32>,
-}
-impl CartIndex {
-    fn usable() -> bool {
-        horizon_client::mod_api::mods().is_empty()
-    }
-    /// The cart in slot `i` has these bounds now.
-    fn moved(&mut self, i: usize, bounds: Aabb) {
-        if let Some((grid, ids)) = &mut self.carts
-            && i < ids.len()
-        {
-            grid.update(i, bounds);
-        }
-    }
-    fn forget_carts(&mut self) {
-        self.carts = None;
-    }
-    /// The slots of the carts whose box may meet `area`, for the cart in slot
-    /// `i` (just moved); false: scan them all.
-    fn carts_near(&mut self, carts: &[Minecart], i: usize, area: Aabb, out: &mut Vec<u32>) -> bool {
-        if !Self::usable() {
-            return false;
-        }
-        let fresh = |ids: &[u32]| ids.len() == carts.len() && ids[i] == carts[i].id;
-        if !self.carts.as_ref().is_some_and(|(_, ids)| fresh(ids)) {
-            self.carts = Some((
-                SeenGrid::new(carts.iter().map(Minecart::bounds)),
-                carts.iter().map(|c| c.id).collect(),
-            ));
-        }
-        let Some((grid, ids)) = &mut self.carts else {
-            return false;
-        };
-        grid.update(i, carts[i].bounds());
-        if !grid.candidates(area, out) {
-            return false;
-        }
-        if out.iter().any(|&j| ids[j as usize] != carts[j as usize].id) {
-            // A cart was replaced in place: start over next time.
-            self.carts = None;
-            return false;
-        }
-        true
-    }
-    /// The slots of the mobs whose box may meet `area` into `out`, and
-    /// whether a mob rides cart `cart`; None: scan them all.
-    fn mobs_near(
-        &mut self,
-        mobs: &JoinList<Mob>,
-        cart: u32,
-        area: Aabb,
-        out: &mut Vec<u32>,
-    ) -> Option<bool> {
-        if !Self::usable() {
-            return None;
-        }
-        if !self
-            .mobs
-            .as_ref()
-            .is_some_and(|(stamp, ..)| *stamp == mobs.stamp())
-        {
-            self.mobs = Some((
-                mobs.stamp(),
-                SeenGrid::new(mobs.iter().map(Mob::bounds)),
-                mobs.iter().filter_map(|m| m.extra.mount).collect(),
-            ));
-        }
-        let (_, grid, mounted) = self.mobs.as_ref()?;
-        grid.candidates(area, out).then(|| mounted.contains(&cart))
-    }
-}
-/// Where the cart `id` is in `carts`: at `hint` (where it was a moment ago,
-/// the usual case while carts tick in order) or found by a scan. A world
-/// with hundreds of mineshaft chest carts asked this of every cart several
-/// times a tick.
-fn cart_at(carts: &[Minecart], id: u32, hint: usize) -> Option<usize> {
-    if carts.get(hint).is_some_and(|c| c.id == id) {
-        return Some(hint);
-    }
-    carts.iter().position(|c| c.id == id)
-}
 /// `AbstractMinecart.push(entity)` for a non-cart `entity` at `feet`:
 /// the push the cart loses (the entity gets a quarter of it back).
 pub(super) fn cart_push_from(feet: Vec3, cart: Vec3) -> Option<(f64, f64)> {
@@ -2984,177 +2892,6 @@ impl Game<'_> {
             .render_state(&scene, state.0, m, light, out);
     }
 }
-/// Saving and loading.
-impl Minecart {
-    pub fn to_nbt(
-        &self,
-        uuid: [i32; 4],
-        raw: Option<&horizon_world::nbt::Tag>,
-    ) -> horizon_world::nbt::Tag {
-        use horizon_world::nbt::{JavaString, Tag};
-        let mut tag = horizon_client::entity_nbt::vehicle_to_nbt(
-            self.kind.id(),
-            self.position,
-            self.velocity,
-            [self.yaw, self.pitch],
-            (self.on_ground, self.fall_distance),
-            uuid,
-            raw,
-        );
-        horizon_client::entity_nbt::write_saved_flags(&mut tag, self.on_ground, self.no_gravity);
-        if let Tag::Compound(map) = &mut tag {
-            // ContainerEntity.addChestVehicleSaveData belongs only to the
-            // container subclasses, never to a plain or specialized cart.
-            if self.kind.slots() == 0 {
-                map.remove(&JavaString::from("Items"));
-            }
-            if self.kind == CartKind::CommandBlock {
-                for key in ["LastOutput", "LastExecution"] {
-                    map.remove(&JavaString::from(key));
-                }
-            }
-            map.remove(&JavaString::from("DisplayOffset"));
-            map.remove(&JavaString::from("DisplayState"));
-            let mut put = |k: &str, v: Tag| {
-                map.insert(JavaString::from(k), v);
-            };
-            put("FlippedRotation", Tag::Byte(i8::from(self.flipped)));
-            // AbstractMinecart saves firstTick as HasTicked. A cart never burns:
-            // Entity.move sets -getFireImmuneTicks(), 0 for all but players.
-            put("HasTicked", Tag::Byte(i8::from(self.first_tick)));
-            put("Fire", Tag::Short(0));
-            // addAdditionalSaveData: the offset only off its default, the state only when set.
-            if let Some(offset) = self.custom_offset
-                && f64::from(offset) != default_display_offset(self.kind)
-            {
-                put("DisplayOffset", Tag::Int(offset));
-            }
-            if let Some(state) = &self.custom_display {
-                put("DisplayState", state.clone());
-            }
-            match self.kind {
-                CartKind::Chest | CartKind::Hopper => {
-                    put("Items", horizon_client::save::encode_items(&self.items));
-                    if self.kind == CartKind::Hopper {
-                        put("Enabled", Tag::Byte(i8::from(self.enabled)));
-                    }
-                }
-                CartKind::Furnace => {
-                    put("PushX", Tag::Double(self.push.x.to_bits()));
-                    put("PushZ", Tag::Double(self.push.z.to_bits()));
-                    put("Fuel", Tag::Short(self.fuel as i16));
-                }
-                CartKind::Tnt => put("fuse", Tag::Int(self.fuse)),
-                // BaseCommandBlock.save (its CustomName shares the entity's key).
-                CartKind::CommandBlock => {
-                    for (key, value) in self.command.save() {
-                        if !matches!(key, "CustomName" | "powered" | "conditionMet" | "auto") {
-                            put(key, value);
-                        }
-                    }
-                }
-                // BaseSpawner.save: the delays, ranges, SpawnData and SpawnPotentials.
-                CartKind::Spawner => {
-                    if let Some(spawner) = &self.spawner {
-                        for (key, value) in
-                            horizon_client::mobs::spawner::SpawnerExt::save(&**spawner)
-                        {
-                            put(key, value);
-                        }
-                    }
-                }
-                CartKind::Rideable => {}
-            }
-            // A loaded loot table goes back while the items are still its roll;
-            // otherwise the items replace it, as vanilla's unpackLootTable does.
-            if self.loot.as_ref().is_some_and(|l| l.restore(map)) {
-                if let Some(table) = horizon_client::save::text(map.get(&"LootTable".into()))
-                    .and_then(|id| horizon_client_core::identifier::normalize_id(&id))
-                {
-                    map.insert("LootTable".into(), Tag::String(table.as_str().into()));
-                }
-            } else {
-                map.remove(&JavaString::from("LootTable"));
-                map.remove(&JavaString::from("LootTableSeed"));
-            }
-        }
-        tag
-    }
-    pub fn from_nbt(tag: &horizon_world::nbt::Tag, id: u32, kind: CartKind) -> Option<Self> {
-        let (position, _, _) = horizon_client::entity_nbt::boat_from_nbt(tag)?;
-        let mut c = Self::new(id, kind, position);
-        c.load(tag)?;
-        Some(c)
-    }
-    /// `Entity.load` on this cart: the saved fields are read over the live
-    /// ones, the rest (riders, lerp, hurt state) stays; its kind never changes.
-    /// `None`, with nothing changed, when the compound has no position.
-    pub fn load(&mut self, tag: &horizon_world::nbt::Tag) -> Option<()> {
-        use horizon_world::nbt::Tag;
-        let (position, velocity, yaw) = horizon_client::entity_nbt::boat_from_nbt(tag)?;
-        let kind = self.kind;
-        let c = self;
-        c.position = position;
-        c.previous = position;
-        c.velocity = velocity;
-        c.yaw = yaw;
-        c.previous_yaw = yaw;
-        c.no_gravity = horizon_client::entity_nbt::flag(tag, "NoGravity");
-        c.on_ground = horizon_client::entity_nbt::flag(tag, "OnGround");
-        c.pitch = horizon_client::entity_nbt::rotation(tag)[1];
-        c.previous_pitch = c.pitch;
-        // ValueInput's numeric getters take any NumericTag: getIntOr is its
-        // intValue, getShortOr the low 16 bits of it, getBooleanOr
-        // `byteValue() != 0` (the low 8), getDoubleOr its doubleValue.
-        let int = |k: &str| {
-            tag.get(k)
-                .and_then(horizon_client_core::nbt_path::int_value)
-        };
-        let flag = |k: &str, default: bool| int(k).map_or(default, |v| v as i8 != 0);
-        let double = |k: &str| match tag.get(k) {
-            Some(Tag::Byte(v)) => f64::from(*v),
-            Some(Tag::Short(v)) => f64::from(*v),
-            Some(Tag::Int(v)) => f64::from(*v),
-            Some(Tag::Long(v)) => *v as f64,
-            Some(Tag::Float(v)) => f64::from(f32::from_bits(*v)),
-            Some(Tag::Double(v)) => f64::from_bits(*v),
-            _ => 0.0,
-        };
-        // Entity.load: OnGround and fall_distance, as saved.
-        (c.on_ground, c.fall_distance) = horizon_client::entity_nbt::ground_from_nbt(tag);
-        c.flipped = flag("FlippedRotation", false);
-        c.first_tick = flag("HasTicked", false);
-        if kind.slots() > 0 {
-            c.items = horizon_client::save::decode_items(tag.get("Items"), kind.slots());
-        }
-        c.enabled = flag("Enabled", true);
-        c.fuel = int("Fuel").map_or(0, |v| i32::from(v as i16));
-        // readAdditionalSaveData: the saved push has no y.
-        c.push = Vec3::new(double("PushX"), 0.0, double("PushZ"));
-        c.fuse = int("fuse").unwrap_or(-1);
-        // readAdditionalSaveData: DisplayState, DisplayOffset (default offset when absent).
-        c.custom_display = tag.get("DisplayState").cloned();
-        c.custom_offset = int("DisplayOffset");
-        if kind == CartKind::CommandBlock {
-            c.command = horizon_client::command_block::CommandBlock::load(tag);
-            // MinecartCommandBlock.readAdditionalSaveData sets the synched command.
-            // A changed value invokes onSyncedDataUpdated -> setCommand, resetting successes.
-            if c.synced_command != c.command.command {
-                c.synced_command.clone_from(&c.command.command);
-                c.command.set_command(&c.synced_command);
-            }
-            c.synced_output = c.command.last_output_string();
-        }
-        // MinecartSpawner.readAdditionalSaveData: BaseSpawner.load.
-        if kind == CartKind::Spawner {
-            c.spawner = Some(Box::new(horizon_client::mobs::spawner::SpawnerExt::load(
-                tag,
-            )));
-        }
-        Some(())
-    }
-}
-
 /// `VehicleEntity.hurtServer`'s destroy test: a creative player, damage past
 /// 40, or (`MinecartTNT.shouldSourceDestroy`) fire or an explosion hitting a
 /// TNT cart.

crates/horizon-client/src/game/minecarts/index.rs

@@ -0,0 +1,105 @@
+//! The carts' and mobs' boxes for a tick's cart pushes ([`CartIndex`]).
+use super::*;
+
+/// The carts' and mobs' boxes for one tick's cart pushes (`push_from_cart`,
+/// `pickup_from_cart`), so a cart reads its neighbours instead of every cart and
+/// every mob of the level. Both answer in slot order, as the scans did.
+///
+/// The cart grid follows each ticked cart ([`CartIndex::moved`]); it is
+/// rebuilt once the list's length changed (a cart gone or added), and dropped
+/// after a command, which can move or replace any cart
+/// ([`CartIndex::forget_carts`]). The mob grid holds until the mob
+/// list's next write ([`ListStamp`]). A native mod's hook can move either kind
+/// unseen, so with mods loaded both scans stay.
+#[derive(Default)]
+pub(in crate::game) struct CartIndex {
+    pub(super) carts: Option<(SeenGrid, Vec<u32>)>,
+    /// The grid, and the carts a mob rides.
+    pub(super) mobs: Option<(ListStamp, SeenGrid, FxHashSet<u32>)>,
+    pub(super) near: Vec<u32>,
+}
+impl CartIndex {
+    pub(super) fn usable() -> bool {
+        horizon_client::mod_api::mods().is_empty()
+    }
+    /// The cart in slot `i` has these bounds now.
+    pub(super) fn moved(&mut self, i: usize, bounds: Aabb) {
+        if let Some((grid, ids)) = &mut self.carts
+            && i < ids.len()
+        {
+            grid.update(i, bounds);
+        }
+    }
+    pub(super) fn forget_carts(&mut self) {
+        self.carts = None;
+    }
+    /// The slots of the carts whose box may meet `area`, for the cart in slot
+    /// `i` (just moved); false: scan them all.
+    pub(super) fn carts_near(
+        &mut self,
+        carts: &[Minecart],
+        i: usize,
+        area: Aabb,
+        out: &mut Vec<u32>,
+    ) -> bool {
+        if !Self::usable() {
+            return false;
+        }
+        let fresh = |ids: &[u32]| ids.len() == carts.len() && ids[i] == carts[i].id;
+        if !self.carts.as_ref().is_some_and(|(_, ids)| fresh(ids)) {
+            self.carts = Some((
+                SeenGrid::new(carts.iter().map(Minecart::bounds)),
+                carts.iter().map(|c| c.id).collect(),
+            ));
+        }
+        let Some((grid, ids)) = &mut self.carts else {
+            return false;
+        };
+        grid.update(i, carts[i].bounds());
+        if !grid.candidates(area, out) {
+            return false;
+        }
+        if out.iter().any(|&j| ids[j as usize] != carts[j as usize].id) {
+            // A cart was replaced in place: start over next time.
+            self.carts = None;
+            return false;
+        }
+        true
+    }
+    /// The slots of the mobs whose box may meet `area` into `out`, and
+    /// whether a mob rides cart `cart`; None: scan them all.
+    pub(super) fn mobs_near(
+        &mut self,
+        mobs: &JoinList<Mob>,
+        cart: u32,
+        area: Aabb,
+        out: &mut Vec<u32>,
+    ) -> Option<bool> {
+        if !Self::usable() {
+            return None;
+        }
+        if !self
+            .mobs
+            .as_ref()
+            .is_some_and(|(stamp, ..)| *stamp == mobs.stamp())
+        {
+            self.mobs = Some((
+                mobs.stamp(),
+                SeenGrid::new(mobs.iter().map(Mob::bounds)),
+                mobs.iter().filter_map(|m| m.extra.mount).collect(),
+            ));
+        }
+        let (_, grid, mounted) = self.mobs.as_ref()?;
+        grid.candidates(area, out).then(|| mounted.contains(&cart))
+    }
+}
+/// Where the cart `id` is in `carts`: at `hint` (where it was a moment ago,
+/// the usual case while carts tick in order) or found by a scan. A world
+/// with hundreds of mineshaft chest carts asked this of every cart several
+/// times a tick.
+pub(super) fn cart_at(carts: &[Minecart], id: u32, hint: usize) -> Option<usize> {
+    if carts.get(hint).is_some_and(|c| c.id == id) {
+        return Some(hint);
+    }
+    carts.iter().position(|c| c.id == id)
+}

crates/horizon-client/src/game/minecarts/nbt.rs

@@ -0,0 +1,173 @@
+//! Saving and loading a minecart.
+use super::*;
+
+/// Saving and loading.
+impl Minecart {
+    pub fn to_nbt(
+        &self,
+        uuid: [i32; 4],
+        raw: Option<&horizon_world::nbt::Tag>,
+    ) -> horizon_world::nbt::Tag {
+        use horizon_world::nbt::{JavaString, Tag};
+        let mut tag = horizon_client::entity_nbt::vehicle_to_nbt(
+            self.kind.id(),
+            self.position,
+            self.velocity,
+            [self.yaw, self.pitch],
+            (self.on_ground, self.fall_distance),
+            uuid,
+            raw,
+        );
+        horizon_client::entity_nbt::write_saved_flags(&mut tag, self.on_ground, self.no_gravity);
+        if let Tag::Compound(map) = &mut tag {
+            // ContainerEntity.addChestVehicleSaveData belongs only to the
+            // container subclasses, never to a plain or specialized cart.
+            if self.kind.slots() == 0 {
+                map.remove(&JavaString::from("Items"));
+            }
+            if self.kind == CartKind::CommandBlock {
+                for key in ["LastOutput", "LastExecution"] {
+                    map.remove(&JavaString::from(key));
+                }
+            }
+            map.remove(&JavaString::from("DisplayOffset"));
+            map.remove(&JavaString::from("DisplayState"));
+            let mut put = |k: &str, v: Tag| {
+                map.insert(JavaString::from(k), v);
+            };
+            put("FlippedRotation", Tag::Byte(i8::from(self.flipped)));
+            // AbstractMinecart saves firstTick as HasTicked. A cart never burns:
+            // Entity.move sets -getFireImmuneTicks(), 0 for all but players.
+            put("HasTicked", Tag::Byte(i8::from(self.first_tick)));
+            put("Fire", Tag::Short(0));
+            // addAdditionalSaveData: the offset only off its default, the state only when set.
+            if let Some(offset) = self.custom_offset
+                && f64::from(offset) != default_display_offset(self.kind)
+            {
+                put("DisplayOffset", Tag::Int(offset));
+            }
+            if let Some(state) = &self.custom_display {
+                put("DisplayState", state.clone());
+            }
+            match self.kind {
+                CartKind::Chest | CartKind::Hopper => {
+                    put("Items", horizon_client::save::encode_items(&self.items));
+                    if self.kind == CartKind::Hopper {
+                        put("Enabled", Tag::Byte(i8::from(self.enabled)));
+                    }
+                }
+                CartKind::Furnace => {
+                    put("PushX", Tag::Double(self.push.x.to_bits()));
+                    put("PushZ", Tag::Double(self.push.z.to_bits()));
+                    put("Fuel", Tag::Short(self.fuel as i16));
+                }
+                CartKind::Tnt => put("fuse", Tag::Int(self.fuse)),
+                // BaseCommandBlock.save (its CustomName shares the entity's key).
+                CartKind::CommandBlock => {
+                    for (key, value) in self.command.save() {
+                        if !matches!(key, "CustomName" | "powered" | "conditionMet" | "auto") {
+                            put(key, value);
+                        }
+                    }
+                }
+                // BaseSpawner.save: the delays, ranges, SpawnData and SpawnPotentials.
+                CartKind::Spawner => {
+                    if let Some(spawner) = &self.spawner {
+                        for (key, value) in
+                            horizon_client::mobs::spawner::SpawnerExt::save(&**spawner)
+                        {
+                            put(key, value);
+                        }
+                    }
+                }
+                CartKind::Rideable => {}
+            }
+            // A loaded loot table goes back while the items are still its roll;
+            // otherwise the items replace it, as vanilla's unpackLootTable does.
+            if self.loot.as_ref().is_some_and(|l| l.restore(map)) {
+                if let Some(table) = horizon_client::save::text(map.get(&"LootTable".into()))
+                    .and_then(|id| horizon_client_core::identifier::normalize_id(&id))
+                {
+                    map.insert("LootTable".into(), Tag::String(table.as_str().into()));
+                }
+            } else {
+                map.remove(&JavaString::from("LootTable"));
+                map.remove(&JavaString::from("LootTableSeed"));
+            }
+        }
+        tag
+    }
+    pub fn from_nbt(tag: &horizon_world::nbt::Tag, id: u32, kind: CartKind) -> Option<Self> {
+        let (position, _, _) = horizon_client::entity_nbt::boat_from_nbt(tag)?;
+        let mut c = Self::new(id, kind, position);
+        c.load(tag)?;
+        Some(c)
+    }
+    /// `Entity.load` on this cart: the saved fields are read over the live
+    /// ones, the rest (riders, lerp, hurt state) stays; its kind never changes.
+    /// `None`, with nothing changed, when the compound has no position.
+    pub fn load(&mut self, tag: &horizon_world::nbt::Tag) -> Option<()> {
+        use horizon_world::nbt::Tag;
+        let (position, velocity, yaw) = horizon_client::entity_nbt::boat_from_nbt(tag)?;
+        let kind = self.kind;
+        let c = self;
+        c.position = position;
+        c.previous = position;
+        c.velocity = velocity;
+        c.yaw = yaw;
+        c.previous_yaw = yaw;
+        c.no_gravity = horizon_client::entity_nbt::flag(tag, "NoGravity");
+        c.on_ground = horizon_client::entity_nbt::flag(tag, "OnGround");
+        c.pitch = horizon_client::entity_nbt::rotation(tag)[1];
+        c.previous_pitch = c.pitch;
+        // ValueInput's numeric getters take any NumericTag: getIntOr is its
+        // intValue, getShortOr the low 16 bits of it, getBooleanOr
+        // `byteValue() != 0` (the low 8), getDoubleOr its doubleValue.
+        let int = |k: &str| {
+            tag.get(k)
+                .and_then(horizon_client_core::nbt_path::int_value)
+        };
+        let flag = |k: &str, default: bool| int(k).map_or(default, |v| v as i8 != 0);
+        let double = |k: &str| match tag.get(k) {
+            Some(Tag::Byte(v)) => f64::from(*v),
+            Some(Tag::Short(v)) => f64::from(*v),
+            Some(Tag::Int(v)) => f64::from(*v),
+            Some(Tag::Long(v)) => *v as f64,
+            Some(Tag::Float(v)) => f64::from(f32::from_bits(*v)),
+            Some(Tag::Double(v)) => f64::from_bits(*v),
+            _ => 0.0,
+        };
+        // Entity.load: OnGround and fall_distance, as saved.
+        (c.on_ground, c.fall_distance) = horizon_client::entity_nbt::ground_from_nbt(tag);
+        c.flipped = flag("FlippedRotation", false);
+        c.first_tick = flag("HasTicked", false);
+        if kind.slots() > 0 {
+            c.items = horizon_client::save::decode_items(tag.get("Items"), kind.slots());
+        }
+        c.enabled = flag("Enabled", true);
+        c.fuel = int("Fuel").map_or(0, |v| i32::from(v as i16));
+        // readAdditionalSaveData: the saved push has no y.
+        c.push = Vec3::new(double("PushX"), 0.0, double("PushZ"));
+        c.fuse = int("fuse").unwrap_or(-1);
+        // readAdditionalSaveData: DisplayState, DisplayOffset (default offset when absent).
+        c.custom_display = tag.get("DisplayState").cloned();
+        c.custom_offset = int("DisplayOffset");
+        if kind == CartKind::CommandBlock {
+            c.command = horizon_client::command_block::CommandBlock::load(tag);
+            // MinecartCommandBlock.readAdditionalSaveData sets the synched command.
+            // A changed value invokes onSyncedDataUpdated -> setCommand, resetting successes.
+            if c.synced_command != c.command.command {
+                c.synced_command.clone_from(&c.command.command);
+                c.command.set_command(&c.synced_command);
+            }
+            c.synced_output = c.command.last_output_string();
+        }
+        // MinecartSpawner.readAdditionalSaveData: BaseSpawner.load.
+        if kind == CartKind::Spawner {
+            c.spawner = Some(Box::new(horizon_client::mobs::spawner::SpawnerExt::load(
+                tag,
+            )));
+        }
+        Some(())
+    }
+}

crates/horizon-client/src/game/mob_looting.rs

@@ -157,7 +157,7 @@ impl Game<'_> {
     /// The numbers `Mob.compareArmor` and `compareWeapons` read off `stack`
     /// in `slot` for the mob `m`.
     pub(super) fn stack_facts(&self, m: &Mob, stack: &ItemStack, slot: Slot) -> Facts {
-        let (armor, toughness, attack) = self.attributes(m, &stack.item, slot);
+        let (armor, toughness, attack) = self.attributes(m, stack, slot);
         Facts {
             armor,
             armor_toughness: toughness,
@@ -173,22 +173,18 @@ impl Game<'_> {
 
     /// `Mob.getApproximateAttributeWith` for the item `id` in `slot`: each
     /// attribute starts from the mob's own value. (armour, toughness, damage)
-    fn attributes(&self, m: &Mob, id: &str, slot: Slot) -> (f64, f64, f64) {
-        let empty: &[(String, String, f64, String, String)] = &[];
-        let modifiers = self
-            .items()
-            .get(id)
-            .map_or(empty, |i| i.modifiers.as_slice());
+    fn attributes(&self, m: &Mob, stack: &ItemStack, slot: Slot) -> (f64, f64, f64) {
+        let modifiers = self.items().attribute_modifiers(stack);
         (
-            equip::attribute_with(modifiers, "minecraft:armor", f64::from(m.kind.armor), slot),
+            equip::attribute_with(&modifiers, "minecraft:armor", f64::from(m.kind.armor), slot),
             equip::attribute_with(
-                modifiers,
+                &modifiers,
                 "minecraft:armor_toughness",
                 f64::from(m.kind.armor_toughness),
                 slot,
             ),
             equip::attribute_with(
-                modifiers,
+                &modifiers,
                 "minecraft:attack_damage",
                 f64::from(m.attrs.attack_damage),
                 slot,

crates/horizon-client/src/game/native_client_services.rs

@@ -10,11 +10,7 @@ use horizon_client::{
     net::FRIEND,
 };
 use horizon_core::geometry::Vec3;
-#[cfg(feature = "friends")]
-use horizon_friends::invite::{self, Parsed};
 use std::borrow::Cow;
-#[cfg(feature = "friends")]
-use std::net::SocketAddr;
 use winit::keyboard::KeyCode;
 
 /// HUD and first-person hand visibility. Other hand-render restrictions still apply.
@@ -109,28 +105,11 @@ impl NativeWorldId {
     }
 }
 
-/// The part of a friend's invite anyone may see. A host's code is fresh each
-/// time it shares, so a friend's world is known for that sharing only. The
-/// relay is kept beside the addresses: two hosts on other networks can share
-/// a private address and the fixed direct port.
-#[cfg(feature = "friends")]
-fn invite_public_part(code: &str) -> String {
-    match invite::parse(code) {
-        Some(Parsed::Short(code)) => code.nameplate,
-        Some(Parsed::Long(invite)) => {
-            let relay = invite
-                .relay
-                .map(|r| format!("{}/{}", r.address, r.code.nameplate));
-            let endpoints = invite.endpoints.iter().map(SocketAddr::to_string);
-            endpoints.chain(relay).collect::<Vec<_>>().join(",")
-        }
-        None => String::new(),
-    }
-}
+/// The part of a friend's invite anyone may see (`horizon_hooks::tunnel::Resolver::public_part`).
+/// A host's code is fresh each time it shares, so a friend's world is known for that sharing only.
 /// Without Play with Friends no invite is read: a `friend:` world shows no part of it.
-#[cfg(not(feature = "friends"))]
-fn invite_public_part(_code: &str) -> String {
-    String::new()
+fn invite_public_part(code: &str) -> String {
+    horizon_hooks::engine::tunnel().map_or_else(String::new, |r| r.public_part(code))
 }
 
 /// A living entity known to the client, before interpolation. No authoritative writes.
@@ -558,8 +537,6 @@ impl Game<'_> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    #[cfg(feature = "friends")]
-    use horizon_friends::code::Code;
 
     #[test]
     fn a_world_is_its_save_in_single_player_and_its_address_on_a_server() {
@@ -573,52 +550,6 @@ mod tests {
         );
     }
 
-    #[test]
-    #[cfg(feature = "friends")]
-    fn friends_worlds_are_told_apart_by_their_hosts_never_by_their_secrets() {
-        const PORT: u16 = 50000;
-        const RELAY: &str = "relay.example.com:443";
-        // A short code: its nameplate, then its secret.
-        let short = |nameplate: &str, secret: &str| Code {
-            nameplate: nameplate.into(),
-            secret: secret.into(),
-        };
-        let invite = |secret: u8, host: &str, relay: Option<Code>| {
-            let code = invite::Invite {
-                secret: [secret; invite::SECRET],
-                port: PORT,
-                endpoints: vec![format!("{host}:{PORT}").parse().unwrap()],
-                relay: relay.map(|code| invite::RelayRef {
-                    address: RELAY.into(),
-                    code,
-                }),
-            }
-            .encode();
-            NativeWorldId::of(None, &format!("{FRIEND}{code}"))
-        };
-        assert_ne!(
-            invite(1, "192.168.1.5", None),
-            invite(1, "192.168.1.6", None),
-            "two friends"
-        );
-        assert_ne!(
-            invite(1, "192.168.1.5", Some(short("ABCD", "WXYZ"))),
-            invite(1, "192.168.1.5", Some(short("EFGH", "WXYZ"))),
-            "two friends on other networks behind the same private address"
-        );
-        assert_eq!(
-            invite(1, "192.168.1.5", Some(short("ABCD", "WXYZ"))),
-            invite(2, "192.168.1.5", Some(short("ABCD", "QRST"))),
-            "the invite's and the relay code's secrets take no part"
-        );
-        let typed = |code: Code| NativeWorldId::of(None, &format!("{FRIEND}{code}"));
-        assert_eq!(typed(short("ABCD", "WXYZ")), typed(short("ABCD", "QRST")));
-        assert_eq!(
-            typed(short("ABCD", "WXYZ")),
-            NativeWorldId::Server(format!("{FRIEND}ABCD"))
-        );
-    }
-
     #[test]
     fn a_hud_tells_chat_and_death_from_other_screens() {
         assert_eq!(

crates/horizon-client/src/game/nautili.rs

@@ -102,8 +102,16 @@ impl Game<'_> {
             if food && m.health < m.attrs.max_health {
                 // feed(player, hand, stack, 2, 1).
                 let sound = nautilus::eat_sound(m);
+                // TamableAnimal.feed: heals 2 x the food's nutrition, 1 for an
+                // item with no food component.
+                let nutrition = self
+                    .res
+                    .items()
+                    .get(item)
+                    .and_then(|i| i.food.as_ref())
+                    .map(|f| f.0 as i32);
                 let m = &mut self.mobs[index];
-                m.heal(2.0);
+                m.heal(nautilus::feed_heal(nutrition));
                 self.use_nautilus_food(item);
                 self.nautilus_sound(index, sound);
                 return true;

crates/horizon-client/src/game/piston_push.rs

@@ -226,6 +226,25 @@ impl Game<'_> {
         });
     }
 
+    /// `Entity.collide`'s `getEntityCollisions` for a body a piston or a
+    /// shulker lid pushes: the entities it can collide with
+    /// (`canCollideWith`, which for every mover but a vehicle is
+    /// `canBeCollidedWith`): a boat, a living shulker, a happy ghast held
+    /// still. A pushed boat or minecart collides by `canVehicleCollide`
+    /// instead, which this doesn't cover, and the player moves itself.
+    fn pushed_entity_colliders(&self, target: Target) -> Vec<Aabb> {
+        match target {
+            Target::Entity(EntityHandle::Boat(_) | EntityHandle::Cart(_)) => Vec::new(),
+            Target::Entity(handle) => {
+                let own = with_entity!(self, handle, entity => Entity::bounds(entity));
+                let mut boxes = self.item_entity_collisions();
+                boxes.retain(|b| *b != own);
+                boxes
+            }
+            _ => Vec::new(),
+        }
+    }
+
     /// The collision view of the moving piston at `pos` takes the progress
     /// its tick gave it. One no longer moving keeps its entry until
     /// `sync_moving_pistons`.
@@ -284,6 +303,7 @@ impl Game<'_> {
                 self.shulker_push_player(movement);
                 return;
             }
+            let entities = self.pushed_entity_colliders(target);
             let Ok(moved) = pushed_movement(
                 SceneCollisions {
                     world: &self.world,
@@ -298,6 +318,7 @@ impl Game<'_> {
                 body.step_height,
                 body.on_ground,
                 None,
+                &entities,
             ) else {
                 return;
             };
@@ -665,6 +686,7 @@ impl Game<'_> {
                 self.projectile_piston_block_effects(i, at);
             }
             self.piston_block_triggers(before, before);
+            self.release_after_block_move(target);
             return;
         }
         // `Entity.move`: a projectile a cobweb or powder snow holds stops dead
@@ -695,6 +717,7 @@ impl Game<'_> {
             }
             _ => None,
         };
+        let entities = self.pushed_entity_colliders(target);
         let resolved = with_piston_noclip(piston_direction, || {
             pushed_movement(
                 SceneCollisions {
@@ -709,6 +732,7 @@ impl Game<'_> {
                 step_height,
                 on_ground,
                 tnt.as_ref().map(|t| t.3),
+                &entities,
             )
             .unwrap_or(Vec3::ZERO)
         });
@@ -747,6 +771,9 @@ impl Game<'_> {
             || limited.length_squared() - resolved.length_squared() < 1.0e-7;
         if moved {
             self.apply_push(target, resolved);
+        } else {
+            // A move the collisions cut to nothing still ends in the check.
+            self.release_after_block_move(target);
         }
         if let Some((i, from, ..)) = tnt {
             self.finish_tnt_piston_move(i, from, resolved);
@@ -864,26 +891,37 @@ impl Game<'_> {
             }
             Target::Entity(handle) => {
                 with_entity_mut!(self, handle, entity => entity.move_by_piston(movement));
-                let Some(bounds) =
-                    with_entity!(self, handle, entity => entity.piston_release_bounds())
-                else {
-                    return;
-                };
-                let no_block_collision = {
-                    let mut scene = SceneCollisions {
-                        world: &self.world,
-                        binding: self.collision,
-                        subject: None,
-                    };
-                    no_collision_empty(&mut scene, bounds)
-                };
-                with_entity_mut!(self, handle, entity => {
-                    entity.release_after_piston(no_block_collision)
-                });
+                self.release_after_block_move(target);
             }
         }
     }
 
+    /// `AbstractArrow.move` with a mover other than the arrow itself (a
+    /// piston, a shulker lid): after `Entity.move`, whether or not it went
+    /// anywhere, a stuck arrow or trident with nothing to collide with within
+    /// 0.06 starts falling (`shouldFall`, `startFalling`). Its own tick only
+    /// checks once the block at its position changes, a tick later.
+    fn release_after_block_move(&mut self, target: Target) {
+        let Target::Entity(handle) = target else {
+            return;
+        };
+        let Some(bounds) = with_entity!(self, handle, entity => entity.piston_release_bounds())
+        else {
+            return;
+        };
+        let no_block_collision = {
+            let mut scene = SceneCollisions {
+                world: &self.world,
+                binding: self.collision,
+                subject: None,
+            };
+            no_collision_empty(&mut scene, bounds)
+        };
+        with_entity_mut!(self, handle, entity => {
+            entity.release_after_piston(no_block_collision)
+        });
+    }
+
     /// `causeBounce`: a slime block sets the velocity along the movement axis.
     fn bounce(&mut self, target: Target, movement: Direction) {
         match target {
@@ -939,19 +977,16 @@ fn pushed_movement<W>(
     step_height: f32,
     on_ground: bool,
     context: Option<CollisionContext<'_>>,
+    entities: &[Aabb],
 ) -> horizon_client::Result<Vec3>
 where
     W: BlockCollisionWorld<Error = std::io::Error> + EntityMovementWorld<Error = std::io::Error>,
 {
     // Without the entity's own context, the one `resolve` reads at its feet.
     let context = context.unwrap_or_else(|| CollisionContext::position(before.min_position().y));
-    EntityCollisions::with_border(blocks, border, at).resolve_with_context(
-        before,
-        movement,
-        step_height,
-        on_ground,
-        context,
-    )
+    let mut collisions = EntityCollisions::with_border(blocks, border, at);
+    collisions.entities = entities;
+    collisions.resolve_with_context(before, movement, step_height, on_ground, context)
 }
 
 #[cfg(test)]
@@ -980,6 +1015,7 @@ mod tests {
             0.0,
             false,
             None,
+            &[],
         )
         .expect("the push resolves");
         // The wall stops the body 0.4 blocks short of the whole push.
@@ -1003,6 +1039,7 @@ mod tests {
             0.0,
             false,
             None,
+            &[],
         )
         .expect("the push resolves");
         assert!(
@@ -1521,6 +1558,48 @@ mod h255_mob_piston_ground_tests {
             &mut std::collections::HashMap::new(),
         );
     }
+    /// `AbstractArrow.move` after a push the collisions cut to nothing: a stuck
+    /// arrow with nothing within 0.06 of it starts falling all the same.
+    #[test]
+    #[ignore = "needs prepared resources in HORIZON_TEST_RESOURCES"]
+    fn a_stuck_arrow_whose_push_a_wall_stops_falls_when_nothing_holds_it() {
+        with_game(|game| {
+            assert!(game.run_command("setblock 6 202 4 minecraft:stone"));
+            game.creatures.projectiles.clear();
+            assert!(game.run_command("summon minecraft:arrow 5.75 202.5 4.5 {NoGravity:0b}"));
+            let i = game
+                .creatures
+                .projectiles
+                .iter()
+                .position(|p| p.arrow.is_some())
+                .expect("the arrow");
+            {
+                let p = &mut game.creatures.projectiles[i];
+                p.velocity = Vec3::ZERO;
+                p.stuck = true;
+                p.arrow.as_mut().unwrap().in_ground = true;
+            }
+            let p = &game.creatures.projectiles[i];
+            let (bounds, at) = (p.bounds(), [p.position.x, p.position.z]);
+            let before = p.position;
+            game.move_pushed(
+                Target::Entity(EntityHandle::Projectile(i)),
+                bounds,
+                at,
+                0.0,
+                false,
+                Vec3::new(0.3, 0.0, 0.0),
+                Direction::East,
+                &mut std::collections::HashMap::new(),
+            );
+            let p = &game.creatures.projectiles[i];
+            assert_eq!(p.position, before, "the stone stops the push");
+            assert!(
+                !p.arrow.as_ref().unwrap().in_ground,
+                "nothing holds it, so it falls"
+            );
+        });
+    }
     #[test]
     #[ignore = "needs prepared resources in HORIZON_TEST_RESOURCES"]
     fn h255_added_no_request_and_exhausted_budget_keep_state() {

crates/horizon-client/src/game/play_ping_tests.rs

@@ -0,0 +1,334 @@
+//! Registered play-Ping regression with the production sender-flush completion boundary.
+use crate::game::{Game, lan::LanSettings};
+use horizon_client::lan::{Joined, NetConfig, Out, PlayerSender, guest::Guest, hub::HubConfig};
+use horizon_protocol::{
+    buf::Reader,
+    packets::{
+        configuration::ClientInformation,
+        play::{Clientbound as C, Serverbound as S},
+        status,
+    },
+};
+use std::sync::{Arc, atomic::AtomicI32, mpsc};
+
+fn decode(packet: S) -> (S, usize) {
+    let bytes = packet.encode();
+    let mut reader = Reader::new(&bytes);
+    let id = reader.varint().unwrap();
+    (S::decode(id, reader.rest()).unwrap(), bytes.len())
+}
+
+fn output(rx: &mpsc::Receiver<Out>) -> Vec<C> {
+    rx.try_iter()
+        .flat_map(|out| match out {
+            Out::Packet(body) => vec![body],
+            Out::Packets(bodies) => bodies,
+            Out::Disconnect(reason) => panic!("unexpected disconnect: {reason:?}"),
+        })
+        .map(|body| {
+            println!("actual outbound play body={body:02x?}");
+            let mut reader = Reader::new(&body);
+            let id = reader.varint().unwrap();
+            C::decode(id, reader.rest()).unwrap()
+        })
+        .collect()
+}
+
+fn pass(game: &mut Game<'_>, conn: u32, packet: S) {
+    let (packet, bytes) = decode(packet);
+    if let S::PingRequest(p) = &packet {
+        println!(
+            "actual decoded play PingRequest conn={conn} value={} bits={:016x}",
+            p.time, p.time as u64
+        );
+    }
+    let hub = &game.lan.as_ref().unwrap().hub;
+    assert_eq!(hub.guests.len(), 2);
+    assert_ne!(hub.guests[0].uuid, hub.guests[1].uuid);
+    assert_ne!(hub.guests[0].conn, hub.guests[1].conn);
+    let registered = hub.guest(conn).expect("origin connection registered");
+    assert_eq!(registered.uuid, u128::from(conn));
+    assert!(!registered.fake && !registered.sender.is_fake());
+    assert!(registered.left_reason.is_empty());
+    assert_eq!(registered.dimension, "minecraft:overworld");
+    let guest = game.lan.as_mut().unwrap().hub.guest_mut(conn).unwrap();
+    guest.inbox.push_back((packet, bytes));
+    guest.inbox_bytes += bytes;
+    // Already registered connections: this is a second level pass, without polling sockets.
+    game.level_pass.first = false;
+    game.level_pass.packets_drained = false;
+    let clock_before = game.world.game_time;
+    game.tick_lan_packets();
+    // tick_lan_packets has ended its Holding scope; production flushes these senders later.
+    horizon_client::lan::flush_all(
+        game.lan
+            .as_ref()
+            .unwrap()
+            .hub
+            .guests
+            .iter()
+            .map(|g| &g.sender),
+    );
+    assert_eq!(
+        game.world.game_time, clock_before,
+        "sender completion adds no world tick"
+    );
+    println!("actual sender completion conn={conn} world_clock={clock_before}");
+    assert!(
+        game.level_pass.packets_drained,
+        "real Game packet phase completed"
+    );
+    assert!(
+        game.lan
+            .as_ref()
+            .unwrap()
+            .hub
+            .guest(conn)
+            .unwrap()
+            .inbox
+            .is_empty(),
+        "decoded request was drained by the actual Hub"
+    );
+}
+
+fn fixture() -> (Game<'static>, [mpsc::Receiver<Out>; 2]) {
+    let mut game = crate::game::native_machines::tests::server_game();
+    game.build_registries();
+    game.lan_host(
+        LanSettings {
+            port: 0,
+            guest_commands: false,
+            force_game_mode: false,
+        },
+        NetConfig {
+            announce: false,
+            ..NetConfig::loopback(0, "play-ping-test".into(), 2)
+        },
+        HubConfig {
+            default_game_mode: 0,
+            guest_commands: false,
+            force_game_mode: false,
+            hardcore: false,
+            view_distance: 2,
+            simulation_distance: 2,
+            dimension: "minecraft:overworld".into(),
+            allow_flight: false,
+            seed: 0,
+            max_players: 2,
+            integrated: false,
+            levels: Default::default(),
+        },
+    )
+    .unwrap();
+    let receivers = [1, 2].map(|conn| {
+        let (tx, rx) = mpsc::channel();
+        let mut guest = Guest::new(
+            Joined {
+                conn,
+                uuid: u128::from(conn),
+                name: format!("PingGuest{conn}"),
+                properties: Vec::new(),
+                info: ClientInformation::new(2),
+                brand: "test".into(),
+                sender: PlayerSender::new(tx, Arc::default()),
+                latency: Arc::new(AtomicI32::new(0)),
+                address: "127.0.0.1:25565".parse().unwrap(),
+                expected: false,
+                configured: Default::default(),
+            },
+            conn as i32,
+            [0.5, 80.0, 0.5],
+            2,
+        );
+        guest.placed = true;
+        guest.loaded = true;
+        guest.loading = false;
+        guest.load_timeout = 0;
+        guest.last_action_tick = 7;
+        game.lan.as_mut().unwrap().hub.guests.push(guest);
+        rx
+    });
+    game.lan.as_mut().unwrap().hub.ticks = 123;
+    (game, receivers)
+}
+
+#[test]
+#[ignore = "needs prepared resources and isolated scratch homes/cwd"]
+fn registered_play_ping_echoes_exact_long_to_only_its_connection() {
+    let (mut game, receivers) = fixture();
+    for (turn, time) in [
+        1,
+        0,
+        -1,
+        i64::MIN,
+        i64::MAX,
+        0x0123_4567_89ab_cdef,
+        0xfedc_ba98_7654_3210_u64 as i64,
+    ]
+    .into_iter()
+    .enumerate()
+    {
+        let index = turn % 2;
+        let conn = index as u32 + 1;
+        pass(&mut game, conn, S::PingRequest(status::Ping { time }));
+        let packets = output(&receivers[index]);
+        let echoed: Vec<_> = packets
+            .iter()
+            .filter_map(|p| match p {
+                C::PongResponse(p) => Some(p.time),
+                _ => None,
+            })
+            .collect();
+        assert_eq!(
+            echoed,
+            vec![time],
+            "missing or incorrect registered Game play-Ping reply"
+        );
+        assert_eq!(packets.len(), 1, "one request produces exactly one reply");
+        assert_eq!(
+            game.lan
+                .as_ref()
+                .unwrap()
+                .hub
+                .guest(conn)
+                .unwrap()
+                .last_action_tick,
+            7,
+            "transport ping does not count as a player action"
+        );
+        assert!(
+            output(&receivers[1 - index]).is_empty(),
+            "no reply to the other connection"
+        );
+    }
+}
+
+#[test]
+#[ignore = "needs prepared resources and isolated scratch homes/cwd"]
+fn dead_guest_play_ping_is_transport_not_an_action() {
+    let (mut game, receivers) = fixture();
+    game.lan.as_mut().unwrap().hub.guest_mut(1).unwrap().dead = true;
+    pass(
+        &mut game,
+        1,
+        S::PingRequest(status::Ping { time: i64::MIN }),
+    );
+    let packets = output(&receivers[0]);
+    assert!(matches!(packets.as_slice(), [C::PongResponse(p)] if p.time == i64::MIN));
+    assert!(output(&receivers[1]).is_empty());
+    assert_eq!(
+        game.lan
+            .as_ref()
+            .unwrap()
+            .hub
+            .guest(1)
+            .unwrap()
+            .last_action_tick,
+        7
+    );
+}
+
+#[test]
+#[ignore = "needs prepared resources and isolated scratch homes/cwd"]
+fn server_ping_client_pong_keeps_the_existing_prediction_route() {
+    let (mut game, receivers) = fixture();
+    let hub = &mut game.lan.as_mut().unwrap().hub;
+    let mut config = horizon_anticheat::Config::default();
+    config.log.clear();
+    config.strikes.clear();
+    config.prediction.enabled = true;
+    hub.set_anticheat(config);
+    hub.ticks = 123;
+    let holding = horizon_client::lan::Holding::start();
+    hub.anticheat_ping();
+    drop(holding);
+    // Ending Holding is not delivery: independently admit the existing flush boundary first.
+    for receiver in &receivers {
+        assert!(
+            output(receiver).is_empty(),
+            "actual server Ping is unavailable before flush"
+        );
+    }
+    println!("actual reverse Ping unavailable after Holding drop, before flush");
+    horizon_client::lan::flush_all(hub.guests.iter().map(|g| &g.sender));
+    for receiver in &receivers {
+        assert!(matches!(output(receiver).as_slice(), [C::Ping(p)] if p.id == 123));
+    }
+    pass(
+        &mut game,
+        1,
+        S::Pong(horizon_protocol::packets::configuration::Ping { id: 123 }),
+    );
+    let record = game
+        .lan
+        .as_mut()
+        .unwrap()
+        .hub
+        .guest_mut(1)
+        .unwrap()
+        .anticheat
+        .record
+        .as_deref_mut()
+        .expect("existing client Pong updates prediction");
+    assert_eq!(record.tick_end(0, false).seen, Some(123));
+    for receiver in &receivers {
+        assert!(output(receiver).is_empty());
+    }
+}
+
+#[test]
+#[ignore = "needs prepared resources and isolated scratch homes/cwd"]
+fn held_guest_play_ping_survives_the_acknowledgement_filter() {
+    let (mut game, receivers) = fixture();
+    let guest = game.lan.as_mut().unwrap().hub.guest_mut(1).unwrap();
+    guest.placed = false;
+    guest.held = true;
+    pass(&mut game, 1, S::PingRequest(status::Ping { time: -1 }));
+    assert!(matches!(output(&receivers[0]).as_slice(), [C::PongResponse(p)] if p.time == -1));
+    assert!(output(&receivers[1]).is_empty());
+    assert_eq!(
+        game.lan
+            .as_ref()
+            .unwrap()
+            .hub
+            .guest(1)
+            .unwrap()
+            .last_action_tick,
+        7
+    );
+}
+
+#[test]
+#[ignore = "needs prepared resources and isolated scratch homes/cwd"]
+fn handover_guest_play_ping_survives_the_acknowledgement_filter() {
+    let (mut game, receivers) = fixture();
+    let handover = horizon_client::lan::arrivals::Handover {
+        id: 0x1234,
+        since: 123,
+        record: serde_json::json!({"fixture": "handover-state-sentinel"}),
+    };
+    game.lan
+        .as_mut()
+        .unwrap()
+        .hub
+        .guest_mut(1)
+        .unwrap()
+        .handover = Some(handover.clone());
+    pass(
+        &mut game,
+        1,
+        S::PingRequest(status::Ping {
+            time: 0xfedc_ba98_7654_3210_u64 as i64,
+        }),
+    );
+    let packets = output(&receivers[0]);
+    assert!(
+        matches!(packets.as_slice(), [C::PongResponse(p)]
+        if p.time == 0xfedc_ba98_7654_3210_u64 as i64),
+        "missing matching handover play-Ping reply"
+    );
+    assert!(output(&receivers[1]).is_empty());
+    let guest = game.lan.as_ref().unwrap().hub.guest(1).unwrap();
+    assert_eq!(guest.last_action_tick, 7);
+    assert_eq!(guest.handover.as_ref(), Some(&handover));
+}

crates/horizon-client/src/game/remote.rs

@@ -11496,8 +11496,7 @@ impl Remote {
     pub(super) fn listed_player_count(&self) -> usize {
         self.listed.len()
     }
-    /// Players in the server's player list, this one included (for Discord).
-    #[cfg(feature = "discord")]
+    /// Players in the server's player list, this one included (for the activity hooks).
     pub(super) fn player_count(&self) -> usize {
         self.players.len()
     }

crates/horizon-client/src/game/render_tick.rs

@@ -726,6 +726,37 @@ impl Game<'_> {
             }
         }
     }
+
+    /// The ticks the frame shows (animated textures, the HUD, a shader pack's clock): the
+    /// client's, or under `HORIZON_STILL` (`FixedStep::still`) the world's game time, which
+    /// moves only while the world runs.
+    pub(super) fn visual_ticks(&self) -> u64 {
+        if self.clock.still() {
+            self.world.game_time.max(0) as u64
+        } else {
+            self.ticks
+        }
+    }
+
+    /// The clock of the animated textures: `Minecraft.runTick` ticks the `TextureManager`
+    /// only while the level runs normally. Under `HORIZON_STILL` it is the world's ticks.
+    pub(super) fn texture_clock(&self) -> u64 {
+        if self.clock.still() {
+            self.visual_ticks()
+        } else {
+            self.texture_ticks
+        }
+    }
+
+    /// `Util.getMillis` for what the frame shows (the world border's scroll, the hearts' blink,
+    /// the glint's under the switch): under `HORIZON_STILL`, the world's ticks in milliseconds.
+    pub(super) fn visual_millis(&self) -> i64 {
+        if self.clock.still() {
+            self.visual_ticks() as i64 * 50
+        } else {
+            self.started.elapsed().as_millis() as i64
+        }
+    }
 }
 impl Game<'_> {
     /// What the packs' Polytone animation modes read this tick (wiki "Variant Textures"): the

crates/horizon-client/src/game/resource_loader.rs

@@ -306,8 +306,6 @@ pub(super) fn run_loading(
         App::Loading(loading) => leave_fullscreen_after(&result, &mut loading.settings),
     }
     result?;
-    #[cfg(feature = "discord")]
-    horizon_client::discord_presence::stop();
     match app {
         App::Ready(mut split) => {
             write_report(&split.host)?;

crates/horizon-client/src/game/screens.rs

@@ -141,11 +141,12 @@ fn pause_buttons(
     remote: bool,
     links: bool,
     additions: bool,
-    split: bool,
+    rows: &[(&'static str, u8)],
 ) -> Vec<(f32, f32, f32, &'static str, u8, bool)> {
     let row3 = links || additions;
-    let (x0, y0) = pause_grid(w, h, u8::from(row3) + u8::from(split));
-    let down = 24.0 * f32::from(u8::from(row3) + u8::from(split));
+    let extra = u8::from(row3) + rows.len() as u8;
+    let (x0, y0) = pause_grid(w, h, extra);
+    let down = 24.0 * f32::from(extra);
     let mut v = vec![
         (x0 + 4.0, y0 + 50.0, 204.0, "menu.returnToGame", 0, true),
         (x0 + 4.0, y0 + 74.0, 98.0, "gui.advancements", 4, true),
@@ -159,9 +160,9 @@ fn pause_buttons(
         // CommonDialogData.computeExternalTitle of Dialogs.SERVER_LINKS.
         v.push((x0 + 4.0, y0 + 122.0, 204.0, "menu.server_links", 11, true));
     }
-    if split {
-        let y = y0 + 122.0 + if row3 { 24.0 } else { 0.0 };
-        v.push((x0 + 4.0, y, 204.0, SPLIT_SETTINGS, 30, true));
+    for (k, &(key, id)) in rows.iter().enumerate() {
+        let y = y0 + 122.0 + 24.0 * (f32::from(u8::from(row3)) + k as f32);
+        v.push((x0 + 4.0, y, 204.0, key, id, true));
     }
     v.extend([
         (x0 + 4.0, y0 + 122.0 + down, 98.0, "menu.options", 1, true),
@@ -228,14 +229,17 @@ fn pause_icon_focus_ids(friends: bool) -> Vec<u8> {
         .collect()
 }
 const SPLIT_SETTINGS: &str = "horizon.pages.split_settings";
+/// The pause menu's first id for the pages crates registered there: id `ADDED_PAGES + i` opens
+/// registered page `i`.
+const ADDED_PAGES: u8 = 40;
 fn pause_icons(
     w: f32,
     h: f32,
     links: bool,
     additions: bool,
-    split: bool,
+    rows: &[(&'static str, u8)],
 ) -> [(f32, f32, &'static str); 4] {
-    let (x0, y0) = pause_grid(w, h, u8::from(links || additions) + u8::from(split));
+    let (x0, y0) = pause_grid(w, h, u8::from(links || additions) + rows.len() as u8);
     let (x0, y) = (x0 + 60.0, y0 + 98.0);
     [
         (x0, y, "gui/sprites/pause_menu/bug"),
@@ -307,7 +311,7 @@ impl Game<'_> {
         self.remote.is_some() && self.integrated.is_none()
     }
     pub(super) fn draw_pause_menu(&mut self, batch: &mut HudBatch) {
-        let friends = self.friends_view().shown;
+        let friends = self.friends_shown();
         let atlas = &self.gui.atlas;
         let (w, h) = (batch.width, batch.height);
         ui::menu_background(batch, atlas, 0.0, 0.0, w, h, true);
@@ -331,7 +335,7 @@ impl Game<'_> {
             self.external_server(),
             links,
             additions.is_some(),
-            self.options.split_guest || self.split_hud.menu,
+            &self.pause_rows(),
         ) {
             let is_focused = self.pause_focus == Some(id);
             let hover = active && (ui::hovered(self.cursor, x, y, bw, 20.0) || is_focused);
@@ -358,15 +362,9 @@ impl Game<'_> {
                 tooltip = Some(Text::translate("menu.custom_options.tooltip", &[]));
             }
         }
-        for (i, (x, y, sprite)) in pause_icons(
-            w,
-            h,
-            links,
-            additions.is_some(),
-            self.options.split_guest || self.split_hud.menu,
-        )
-        .into_iter()
-        .enumerate()
+        for (i, (x, y, sprite)) in pause_icons(w, h, links, additions.is_some(), &self.pause_rows())
+            .into_iter()
+            .enumerate()
         {
             let active = icon_active(i, friends);
             let is_focused = (self.pause_focus == Some(10) && i == FRIENDS_ICON)
@@ -375,11 +373,7 @@ impl Game<'_> {
             // The icon has no label: name it for controller focus and the
             // control socket's widget tree.
             if i == FRIENDS_ICON {
-                horizon_client::widgets::record(
-                    horizon_client::friends_screen::TITLE,
-                    [x, y, 20.0, 20.0],
-                    active,
-                );
+                horizon_client::widgets::record(super::friends::TITLE, [x, y, 20.0, 20.0], active);
             }
             ui::button(
                 batch,
@@ -416,7 +410,7 @@ impl Game<'_> {
             batch.sprite_scaled(atlas, sprite, x + 3.0, y + 3.0, 15.0, 15.0, u32::MAX);
             if hover {
                 tooltip = Some(if i == FRIENDS_ICON {
-                    Text::literal(horizon_client::friends_screen::title())
+                    Text::literal(super::friends::title())
                 } else {
                     Text::translate(ICON_LABELS[i], &[])
                 });
@@ -456,6 +450,10 @@ impl Game<'_> {
             // PauseScreen: `new SocialInteractionsScreen(this)`.
             15 => self.open_social(true),
             30 => self.open_split_settings(),
+            id @ ADDED_PAGES.. => {
+                let page = usize::from(id - ADDED_PAGES);
+                self.open_options_at(false, horizon_client::options_ui::Page::Added(page));
+            }
             // addCustomDialogButtons: DialogConnectionAccess.openDialog of the
             // additions dialog, from the pause menu.
             14 => {
@@ -471,6 +469,23 @@ impl Game<'_> {
         }
         Ok(())
     }
+    /// The pause menu's full-width rows above Options: Splitscreen's settings, then the pages
+    /// crates registered for the pause menu (`horizon_hooks::pages`), by their title.
+    fn pause_rows(&self) -> Vec<(&'static str, u8)> {
+        let split = self.options.split_guest || self.split_hud.menu;
+        let pages = horizon_hooks::pages::engine::all().iter().enumerate();
+        let added = pages
+            .filter(|(i, page)| {
+                page.place() == horizon_hooks::pages::Place::Pause
+                    && *i < usize::from(u8::MAX - ADDED_PAGES)
+            })
+            .map(|(i, page)| (page.title(), ADDED_PAGES + i as u8));
+        split
+            .then_some((SPLIT_SETTINGS, 30))
+            .into_iter()
+            .chain(added)
+            .collect()
+    }
     pub(super) fn pause_click(&mut self) -> Result<()> {
         let (w, h) = {
             let size = self
@@ -482,13 +497,7 @@ impl Game<'_> {
         };
         let links = !self.server_links().is_empty();
         let additions = self.pause_screen_additions();
-        let icons = pause_icons(
-            w,
-            h,
-            links,
-            additions.is_some(),
-            self.options.split_guest || self.split_hud.menu,
-        );
+        let icons = pause_icons(w, h, links, additions.is_some(), &self.pause_rows());
         let friends = icons[FRIENDS_ICON];
         let hit = pause_buttons(
             w,
@@ -496,7 +505,7 @@ impl Game<'_> {
             self.external_server(),
             links,
             additions.is_some(),
-            self.options.split_guest || self.split_hud.menu,
+            &self.pause_rows(),
         )
         .into_iter()
         .find(|b| b.5 && ui::hovered(self.cursor, b.0, b.1, b.2, 20.0))
@@ -509,9 +518,8 @@ impl Game<'_> {
                 .map(|i| 12 + i as u8)
         })
         .or_else(|| {
-            (self.friends_view().shown
-                && ui::hovered(self.cursor, friends.0, friends.1, 20.0, 20.0))
-            .then_some(10)
+            (self.friends_shown() && ui::hovered(self.cursor, friends.0, friends.1, 20.0, 20.0))
+                .then_some(10)
         });
         if let Some(id) = hit {
             self.pause_focus = Some(id);
@@ -536,10 +544,10 @@ impl Game<'_> {
             self.external_server(),
             links,
             self.pause_screen_additions().is_some(),
-            self.options.split_guest || self.split_hud.menu,
+            &self.pause_rows(),
         );
         let mut active_ids: Vec<u8> = buttons.into_iter().filter(|b| b.5).map(|b| b.4).collect();
-        let friends = self.friends_view().shown;
+        let friends = self.friends_shown();
         active_ids.extend(pause_icon_focus_ids(friends));
         if active_ids.is_empty() {
             return Ok(());
@@ -584,20 +592,20 @@ impl Game<'_> {
                     self.external_server(),
                     links,
                     self.pause_screen_additions().is_some(),
-                    self.options.split_guest || self.split_hud.menu,
+                    &self.pause_rows(),
                 );
                 let mut rects: Vec<(u8, f32, f32, f32)> = buttons
                     .into_iter()
                     .filter(|b| b.5)
                     .map(|b| (b.4, b.0, b.1, b.2))
                     .collect();
-                let friends = self.friends_view().shown;
+                let friends = self.friends_shown();
                 for (i, (x, y, _)) in pause_icons(
                     w,
                     h,
                     links,
                     self.pause_screen_additions().is_some(),
-                    self.options.split_guest || self.split_hud.menu,
+                    &self.pause_rows(),
                 )
                 .into_iter()
                 .enumerate()
@@ -915,7 +923,10 @@ impl Game<'_> {
 
 #[cfg(test)]
 mod tests {
-    use super::{Screen, death_buttons, pause_buttons, pause_icon_focus_ids, pause_icons};
+    use super::{
+        ADDED_PAGES, SPLIT_SETTINGS, Screen, death_buttons, pause_buttons, pause_icon_focus_ids,
+        pause_icons,
+    };
 
     #[test]
     fn death_buttons_sit_on_whole_gui_pixels() {
@@ -998,7 +1009,7 @@ mod tests {
     #[test]
     fn pause_menu_uses_disconnect_for_servers_and_keeps_world_options() {
         for (remote, label) in [(false, "menu.returnToMenu"), (true, "menu.disconnect")] {
-            let buttons = pause_buttons(427.0, 240.0, remote, false, false, false);
+            let buttons = pause_buttons(427.0, 240.0, remote, false, false, &[]);
             let quit = buttons.iter().find(|b| b.4 == 2).unwrap();
             assert_eq!(quit.3, label);
             assert!(quit.5);
@@ -1023,14 +1034,14 @@ mod tests {
 
     #[test]
     fn server_links_adds_a_full_width_row_above_options() {
-        let with = pause_buttons(427.0, 240.0, true, true, false, false);
-        let without = pause_buttons(427.0, 240.0, true, false, false, false);
+        let with = pause_buttons(427.0, 240.0, true, true, false, &[]);
+        let without = pause_buttons(427.0, 240.0, true, false, false, &[]);
         let links = with.iter().find(|b| b.4 == 11).unwrap();
         assert_eq!(links.2, 204.0);
         assert_eq!(links.3, "menu.server_links");
         assert!(links.5);
         // The icon row sits above it; Options and Disconnect move down 24.
-        let icons = pause_icons(427.0, 240.0, true, false, false);
+        let icons = pause_icons(427.0, 240.0, true, false, &[]);
         let y0_icons = ((240.0f32 - 190.0) * 0.25).floor() + 98.0;
         assert_eq!(icons[0].1, y0_icons);
         assert!(links.1 > icons[0].1);
@@ -1046,8 +1057,8 @@ mod tests {
     fn pause_screen_additions_takes_the_server_links_row() {
         // getCustomAdditions: one additions button in row 3, never next to the
         // links button, so the grid keeps one extra row either way.
-        let with = pause_buttons(427.0, 240.0, true, true, true, false);
-        let links = pause_buttons(427.0, 240.0, true, true, false, false);
+        let with = pause_buttons(427.0, 240.0, true, true, true, &[]);
+        let links = pause_buttons(427.0, 240.0, true, true, false, &[]);
         assert!(with.iter().all(|b| b.4 != 11));
         let button = with.iter().find(|b| b.4 == 14).unwrap();
         assert_eq!(
@@ -1060,14 +1071,42 @@ mod tests {
             assert_eq!(add.1, link.1);
         }
         assert_eq!(
-            pause_icons(427.0, 240.0, true, true, false)[0].1,
-            pause_icons(427.0, 240.0, true, false, false)[0].1
+            pause_icons(427.0, 240.0, true, true, &[])[0].1,
+            pause_icons(427.0, 240.0, true, false, &[])[0].1
         );
     }
     #[test]
+    fn registered_pages_stack_above_options_in_the_pause_menu() {
+        let rows = [
+            (SPLIT_SETTINGS, 30),
+            ("test.page.a", ADDED_PAGES),
+            ("test.page.b", ADDED_PAGES + 2),
+        ];
+        let buttons = pause_buttons(427.0, 300.0, true, false, false, &rows);
+        let y = |id| buttons.iter().find(|b| b.4 == id).unwrap().1;
+        assert_eq!(y(ADDED_PAGES), y(30) + 24.0);
+        assert_eq!(y(ADDED_PAGES + 2), y(ADDED_PAGES) + 24.0);
+        assert_eq!(
+            y(1),
+            y(ADDED_PAGES + 2) + 24.0,
+            "Options under the last one"
+        );
+        // The grid stays centred: three more rows start it higher.
+        let without = pause_buttons(427.0, 300.0, true, false, false, &[]);
+        let back = |b: &[(f32, f32, f32, &str, u8, bool)]| b.iter().find(|b| b.4 == 0).unwrap().1;
+        assert!(back(&buttons) < back(&without));
+    }
+    #[test]
     fn split_settings_preserves_dialog_rows_and_icon_actions() {
         for (links, additions) in [(false, false), (true, false), (false, true), (true, true)] {
-            let buttons = pause_buttons(427.0, 300.0, true, links, additions, true);
+            let buttons = pause_buttons(
+                427.0,
+                300.0,
+                true,
+                links,
+                additions,
+                &[(SPLIT_SETTINGS, 30)],
+            );
             let split = buttons.iter().find(|b| b.4 == 30).unwrap();
             let options = buttons.iter().find(|b| b.4 == 1).unwrap();
             assert_eq!(options.1, split.1 + 24.0);
@@ -1080,7 +1119,7 @@ mod tests {
             }
             assert!(buttons.iter().all(|b| b.4 != 12 && b.4 != 13));
             assert!(
-                !pause_buttons(427.0, 300.0, true, links, additions, false)
+                !pause_buttons(427.0, 300.0, true, links, additions, &[])
                     .iter()
                     .any(|b| b.4 == 30)
             );

crates/horizon-client/src/game/tempban.rs

@@ -6,10 +6,10 @@
 //! the time left. Vanilla has no such commands: they reach operators' command trees (completions included)
 //! as a native mod's commands do (`moderation_commands`), and the game runs them itself.
 use super::{Game, chat_filter::Reply, dedicated, lan::LanHost};
-use horizon_chat_filter::{duration_text, now_millis, parse_duration};
 use horizon_client::{mod_api::NativeCommand, text::Text};
 use horizon_protocol::packets::play::{self, Clientbound as C};
 use horizon_protocol::text::translatable;
+use horizon_server_files::duration::{duration_text, now_millis, parse_duration};
 use horizon_server_files::user_lists::{BanEntry, BanList, NameAndId, format_date};
 
 /// The operator level `/tempban` needs, as `/ban`'s.

crates/horizon-client/src/lan/advancements.rs

@@ -504,6 +504,69 @@ impl ServerAdvancements {
                 w.f32(r["experience"].as_f64().unwrap_or(0.0) as f32);
                 (cooking_category(kind, r), vec![&r["ingredient"]])
             }
+            // DyeRecipe.display: the target, then the dyes kept to those with
+            // the DYE component, shown as the demo of dyeing that target.
+            // Its placement is the target and the dye.
+            "minecraft:crafting_dye" => {
+                let Some(dye_component) = sync.id("minecraft:data_component_type", "minecraft:dye")
+                else {
+                    return Vec::new();
+                };
+                let (target, dye) = (&r["target"], &r["dye"]);
+                w.varint(
+                    sync.id("minecraft:recipe_display", "minecraft:crafting_shapeless")
+                        .unwrap_or(0),
+                );
+                w.varint(2);
+                w.varint(slot("minecraft:tag"));
+                holder_set(&mut w, target, &item);
+                w.varint(slot("minecraft:only_with_component"));
+                w.varint(slot("minecraft:tag"));
+                holder_set(&mut w, dye, &item);
+                w.varint(dye_component);
+                w.varint(slot("minecraft:dyed"));
+                w.varint(slot("minecraft:only_with_component"));
+                w.varint(slot("minecraft:tag"));
+                holder_set(&mut w, dye, &item);
+                w.varint(dye_component);
+                w.varint(slot("minecraft:tag"));
+                holder_set(&mut w, target, &item);
+                station(&mut w, "minecraft:crafting_table");
+                (
+                    crafting_category(r["category"].as_str().unwrap_or("")).name(),
+                    vec![target, dye],
+                )
+            }
+            // ImbueRecipe.display: four materials, the source kept to any
+            // potion, four materials again, and the potion-wrapped result.
+            // Its placement names the source in the middle cell.
+            "minecraft:crafting_imbue" => {
+                let (source, material) = (&r["source"], &r["material"]);
+                w.varint(
+                    sync.id("minecraft:recipe_display", "minecraft:crafting_shaped")
+                        .unwrap_or(0),
+                );
+                w.varint(3);
+                w.varint(3);
+                w.varint(9);
+                for cell in 0..9 {
+                    if cell == 4 {
+                        w.varint(slot("minecraft:with_any_potion"));
+                    }
+                    w.varint(slot("minecraft:tag"));
+                    holder_set(&mut w, if cell == 4 { source } else { material }, &item);
+                }
+                w.varint(slot("minecraft:with_any_potion"));
+                result(&mut w);
+                station(&mut w, "minecraft:crafting_table");
+                (
+                    crafting_category(r["category"].as_str().unwrap_or("")).name(),
+                    vec![
+                        material, material, material, material, source, material, material,
+                        material, material,
+                    ],
+                )
+            }
             _ => return Vec::new(),
         };
         self.entry_tail(&mut w, r, sync, category, &placed, flags);
@@ -756,7 +819,15 @@ mod tests {
         "minecraft:redstone_ore": {"protocol_id": 2},
         "minecraft:redstone": {"protocol_id": 3},
         "minecraft:furnace": {"protocol_id": 4},
-        "minecraft:blast_furnace": {"protocol_id": 5}
+        "minecraft:blast_furnace": {"protocol_id": 5},
+        "minecraft:leather_helmet": {"protocol_id": 6},
+        "minecraft:crafting_table": {"protocol_id": 7},
+        "minecraft:arrow": {"protocol_id": 8},
+        "minecraft:lingering_potion": {"protocol_id": 9},
+        "minecraft:tipped_arrow": {"protocol_id": 10}
+      }},
+      "minecraft:data_component_type": {"entries": {
+        "minecraft:dye": {"protocol_id": 46}
       }},
       "minecraft:slot_display": {"entries": {
         "minecraft:empty": {"protocol_id": 0},
@@ -962,6 +1033,105 @@ mod tests {
         std::fs::remove_dir_all(&root).unwrap();
     }
 
+    /// DyeRecipe.display: the target, then the dyes kept to what carries the
+    /// DYE component, the demo of dyeing the target with one, a crafting
+    /// table; its placement is the target and the dye.
+    #[test]
+    fn a_dye_recipe_reaches_the_book_as_its_dyed_demo() {
+        let root = resources(
+            "dye_recipe",
+            &[(
+                "leather_helmet_dyed",
+                r##"{"type":"minecraft:crafting_dye","dye":"#minecraft:dyes",
+                "group":"dyed_armor","result":{"id":"minecraft:leather_helmet"},
+                "target":"minecraft:leather_helmet"}"##,
+            )],
+        );
+        let (sync, e) = entry(&root, "minecraft:leather_helmet_dyed");
+        let item = |n: &str| sync.id("minecraft:item", n).unwrap();
+        let leather = item("minecraft:leather_helmet");
+        let dye = SlotDisplay::OnlyWithComponent(
+            Box::new(SlotDisplay::Tag(HolderSet::Tag("minecraft:dyes".into()))),
+            sync.id("minecraft:data_component_type", "minecraft:dye")
+                .unwrap(),
+        );
+        assert_eq!(
+            e.display,
+            RecipeDisplay::Shapeless {
+                ingredients: vec![
+                    SlotDisplay::Tag(HolderSet::Items(vec![leather])),
+                    dye.clone(),
+                ],
+                result: SlotDisplay::Dyed {
+                    dye: Box::new(dye),
+                    target: Box::new(SlotDisplay::Tag(HolderSet::Items(vec![leather]))),
+                },
+                station: SlotDisplay::Item(item("minecraft:crafting_table")),
+            }
+        );
+        assert_eq!(
+            e.requirements,
+            Some(vec![
+                HolderSet::Items(vec![leather]),
+                HolderSet::Tag("minecraft:dyes".into()),
+            ])
+        );
+        let _ = std::fs::remove_dir_all(&root);
+    }
+
+    /// ImbueRecipe.display: a 3×3 of four materials, the source kept to any
+    /// potion, four materials again; the result is potion-wrapped, and the
+    /// source sits in the middle of the placement.
+    #[test]
+    fn an_imbue_recipe_reaches_the_book_with_any_potion() {
+        let root = resources(
+            "imbue_recipe",
+            &[(
+                "tipped_arrow",
+                r#"{"type":"minecraft:crafting_imbue","material":"minecraft:arrow",
+                "result":{"count":8,"id":"minecraft:tipped_arrow"},
+                "source":"minecraft:lingering_potion"}"#,
+            )],
+        );
+        let (sync, e) = entry(&root, "minecraft:tipped_arrow");
+        let item = |n: &str| sync.id("minecraft:item", n).unwrap();
+        let material = SlotDisplay::Tag(HolderSet::Items(vec![item("minecraft:arrow")]));
+        let source = SlotDisplay::Tag(HolderSet::Items(vec![item("minecraft:lingering_potion")]));
+        let mut cells = vec![material.clone(); 4];
+        cells.push(SlotDisplay::WithAnyPotion(Box::new(source.clone())));
+        cells.extend(std::iter::repeat_n(material, 4));
+        assert_eq!(
+            e.display,
+            RecipeDisplay::Shaped {
+                width: 3,
+                height: 3,
+                ingredients: cells,
+                result: SlotDisplay::WithAnyPotion(Box::new(SlotDisplay::ItemStack(Stack::new(
+                    item("minecraft:tipped_arrow"),
+                    8,
+                )))),
+                station: SlotDisplay::Item(item("minecraft:crafting_table")),
+            }
+        );
+        let arrow = HolderSet::Items(vec![item("minecraft:arrow")]);
+        let potion = HolderSet::Items(vec![item("minecraft:lingering_potion")]);
+        assert_eq!(
+            e.requirements,
+            Some(vec![
+                arrow.clone(),
+                arrow.clone(),
+                arrow.clone(),
+                arrow.clone(),
+                potion,
+                arrow.clone(),
+                arrow.clone(),
+                arrow.clone(),
+                arrow,
+            ])
+        );
+        let _ = std::fs::remove_dir_all(&root);
+    }
+
     #[test]
     fn a_recipe_with_an_unknown_ingredient_kind_stays_out_of_the_book() {
         let root = resources(

crates/horizon-client/src/lan/hub.rs

@@ -38,6 +38,7 @@ use horizon_world::{
 };
 use std::sync::{Arc, Mutex, atomic::Ordering};
 
+mod acknowledgements;
 /// GameEvent types (ClientboundGameEventPacket).
 pub mod chat;
 pub mod chat_filter;
@@ -2416,41 +2417,6 @@ impl Hub {
         events
     }
 
-    /// Keeps, in a frozen player's inbox, the packets that answer the server
-    /// (teleport, chunk batch, loaded, keep-alive, ping, tick end, client
-    /// information) and drops the rest. A chat message or signed command is
-    /// dropped too, but the messages it says the client has seen are taken
-    /// first (`unpackAndApplyLastSeen`), and a chat acknowledgement is handled
-    /// here, in the order they came: the client counts them as acknowledged,
-    /// and its next message after the freeze would not validate otherwise.
-    pub(crate) fn keep_acknowledgements(&mut self, i: usize, events: &mut Vec<HostEvent>) {
-        let inbox = std::mem::take(&mut self.guests[i].inbox);
-        let mut bytes = 0;
-        for (packet, size) in inbox {
-            match &packet {
-                S::Chat(c) => {
-                    self.apply_last_seen(i, &c.last_seen, events);
-                }
-                S::ChatCommandSigned(c) => {
-                    self.apply_last_seen(i, &c.last_seen, events);
-                }
-                S::ChatAck(c) => self.chat_ack(i, c.offset, events),
-                S::AcceptTeleportation(_)
-                | S::PlayerLoaded(_)
-                | S::ChunkBatchReceived(_)
-                | S::ClientInformation(_)
-                | S::ClientTickEnd(_)
-                | S::KeepAlive(_)
-                | S::Pong(_) => {
-                    bytes += size;
-                    self.guests[i].inbox.push_back((packet, size));
-                }
-                _ => {}
-            }
-        }
-        self.guests[i].inbox_bytes = bytes;
-    }
-
     /// Handle the players in this level's packets (`ServerGamePacketListenerImpl`
     /// for each), before the level's scheduled block ticks so a place landed in
     /// the same tick as a falling block's schedule still sees the support
@@ -4069,7 +4035,8 @@ impl Hub {
                 | S::RecipeBookSeenRecipe(_)
                 | S::ClientTickEnd(_)
                 | S::KeepAlive(_)
-                | S::Pong(_) => false,
+                | S::Pong(_)
+                | S::PingRequest(_) => false,
                 S::MovePlayerPos(p) => self.moved_far(i, [p.x, p.y, p.z]),
                 S::MovePlayerPosRot(p) => self.moved_far(i, [p.x, p.y, p.z]),
                 S::PlayerInput(_) => self.guests[i].client_loaded(),
@@ -4167,6 +4134,8 @@ impl Hub {
                     g.max_unacknowledged = 10;
                 }
                 S::Pong(p) => self.anticheat_pong(i, p.id),
+                // ServerGamePacketListenerImpl.handlePingRequest: echo on this connection.
+                S::PingRequest(p) => self.send_to(conn, &C::PongResponse(p)),
                 // handleAttack is the game's too: a move queued behind an attack would move
                 // the player (or land them on the ground, losing a falling attack's critical
                 // hit) before the game checks their reach and state.

crates/horizon-client/src/lan/hub/acknowledgements.rs

@@ -0,0 +1,40 @@
+//! Transport acknowledgements retained while a guest is held or handed over.
+use super::*;
+
+impl Hub {
+    /// Keeps, in a frozen player's inbox, the packets that answer the server
+    /// (teleport, chunk batch, loaded, keep-alive, ping, tick end, client
+    /// information) and drops the rest. A chat message or signed command is
+    /// dropped too, but the messages it says the client has seen are taken
+    /// first (`unpackAndApplyLastSeen`), and a chat acknowledgement is handled
+    /// here, in the order they came: the client counts them as acknowledged,
+    /// and its next message after the freeze would not validate otherwise.
+    pub(crate) fn keep_acknowledgements(&mut self, i: usize, events: &mut Vec<HostEvent>) {
+        let inbox = std::mem::take(&mut self.guests[i].inbox);
+        let mut bytes = 0;
+        for (packet, size) in inbox {
+            match &packet {
+                S::Chat(c) => {
+                    self.apply_last_seen(i, &c.last_seen, events);
+                }
+                S::ChatCommandSigned(c) => {
+                    self.apply_last_seen(i, &c.last_seen, events);
+                }
+                S::ChatAck(c) => self.chat_ack(i, c.offset, events),
+                S::AcceptTeleportation(_)
+                | S::PlayerLoaded(_)
+                | S::ChunkBatchReceived(_)
+                | S::ClientInformation(_)
+                | S::ClientTickEnd(_)
+                | S::KeepAlive(_)
+                | S::Pong(_)
+                | S::PingRequest(_) => {
+                    bytes += size;
+                    self.guests[i].inbox.push_back((packet, size));
+                }
+                _ => {}
+            }
+        }
+        self.guests[i].inbox_bytes = bytes;
+    }
+}

crates/horizon-client/src/mobs/ai.rs

@@ -2362,19 +2362,13 @@ fn never_removed_when_far(s: Species) -> bool {
             | Species::Wither
     )
 }
-/// Movement speed bonus multiplier (baby zombies are 50% faster, etc.).
+/// The movement speed multiplier of the mob's transient `minecraft:baby`
+/// modifier (`Zombie.SPEED_MODIFIER_BABY` +0.5, `Piglin.SPEED_MODIFIER_BABY`
+/// +0.2, both `ADD_MULTIPLIED_BASE`): the same modifier `/attribute` reads, so
+/// one taken away with `modifier remove` no longer speeds the baby up.
 pub fn speed_bonus(m: &Mob) -> f64 {
-    match m.species() {
-        Species::Zombie
-        | Species::Husk
-        | Species::Drowned
-        | Species::ZombieVillager
-        | Species::ZombifiedPiglin
-        | Species::Piglin
-            if m.is_baby() =>
-        {
-            1.5
-        }
+    match super::finalize::transient(m, super::finalize::Attr::MovementSpeed) {
+        Some((amount, super::finalize::Op::AddMultipliedBase)) => 1.0 + amount,
         _ => 1.0,
     }
 }
@@ -6290,3 +6284,45 @@ mod hurt_teleport_contact_tests {
         );
     }
 }
+
+#[cfg(test)]
+mod baby_speed_tests {
+    use super::*;
+    use crate::mobs::{finalize, sensor_scan_tests::kind};
+    use horizon_core::geometry::Vec3;
+    use std::sync::Arc;
+
+    fn baby(species: Species, id: &str) -> Mob {
+        let mut k = kind();
+        let km = Arc::make_mut(&mut k);
+        km.id = id.into();
+        km.species = species;
+        let mut m = Mob::new(1, k, Vec3::ZERO, 0.0);
+        finalize::set_baby(&mut m, true);
+        m
+    }
+
+    /// #11994: movement reads the transient `minecraft:baby` modifier itself:
+    /// `Zombie.SPEED_MODIFIER_BABY` +0.5 and `Piglin.SPEED_MODIFIER_BABY` +0.2
+    /// (`ADD_MULTIPLIED_BASE`), and none once `/attribute ... modifier remove`
+    /// took it away, until the next `setBaby`.
+    #[test]
+    fn a_babys_speed_follows_its_baby_modifier() {
+        let mut zombie = baby(Species::Zombie, "minecraft:zombie");
+        assert_eq!(speed_bonus(&zombie), 1.5);
+        zombie
+            .extra
+            .attributes
+            .get_or_insert_default()
+            .baby_speed_removed = true;
+        assert_eq!(speed_bonus(&zombie), 1.0, "removed with /attribute");
+        finalize::set_baby(&mut zombie, true);
+        assert_eq!(speed_bonus(&zombie), 1.5, "setBaby adds it back");
+        // The piglin's is 0.2F widened to a double, not the zombie's 0.5.
+        let piglin = baby(Species::Piglin, "minecraft:piglin");
+        assert_eq!(speed_bonus(&piglin), 1.0 + f64::from(0.2f32));
+        let mut adult = baby(Species::Zombie, "minecraft:zombie");
+        finalize::set_baby(&mut adult, false);
+        assert_eq!(speed_bonus(&adult), 1.0);
+    }
+}

crates/horizon-client/src/mobs/bee.rs

@@ -1218,8 +1218,13 @@ impl Goal for Wander {
 pub fn stable_destination(w: &MobWorld, p: [i32; 3]) -> bool {
     !w.facts.is_air(w.world.block(p[0], p[1] - 1, p[2]))
 }
-/// `Bee.addAdditionalSaveData` (and NeutralMob's `anger_end_time`).
-pub fn to_nbt(m: &Mob, map: &mut horizon_world::nbt::Compound) {
+/// `Bee.addAdditionalSaveData` (and NeutralMob's `anger_end_time` and
+/// `angry_at`).
+pub fn to_nbt(
+    m: &Mob,
+    map: &mut horizon_world::nbt::Compound,
+    uuid_of: &mut impl FnMut(u32) -> Option<[i32; 4]>,
+) {
     use horizon_world::nbt::Tag;
     let b = get(m).cloned().unwrap_or_default();
     for (key, pos) in [("hive_pos", b.hive), ("flower_pos", b.flower)] {
@@ -1241,6 +1246,20 @@ pub fn to_nbt(m: &Mob, map: &mut horizon_world::nbt::Compound) {
     map.insert("CannotEnterHiveTicks".into(), Tag::Int(b.stay_out_of_hive));
     map.insert("CropsGrownSincePollination".into(), Tag::Int(b.crops_grown));
     map.insert("anger_end_time".into(), Tag::Long(b.anger_end));
+    // `NeutralMob.addPersistentAngerSaveData`: `storeNullable`, nothing when
+    // the bee has no target. A mob target read from the save but not in the
+    // level (`Who::Mob(0)`) keeps the loaded UUID.
+    match b.angry_at {
+        Some(Who::Mob(0)) => {}
+        target => match target.and_then(|who| crate::entity_nbt::who_uuid(who, uuid_of)) {
+            Some(uuid) => {
+                map.insert("angry_at".into(), Tag::IntArray(uuid.to_vec()));
+            }
+            None => {
+                map.remove(&"angry_at".into());
+            }
+        },
+    }
 }
 /// `Bee.readAdditionalSaveData`.
 pub fn from_nbt(m: &mut Mob, tag: &horizon_world::nbt::Tag) {
@@ -1260,6 +1279,13 @@ pub fn from_nbt(m: &mut Mob, tag: &horizon_world::nbt::Tag) {
         Some(Tag::Long(v)) => *v,
         _ => -1,
     };
+    // `EntityReference.read`: the player's UUID is the player, any other one a
+    // mob the level may not have loaded (`Who::Mob(0)`).
+    let angry_at = match crate::save::uuid_from_tag(tag.get("angry_at")) {
+        Some(uuid) if uuid == crate::entity_nbt::player_uuid() => Some(Who::Player),
+        Some(_) => Some(Who::Mob(0)),
+        None => None,
+    };
     let b = st(m);
     b.ticks_without_nectar = int("TicksSincePollination").unwrap_or(0);
     b.stay_out_of_hive = int("CannotEnterHiveTicks").unwrap_or(0);
@@ -1267,6 +1293,7 @@ pub fn from_nbt(m: &mut Mob, tag: &horizon_world::nbt::Tag) {
     b.hive = pos("hive_pos");
     b.flower = pos("flower_pos");
     b.anger_end = anger_end;
+    b.angry_at = angry_at;
 }
 
 #[cfg(test)]
@@ -1419,4 +1446,39 @@ mod tests {
             }
         });
     }
+
+    /// `NeutralMob.addPersistentAngerSaveData` and
+    /// `readPersistentAngerSaveData`: `anger_end_time` and `angry_at`, the
+    /// reference to the player the bee is angry at (`Bee` keeps the anger
+    /// itself). `mob_to_nbt`/`mob_from_nbt` are the pair `Game::mob_tree_nbt`
+    /// and `Game::load_mob` go through. Horizon modelled the target in
+    /// `Bee.angry_at` and wrote only the timer, so a bee that had stung a
+    /// player came back with its anger still counting but no one to attack.
+    #[test]
+    fn a_bees_anger_target_survives_a_save() {
+        use crate::entity_nbt::{mob_from_nbt, mob_to_nbt, player_uuid};
+        use horizon_world::nbt::Tag;
+        let mut m = bee();
+        {
+            let b = super::st(&mut m);
+            b.anger_end = 500;
+            b.angry_at = Some(Who::Player);
+        }
+        let saved = mob_to_nbt(&m, [1, 2, 3, 4], None, None, |_| None);
+        assert_eq!(
+            saved.get("angry_at"),
+            Some(&Tag::IntArray(player_uuid().to_vec())),
+            "the save names the player"
+        );
+        let types = std::collections::HashMap::from([(m.kind.id.clone(), m.kind.clone())]);
+        let back = mob_from_nbt(&saved, &types, 2, None).unwrap();
+        let b = super::get(&back).unwrap();
+        assert_eq!(b.angry_at, Some(Who::Player), "the reloaded target");
+        assert_eq!(b.anger_end, 500, "the reloaded timer");
+        // `storeNullable`: a calm bee writes no `angry_at`, even over a
+        // compound that still names one.
+        let calm = bee();
+        let saved = mob_to_nbt(&calm, [1, 2, 3, 4], Some(&saved), None, |_| None);
+        assert_eq!(saved.get("angry_at"), None, "no target, no key");
+    }
 }

crates/horizon-client/src/mobs/gear.rs

@@ -151,20 +151,26 @@ pub fn damage_bonus(levels: &[(Arc<str>, u32)], target: Option<Species>) -> f32
 /// to the attribute map when the item is equipped.
 pub fn attack_damage(m: &Mob, items: Option<&crate::items::Items>) -> f32 {
     let base = f64::from(m.attrs.attack_damage);
-    let modifiers = m
-        .extra
-        .main_hand
-        .as_deref()
-        .and_then(|id| items?.get(id))
-        .map(|i| i.modifiers.as_slice());
-    modifiers.map_or(base, |modifiers| {
-        super::equip::attribute_with(
-            modifiers,
-            "minecraft:attack_damage",
-            base,
-            super::equip::Slot::MainHand,
-        )
-    }) as f32
+    let modifiers = match items {
+        Some(items) => m.extra.main_hand_stack().map_or_else(
+            || {
+                m.extra
+                    .main_hand
+                    .as_deref()
+                    .and_then(|id| items.get(id))
+                    .map(|i| i.modifiers.clone())
+                    .unwrap_or_default()
+            },
+            |stack| items.attribute_modifiers(stack),
+        ),
+        None => Vec::new(),
+    };
+    super::equip::attribute_with(
+        &modifiers,
+        "minecraft:attack_damage",
+        base,
+        super::equip::Slot::MainHand,
+    ) as f32
 }
 /// The extra damage of the mob's held weapon against a target species.
 pub fn melee_bonus(m: &Mob, target: Option<Species>) -> f32 {

crates/horizon-client/src/mobs/living.rs

@@ -830,6 +830,12 @@ impl Mob {
         let length = moved.x * moved.x + moved.y * moved.y + moved.z * moved.z;
         let wanted_length = wanted.x * wanted.x + wanted.y * wanted.y + wanted.z * wanted.z;
         if length > 1.0e-7 || wanted_length - length < 1.0e-7 {
+            // A move of a block or more through water or a reset block (a
+            // vine, a ladder) resets the fall before the move's drop counts.
+            if self.fall_distance != 0.0 && length >= 1.0 && fall_reset_hit(w, self.position, moved)
+            {
+                self.fall_distance = 0.0;
+            }
             self.position = Vec3::new(
                 self.position.x + moved.x,
                 self.position.y + moved.y,
@@ -2189,3 +2195,18 @@ impl RestitutionWorld for MobRestitution<'_, '_> {
 #[cfg(test)]
 #[path = "living_tests.rs"]
 mod tests;
+/// `Entity.move`'s fall-reset ray for a mob, with the world's
+/// `minecraft:fall_damage_resetting` blocks.
+fn fall_reset_hit(w: &MobWorld, from: Vec3, moved: Vec3) -> bool {
+    let reset = w.block_tags.get("minecraft:fall_damage_resetting");
+    crate::entities::fall_reset_hit(
+        w.world,
+        w.fluid_tables,
+        |p| {
+            let name = &w.facts.get(w.world.block(p.x, p.y, p.z)).name;
+            reset.is_some_and(|t| t.contains(&**name))
+        },
+        from,
+        moved,
+    )
+}

crates/horizon-client/src/mobs/nautilus.rs

@@ -90,6 +90,11 @@ pub fn is_food(m: &Mob, item: &str, taming: &[String]) -> bool {
         m.kind.food.iter().any(|t| t == item)
     }
 }
+/// `TamableAnimal.feed`'s heal: twice the food's nutrition, or 1 for an item
+/// without a food component (a fish bucket).
+pub fn feed_heal(nutrition: Option<i32>) -> f32 {
+    nutrition.map_or(1.0, |n| 2.0 * n as f32)
+}
 /// The ambient, hurt and death sounds by age and whether it is under water.
 pub fn sounds(m: &Mob) -> [&'static str; 3] {
     let under = m.fluids.eye_in_water;
@@ -1122,3 +1127,22 @@ mod cooldown_memory_tests {
         );
     }
 }
+
+#[cfg(test)]
+mod feed_heal_tests {
+    use super::feed_heal;
+
+    #[test]
+    fn heals_twice_the_nutrition_of_vanilla_foods() {
+        // Foods.java: cod 2, pufferfish 1, cooked cod 5, cooked salmon 6.
+        assert_eq!(feed_heal(Some(2)), 4.0);
+        assert_eq!(feed_heal(Some(1)), 2.0);
+        assert_eq!(feed_heal(Some(5)), 10.0);
+        assert_eq!(feed_heal(Some(6)), 12.0);
+    }
+
+    #[test]
+    fn item_without_food_component_heals_one() {
+        assert_eq!(feed_heal(None), 1.0);
+    }
+}

crates/horizon-client/src/mobs/seen_grid.rs

@@ -48,39 +48,144 @@ impl SeenGrid {
             return;
         }
         if let Some(list) = self.cells.get_mut(&old)
-            && let Some(k) = list.iter().position(|&j| j == i as u32)
+            && let Ok(k) = list.binary_search(&(i as u32))
         {
-            list.swap_remove(k);
+            list.remove(k);
         }
-        self.cells.entry(at).or_default().push(i as u32);
+        let list = self.cells.entry(at).or_default();
+        let idx = match list.binary_search(&(i as u32)) {
+            Ok(k) | Err(k) => k,
+        };
+        list.insert(idx, i as u32);
     }
     /// The indices, ascending, of every entry whose box can meet `area`
     /// (a superset: callers still test it). False when the area spans more
-    /// columns than the grid holds (or is not finite): scan them all.
+    /// columns than the grid has entries (at least 64), or is not finite:
+    /// scan them all.
     pub fn candidates(&self, area: Aabb, out: &mut Vec<u32>) -> bool {
         out.clear();
         // A box meets `area` only if its minimum corner is below area.max
         // and within `reach` (plus a margin for rounding) of area.min.
         let margin = self.reach + 1.0;
-        let lo = column(area.min(Axis::X) - margin, area.min(Axis::Z) - margin);
-        let hi = column(area.max(Axis::X), area.max(Axis::Z));
-        let span = |a: i32, b: i32| i64::from(b) - i64::from(a) + 1;
-        let (nx, nz) = (span(lo.0, hi.0), span(lo.1, hi.1));
-        if nx < 1 || nz < 1 || nx.saturating_mul(nz) > self.cells.len() as i64 {
+        let min_x = area.min(Axis::X) - margin;
+        let min_z = area.min(Axis::Z) - margin;
+        let max_x = area.max(Axis::X);
+        let max_z = area.max(Axis::Z);
+        if !min_x.is_finite() || !min_z.is_finite() || !max_x.is_finite() || !max_z.is_finite() {
             return false;
         }
+        let lo = column(min_x, min_z);
+        let hi = column(max_x, max_z);
+        let span = |a: i32, b: i32| i64::from(b) - i64::from(a) + 1;
+        let (nx, nz) = (span(lo.0, hi.0), span(lo.1, hi.1));
+        let max_cells = (self.cell_of.len() as i64).max(64);
+        if nx < 1 || nz < 1 || nx.saturating_mul(nz) > max_cells {
+            return false;
+        }
+        let mut slices = [&[][..]; 16];
+        let mut num_slices = 0;
+        let mut overflow = false;
         for x in lo.0..=hi.0 {
             for z in lo.1..=hi.1 {
-                if let Some(list) = self.cells.get(&(x, z)) {
-                    out.extend_from_slice(list);
+                if let Some(list) = self.cells.get(&(x, z))
+                    && !list.is_empty()
+                {
+                    if num_slices < slices.len() {
+                        slices[num_slices] = list.as_slice();
+                        num_slices += 1;
+                    } else {
+                        overflow = true;
+                        out.extend_from_slice(list);
+                    }
                 }
             }
         }
-        out.sort_unstable();
+        if overflow {
+            for s in &slices[..num_slices] {
+                out.extend_from_slice(s);
+            }
+            out.sort_unstable();
+            return true;
+        }
+        merge_slices(&slices[..num_slices], out);
         true
     }
 }
 
+fn merge_2(s0: &[u32], s1: &[u32], out: &mut Vec<u32>) {
+    out.reserve(s0.len() + s1.len());
+    let (mut i, mut j) = (0, 0);
+    while i < s0.len() && j < s1.len() {
+        if s0[i] < s1[j] {
+            out.push(s0[i]);
+            i += 1;
+        } else {
+            out.push(s1[j]);
+            j += 1;
+        }
+    }
+    out.extend_from_slice(&s0[i..]);
+    out.extend_from_slice(&s1[j..]);
+}
+
+fn merge_slices(slices: &[&[u32]], out: &mut Vec<u32>) {
+    match slices.len() {
+        0 => {}
+        1 => out.extend_from_slice(slices[0]),
+        2 => merge_2(slices[0], slices[1], out),
+        3 => {
+            let (mut i, mut j, mut k) = (0, 0, 0);
+            let (s0, s1, s2) = (slices[0], slices[1], slices[2]);
+            out.reserve(s0.len() + s1.len() + s2.len());
+            while i < s0.len() || j < s1.len() || k < s2.len() {
+                let v0 = if i < s0.len() { s0[i] } else { u32::MAX };
+                let v1 = if j < s1.len() { s1[j] } else { u32::MAX };
+                let v2 = if k < s2.len() { s2[k] } else { u32::MAX };
+                if v0 <= v1 && v0 <= v2 {
+                    out.push(v0);
+                    i += 1;
+                } else if v1 <= v2 {
+                    out.push(v1);
+                    j += 1;
+                } else {
+                    out.push(v2);
+                    k += 1;
+                }
+            }
+        }
+        4 => {
+            let (mut i, mut j, mut k, mut l) = (0, 0, 0, 0);
+            let (s0, s1, s2, s3) = (slices[0], slices[1], slices[2], slices[3]);
+            out.reserve(s0.len() + s1.len() + s2.len() + s3.len());
+            while i < s0.len() || j < s1.len() || k < s2.len() || l < s3.len() {
+                let v0 = if i < s0.len() { s0[i] } else { u32::MAX };
+                let v1 = if j < s1.len() { s1[j] } else { u32::MAX };
+                let v2 = if k < s2.len() { s2[k] } else { u32::MAX };
+                let v3 = if l < s3.len() { s3[l] } else { u32::MAX };
+                if v0 <= v1 && v0 <= v2 && v0 <= v3 {
+                    out.push(v0);
+                    i += 1;
+                } else if v1 <= v2 && v1 <= v3 {
+                    out.push(v1);
+                    j += 1;
+                } else if v2 <= v3 {
+                    out.push(v2);
+                    k += 1;
+                } else {
+                    out.push(v3);
+                    l += 1;
+                }
+            }
+        }
+        _ => {
+            for s in slices {
+                out.extend_from_slice(s);
+            }
+            out.sort_unstable();
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -145,4 +250,91 @@ mod tests {
         );
         assert!(!grid.candidates(huge, &mut out));
     }
+
+    #[test]
+    fn candidates_merges_multiple_cells_in_strict_order() {
+        // Place boxes across 4 adjacent grid cells: (0, 0), (4, 0), (0, 4), (4, 4)
+        // With interleaving snapshot indices to test 1, 2, 3, and 4-way merges.
+        let boxes = vec![
+            boxed(0.5, 64.0, 0.5, 0.6), // 0: cell (0, 0)
+            boxed(4.5, 64.0, 0.5, 0.6), // 1: cell (1, 0)
+            boxed(0.5, 64.0, 4.5, 0.6), // 2: cell (0, 1)
+            boxed(4.5, 64.0, 4.5, 0.6), // 3: cell (1, 1)
+            boxed(0.8, 64.0, 0.8, 0.6), // 4: cell (0, 0)
+            boxed(4.8, 64.0, 0.8, 0.6), // 5: cell (1, 0)
+            boxed(0.8, 64.0, 4.8, 0.6), // 6: cell (0, 1)
+            boxed(4.8, 64.0, 4.8, 0.6), // 7: cell (1, 1)
+        ];
+        let grid = SeenGrid::new(boxes.into_iter());
+        let mut out = Vec::new();
+
+        // Query covering only cell (0, 0): indices 0, 4
+        let q1 = boxed(0.1, 64.0, 0.1, 1.5);
+        assert!(grid.candidates(q1, &mut out));
+        assert_eq!(out, vec![0, 4]);
+
+        // Query covering cells (0, 0) and (1, 0): indices 0, 1, 4, 5
+        let q2 = Aabb::new(Vec3::new(0.0, 64.0, 0.0), Vec3::new(6.0, 66.0, 1.5));
+        assert!(grid.candidates(q2, &mut out));
+        assert_eq!(out, vec![0, 1, 4, 5]);
+
+        // Query covering all 4 cells: indices 0..8 in order
+        let q4 = Aabb::new(Vec3::new(0.0, 64.0, 0.0), Vec3::new(6.0, 66.0, 6.0));
+        assert!(grid.candidates(q4, &mut out));
+        assert_eq!(out, vec![0, 1, 2, 3, 4, 5, 6, 7]);
+    }
+
+    #[test]
+    #[ignore]
+    fn bench_dense_farm() {
+        let n = 300;
+        let mut seed = 0x1234_5678_9abc_def0_u64;
+        let mut next = |range: f64| {
+            seed = seed.wrapping_mul(6_364_136_223_846_793_005).wrapping_add(1);
+            (seed >> 11) as f64 / (1u64 << 53) as f64 * range
+        };
+        // 300 mobs in a 1.5 x 1.5 block pen around (3.5, 64.0, 3.5) crossing cell boundary at 4.0
+        let mut boxes: Vec<Aabb> = (0..n)
+            .map(|_| {
+                let x = 3.5 + next(1.5);
+                let z = 3.5 + next(1.5);
+                boxed(x, 64.0, z, 0.6)
+            })
+            .collect();
+        let mut grid = SeenGrid::new(boxes.iter().copied());
+        let mut out = Vec::new();
+
+        let t = std::time::Instant::now();
+        let rounds = 100;
+        let mut fallback_count = 0;
+        let mut query_dur = std::time::Duration::ZERO;
+        let mut update_dur = std::time::Duration::ZERO;
+        for _ in 0..rounds {
+            for i in 0..n {
+                let area = boxes[i];
+                let t0 = std::time::Instant::now();
+                if !grid.candidates(area, &mut out) {
+                    fallback_count += 1;
+                    out.clear();
+                    out.extend(0..n as u32);
+                }
+                query_dur += t0.elapsed();
+                // small jitter
+                let x = 3.5 + next(1.5);
+                let z = 3.5 + next(1.5);
+                boxes[i] = boxed(x, 64.0, z, 0.6);
+                let t1 = std::time::Instant::now();
+                grid.update(i, boxes[i]);
+                update_dur += t1.elapsed();
+            }
+        }
+        let elapsed = t.elapsed();
+        println!(
+            "{rounds} ticks of {n} mobs in 1.5x1.5 pen: {elapsed:?} (query: {:.3} ms, update: {:.3} ms, per tick: {:.3} ms, fallback: {fallback_count}/{})",
+            query_dur.as_secs_f64() * 1e3 / rounds as f64,
+            update_dur.as_secs_f64() * 1e3 / rounds as f64,
+            elapsed.as_secs_f64() * 1e3 / rounds as f64,
+            rounds * n
+        );
+    }
 }

crates/horizon-client/src/mobs/world.rs

@@ -30,6 +30,63 @@ pub struct TargetInfo {
     /// `isPassenger`.
     pub passenger: bool,
 }
+thread_local! {
+    static NEAR_BUF_POOL: std::cell::RefCell<Vec<Vec<u32>>> = const { std::cell::RefCell::new(Vec::new()) };
+}
+
+pub struct NearIter<'a> {
+    others: &'a [Seen],
+    indices: Option<Vec<u32>>,
+    pos: usize,
+    fallback: Option<std::slice::Iter<'a, Seen>>,
+}
+
+impl<'a> Iterator for NearIter<'a> {
+    type Item = &'a Seen;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(indices) = &self.indices
+            && self.pos < indices.len()
+        {
+            let idx = indices[self.pos];
+            self.pos += 1;
+            return Some(&self.others[idx as usize]);
+        }
+        if let Some(all) = &mut self.fallback {
+            return all.next();
+        }
+        None
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        if let Some(indices) = &self.indices {
+            let rem = indices.len().saturating_sub(self.pos);
+            (rem, Some(rem))
+        } else if let Some(all) = &self.fallback {
+            all.size_hint()
+        } else {
+            (0, Some(0))
+        }
+    }
+}
+
+impl Drop for NearIter<'_> {
+    fn drop(&mut self) {
+        if let Some(mut buf) = self.indices.take() {
+            buf.clear();
+            NEAR_BUF_POOL.with(|pool| {
+                if let Ok(mut pool) = pool.try_borrow_mut()
+                    && pool.len() < 8
+                {
+                    pool.push(buf);
+                }
+            });
+        }
+    }
+}
+
 /// Chunk and section cache for raycast block traversals.
 /// Caches the current section to avoid section index checks and hashmap lookups
 /// for consecutive voxels in the same 16x16x16 section.
@@ -512,15 +569,39 @@ impl MobWorld<'_> {
     }
     /// The other mobs whose boxes may meet `area` (callers test the boxes),
     /// in snapshot order: through the grid when there is one, else all.
-    pub fn others_near(&self, area: Aabb) -> impl Iterator<Item = &Seen> {
-        let mut near = Vec::new();
+    pub fn others_near(&self, area: Aabb) -> NearIter<'_> {
+        let mut buf = NEAR_BUF_POOL.with(|pool| {
+            pool.try_borrow_mut()
+                .ok()
+                .and_then(|mut p| p.pop())
+                .unwrap_or_default()
+        });
         let indexed = self
             .others_grid
-            .is_some_and(|grid| grid.candidates(area, &mut near));
-        let all = (!indexed).then(|| self.others.iter());
-        near.into_iter()
-            .map(|i| &self.others[i as usize])
-            .chain(all.into_iter().flatten())
+            .is_some_and(|grid| grid.candidates(area, &mut buf));
+        if indexed {
+            NearIter {
+                others: self.others,
+                indices: Some(buf),
+                pos: 0,
+                fallback: None,
+            }
+        } else {
+            buf.clear();
+            NEAR_BUF_POOL.with(|pool| {
+                if let Ok(mut pool) = pool.try_borrow_mut()
+                    && pool.len() < 8
+                {
+                    pool.push(buf);
+                }
+            });
+            NearIter {
+                others: self.others,
+                indices: None,
+                pos: 0,
+                fallback: Some(self.others.iter()),
+            }
+        }
     }
     pub fn seen(&self, id: u32) -> Option<&Seen> {
         match self.others_index {

crates/horizon-client/src/multiplayer.rs

@@ -330,7 +330,7 @@ fn ping_all(servers: &[ServerEntry], pings: &Pings, icons: &Icons, file: &Path)
 /// Save the list after a move or delete, keeping the icons pings stored in
 /// servers.dat since it was loaded, and the Code of Conduct accepted on a server.
 fn save_servers(file: &Path, servers: &mut [ServerEntry]) {
-    let _guard = SAVING.lock();
+    let _guard = servers::lock();
     let saved = servers::load(file);
     for entry in servers.iter_mut() {
         if let Some(s) = saved.iter().find(|s| s.ip == entry.ip) {
@@ -340,11 +340,9 @@ fn save_servers(file: &Path, servers: &mut [ServerEntry]) {
     }
     let _ = servers::save(file, servers);
 }
-/// Held while servers.dat is read and written back.
-static SAVING: Mutex<()> = Mutex::new(());
 /// Store `icon` on the entries for `address` (OnlineServerEntry.updateServerList).
 fn save_icon(file: &Path, address: &str, icon: Option<String>) {
-    let _guard = SAVING.lock();
+    let _guard = servers::lock();
     let mut list = servers::load(file);
     let mut changed = false;
     for entry in list.iter_mut().filter(|e| e.ip == address) {
@@ -364,113 +362,6 @@ pub fn save_server_icon(saves: &Path, address: &str, png: &[u8]) {
     }
 }
 
-/// Horizon's official survival server: a name and an address like any entry. The address is
-/// `horizon_telemetry::server_status::OFFICIAL_ADDRESS`, the one place it is kept.
-pub const OFFICIAL_SERVER: (&str, &str) = (
-    "Horizon Official",
-    horizon_telemetry::server_status::OFFICIAL_ADDRESS,
-);
-/// Beside servers.dat once the official server was offered, so a player who
-/// deletes it never gets it back: the address offered, so a new one moves the
-/// list once. The launcher writes the same file.
-const OFFICIAL_MARKER: &str = "horizon_official_server.txt";
-
-/// An address as the game connects to it: any case, 25565 when no port is given.
-fn address_key(ip: &str) -> Option<(String, u16)> {
-    servers::parse_address(ip).map(|(h, p)| (h.to_ascii_lowercase(), p))
-}
-
-/// Puts the official server at the top of the list in `game_dir`, once: not
-/// again after the player deletes it, and not when the list has its address.
-/// When it moved (the marker names another address), the entries for its
-/// earlier addresses move to the new one, once (`move_official`).
-pub fn add_official_server(game_dir: &Path) -> std::io::Result<()> {
-    let (name, address) = OFFICIAL_SERVER;
-    let marker = game_dir.join(OFFICIAL_MARKER);
-    // A marker that is there but can't be read: offered already, at an address not known.
-    let offered = match std::fs::read_to_string(&marker) {
-        Ok(text) => Some(text),
-        Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
-        Err(_) => Some(String::new()),
-    };
-    if offered
-        .as_deref()
-        .is_some_and(|a| address_key(a) == address_key(address))
-    {
-        return Ok(());
-    }
-    let file = game_dir.join("servers.dat");
-    let _guard = SAVING.lock();
-    let mut list = servers::load(&file);
-    let previous = horizon_telemetry::server_status::OFFICIAL_PREVIOUS;
-    if move_official(&mut list, address, previous) {
-        servers::save(&file, &list)?;
-    }
-    if offered.is_none()
-        && !list
-            .iter()
-            .any(|s| address_key(&s.ip) == address_key(address))
-    {
-        servers::prepend(&file, &ServerEntry::new(name, address))?;
-    }
-    std::fs::write(marker, format!("{address}\n"))
-}
-
-/// Afri-Network, which the game added once below the official server (#9299) until the
-/// partnership ended: the name and address the game gave its entry.
-const WITHDRAWN_PARTNER: (&str, &str) = ("Afri-Network (South Africa)", "afri-network.co.za");
-/// Beside servers.dat: the partner addresses the game offered, one per line (#9299).
-const PARTNER_MARKER: &str = "horizon_partner_servers.txt";
-
-/// Takes the withdrawn partner server back out of the list in `game_dir`, once, where the game
-/// added it: the marker says it was offered and the entry still has the name the game gave it
-/// (an entry the player made or renamed keeps its place). Then the marker goes.
-pub fn withdraw_partner_servers(game_dir: &Path) -> std::io::Result<()> {
-    let marker = game_dir.join(PARTNER_MARKER);
-    let offered = match std::fs::read_to_string(&marker) {
-        Ok(text) => text,
-        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(()),
-        Err(e) => return Err(e),
-    };
-    let (name, address) = WITHDRAWN_PARTNER;
-    if offered
-        .lines()
-        .any(|l| address_key(l) == address_key(address))
-    {
-        let _guard = SAVING.lock();
-        servers::remove_where(&game_dir.join("servers.dat"), |n, ip| {
-            n == name && address_key(ip) == address_key(address)
-        })?;
-    }
-    std::fs::remove_file(marker)
-}
-
-/// Points the entries for an earlier official address at `address`, each
-/// keeping the player's name and fields. One entry for the server at most: an
-/// old one goes when the list already has `address`. Whether anything changed.
-fn move_official(list: &mut Vec<ServerEntry>, address: &str, previous: &[&str]) -> bool {
-    let new = address_key(address);
-    let old = |ip: &str| {
-        let ip = address_key(ip);
-        ip.is_some() && ip != new && previous.iter().any(|p| address_key(p) == ip)
-    };
-    let mut present = list.iter().any(|s| address_key(&s.ip) == new);
-    let mut changed = false;
-    list.retain_mut(|s| {
-        if !old(&s.ip) {
-            return true;
-        }
-        changed = true;
-        if present {
-            return false;
-        }
-        present = true;
-        s.ip = address.to_owned();
-        true
-    });
-    changed
-}
-
 /// The address and kind of list row `index`: saved servers, then discovered LAN games.
 fn entry_address(servers: &[ServerEntry], lan: &Scanner, index: usize) -> Option<(String, bool)> {
     match servers.get(index) {
@@ -2100,7 +1991,7 @@ pub fn remember_direct_join(saves: &Path, address: &str) {
         return;
     }
     let file = servers_file(saves);
-    let _guard = SAVING.lock();
+    let _guard = servers::lock();
     let (shown, hidden) = servers::load_all(&file);
     if shown.iter().chain(&hidden).any(|s| s.ip == address) {
         return;
@@ -2297,22 +2188,10 @@ mod tests {
         ));
     }
 
-    #[cfg(feature = "friends")]
     #[test]
-    fn direct_connection_joins_a_pasted_invite_and_keeps_host_names() {
-        let invite = horizon_friends::invite::Invite {
-            secret: *b"0123456789",
-            port: 25580,
-            endpoints: vec!["192.168.1.20:25580".parse().unwrap()],
-            relay: None,
-        }
-        .encode();
-        assert_eq!(
-            direct_address(&format!(" {invite} ")),
-            format!("{}{invite}", crate::net::FRIEND)
-        );
+    fn direct_connection_keeps_host_names() {
         for host in ["localhost", "example.org:25566", "abcdefgh", "[::1]:25568"] {
-            assert_eq!(direct_address(host), host);
+            assert_eq!(direct_address(&format!(" {host} ")), host);
         }
     }
 
@@ -2546,138 +2425,6 @@ mod tests {
         assert!(favicon_bytes(&serde_json::json!({ "favicon": encoded })).is_none());
     }
 
-    #[test]
-    fn the_official_server_is_added_once_at_the_top() {
-        let dir = std::env::temp_dir().join(format!("horizon-mp-official-{}", std::process::id()));
-        let (name, address) = OFFICIAL_SERVER;
-        let file = dir.join("servers.dat");
-        let ips = || -> Vec<String> { servers::load(&file).into_iter().map(|s| s.ip).collect() };
-        let fresh = |list: &[ServerEntry]| {
-            let _ = std::fs::remove_dir_all(&dir);
-            std::fs::create_dir_all(&dir).unwrap();
-            if !list.is_empty() {
-                servers::save(&file, list).unwrap();
-            }
-        };
-        // A fresh list: just the official server, named like it.
-        fresh(&[]);
-        add_official_server(&dir).unwrap();
-        assert_eq!(servers::load(&file), [ServerEntry::new(name, address)]);
-        // An existing list: on top, the player's servers kept in their order.
-        let mine = [
-            ServerEntry::new("Mine", "127.0.0.1:2"),
-            ServerEntry::new("Other", "example.org"),
-        ];
-        fresh(&mine);
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), [address, "127.0.0.1:2", "example.org"]);
-        // Once only: a second start adds nothing.
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), [address, "127.0.0.1:2", "example.org"]);
-        // Already there under the player's own name and spelling: not duplicated.
-        fresh(&[
-            ServerEntry::new("SMP", "Play.PlayHorizon.dev:25565"),
-            mine[0].clone(),
-        ]);
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), ["Play.PlayHorizon.dev:25565", "127.0.0.1:2"]);
-        // Deleted by the player: never back.
-        fresh(&mine);
-        add_official_server(&dir).unwrap();
-        servers::save(&file, &mine).unwrap();
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), ["127.0.0.1:2", "example.org"]);
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn the_withdrawn_partner_server_leaves_lists_the_game_put_it_in_once() {
-        let dir = std::env::temp_dir().join(format!("horizon-mp-partner-{}", std::process::id()));
-        let official = OFFICIAL_SERVER.1;
-        let file = dir.join("servers.dat");
-        let marker = dir.join(PARTNER_MARKER);
-        let ips = || -> Vec<String> { servers::load(&file).into_iter().map(|s| s.ip).collect() };
-        let fresh = |list: &[ServerEntry], offered: bool| {
-            let _ = std::fs::remove_dir_all(&dir);
-            std::fs::create_dir_all(&dir).unwrap();
-            servers::save(&file, list).unwrap();
-            if offered {
-                std::fs::write(&marker, "afri-network.co.za\n").unwrap();
-            }
-        };
-        let added = ServerEntry::new("Afri-Network (South Africa)", "afri-network.co.za");
-        // The game added it: it goes, the rest stays in order, and only once.
-        fresh(
-            &[
-                ServerEntry::new("Horizon Official", official),
-                added.clone(),
-                ServerEntry::new("Mine", "127.0.0.1:2"),
-            ],
-            true,
-        );
-        withdraw_partner_servers(&dir).unwrap();
-        assert_eq!(ips(), [official, "127.0.0.1:2"]);
-        assert!(!marker.exists());
-        servers::save(&file, std::slice::from_ref(&added)).unwrap();
-        withdraw_partner_servers(&dir).unwrap();
-        assert_eq!(ips(), ["afri-network.co.za"]);
-        // The player's own entry for that address (their name) stays.
-        fresh(&[ServerEntry::new("ZA", "Afri-Network.co.za:25565")], true);
-        withdraw_partner_servers(&dir).unwrap();
-        assert_eq!(ips(), ["Afri-Network.co.za:25565"]);
-        // Never offered (no marker): nothing changes.
-        fresh(&[added], false);
-        withdraw_partner_servers(&dir).unwrap();
-        assert_eq!(ips(), ["afri-network.co.za"]);
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn a_moved_official_server_moves_the_old_entry_once() {
-        let dir = std::env::temp_dir().join(format!("horizon-mp-moved-{}", std::process::id()));
-        let address = OFFICIAL_SERVER.1;
-        let file = dir.join("servers.dat");
-        let marker = dir.join(OFFICIAL_MARKER);
-        let ips = || -> Vec<String> { servers::load(&file).into_iter().map(|s| s.ip).collect() };
-        let offered_before = |list: &[ServerEntry]| {
-            let _ = std::fs::remove_dir_all(&dir);
-            std::fs::create_dir_all(&dir).unwrap();
-            servers::save(&file, list).unwrap();
-            std::fs::write(&marker, "horizon.bunchy7s.dev\n").unwrap();
-        };
-        // The old address under the player's own name and spelling: moved, name and place kept.
-        let mut old = ServerEntry::new("Our SMP", "Horizon.Bunchy7s.dev:25565");
-        old.icon = Some("AAAA".into());
-        offered_before(&[ServerEntry::new("Mine", "127.0.0.1:2"), old]);
-        add_official_server(&dir).unwrap();
-        let list = servers::load(&file);
-        assert_eq!(ips(), ["127.0.0.1:2", address]);
-        assert_eq!(
-            (list[1].name.as_str(), list[1].icon.as_deref()),
-            ("Our SMP", Some("AAAA"))
-        );
-        assert_eq!(
-            std::fs::read_to_string(&marker).unwrap(),
-            format!("{address}\n")
-        );
-        // Once: the old address added back afterwards is the player's.
-        servers::prepend(&file, &ServerEntry::new("Old", "horizon.bunchy7s.dev")).unwrap();
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), ["horizon.bunchy7s.dev", "127.0.0.1:2", address]);
-        // The new address already listed: no second entry.
-        offered_before(&[
-            ServerEntry::new("Old", "horizon.bunchy7s.dev"),
-            ServerEntry::new("New", address),
-        ]);
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), [address]);
-        // Deleted by the player before the move: not offered again; another port is left alone.
-        offered_before(&[ServerEntry::new("Test", "horizon.bunchy7s.dev:25570")]);
-        add_official_server(&dir).unwrap();
-        assert_eq!(ips(), ["horizon.bunchy7s.dev:25570"]);
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
     #[test]
     fn arrow_keys_select_servers_and_shift_moves_them() {
         let dir = std::env::temp_dir().join(format!("horizon-mp-keys-{}", std::process::id()));

crates/horizon-client/src/net.rs

@@ -30,6 +30,8 @@ use std::{
     time::Duration,
 };
 
+use horizon_hooks::tunnel;
+
 /// `CommonListenerCookie.serverCookies`: cookies the server asked the client
 /// to store (`ClientboundStoreCookiePacket`), answered to
 /// `ClientboundCookieRequestPacket`. A `transfer` carries them to the next
@@ -496,62 +498,36 @@ impl Drop for Session {
 }
 
 /// An address of the form `friend:K7QM-3XPD` joins a friend's world through
-/// its invite code (horizon-friends): the session goes through a tunnel the
-/// client reaches on a loopback port, so everything after is a plain join.
-#[cfg(feature = "friends")]
-pub const FRIEND: &str = horizon_friends::ADDRESS_PREFIX;
-/// Without the `friends` feature such an address is refused (`join_friend`).
-#[cfg(not(feature = "friends"))]
-pub const FRIEND: &str = "friend:";
+/// its invite code (Play with Friends, through a hook's [`tunnel::Resolver`]):
+/// the session goes through a tunnel the client reaches on a loopback port, so
+/// everything after is a plain join.
+pub const FRIEND: &str = tunnel::PREFIX;
 
 /// Whether `code` is an invite code; with `full`, only a full one (a short
-/// relay code could also be a host name).
-#[cfg(feature = "friends")]
+/// relay code could also be a host name). Without a resolver nothing is one.
 pub fn is_invite(code: &str, full: bool) -> bool {
-    use horizon_friends::invite::{Parsed, parse};
-    match parse(code) {
-        Some(Parsed::Long(_)) => true,
-        Some(Parsed::Short(_)) => !full,
-        None => false,
-    }
-}
-/// Without the `friends` feature nothing is one.
-#[cfg(not(feature = "friends"))]
-pub fn is_invite(_code: &str, _full: bool) -> bool {
-    false
+    horizon_hooks::engine::tunnel().is_some_and(|r| r.is_code(code, full))
 }
 
 /// An address as players and logs see it: a friend's invite code stays
 /// out of it (its secret is in there).
 pub fn shown_address(address: &str) -> String {
     match address.strip_prefix(FRIEND) {
-        #[cfg(feature = "friends")]
-        Some(code) => match horizon_friends::invite::parse(code) {
-            Some(horizon_friends::invite::Parsed::Short(c)) => {
-                format!("Friend's world ({}-****)", c.nameplate)
-            }
-            _ => "Friend's world".to_owned(),
+        Some(code) => match horizon_hooks::engine::tunnel().and_then(|r| r.nameplate(code)) {
+            Some(nameplate) => format!("Friend's world ({nameplate}-****)"),
+            None => "Friend's world".to_owned(),
         },
-        #[cfg(not(feature = "friends"))]
-        Some(_) => "Friend's world".to_owned(),
         None => address.to_owned(),
     }
 }
 
 /// The relay the player set (`friendsRelay` in horizon.txt, beside
-/// options.txt), else `HORIZON_RELAY_URL`. None by default.
+/// options.txt), else the resolver's (`HORIZON_RELAY_URL`). None by default.
 pub fn friends_relay_setting() -> Option<String> {
     let dir = std::env::current_dir().ok()?;
     crate::ui_theme::preference(&dir, "friendsRelay")
         .filter(|r| !r.is_empty())
-        .or_else(relay_from_env)
-}
-#[cfg(feature = "friends")]
-use horizon_friends::relay_url as relay_from_env;
-/// `HORIZON_RELAY_URL` is the friends feature's: none without it.
-#[cfg(not(feature = "friends"))]
-fn relay_from_env() -> Option<String> {
-    None
+        .or_else(|| horizon_hooks::engine::tunnel().and_then(|r| r.relay_from_env()))
 }
 /// Remember the relay typed on Join a friend (empty forgets it).
 pub fn save_friends_relay(relay: &str) {
@@ -562,55 +538,35 @@ pub fn save_friends_relay(relay: &str) {
 
 /// Reach the friend's world from the code (directly, or through a relay)
 /// and open the tunnel: the loopback address to connect to, and the token to send on it first.
-#[cfg(feature = "friends")]
+/// Without a resolver (a build without Play with Friends) the address is refused, never retried.
 fn join_friend(
     code: &str,
     lang: &Language,
     send: &Sender<Event>,
 ) -> Result<(String, u16, Vec<u8>), Reason> {
-    use horizon_friends::{
-        PathMode,
-        guest::{self, GuestConfig},
+    let Some(resolver) = horizon_hooks::engine::tunnel() else {
+        return Err(Reason::keyed_arg(
+            "horizon.multiplayer.invalid_address",
+            lang,
+            &shown_address(&format!("{FRIEND}{code}")),
+        ));
     };
-    status(send, &tr(lang, "horizon.multiplayer.finding_friend"));
-    let tunnel = guest::join(&GuestConfig {
-        code: code.to_owned(),
-        relay: friends_relay_setting(),
-        protocol: PROTOCOL_VERSION,
-        game: horizon_protocol::GAME_VERSION.to_owned(),
-        path: PathMode::from_env(),
-    })
-    .map_err(|e| Reason::plain(e.to_string()))?;
-    status(
-        send,
-        &if tunnel.direct {
-            tr(lang, "horizon.multiplayer.connected_friend_direct")
-        } else {
-            tr(lang, "horizon.multiplayer.connected_friend_relay")
-        },
-    );
-    let loopback = tunnel
-        .serve_loopback()
-        .map_err(|e| Reason::plain(e.to_string()))?;
-    Ok((
-        "127.0.0.1".to_owned(),
-        loopback.port,
-        loopback.token.to_vec(),
-    ))
-}
-
-/// A build without Play with Friends: the address is refused, never retried.
-#[cfg(not(feature = "friends"))]
-fn join_friend(
-    code: &str,
-    lang: &Language,
-    _: &Sender<Event>,
-) -> Result<(String, u16, Vec<u8>), Reason> {
-    Err(Reason::keyed_arg(
-        "horizon.multiplayer.invalid_address",
-        lang,
-        &shown_address(&format!("{FRIEND}{code}")),
-    ))
+    let mut progress = |p: tunnel::Progress| {
+        let key = match p {
+            tunnel::Progress::Finding => "horizon.multiplayer.finding_friend",
+            tunnel::Progress::Connected { direct: true } => {
+                "horizon.multiplayer.connected_friend_direct"
+            }
+            tunnel::Progress::Connected { direct: false } => {
+                "horizon.multiplayer.connected_friend_relay"
+            }
+        };
+        status(send, &tr(lang, key));
+    };
+    let opened = resolver
+        .open(code, friends_relay_setting(), &mut progress)
+        .map_err(Reason::plain)?;
+    Ok(("127.0.0.1".to_owned(), opened.port, opened.token))
 }
 
 fn status(send: &Sender<Event>, text: &str) {

crates/horizon-client/src/structure_blocks.rs

@@ -232,10 +232,7 @@ pub fn roll_container(
 
 /// A saved `LootTableSeed`, if any.
 pub fn loot_seed(nbt: &Tag) -> Option<i64> {
-    match nbt.get("LootTableSeed") {
-        Some(Tag::Long(seed)) => Some(*seed),
-        _ => None,
-    }
+    horizon_client_core::nbt_value::number(nbt.get("LootTableSeed"))
 }
 
 fn text(nbt: &Compound, key: &str) -> Option<String> {
@@ -318,6 +315,18 @@ mod tests {
     use super::*;
     use horizon_world::loot::{ExplorationMap, LootStack};
 
+    #[test]
+    fn a_loot_seed_is_any_number() {
+        assert_eq!(
+            loot_seed(&Tag::compound([("LootTableSeed", Tag::Int(42))])),
+            Some(42)
+        );
+        assert_eq!(
+            loot_seed(&Tag::compound([("LootTableSeed", Tag::Long(7))])),
+            Some(7)
+        );
+    }
+
     #[test]
     fn a_saved_mod_sign_uses_its_vanilla_entity_type() {
         for hanging in [false, true] {

crates/horizon-client/src/telemetry.rs

@@ -60,28 +60,10 @@ pub fn set_display(width: u32, height: u32, refresh_hz: u32, scale: f64) {
     });
 }
 
-/// The screen `window` is on, else the primary one, else the only one: right after the window
-/// is made, Wayland doesn't say yet which screen it is on.
-pub fn monitor(window: &winit::window::Window) -> Option<winit::monitor::MonitorHandle> {
-    let only = || {
-        let mut all = window.available_monitors();
-        all.next().filter(|_| all.next().is_none())
-    };
-    window
-        .current_monitor()
-        .or_else(|| window.primary_monitor())
-        .or_else(only)
-}
-
-/// Keeps [`monitor`]'s size, refresh rate and scale for the items' `system.display`.
+/// Keeps the screen `window` is on ([`crate::window::display`]) for the items' `system.display`.
 pub fn note_display(window: &winit::window::Window) {
-    if let Some(m) = monitor(window) {
-        set_display(
-            m.size().width,
-            m.size().height,
-            m.refresh_rate_millihertz().map_or(0, |r| r.div_ceil(1000)),
-            m.scale_factor(),
-        );
+    if let Some(d) = crate::window::display(window) {
+        set_display(d.width, d.height, d.refresh_hz.unwrap_or(0), d.scale);
     }
 }
 

crates/horizon-discord/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "horizon-discord"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+description = "Discord Rich Presence: \"Playing Horizon\" on the player's Discord profile (docs/native-client.md)"
+
+[dependencies]
+horizon-platform = { path = "../horizon-platform" }
+log = "0.4"
+serde_json = "1.0.151"
+
+[lints]
+workspace = true

crates/horizon-discord/src/lib.rs

@@ -1,21 +1,30 @@
 //! Discord Rich Presence: "Playing Horizon" on the player's Discord profile, with what they are
 //! doing (docs/native-client.md). A thread of its own talks to the Discord app on this computer
 //! through its local IPC socket (Discord's RPC docs: `discord-ipc-N`, frames of opcode u32 LE +
-//! length u32 LE + JSON). The game only calls [`set`] each frame: a change wakes the thread,
+//! length u32 LE + JSON). The game says what the player does on each change ([`set`]), which wakes the thread,
 //! which connects when Discord runs, retries every 15 s when it doesn't, keeps under Discord's
 //! update limit and clears the activity on quit. Nothing is sent with the setting off,
-//! or with `HORIZON_NO_DISCORD=1`. It uses nothing else of the game (docs/layers.md: Horizon layer):
-//! `game/discord.rs` says what the player does.
+//! or with `HORIZON_NO_DISCORD=1`.
+//!
+//! A Horizon crate (docs/layers.md): the game tells it what the player does through the
+//! platform's hooks ([`HOOKS`]: `client_started`, `activity`, `shutdown`), which the official
+//! executable (`horizon-official`) registers with the switch: its line of `horizon-extras.txt`
+//! ([`SETTING`]) and its row in Extras' Multiplayer group ([`SECTION`]). horizon-client's own
+//! executable has no presence.
+#![forbid(unsafe_code)]
 use std::collections::VecDeque;
 use std::io::{self, Read, Write};
 use std::path::PathBuf;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Condvar, Mutex, OnceLock};
 use std::thread::Thread;
 use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 
 use serde_json::{Value, json};
 
-use horizon_command::args::GameMode;
+use horizon_platform::hooks::{self, Activity, Dimension, GameMode, Hooks, Play};
+use horizon_platform::pages::{Act, Label, Page, Place, Row};
+use horizon_platform::settings::Store;
 
 /// The "Horizon" application on Discord's developer portal (public: it names the game). Its
 /// Rich Presence assets: `horizon`, the logo.
@@ -40,24 +49,134 @@ const CLOSE: u32 = 2;
 const PING: u32 = 3;
 const PONG: u32 = 4;
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Dimension {
-    Overworld,
-    Nether,
-    End,
+/// The presence's hooks, for `horizon_platform::hooks::register`.
+pub static HOOKS: Presence = Presence;
+
+pub struct Presence;
+
+impl Hooks for Presence {
+    /// Starts the presence thread with the game's window (never for a dedicated server).
+    fn client_started(&self, client: &hooks::Client) {
+        start(client.automated);
+    }
+
+    fn activity(&self, now: Activity) {
+        set(match now {
+            Activity::Menus => Status::Menus,
+            Activity::World {
+                play,
+                dimension,
+                mode,
+            } => Status::World {
+                play,
+                dimension,
+                mode,
+            },
+            // Anything a later game says that this crate doesn't know yet.
+            _ => Status::Off,
+        });
+    }
+
+    /// On quit: the activity is cleared.
+    fn shutdown(&self) {
+        stop();
+    }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Play {
-    Singleplayer,
-    /// A server or someone else's LAN world. Its address and name are never shown.
-    Multiplayer,
-    /// This world is open to LAN or friends; `players` counts the host, `max` is how many
-    /// may join.
-    Hosting {
-        players: usize,
-        max: usize,
-    },
+/// The switch's line in `horizon-extras.txt`, where the engine's Extras kept it before.
+const KEY: &str = "discordPresence";
+/// The switch's row, and what it says on hover.
+const LABEL: &str = "horizon.extras.discord_presence";
+const ABOUT: &str = "horizon.extras.discord_presence.tooltip";
+
+/// The switch (on by default): the player's own settings' line, the game's first player's. A
+/// splitscreen player's settings file loads after the first player's and keeps it.
+static ON: AtomicBool = AtomicBool::new(true);
+/// Whether the player's settings were loaded once: the later loads are splitscreen players'.
+static LOADED: AtomicBool = AtomicBool::new(false);
+
+/// Turns the presence on or off; off clears the activity at once.
+pub fn set_enabled(on: bool) {
+    ON.store(on, Ordering::Relaxed);
+    let mut shared = lock();
+    let status = shown(shared.game);
+    let changed = shared.wanted.update(status, unix_now());
+    drop(shared);
+    if let Some(thread) = THREAD.get().filter(|_| changed) {
+        thread.unpark();
+    }
+}
+
+pub fn enabled() -> bool {
+    ON.load(Ordering::Relaxed)
+}
+
+/// What Discord is told for the game's `status`: nothing with the switch off.
+fn shown(status: Status) -> Status {
+    if enabled() { status } else { Status::Off }
+}
+
+/// The switch's line of `horizon-extras.txt`, for `horizon_platform::settings::register`.
+pub static SETTING: Setting = Setting;
+
+pub struct Setting;
+
+impl Store for Setting {
+    fn file(&self) -> &'static str {
+        "horizon-extras.txt"
+    }
+    fn owns(&self, key: &str) -> bool {
+        key == KEY
+    }
+    fn load(&self, _key: &str, value: &str) {
+        // The first player's settings load first; the first load is theirs.
+        if LOADED.swap(true, Ordering::Relaxed) {
+            return;
+        }
+        match value {
+            "true" => set_enabled(true),
+            "false" => set_enabled(false),
+            _ => {}
+        }
+    }
+    fn save(&self, line: &mut dyn FnMut(&str, &str)) {
+        line(KEY, if enabled() { "true" } else { "false" });
+    }
+    fn is_default(&self) -> bool {
+        enabled()
+    }
+}
+
+/// The switch's row in the Extras page's Multiplayer group, for
+/// `horizon_platform::pages::register`.
+pub static SECTION: Section = Section;
+
+pub struct Section;
+
+impl Page for Section {
+    fn id(&self) -> &'static str {
+        "horizon-discord.extras"
+    }
+    fn title(&self) -> &'static str {
+        "horizon.extras.header.multiplayer"
+    }
+    fn place(&self) -> Place {
+        Place::Extras
+    }
+    fn rows(&self, rows: &mut Vec<Row>) {
+        rows.push(Row::Toggle {
+            label: LABEL,
+            on: enabled(),
+        });
+    }
+    fn act(&self, row: usize, act: Act) {
+        if row == 0 && matches!(act, Act::Press | Act::PressBack) {
+            set_enabled(!enabled());
+        }
+    }
+    fn tooltip(&self, _row: usize) -> Option<Label> {
+        Some(Label::Key(ABOUT))
+    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -97,11 +216,15 @@ impl Wanted {
 }
 
 struct Shared {
+    /// What the game said last.
+    game: Status,
+    /// What Discord is to show: the game's, or nothing with the switch off.
     wanted: Wanted,
     stop: bool,
     stopped: bool,
 }
 static SHARED: Mutex<Shared> = Mutex::new(Shared {
+    game: Status::Menus,
     wanted: Wanted {
         status: Status::Menus,
         since: None,
@@ -114,7 +237,8 @@ static THREAD: OnceLock<Thread> = OnceLock::new();
 
 /// Starts the presence thread, once: when the game starts, never for a dedicated server.
 /// `automated` runs (offscreen, benchmarks) only talk to a test's fake Discord.
-pub fn start(enabled: bool, automated: bool) {
+/// The status [`set`] gave before, the switch included, is the first one sent.
+pub fn start(automated: bool) {
     let fake_discord = std::env::var_os(IPC_DIR_ENV).is_some();
     if THREAD.get().is_some()
         || std::env::var_os("HORIZON_NO_DISCORD").is_some_and(|v| v != "0")
@@ -122,9 +246,6 @@ pub fn start(enabled: bool, automated: bool) {
     {
         return;
     }
-    if !enabled {
-        lock().wanted.status = Status::Off;
-    }
     match std::thread::Builder::new()
         .name("Discord presence".into())
         .spawn(run)
@@ -136,12 +257,13 @@ pub fn start(enabled: bool, automated: bool) {
     }
 }
 
-/// What the player does now; only a change wakes the thread. Free without [`start`].
+/// What the player does now; only a change wakes the thread. Kept for [`start`] before it.
 pub fn set(status: Status) {
-    let Some(thread) = THREAD.get() else {
-        return;
-    };
-    if lock().wanted.update(status, unix_now()) {
+    let mut shared = lock();
+    shared.game = status;
+    let changed = shared.wanted.update(shown(status), unix_now());
+    drop(shared);
+    if let Some(thread) = THREAD.get().filter(|_| changed) {
         thread.unpark();
     }
 }
@@ -582,6 +704,39 @@ mod tests {
 
     /// A fake Discord: answers the handshake with READY, each command with its nonce, after a ping.
     #[cfg(unix)]
+    /// The switch as the player's settings and the Extras page see it. The only test that
+    /// touches the presence's statics.
+    #[test]
+    fn the_switch_clears_the_activity_and_keeps_the_first_players_line() {
+        let wanted = || lock().wanted.status;
+        Setting.load(KEY, "false");
+        // A splitscreen player's settings file loads later and keeps the first player's.
+        Setting.load(KEY, "true");
+        set(Status::Menus);
+        assert!(!enabled());
+        assert_eq!(wanted(), Status::Off);
+        let mut rows = Vec::new();
+        SECTION.rows(&mut rows);
+        assert_eq!(
+            rows,
+            [Row::Toggle {
+                label: LABEL,
+                on: false
+            }]
+        );
+        let mut lines = Vec::new();
+        Setting.save(&mut |k, v| lines.push(format!("{k}:{v}")));
+        assert_eq!(lines, ["discordPresence:false"]);
+        assert!(!Setting.is_default());
+        // On from the page: what the game said last is shown at once.
+        SECTION.act(0, Act::Press);
+        assert_eq!(wanted(), Status::Menus);
+        assert!(Setting.is_default());
+        SECTION.act(0, Act::Press);
+        assert_eq!(wanted(), Status::Off);
+        SECTION.act(0, Act::Press);
+    }
+
     #[test]
     fn talks_to_discord_over_its_socket() {
         let dir = std::env::temp_dir().join(format!("horizon-discord-{}", std::process::id()));

crates/horizon-friends/Cargo.toml

@@ -8,6 +8,8 @@ description = "Play with friends: invite codes, the relay protocol, the end-to-e
 
 [dependencies]
 horizon-addresses = { path = "../horizon-addresses" }
+# The game's side (`game`): the platform's hooks, for horizon-official.
+horizon-platform = { path = "../horizon-platform", optional = true }
 # The key exchange keyed by the code's secret, then the frames.
 spake2 = { version = "0.4", features = ["getrandom"] }
 chacha20poly1305 = "0.10"
@@ -21,5 +23,10 @@ if-addrs = "0.15"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1.0.151"
 
+[features]
+# Play with Friends in the game: the resolver of `friend:` addresses on the platform's hooks
+# (`game.rs`), which horizon-official registers. The launcher and the relay don't need it.
+game = ["dep:horizon-platform"]
+
 [lints]
 workspace = true

crates/horizon-friends/src/game.rs

@@ -0,0 +1,174 @@
+//! Play with Friends in the game, joining side (the `game` feature): the engine's `friend:`
+//! addresses (`horizon_platform::hooks::tunnel`) read as invite codes, and joined through this
+//! crate's tunnel. `horizon-official` registers [`HOOKS`]; the game's own executable has none, so
+//! there no invite code joins.
+use crate::{
+    PathMode,
+    guest::{self, GuestConfig},
+    invite::{Parsed, parse},
+};
+use horizon_platform::{
+    hooks::{
+        Hooks,
+        tunnel::{Opened, Progress, Resolver},
+    },
+    version::{PROTOCOL_VERSION, VANILLA_VERSION},
+};
+use std::net::SocketAddr;
+
+/// What `horizon-official` registers: Play with Friends' hooks.
+pub static HOOKS: Friends = Friends;
+
+pub struct Friends;
+
+impl Hooks for Friends {
+    fn tunnel(&self) -> Option<&dyn Resolver> {
+        Some(&Invites)
+    }
+}
+
+struct Invites;
+
+impl Resolver for Invites {
+    fn is_code(&self, code: &str, full: bool) -> bool {
+        match parse(code) {
+            Some(Parsed::Long(_)) => true,
+            Some(Parsed::Short(_)) => !full,
+            None => false,
+        }
+    }
+
+    fn nameplate(&self, code: &str) -> Option<String> {
+        match parse(code) {
+            Some(Parsed::Short(c)) => Some(c.nameplate),
+            _ => None,
+        }
+    }
+
+    /// The relay is kept beside the addresses: two hosts on other networks can
+    /// share a private address and the fixed direct port.
+    fn public_part(&self, code: &str) -> String {
+        match parse(code) {
+            Some(Parsed::Short(code)) => code.nameplate,
+            Some(Parsed::Long(invite)) => {
+                let relay = invite
+                    .relay
+                    .map(|r| format!("{}/{}", r.address, r.code.nameplate));
+                let endpoints = invite.endpoints.iter().map(SocketAddr::to_string);
+                endpoints.chain(relay).collect::<Vec<_>>().join(",")
+            }
+            None => String::new(),
+        }
+    }
+
+    fn relay_from_env(&self) -> Option<String> {
+        crate::relay_url()
+    }
+
+    fn open(
+        &self,
+        code: &str,
+        relay: Option<String>,
+        progress: &mut dyn FnMut(Progress),
+    ) -> Result<Opened, String> {
+        progress(Progress::Finding);
+        let tunnel = guest::join(&GuestConfig {
+            code: code.to_owned(),
+            relay,
+            protocol: PROTOCOL_VERSION,
+            game: VANILLA_VERSION.to_owned(),
+            path: PathMode::from_env(),
+        })
+        .map_err(|e| e.to_string())?;
+        progress(Progress::Connected {
+            direct: tunnel.direct,
+        });
+        let loopback = tunnel.serve_loopback().map_err(|e| e.to_string())?;
+        Ok(Opened {
+            port: loopback.port,
+            token: loopback.token.to_vec(),
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Invites, Resolver};
+    use crate::{
+        code::Code,
+        invite::{self, Invite},
+    };
+    use horizon_platform::hooks::tunnel;
+
+    fn short(nameplate: &str, secret: &str) -> Code {
+        Code {
+            nameplate: nameplate.into(),
+            secret: secret.into(),
+        }
+    }
+
+    #[test]
+    fn the_engine_and_the_codes_name_the_same_addresses() {
+        assert_eq!(tunnel::PREFIX, crate::ADDRESS_PREFIX);
+    }
+
+    #[test]
+    fn invites_are_read_and_their_secret_never_shown() {
+        let invite = Invite {
+            secret: *b"0123456789",
+            port: 25580,
+            endpoints: vec!["192.168.1.20:25580".parse().unwrap()],
+            relay: None,
+        }
+        .encode();
+        // Direct Connection takes a full invite; a short code needs Join a Friend.
+        assert!(Invites.is_code(&invite, true));
+        let short = short("K7QM", "3XPD").to_string();
+        assert!(Invites.is_code(&short, false));
+        assert!(!Invites.is_code(&short, true));
+        // A short code could be a host name, so Direct Connection keeps host names.
+        for host in ["localhost", "example.org:25566", "abcdefgh", "[::1]:25568"] {
+            assert!(!Invites.is_code(host, true), "{host}");
+        }
+        // Only a short code's name may be shown; a full invite is all secret.
+        assert_eq!(Invites.nameplate(&invite), None);
+        assert_eq!(Invites.nameplate(&short).as_deref(), Some("K7QM"));
+    }
+
+    #[test]
+    fn friends_worlds_are_told_apart_by_their_hosts_never_by_their_secrets() {
+        const PORT: u16 = 50000;
+        const RELAY: &str = "relay.example.com:443";
+        let invite = |secret: u8, host: &str, relay: Option<Code>| {
+            let code = Invite {
+                secret: [secret; invite::SECRET],
+                port: PORT,
+                endpoints: vec![format!("{host}:{PORT}").parse().unwrap()],
+                relay: relay.map(|code| invite::RelayRef {
+                    address: RELAY.into(),
+                    code,
+                }),
+            }
+            .encode();
+            Invites.public_part(&code)
+        };
+        assert_ne!(
+            invite(1, "192.168.1.5", None),
+            invite(1, "192.168.1.6", None),
+            "two friends"
+        );
+        assert_ne!(
+            invite(1, "192.168.1.5", Some(short("ABCD", "WXYZ"))),
+            invite(1, "192.168.1.5", Some(short("EFGH", "WXYZ"))),
+            "two friends on other networks behind the same private address"
+        );
+        assert_eq!(
+            invite(1, "192.168.1.5", Some(short("ABCD", "WXYZ"))),
+            invite(2, "192.168.1.5", Some(short("ABCD", "QRST"))),
+            "the invite's and the relay code's secrets take no part"
+        );
+        let typed = |code: Code| Invites.public_part(&code.to_string());
+        assert_eq!(typed(short("ABCD", "WXYZ")), typed(short("ABCD", "QRST")));
+        assert_eq!(typed(short("ABCD", "WXYZ")), "ABCD");
+    }
+}

crates/horizon-friends/src/lib.rs

@@ -11,6 +11,8 @@
 pub mod code;
 pub mod crypto;
 pub mod direct;
+#[cfg(feature = "game")]
+pub mod game;
 pub mod guest;
 pub mod host;
 pub mod invite;

crates/horizon-hooks/src/hud.rs

@@ -0,0 +1,57 @@
+//! HUD drawing (docs/layers.md, "Platform registries"): a crate above the engine draws on the HUD
+//! where the extras do, in the corners they share, without an engine file naming it. With no layer
+//! registered the engine builds no canvas.
+use crate::TooLate;
+use crate::registry::Registry;
+
+/// A corner of the screen. Boxes placed in one stack away from its edge.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Corner {
+    TopLeft,
+    TopRight,
+    BottomLeft,
+    BottomRight,
+}
+
+/// What a layer draws with, in GUI pixels (the player's GUI scale applied). Colours are
+/// `0xAARRGGBB`.
+pub trait Canvas {
+    /// The screen's width and height.
+    fn size(&self) -> (f32, f32);
+    /// The text of a translation key in the player's language.
+    fn tr(&self, key: &str) -> String;
+    /// How wide `text` is drawn.
+    fn text_width(&self, text: &str) -> f32;
+    /// A line of text from its top-left corner, with the game's text shadow or not.
+    fn text(&mut self, x: f32, y: f32, text: &str, argb: u32, shadow: bool);
+    /// A filled rectangle.
+    fn fill(&mut self, x: f32, y: f32, w: f32, h: f32, argb: u32);
+    /// Where a `w` × `h` box goes in `corner`: below (or above) what the corner holds already,
+    /// the minimap, the PvP widgets and mods' boxes. `None` while the corner is hidden (the debug
+    /// screen covers the top left): draw nothing there then.
+    fn place(&mut self, corner: Corner, w: f32, h: f32) -> Option<(f32, f32)>;
+}
+
+/// Something a crate draws on the HUD, every frame the HUD is drawn (not with F1, nor under a
+/// screen that hides it). It reads its own state and must return quickly.
+pub trait Layer: Sync {
+    fn draw(&self, canvas: &mut dyn Canvas);
+}
+
+static LAYERS: Registry<dyn Layer> = Registry::new();
+
+/// Adds `layer` to the HUD, above the layers registered before it. Before the game starts, as
+/// [`crate::register`].
+pub fn register(layer: &'static dyn Layer) -> Result<(), TooLate> {
+    LAYERS.register(layer)
+}
+
+/// The engine's side. Only the engine calls it.
+pub mod engine {
+    use super::*;
+
+    /// Every registered layer, sealing the list on the first call.
+    pub fn all() -> &'static [&'static dyn Layer] {
+        LAYERS.all()
+    }
+}

crates/horizon-hooks/src/lib.rs

@@ -13,11 +13,15 @@
 //! does the matching thing.
 //!
 //! The platform registries (docs/layers.md, "Platform registries") have the same shape:
-//! [`settings`] for the settings each crate keeps in its own lines.
+//! [`settings`] for the settings each crate keeps in its own lines, [`pages`] for its settings
+//! pages, [`hud`] for what it draws on the HUD.
 #![forbid(unsafe_code)]
 
+pub mod hud;
+pub mod pages;
 mod registry;
 pub mod settings;
+pub mod tunnel;
 
 use registry::Registry;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -37,6 +41,76 @@ pub trait Hooks: Sync {
 
     /// The game is ending normally: its window closed and the world is saved. Not after a crash.
     fn shutdown(&self) {}
+
+    /// The resolver of `friend:` addresses this crate offers ([`tunnel`]); the first hook that
+    /// offers one is used. Asked on the network thread when joining and on the game thread when
+    /// an address is shown, never per frame.
+    fn tunnel(&self) -> Option<&dyn tunnel::Resolver> {
+        None
+    }
+
+    /// A game window opened: once, before the first frame, for every run that has a window,
+    /// automated ones included ([`Client::automated`]); never for a dedicated server.
+    fn client_started(&self, _client: &Client) {}
+
+    /// What the player is doing, for a status shown outside the game (Discord's): called when it
+    /// changes, not every frame. Splitscreen: the first player's only.
+    fn activity(&self, _now: Activity) {}
+}
+
+/// What [`Hooks::client_started`] gets.
+#[non_exhaustive]
+pub struct Client {
+    /// A run nobody plays: offscreen, a benchmark, a run that quits by itself after some frames.
+    pub automated: bool,
+}
+
+impl Client {
+    pub fn new(automated: bool) -> Self {
+        Self { automated }
+    }
+}
+
+/// What the player is doing ([`Hooks::activity`]).
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum Activity {
+    /// On the title screen or another menu outside a world.
+    Menus,
+    World {
+        play: Play,
+        dimension: Dimension,
+        mode: GameMode,
+    },
+}
+
+/// How the player is in a world.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Play {
+    Singleplayer,
+    /// A server or someone else's LAN world.
+    Multiplayer,
+    /// Their world is open to LAN or friends; `players` counts the host, `max` is how many may
+    /// join.
+    Hosting {
+        players: usize,
+        max: usize,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Dimension {
+    Overworld,
+    Nether,
+    End,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum GameMode {
+    Survival,
+    Creative,
+    Adventure,
+    Spectator,
 }
 
 /// What [`Hooks::started`] gets.
@@ -44,11 +118,14 @@ pub trait Hooks: Sync {
 pub struct Started<'a> {
     /// The build: the release tag (`0.2.31`), or `dev <crate version>` for a build from source.
     pub version: &'a str,
+    /// The player's game folder: servers.dat, options.txt and saves (the working directory unless
+    /// `--game-dir` names another).
+    pub game_dir: &'a std::path::Path,
 }
 
 impl<'a> Started<'a> {
-    pub fn new(version: &'a str) -> Self {
-        Self { version }
+    pub fn new(version: &'a str, game_dir: &'a std::path::Path) -> Self {
+        Self { version, game_dir }
     }
 }
 
@@ -87,6 +164,8 @@ pub mod engine {
     pub fn seal() {
         all();
         crate::settings::all();
+        crate::pages::engine::all();
+        crate::hud::engine::all();
     }
 
     /// [`Hooks::started`].
@@ -110,12 +189,43 @@ pub mod engine {
         }
     }
 
+    /// [`Hooks::client_started`].
+    pub fn client_started(client: &Client) {
+        for hooks in all() {
+            hooks.client_started(client);
+        }
+    }
+
+    /// The activity at the last call (`None` before the first).
+    static ACTIVITY: std::sync::Mutex<Option<Activity>> = std::sync::Mutex::new(None);
+
+    /// [`Hooks::activity`], when `now` differs from the last call's. Cheap enough to call every
+    /// frame: with no hook registered it only loads the empty list.
+    pub fn activity(now: Activity) {
+        let hooks = all();
+        if hooks.is_empty() {
+            return;
+        }
+        let mut last = ACTIVITY.lock().unwrap_or_else(|e| e.into_inner());
+        if last.replace(now) != Some(now) {
+            drop(last);
+            for h in hooks {
+                h.activity(now);
+            }
+        }
+    }
+
     /// [`Hooks::shutdown`].
     pub fn shutdown() {
         for hooks in all() {
             hooks.shutdown();
         }
     }
+
+    /// [`Hooks::tunnel`]: the first registered hook's resolver.
+    pub fn tunnel() -> Option<&'static dyn tunnel::Resolver> {
+        all().iter().find_map(|hooks| hooks.tunnel())
+    }
 }
 
 #[cfg(test)]
@@ -137,6 +247,9 @@ mod tests {
         fn published(&self, open: bool) {
             self.0.lock().unwrap().push(format!("published {open}"));
         }
+        fn activity(&self, now: Activity) {
+            self.0.lock().unwrap().push(format!("{now:?}"));
+        }
     }
 
     /// Implements nothing: the defaults do nothing.
@@ -149,15 +262,29 @@ mod tests {
     fn registered_hooks_hear_the_game_and_late_ones_are_refused() {
         register(&RECORDER).unwrap();
         register(&Silent).unwrap();
-        engine::started(&Started::new("0.2.31"));
+        engine::started(&Started::new("0.2.31", std::path::Path::new("game")));
         // Changes only: the same state every frame is said once.
         for open in [false, true, true, true, false, false] {
             engine::published(open);
         }
+        let world = Activity::World {
+            play: Play::Singleplayer,
+            dimension: Dimension::Nether,
+            mode: GameMode::Creative,
+        };
+        for now in [Activity::Menus, Activity::Menus, world, world] {
+            engine::activity(now);
+        }
         engine::shutdown();
         assert_eq!(
             *RECORDER.0.lock().unwrap(),
-            ["started 0.2.31", "published true", "published false"]
+            [
+                "started 0.2.31",
+                "published true",
+                "published false",
+                "Menus",
+                "World { play: Singleplayer, dimension: Nether, mode: Creative }"
+            ]
         );
         assert_eq!(register(&Silent), Err(TooLate));
     }

crates/horizon-hooks/src/pages.rs

@@ -0,0 +1,108 @@
+//! Pages (docs/layers.md, "Platform registries"): a crate above the engine adds a settings page to
+//! the options screens without an engine file naming it. The engine draws its rows with the same
+//! widgets, tooltips, narration, controller focus and `horizon-ctl` ids as its own pages, and asks
+//! for them only while the page is open.
+use crate::TooLate;
+use crate::registry::Registry;
+
+/// Where a page's entry is.
+#[non_exhaustive]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Place {
+    /// A button on the Horizon Settings page, after the engine's own pages.
+    HorizonSettings,
+    /// A full-width button of the pause menu, above Options (under Splitscreen's settings). The
+    /// pause menu has it only when a page registered there.
+    Pause,
+    /// A section of Horizon Settings' Extras page, with no entry: its rows join the page's group
+    /// its title names when the page has one (`horizon.extras.header.multiplayer`), else they
+    /// start a group of their own after the page's. A [`Row::Heading`] starts another group. A
+    /// [`Row::Key`] shows its key there, without changing it: give a page of its own to a key.
+    Extras,
+}
+
+/// One page. Its values live in the crate (statics, often its settings [`crate::settings::Store`]);
+/// the engine rebuilds the rows when it draws the page and after each act.
+pub trait Page: Sync {
+    /// Stable and unique: `<crate>.<page>`, as `horizon-ctl` and logs name it.
+    fn id(&self) -> &'static str;
+    /// The page's title and its entry's label: a translation key.
+    fn title(&self) -> &'static str;
+    /// Where its entry is.
+    fn place(&self) -> Place;
+    /// Its rows, top to bottom.
+    fn rows(&self, rows: &mut Vec<Row>);
+    /// The player acted on row `row` (its index in [`Page::rows`]). The options screen saves the
+    /// settings when it closes, as for every setting.
+    fn act(&self, row: usize, act: Act);
+    /// What row `row` says on hover (and the narrator after its label), which may follow its
+    /// value. None by default.
+    fn tooltip(&self, _row: usize) -> Option<Label> {
+        None
+    }
+}
+
+/// A row of a page. Labels are translation keys.
+#[non_exhaustive]
+#[derive(Clone, Debug, PartialEq)]
+pub enum Row {
+    /// A section's heading.
+    Heading(&'static str),
+    /// A line of grey text: a value such as a path, shown as it is.
+    Note(String),
+    /// `<label>: ON` or `OFF`; a press flips it.
+    Toggle { label: &'static str, on: bool },
+    /// `<label>: <value>`; a press steps forward, a shift-press back ([`Act::PressBack`]).
+    Cycle { label: &'static str, value: Label },
+    /// `<label>: <text>` on a slider at `value` (0 to 1); dragging or the arrow keys send
+    /// [`Act::Slide`].
+    Slider {
+        label: &'static str,
+        value: f32,
+        text: Label,
+    },
+    /// A button that does something.
+    Button { label: &'static str },
+    /// A key binding, as Key Binds shows one: `key` is its key name (`key.keyboard.z`,
+    /// `key.mouse.left`). A press waits for the next key or mouse button ([`Act::Bind`]).
+    Key { label: &'static str, key: String },
+}
+
+/// A value shown on a row: a translation key, or text shown as it is (a number, a name).
+#[derive(Clone, Debug, PartialEq)]
+pub enum Label {
+    Key(&'static str),
+    Value(String),
+}
+
+/// What the player did to a row.
+#[non_exhaustive]
+#[derive(Clone, Debug, PartialEq)]
+pub enum Act {
+    /// A click, or Enter or the controller's select on the row.
+    Press,
+    /// The same with Shift held: a cycle steps back.
+    PressBack,
+    /// A slider moved to this position (0 to 1).
+    Slide(f32),
+    /// A key row got its new key: its key name (`key.keyboard.z`).
+    Bind(String),
+}
+
+static PAGES: Registry<dyn Page> = Registry::new();
+
+/// Adds `page` to the game's options screens. Before the game starts, as [`crate::register`];
+/// entries keep the order pages registered in.
+pub fn register(page: &'static dyn Page) -> Result<(), TooLate> {
+    PAGES.register(page)
+}
+
+/// The engine's side. Only the engine calls it.
+pub mod engine {
+    use super::*;
+
+    /// Every registered page, sealing the list on the first call.
+    pub fn all() -> &'static [&'static dyn Page] {
+        PAGES.all()
+    }
+}

crates/horizon-hooks/src/tunnel.rs

@@ -0,0 +1,50 @@
+//! Addresses a higher layer opens a tunnel for: `friend:<code>`, Play with Friends' invite codes
+//! (a Horizon crate, docs/play-with-friends.md). The engine keeps the address form and the join
+//! (`net.rs`); the [`Resolver`] a registered hook offers ([`Hooks::tunnel`](crate::Hooks::tunnel))
+//! reads the codes and opens the tunnel, which the client then reaches on a loopback port like any
+//! server. Without one (horizon-client's own executable, the server build) no code is one, and
+//! such an address is refused, never retried.
+//!
+//! Hosting needs no hook here: the tunnel's host end connects to the world's LAN port over
+//! loopback, so its guests are LAN guests.
+/// What starts a tunnel address.
+pub const PREFIX: &str = "friend:";
+
+/// How a join is going, shown on the connect screen.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Progress {
+    /// Finding the host from the code.
+    Finding,
+    /// The tunnel reached the host: `direct`ly, or through a relay.
+    Connected { direct: bool },
+}
+
+/// The tunnel's local end: the loopback port to connect to, and the token to send on it first
+/// (the port takes only the client that sends it).
+pub struct Opened {
+    pub port: u16,
+    pub token: Vec<u8>,
+}
+
+/// Reads tunnel codes and opens tunnels. The join calls it on the network thread; the address
+/// shown to players asks it on the game thread, never per frame.
+pub trait Resolver: Send + Sync {
+    /// Whether `code` is a code; with `full`, only a full one (a short relay code could also be a
+    /// host name).
+    fn is_code(&self, code: &str, full: bool) -> bool;
+    /// A short code's name, the part players may see (`K7QM` of `K7QM-3XPD`); None for any other
+    /// code, whose secret is all through it.
+    fn nameplate(&self, code: &str) -> Option<String>;
+    /// What tells one shared world from another, without any secret: native mods key a server's
+    /// data by it.
+    fn public_part(&self, code: &str) -> String;
+    /// The relay the environment names, used when the player set none (`friendsRelay`).
+    fn relay_from_env(&self) -> Option<String>;
+    /// Reach the host from `code`, directly or through `relay`, and open the tunnel's local end.
+    fn open(
+        &self,
+        code: &str,
+        relay: Option<String>,
+        progress: &mut dyn FnMut(Progress),
+    ) -> Result<Opened, String>;
+}

crates/horizon-items/src/item_data.rs

@@ -368,9 +368,22 @@ impl ItemStack {
         }
         self.tidy();
     }
-    /// `ItemStack.enchant`: upgrade to the higher level.
+    /// `ItemStack.enchant`: upgrade to the higher level. Vanilla's
+    /// `EnchantmentHelper.updateEnchantments` returns EMPTY when the component
+    /// is absent, so a removal patch makes this a no-op.
     pub fn enchant(&mut self, id: &str, level: u32) {
         let book = &*self.item == "minecraft:enchanted_book";
+        let removal = if book {
+            "!minecraft:stored_enchantments"
+        } else {
+            "!minecraft:enchantments"
+        };
+        if self
+            .data()
+            .is_some_and(|data| data.other(removal).is_some())
+        {
+            return;
+        }
         let data = self.data_mut();
         let list = if book {
             &mut data.stored_enchantments
@@ -2012,6 +2025,30 @@ mod tests {
         check_hive_saved_patch(false);
     }
 
+    #[test]
+    fn an_absent_enchantments_component_is_not_enchantable() {
+        let mut stack = ItemStack::new("minecraft:diamond_sword", 1);
+        stack.data_mut().set_other(
+            "!minecraft:enchantments",
+            Some(horizon_world::nbt::Tag::compound(Vec::<(
+                &str,
+                horizon_world::nbt::Tag,
+            )>::new())),
+        );
+        stack.enchant("minecraft:sharpness", 1);
+        assert!(stack.enchantments().is_empty());
+        let mut book = ItemStack::new("minecraft:enchanted_book", 1);
+        book.data_mut().set_other(
+            "!minecraft:stored_enchantments",
+            Some(horizon_world::nbt::Tag::compound(Vec::<(
+                &str,
+                horizon_world::nbt::Tag,
+            )>::new())),
+        );
+        book.enchant("minecraft:sharpness", 1);
+        assert!(book.stored_enchantments().is_empty());
+    }
+
     #[test]
     fn components_round_trip() {
         let mut stack = ItemStack::new("minecraft:diamond_sword", 1);

crates/horizon-items/src/items.rs

@@ -1278,6 +1278,44 @@ impl Items {
         }
         self.get(&stack.item)?.tool_damage_per_block
     }
+    /// `ItemAttributeModifiers` from the stack's component, else the item's
+    /// prototype: (attribute, id, amount, operation, slot group).
+    pub fn attribute_modifiers(
+        &self,
+        stack: &ItemStack,
+    ) -> Vec<(String, String, f64, String, String)> {
+        if stack
+            .data()
+            .is_some_and(|d| d.other("!minecraft:attribute_modifiers").is_some())
+        {
+            return Vec::new();
+        }
+        if let Some(horizon_world::nbt::Tag::List(entries)) = stack
+            .data()
+            .and_then(|d| d.other("minecraft:attribute_modifiers"))
+        {
+            return entries
+                .iter()
+                .filter_map(|entry| {
+                    let string = |key: &str| match entry.get(key) {
+                        Some(horizon_world::nbt::Tag::String(s)) => Some(s.to_string_lossy()),
+                        _ => None,
+                    };
+                    Some((
+                        string("type")?,
+                        string("id")?,
+                        horizon_world::datafix::dynamic::as_number(entry.get("amount")?)?
+                            .double_value(),
+                        string("operation").unwrap_or_else(|| "add_value".into()),
+                        string("slot").unwrap_or_else(|| "any".into()),
+                    ))
+                })
+                .collect();
+        }
+        self.get(&stack.item)
+            .map(|i| i.modifiers.clone())
+            .unwrap_or_default()
+    }
     /// Mining wear on an already durable item prototype. Custom durability on
     /// non-durable items needs item-aware DAMAGE-presence decoding first.
     pub fn mining_damage_capacity(&self, stack: &ItemStack) -> u32 {
@@ -2933,6 +2971,45 @@ mod tests {
         fs::remove_dir_all(root).unwrap();
     }
 
+    #[test]
+    fn attribute_modifiers_come_from_the_stack() {
+        let items = Items::for_tests(HashMap::new());
+        let mut sword = ItemStack::new("minecraft:diamond_sword", 1);
+        let attack = horizon_world::nbt::Tag::compound([
+            (
+                "type",
+                horizon_world::nbt::Tag::String("minecraft:attack_damage".into()),
+            ),
+            (
+                "id",
+                horizon_world::nbt::Tag::String("minecraft:test".into()),
+            ),
+            ("amount", horizon_world::nbt::Tag::Double(0.1f64.to_bits())),
+            (
+                "operation",
+                horizon_world::nbt::Tag::String("add_value".into()),
+            ),
+            ("slot", horizon_world::nbt::Tag::String("mainhand".into())),
+        ]);
+        sword.data_mut().set_other(
+            "minecraft:attribute_modifiers",
+            Some(horizon_world::nbt::Tag::List(vec![attack])),
+        );
+        let modifiers = items.attribute_modifiers(&sword);
+        assert_eq!(modifiers.len(), 1);
+        assert_eq!(modifiers[0].0, "minecraft:attack_damage");
+        // A double, as `AttributeModifier.amount`: not rounded through a float.
+        assert_eq!(modifiers[0].2, 0.1);
+        sword.data_mut().set_other(
+            "!minecraft:attribute_modifiers",
+            Some(horizon_world::nbt::Tag::compound(Vec::<(
+                &str,
+                horizon_world::nbt::Tag,
+            )>::new())),
+        );
+        assert!(items.attribute_modifiers(&sword).is_empty());
+    }
+
     #[test]
     fn admitted_tool_rules_override_defaults_and_removals_survive_saving() {
         let root =

crates/horizon-official-servers/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "horizon-official-servers"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+description = "Horizon's official server in the multiplayer list, and the withdrawn partner server taken out of it (docs/layers.md)"
+
+[dependencies]
+horizon-addresses = { path = "../horizon-addresses" }
+horizon-platform = { path = "../horizon-platform", features = ["protocol"] }
+log = "0.4"
+
+[lints]
+workspace = true

crates/horizon-official-servers/src/lib.rs

@@ -0,0 +1,278 @@
+//! Horizon's own entries in the multiplayer list: the official server, added once at the top,
+//! and the withdrawn partner server, taken back out once.
+//!
+//! A Horizon crate (docs/layers.md): it plugs into the game through the platform's hooks
+//! ([`HOOKS`], when the game starts), which the official executable (`horizon-official`)
+//! registers, and reads servers.dat through `horizon_platform::servers`. horizon-client's plain
+//! executable adds no server. Its addresses are in `horizon-addresses`.
+#![forbid(unsafe_code)]
+
+use horizon_platform::hooks::{Hooks, Started};
+use horizon_platform::servers::{self, ServerEntry};
+use std::path::Path;
+
+/// The server list's hooks, for `horizon_platform::hooks::register`.
+pub static HOOKS: OfficialServers = OfficialServers;
+
+pub struct OfficialServers;
+
+impl Hooks for OfficialServers {
+    /// Someone is playing (not a server, a benchmark or an automated run): their list, once.
+    fn started(&self, game: &Started<'_>) {
+        update(game.game_dir);
+    }
+}
+
+/// At the start of a player's game: the official server into the list in `game_dir` and the
+/// withdrawn partner server out of it, a failure only logged.
+pub fn update(game_dir: &Path) {
+    if let Err(e) = add_official_server(game_dir) {
+        log::warn!("could not add the official server to servers.dat: {e}");
+    }
+    if let Err(e) = withdraw_partner_servers(game_dir) {
+        log::warn!("could not take the withdrawn partner server out of servers.dat: {e}");
+    }
+}
+
+/// Horizon's official survival server: a name and an address like any entry.
+pub const OFFICIAL_SERVER: (&str, &str) = ("Horizon Official", horizon_addresses::OFFICIAL_SERVER);
+/// Beside servers.dat once the official server was offered, so a player who
+/// deletes it never gets it back: the address offered, so a new one moves the
+/// list once. The launcher writes the same file.
+const OFFICIAL_MARKER: &str = "horizon_official_server.txt";
+
+/// An address as the game connects to it: any case, 25565 when no port is given.
+fn address_key(ip: &str) -> Option<(String, u16)> {
+    servers::parse_address(ip).map(|(h, p)| (h.to_ascii_lowercase(), p))
+}
+
+/// Puts the official server at the top of the list in `game_dir`, once: not
+/// again after the player deletes it, and not when the list has its address.
+/// When it moved (the marker names another address), the entries for its
+/// earlier addresses move to the new one, once (`move_official`).
+pub fn add_official_server(game_dir: &Path) -> std::io::Result<()> {
+    let (name, address) = OFFICIAL_SERVER;
+    let marker = game_dir.join(OFFICIAL_MARKER);
+    // A marker that is there but can't be read: offered already, at an address not known.
+    let offered = match std::fs::read_to_string(&marker) {
+        Ok(text) => Some(text),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
+        Err(_) => Some(String::new()),
+    };
+    if offered
+        .as_deref()
+        .is_some_and(|a| address_key(a) == address_key(address))
+    {
+        return Ok(());
+    }
+    let file = game_dir.join("servers.dat");
+    let _guard = servers::lock();
+    let mut list = servers::load(&file);
+    let previous = horizon_addresses::OFFICIAL_SERVER_PREVIOUS;
+    if move_official(&mut list, address, previous) {
+        servers::save(&file, &list)?;
+    }
+    if offered.is_none()
+        && !list
+            .iter()
+            .any(|s| address_key(&s.ip) == address_key(address))
+    {
+        servers::prepend(&file, &ServerEntry::new(name, address))?;
+    }
+    std::fs::write(marker, format!("{address}\n"))
+}
+
+/// Afri-Network, which the game added once below the official server (#9299) until the
+/// partnership ended: the name and address the game gave its entry.
+const WITHDRAWN_PARTNER: (&str, &str) = (
+    "Afri-Network (South Africa)",
+    horizon_addresses::WITHDRAWN_PARTNER_SERVER,
+);
+/// Beside servers.dat: the partner addresses the game offered, one per line (#9299).
+const PARTNER_MARKER: &str = "horizon_partner_servers.txt";
+
+/// Takes the withdrawn partner server back out of the list in `game_dir`, once, where the game
+/// added it: the marker says it was offered and the entry still has the name the game gave it
+/// (an entry the player made or renamed keeps its place). Then the marker goes.
+pub fn withdraw_partner_servers(game_dir: &Path) -> std::io::Result<()> {
+    let marker = game_dir.join(PARTNER_MARKER);
+    let offered = match std::fs::read_to_string(&marker) {
+        Ok(text) => text,
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(()),
+        Err(e) => return Err(e),
+    };
+    let (name, address) = WITHDRAWN_PARTNER;
+    if offered
+        .lines()
+        .any(|l| address_key(l) == address_key(address))
+    {
+        let _guard = servers::lock();
+        servers::remove_where(&game_dir.join("servers.dat"), |n, ip| {
+            n == name && address_key(ip) == address_key(address)
+        })?;
+    }
+    std::fs::remove_file(marker)
+}
+
+/// Points the entries for an earlier official address at `address`, each
+/// keeping the player's name and fields. One entry for the server at most: an
+/// old one goes when the list already has `address`. Whether anything changed.
+fn move_official(list: &mut Vec<ServerEntry>, address: &str, previous: &[&str]) -> bool {
+    let new = address_key(address);
+    let old = |ip: &str| {
+        let ip = address_key(ip);
+        ip.is_some() && ip != new && previous.iter().any(|p| address_key(p) == ip)
+    };
+    let mut present = list.iter().any(|s| address_key(&s.ip) == new);
+    let mut changed = false;
+    list.retain_mut(|s| {
+        if !old(&s.ip) {
+            return true;
+        }
+        changed = true;
+        if present {
+            return false;
+        }
+        present = true;
+        s.ip = address.to_owned();
+        true
+    });
+    changed
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn the_official_server_is_added_once_at_the_top() {
+        let dir = std::env::temp_dir().join(format!("horizon-mp-official-{}", std::process::id()));
+        let (name, address) = OFFICIAL_SERVER;
+        let file = dir.join("servers.dat");
+        let ips = || -> Vec<String> { servers::load(&file).into_iter().map(|s| s.ip).collect() };
+        let fresh = |list: &[ServerEntry]| {
+            let _ = std::fs::remove_dir_all(&dir);
+            std::fs::create_dir_all(&dir).unwrap();
+            if !list.is_empty() {
+                servers::save(&file, list).unwrap();
+            }
+        };
+        // A fresh list: just the official server, named like it.
+        fresh(&[]);
+        add_official_server(&dir).unwrap();
+        assert_eq!(servers::load(&file), [ServerEntry::new(name, address)]);
+        // An existing list: on top, the player's servers kept in their order.
+        let mine = [
+            ServerEntry::new("Mine", "127.0.0.1:2"),
+            ServerEntry::new("Other", "example.org"),
+        ];
+        fresh(&mine);
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), [address, "127.0.0.1:2", "example.org"]);
+        // Once only: a second start adds nothing.
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), [address, "127.0.0.1:2", "example.org"]);
+        // Already there under the player's own name and spelling: not duplicated.
+        fresh(&[
+            ServerEntry::new("SMP", "Play.PlayHorizon.dev:25565"),
+            mine[0].clone(),
+        ]);
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), ["Play.PlayHorizon.dev:25565", "127.0.0.1:2"]);
+        // Deleted by the player: never back.
+        fresh(&mine);
+        add_official_server(&dir).unwrap();
+        servers::save(&file, &mine).unwrap();
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), ["127.0.0.1:2", "example.org"]);
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn the_withdrawn_partner_server_leaves_lists_the_game_put_it_in_once() {
+        let dir = std::env::temp_dir().join(format!("horizon-mp-partner-{}", std::process::id()));
+        let official = OFFICIAL_SERVER.1;
+        let file = dir.join("servers.dat");
+        let marker = dir.join(PARTNER_MARKER);
+        let ips = || -> Vec<String> { servers::load(&file).into_iter().map(|s| s.ip).collect() };
+        let fresh = |list: &[ServerEntry], offered: bool| {
+            let _ = std::fs::remove_dir_all(&dir);
+            std::fs::create_dir_all(&dir).unwrap();
+            servers::save(&file, list).unwrap();
+            if offered {
+                std::fs::write(&marker, "afri-network.co.za\n").unwrap();
+            }
+        };
+        let added = ServerEntry::new("Afri-Network (South Africa)", "afri-network.co.za");
+        // The game added it: it goes, the rest stays in order, and only once.
+        fresh(
+            &[
+                ServerEntry::new("Horizon Official", official),
+                added.clone(),
+                ServerEntry::new("Mine", "127.0.0.1:2"),
+            ],
+            true,
+        );
+        withdraw_partner_servers(&dir).unwrap();
+        assert_eq!(ips(), [official, "127.0.0.1:2"]);
+        assert!(!marker.exists());
+        servers::save(&file, std::slice::from_ref(&added)).unwrap();
+        withdraw_partner_servers(&dir).unwrap();
+        assert_eq!(ips(), ["afri-network.co.za"]);
+        // The player's own entry for that address (their name) stays.
+        fresh(&[ServerEntry::new("ZA", "Afri-Network.co.za:25565")], true);
+        withdraw_partner_servers(&dir).unwrap();
+        assert_eq!(ips(), ["Afri-Network.co.za:25565"]);
+        // Never offered (no marker): nothing changes.
+        fresh(&[added], false);
+        withdraw_partner_servers(&dir).unwrap();
+        assert_eq!(ips(), ["afri-network.co.za"]);
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn a_moved_official_server_moves_the_old_entry_once() {
+        let dir = std::env::temp_dir().join(format!("horizon-mp-moved-{}", std::process::id()));
+        let address = OFFICIAL_SERVER.1;
+        let file = dir.join("servers.dat");
+        let marker = dir.join(OFFICIAL_MARKER);
+        let ips = || -> Vec<String> { servers::load(&file).into_iter().map(|s| s.ip).collect() };
+        let offered_before = |list: &[ServerEntry]| {
+            let _ = std::fs::remove_dir_all(&dir);
+            std::fs::create_dir_all(&dir).unwrap();
+            servers::save(&file, list).unwrap();
+            std::fs::write(&marker, "horizon.bunchy7s.dev\n").unwrap();
+        };
+        // The old address under the player's own name and spelling: moved, name and place kept.
+        let mut old = ServerEntry::new("Our SMP", "Horizon.Bunchy7s.dev:25565");
+        old.icon = Some("AAAA".into());
+        offered_before(&[ServerEntry::new("Mine", "127.0.0.1:2"), old]);
+        add_official_server(&dir).unwrap();
+        let list = servers::load(&file);
+        assert_eq!(ips(), ["127.0.0.1:2", address]);
+        assert_eq!(
+            (list[1].name.as_str(), list[1].icon.as_deref()),
+            ("Our SMP", Some("AAAA"))
+        );
+        assert_eq!(
+            std::fs::read_to_string(&marker).unwrap(),
+            format!("{address}\n")
+        );
+        // Once: the old address added back afterwards is the player's.
+        servers::prepend(&file, &ServerEntry::new("Old", "horizon.bunchy7s.dev")).unwrap();
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), ["horizon.bunchy7s.dev", "127.0.0.1:2", address]);
+        // The new address already listed: no second entry.
+        offered_before(&[
+            ServerEntry::new("Old", "horizon.bunchy7s.dev"),
+            ServerEntry::new("New", address),
+        ]);
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), [address]);
+        // Deleted by the player before the move: not offered again; another port is left alone.
+        offered_before(&[ServerEntry::new("Test", "horizon.bunchy7s.dev:25570")]);
+        add_official_server(&dir).unwrap();
+        assert_eq!(ips(), ["horizon.bunchy7s.dev:25570"]);
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+}

crates/horizon-official/Cargo.toml

@@ -14,6 +14,9 @@ path = "src/main.rs"
 horizon-game = { path = "../horizon-game" }
 horizon-platform = { path = "../horizon-platform" }
 horizon-heartbeat = { path = "../horizon-heartbeat" }
+horizon-friends = { path = "../horizon-friends", features = ["game"] }
+horizon-official-servers = { path = "../horizon-official-servers" }
+horizon-discord = { path = "../horizon-discord" }
 log = "0.4"
 
 [build-dependencies]

crates/horizon-official/src/lib.rs

@@ -4,23 +4,36 @@
 //! (`game-build.yml`); horizon-client keeps its own plain executable.
 //!
 //! Each Horizon crate that runs in the game gives a `&'static` value implementing
-//! `horizon_platform::hooks::Hooks`, and [`register`] adds it. Nothing here depends on an engine
-//! crate.
+//! `horizon_platform::hooks::Hooks`, and its settings store and pages if it has any, and
+//! [`register`] adds them. Nothing here depends on an engine crate.
 #![forbid(unsafe_code)]
 
 use horizon_platform::hooks::{self, Hooks};
+use horizon_platform::{pages, settings};
 
 /// Every Horizon part in the game, in the order its hooks run.
-const PARTS: [&dyn Hooks; 1] = [
+const PARTS: [&dyn Hooks; 4] = [
     // The anonymous "I'm playing" ping.
     &horizon_heartbeat::HOOKS,
+    // Play with Friends: `friend:` addresses join through its tunnel.
+    &horizon_friends::game::HOOKS,
+    // The official server in the player's server list.
+    &horizon_official_servers::HOOKS,
+    // "Playing Horizon" on the player's Discord profile.
+    &horizon_discord::HOOKS,
 ];
+/// Their settings, in the player's settings files.
+const STORES: [&dyn settings::Store; 1] = [&horizon_discord::SETTING];
+/// Their rows and pages in the options screens.
+const PAGES: [&dyn pages::Page; 1] = [&horizon_discord::SECTION];
 
 /// Registers Horizon's in-game parts with the game. The executable calls it before it runs the
 /// game, and so does the launcher's generated executable for native mods.
 pub fn register() {
-    for part in PARTS {
-        if let Err(e) = hooks::register(part) {
+    let late = PARTS.into_iter().map(hooks::register);
+    let late = late.chain(STORES.into_iter().map(settings::register));
+    for result in late.chain(PAGES.into_iter().map(pages::register)) {
+        if let Err(e) = result {
             // The executable registered after starting the game: a bug, not a player's problem.
             log::warn!("Horizon: an in-game part did not register: {e}");
         }

crates/horizon-platform/Cargo.toml

@@ -10,7 +10,7 @@ description = "The platform's public API: what the Horizon layer and mods may us
 # Each part of the engine a Horizon crate may reach, so a crate builds only the engine it uses.
 # level.dat, servers.dat and region files: NBT, compression, region read and write.
 world = ["dep:horizon-world"]
-# A server's address after its SRV record, and the offline-mode UUID of a name.
+# A server's address after its SRV record, the offline-mode UUID of a name, and servers.dat.
 protocol = ["world", "dep:horizon-protocol"]
 # Preparing the game's files from the player's own Minecraft install.
 prepare = ["dep:horizon-prepare"]

crates/horizon-platform/src/lib.rs

@@ -46,7 +46,9 @@ pub use horizon_server_files as server_files;
 /// [`hooks::register`] it before the game starts (docs/layers.md, "How a Horizon crate plugs
 /// in"). The engine's dispatch side is not part of the API.
 pub mod hooks {
-    pub use horizon_hooks::{Hooks, Started, TooLate, register};
+    pub use horizon_hooks::{
+        Activity, Client, Dimension, GameMode, Hooks, Play, Started, TooLate, register, tunnel,
+    };
 }
 
 /// The settings store (`horizon_hooks::settings`): a crate's own `key:value` lines in the game
@@ -54,3 +56,22 @@ pub mod hooks {
 pub mod settings {
     pub use horizon_hooks::settings::{Store, register};
 }
+
+/// Settings pages a crate adds to the options screens (docs/layers.md, "Platform registries").
+pub mod pages {
+    pub use horizon_hooks::pages::{Act, Label, Page, Place, Row, register};
+}
+
+/// Drawing on the HUD (docs/layers.md, "Platform registries").
+pub mod hud {
+    pub use horizon_hooks::hud::{Canvas, Corner, Layer, register};
+}
+
+/// The multiplayer server list as vanilla stores it (`servers.dat`): read, write, add, remove,
+/// and the lock held while it is read and written back.
+#[cfg(feature = "protocol")]
+pub mod servers {
+    pub use horizon_protocol::servers::{
+        ServerEntry, load, lock, parse_address, prepend, remove_where, save,
+    };
+}

crates/horizon-prepare/src/check.rs

@@ -254,6 +254,32 @@ mod tests {
         remove_stamp(&out).unwrap();
     }
 
+    #[test]
+    #[cfg(unix)]
+    fn preparation_releases_its_lock_with_a_retained_descriptor() {
+        let root = folder("retained-lock");
+        let first = crate::hold_lock(&root, &|_| {}).unwrap();
+        // A duplicate retains the same lock reference as a descriptor inherited
+        // by a forked child, without depending on subprocess scheduling.
+        let retained = first.0.try_clone().unwrap();
+        let second = fs::OpenOptions::new()
+            .write(true)
+            .open(root.join(crate::LOCK))
+            .unwrap();
+        assert!(matches!(
+            second.try_lock(),
+            Err(fs::TryLockError::WouldBlock)
+        ));
+        drop(first);
+        second
+            .try_lock()
+            .expect("the completed preparation kept its lock");
+        second.unlock().unwrap();
+        drop(retained);
+        drop(second);
+        fs::remove_dir_all(root).unwrap();
+    }
+
     #[test]
     fn a_second_preparation_of_a_folder_waits_for_the_first() {
         let root = folder("lock");

crates/horizon-prepare/src/lib.rs

@@ -166,10 +166,20 @@ fn mkdir(path: &Path) -> Result<(), String> {
 /// The lock file each preparation holds in the folders it writes (`LOCK`).
 pub const LOCK: &str = ".horizon-prepare.lock";
 
+pub(crate) struct PreparationLock(fs::File);
+
+impl Drop for PreparationLock {
+    fn drop(&mut self) {
+        // Closing one descriptor does not release a Unix lock while a forked child
+        // still holds another reference. End the preparation's lock explicitly.
+        let _ = self.0.unlock();
+    }
+}
+
 /// One preparation at a time per folder: two launchers or instances preparing into one `--output`,
 /// or sharing `root`'s `.local`, would interleave their writes. A second one waits, saying so;
-/// the lock goes with the returned file, so with the process too.
-pub(crate) fn hold_lock(dir: &Path, log: Log) -> Result<fs::File, String> {
+/// the returned guard releases it when preparation ends, even if a child inherited the file.
+pub(crate) fn hold_lock(dir: &Path, log: Log) -> Result<PreparationLock, String> {
     mkdir(dir)?;
     let path = dir.join(LOCK);
     let error = |e: std::io::Error| format!("{}: {e}", path.display());
@@ -190,7 +200,7 @@ pub(crate) fn hold_lock(dir: &Path, log: Log) -> Result<fs::File, String> {
         }
         Err(fs::TryLockError::Error(e)) => return Err(error(e)),
     }
-    Ok(file)
+    Ok(PreparationLock(file))
 }
 
 /// Whether two folders are one, through `..`, links and case; a missing folder is created first.

crates/horizon-protocol/src/servers.rs

@@ -67,6 +67,13 @@ impl ServerEntry {
     }
 }
 
+/// Held while servers.dat is read and written back, so a ping storing an icon and a list
+/// saved by the screen or at startup don't undo each other's change.
+pub fn lock() -> std::sync::MutexGuard<'static, ()> {
+    static SAVING: std::sync::Mutex<()> = std::sync::Mutex::new(());
+    SAVING.lock().unwrap_or_else(|e| e.into_inner())
+}
+
 /// ServerList.load: the shown entries; missing or unreadable files give an empty list.
 pub fn load(path: &Path) -> Vec<ServerEntry> {
     load_all(path).0

crates/horizon-relay/src/lib.rs

@@ -114,6 +114,12 @@ impl Config {
         if let Some(v) = var::<f64>("RELAY_GLOBAL_UNKNOWN_PER_MIN") {
             c.global_unknown_per_min = v;
         }
+        if let Some(v) = var::<f64>("RELAY_NAMEPLATE_UNKNOWN_PER_MIN") {
+            c.rates.nameplate_unknown_per_min = v;
+        }
+        if let Some(v) = var::<f64>("RELAY_NAMEPLATE_UNKNOWN_BURST") {
+            c.rates.nameplate_unknown_burst = v;
+        }
         if let Some(v) = var::<u8>("RELAY_PER_ADDRESS_LIMITS") {
             c.per_address = v != 0;
         }
@@ -668,8 +674,8 @@ fn join(
     let now = Instant::now();
     state.joins.fetch_add(1, Ordering::Relaxed);
     // The budgets for unknown codes (the site's, then the global one) are checked before the
-    // lookup, so a refusal says nothing about whether the nameplate exists. The site's comes first:
-    // emptying the global budget takes many sites, not the /64s of one home's /56.
+    // lookup, so a refusal says nothing about whether the nameplate exists. The site's comes
+    // first: emptying the global budget takes many sites, not the /64s of one home's /56.
     let allowed = {
         let mut limiter = locked(&state.limiter);
         limiter.allow_join(peer.ip(), now) && limiter.site_unknown_has(peer.ip(), now)
@@ -681,6 +687,15 @@ fn join(
     let Some(nameplate) = code::parse_nameplate(nameplate) else {
         return refuse(&mut stream, ErrorCode::BadRequest);
     };
+    // The nameplate's own budget: what one address set can take of the global unknown budget for
+    // a single short code. Checked before the lookup like the other budgets, so a refusal says
+    // nothing about whether the code exists. It counts unknown short codes only, so a wrong secret
+    // for an existing code stays the host's limit (five, then it retires the code), not the
+    // relay's.
+    if !locked(&state.limiter).nameplate_unknown_has(&nameplate, now) {
+        state.rate_limited.fetch_add(1, Ordering::Relaxed);
+        return refuse(&mut stream, ErrorCode::RateLimited);
+    }
     let session = random_u64();
     let (atx, arx) = sync_channel(1);
     let lookup = {
@@ -720,6 +735,7 @@ fn join(
             {
                 let mut limiter = locked(&state.limiter);
                 limiter.unknown(peer.ip(), now);
+                limiter.nameplate_unknown_take(&nameplate, now);
                 limiter.site_unknown_take(peer.ip(), now);
             }
             locked(&state.global_unknown).try_take(now);

crates/horizon-relay/src/limits.rs

@@ -93,6 +93,11 @@ pub struct Rates {
     /// before the global budget, so emptying that takes many sites rather than one home's /64s.
     pub site_unknown_per_min: f64,
     pub site_unknown_burst: f64,
+    /// Unknown short codes one nameplate may receive a minute (and the burst), from every address
+    /// at once: what one address set can take of the global budget for a single short code. Only
+    /// unknown short codes spend it; a wrong secret for a code that exists is the host's limit.
+    pub nameplate_unknown_per_min: f64,
+    pub nameplate_unknown_burst: f64,
 }
 impl Default for Rates {
     fn default() -> Self {
@@ -108,6 +113,8 @@ impl Default for Rates {
             open_per_address: 64,
             site_unknown_per_min: 24.0,
             site_unknown_burst: 6.0,
+            nameplate_unknown_per_min: 5.0,
+            nameplate_unknown_burst: 10.0,
         }
     }
 }
@@ -170,6 +177,8 @@ pub struct Limiter {
     open: HashMap<(IpAddr, u8), usize>,
     /// Unknown-code budgets by [`site_key`], swept with the addresses.
     sites: HashMap<IpAddr, Site>,
+    /// Unknown-code budgets by nameplate, swept with the sites.
+    nameplates: HashMap<String, Site>,
 }
 impl Limiter {
     pub fn new(rates: Rates, enabled: bool) -> Self {
@@ -181,6 +190,7 @@ impl Limiter {
             hosts: HashMap::new(),
             open: HashMap::new(),
             sites: HashMap::new(),
+            nameplates: HashMap::new(),
         }
     }
     /// Count one more connection open from `ip`, unless its address (or IPv6 site) holds as many
@@ -235,6 +245,46 @@ impl Limiter {
             self.site(ip, now).unknown.try_take(now);
         }
     }
+    fn nameplate(&mut self, nameplate: &str, now: Instant) -> &mut Site {
+        let r = &self.rates;
+        let site = self
+            .nameplates
+            .entry(nameplate.to_owned())
+            .or_insert_with(|| Site {
+                unknown: Bucket::new(
+                    r.nameplate_unknown_per_min / 60.0,
+                    r.nameplate_unknown_burst,
+                    now,
+                ),
+                seen: now,
+            });
+        site.seen = now;
+        site
+    }
+    /// Whether `nameplate` has unknown-code budget left (checked before every join, as the site's
+    /// and the global budget are, so a refusal says nothing about whether the code exists).
+    ///
+    /// A nameplate this relay has not seen has its whole burst left, so the check does not record
+    /// one: only [`Limiter::nameplate_unknown_take`] does, and a join refused later leaves no state.
+    pub fn nameplate_unknown_has(&mut self, nameplate: &str, now: Instant) -> bool {
+        if !self.enabled {
+            return true;
+        }
+        match self.nameplates.get_mut(nameplate) {
+            Some(site) => site.unknown.has(now),
+            None => true,
+        }
+    }
+    /// An unknown code for `nameplate`: spends its own budget, whichever address asked.
+    pub fn nameplate_unknown_take(&mut self, nameplate: &str, now: Instant) {
+        if self.enabled {
+            self.nameplate(nameplate, now).unknown.try_take(now);
+        }
+    }
+    #[cfg(test)]
+    fn nameplates_tracked(&self) -> usize {
+        self.nameplates.len()
+    }
     /// Count one more host open from `ip`, unless its address (or IPv6 site)
     /// holds as many as it may already.
     pub fn open_host(&mut self, ip: IpAddr) -> bool {
@@ -278,6 +328,8 @@ impl Limiter {
             // An idle site's bucket has refilled long before: dropping it changes nothing.
             self.sites
                 .retain(|_, s| now.saturating_duration_since(s.seen) < keep);
+            self.nameplates
+                .retain(|_, s| now.saturating_duration_since(s.seen) < keep);
         }
         let r = &self.rates;
         let a = self
@@ -417,6 +469,43 @@ mod tests {
         assert!(!v6.site_unknown_has("2001:db8:7:1ff::1".parse().unwrap(), t));
     }
 
+    #[test]
+    fn a_nameplate_spends_its_own_unknown_code_budget() {
+        let t = Instant::now();
+        let mut l = Limiter::new(
+            Rates {
+                nameplate_unknown_per_min: 6.0,
+                nameplate_unknown_burst: 2.0,
+                ..Rates::default()
+            },
+            true,
+        );
+        // Guesses against one code spend its budget, whichever address sends them.
+        assert!(
+            l.nameplate_unknown_has("K7QM", t),
+            "a code not probed yet has its whole burst"
+        );
+        assert_eq!(l.nameplates_tracked(), 0, "the check records nothing");
+        l.nameplate_unknown_take("K7QM", t);
+        assert!(l.nameplate_unknown_has("K7QM", t));
+        l.nameplate_unknown_take("K7QM", t);
+        assert!(!l.nameplate_unknown_has("K7QM", t), "the burst is spent");
+        assert_eq!(l.nameplates_tracked(), 1);
+        assert!(
+            l.nameplate_unknown_has("ZZZZ", t),
+            "another code keeps its own"
+        );
+        assert_eq!(
+            l.nameplates_tracked(),
+            1,
+            "checking another code records nothing"
+        );
+        assert!(
+            l.nameplate_unknown_has("K7QM", t + Duration::from_secs(10)),
+            "one a ten seconds back"
+        );
+    }
+
     #[test]
     fn buckets_refill_at_their_rate() {
         let t = Instant::now();

crates/horizon-render-pipeline/Cargo.toml

@@ -1,12 +0,0 @@
-[package]
-name = "horizon-render-pipeline"
-version = "0.1.0"
-edition.workspace = true
-license.workspace = true
-rust-version.workspace = true
-description = "What an external shader pipeline gives the renderer: its buffers, shadow map and programs. Engine layer; the pack formats that fill it are platform crates"
-
-[dependencies]
-
-[lints]
-workspace = true