horizon-ctl friends answers through Hooks::control (spec #14167 step 3a)

Hooks gains control_commands (a group name and its help lines) and control
(words + the world's ShareView, answering JSON or an error). The control
socket asks the hooks after its own groups; hello and help list the groups
crates add. Play with Friends answers `friends ...` through it, so the
engine no longer calls into friends.rs and game/friends_off.rs goes.

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

crates/horizon-client-render/Cargo.toml

@@ -76,6 +76,10 @@ wgpu = { version = "30.0.1", default-features = false, features = ["gles"] }
 audio = ["dep:cpal"]
 # Helpers horizon-client's tests build their fixtures with.
 test-support = []
+# horizon-client's `horizon-extras`: asking the device for hardware ray tracing on request
+# (`gfx/ray_query.rs`, `HORIZON_RAY_TRACING=1`). Without it the device is requested as without
+# the variable.
+horizon-extras = []
 
 [lints]
 workspace = true

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

@@ -382,8 +382,8 @@ impl RenderAssets {
         };
         // After the connected tiles: a tile identical to a block shares its layer, and the
         // overlays skip shared layers.
-        if draws {
-            emissive = crate::native_emissive::load_optifine(root, &mut sprites);
+        if draws && let Some(suffix) = crate::pack_hooks::formats().emissive_suffix(root) {
+            emissive = crate::native_emissive::load_overlays(root, &suffix, &mut sprites);
         }
         sprites.save_disk_cache();
         if draws {

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

@@ -233,11 +233,11 @@ pub fn texture_path(root: &Path, texture: &str, directory: &str) -> PathBuf {
     }
     let (namespace, path) = texture.split_once(':').unwrap_or(("minecraft", texture));
     let rel = format!("assets/{namespace}/{directory}/{path}.png");
-    root.join(if horizon_optifine::paths::valid(&rel) {
-        &rel
-    } else {
-        NOWHERE
-    })
+    // No `.`, `..` or empty segment, and no `\` (a separator on Windows, where `..\..` climbs).
+    let stays = rel
+        .split('/')
+        .all(|segment| !matches!(segment, "" | "." | "..") && !segment.contains('\\'));
+    root.join(if stays { &rel } else { NOWHERE })
 }
 
 /// `SpriteSourceList.list`: every sprite id of the atlas and its origin.

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

@@ -112,7 +112,11 @@ fn add_sections(groups: &mut Vec<Group<ExtraRow>>) {
                     };
                     Row::new(id, lang::get(label), value)
                 }
-                added::Row::Button { label } => Row::new(id, lang::get(label), Value::Press),
+                added::Row::Button {
+                    label,
+                    active: true,
+                    ..
+                } => 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))
@@ -490,9 +494,7 @@ mod tests {
             added::Place::HorizonSettings
         }
         fn rows(&self, rows: &mut Vec<added::Row>) {
-            rows.push(added::Row::Button {
-                label: "test.elsewhere.button",
-            });
+            rows.push(added::Row::button("test.elsewhere.button"));
         }
         fn act(&self, _: usize, _: Act) {}
     }

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

@@ -0,0 +1,79 @@
+//! Hardware ray queries, only on request (#13780, after the #1180 spike): `HORIZON_RAY_TRACING=1`
+//! at startup asks the device for wgpu's `EXPERIMENTAL_RAY_QUERY` when the GPU has it. Nothing
+//! draws with it yet. Without the variable, and in a build without `horizon-extras` (a Horizon
+//! extra, docs/layers.md), the device is opened exactly as before.
+
+/// The ray query feature.
+const RAY_QUERY: wgpu::Features = wgpu::Features::EXPERIMENTAL_RAY_QUERY;
+
+/// Whether the player asked for ray tracing (the device needs the feature from its creation).
+fn requested() -> bool {
+    asked(std::env::var("HORIZON_RAY_TRACING").ok().as_deref())
+}
+
+/// Whether `HORIZON_RAY_TRACING` set to `var` asks for ray tracing: only in a `horizon-extras`
+/// build.
+fn asked(var: Option<&str>) -> bool {
+    cfg!(feature = "horizon-extras") && var == Some("1")
+}
+
+/// The features to request on `adapter`: ray queries, when asked for and offered.
+pub(super) fn features(adapter: &wgpu::Adapter) -> wgpu::Features {
+    let features = pick(requested(), adapter.features());
+    if requested() {
+        let info = adapter.get_info();
+        if features.is_empty() {
+            log::warn!(
+                "Horizon renderer: ray tracing asked for, but {} on {:?} has no hardware ray \
+                 queries; it stays off",
+                info.name,
+                info.backend
+            );
+        } else {
+            log::info!(
+                "Horizon renderer: ray queries on ({} on {:?})",
+                info.name,
+                info.backend
+            );
+        }
+    }
+    features
+}
+
+fn pick(requested: bool, offered: wgpu::Features) -> wgpu::Features {
+    if requested {
+        offered & RAY_QUERY
+    } else {
+        wgpu::Features::empty()
+    }
+}
+
+/// The device's opt-in to `features`' experimental ones.
+pub(super) fn experimental(features: wgpu::Features) -> wgpu::ExperimentalFeatures {
+    if features.contains(RAY_QUERY) {
+        horizon_hdr::experimental_features()
+    } else {
+        wgpu::ExperimentalFeatures::disabled()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn only_an_extras_build_asks_for_ray_tracing() {
+        assert_eq!(asked(Some("1")), cfg!(feature = "horizon-extras"));
+        assert!(!asked(None));
+        assert!(!asked(Some("0")));
+    }
+
+    #[test]
+    fn ray_queries_only_when_asked_and_offered() {
+        let all = wgpu::Features::all();
+        assert_eq!(pick(true, all), RAY_QUERY);
+        assert!(pick(false, all).is_empty());
+        assert!(pick(true, all - RAY_QUERY).is_empty());
+        assert!(!experimental(wgpu::Features::empty()).is_enabled());
+    }
+}

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

@@ -5,6 +5,9 @@ use super::{
     Renderer, check_layers, cull, describe_adapter, is_software, oit, startup_step, surface_format,
     timing,
 };
+// Ray tracing on request, which the device needs from its creation (gfx.rs may not grow).
+#[path = "ray_query.rs"]
+mod ray_query;
 use std::sync::Arc;
 use winit::window::Window;
 
@@ -134,6 +137,7 @@ pub(super) async fn open_adapter(
     let features = timing::GpuTimer::features(adapter)
         | cull::Cull::features(adapter)
         | oit::features(adapter)
+        | ray_query::features(adapter)
         | (adapter.features()
             & (wgpu::Features::INDIRECT_FIRST_INSTANCE
                 | wgpu::Features::MULTI_DRAW_INDIRECT_COUNT
@@ -166,6 +170,7 @@ pub(super) async fn open_adapter(
         // with the larger blocks a few small buffers kept whole blocks the arena's pages had
         // left, and over half the video memory reserved was unused (1,344 MiB for 500).
         memory_hints: wgpu::MemoryHints::MemoryUsage,
+        experimental_features: ray_query::experimental(features),
         ..Default::default()
     };
     #[cfg(not(target_os = "macos"))]

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

@@ -1,6 +1,7 @@
 //! Optional, texture-matched overlays drawn full bright over their base texture in the same
-//! terrain fragment: native mods' (`<ns>:emissive/...`) and OptiFine's emissive block textures
-//! (`block/stone_e.png` beside `block/stone.png`). No extra draw calls or world light changes.
+//! terrain fragment: native mods' (`<ns>:emissive/...`) and a pack's emissive block textures
+//! (OptiFine's `block/stone_e.png` beside `block/stone.png`, the suffix from the pack formats,
+//! [`crate::pack_hooks`]). No extra draw calls or world light changes.
 use crate::sprites::Sprites;
 use std::{collections::BTreeMap, path::Path};
 
@@ -35,14 +36,12 @@ fn tile_file(name: &str) -> Option<&str> {
     name.strip_suffix(".png")
 }
 
-/// OptiFine's emissive overlays of the block sprites already loaded (what the terrain draws;
-/// items draw from the HUD atlas): for each
-/// `<ns>:block/<name>`, or connected-texture tile `assets/<ns>/.../<name>.png`, whose
-/// `<name><suffix>.png` sits beside it, the overlay is loaded too and paired with it, blocks
-/// first, then tiles, each by name, at most [`MAX`] - [`NATIVE`] (native mods keep their share of
-/// the table). A pack without such files adds nothing.
-pub fn load_optifine(root: &Path, sprites: &mut Sprites) -> Vec<(String, String)> {
-    let suffix = horizon_optifine::emissive::suffix(root);
+/// A pack's emissive overlays of the block sprites already loaded (what the terrain draws;
+/// items draw from the HUD atlas): for each `<ns>:block/<name>`, or connected-texture tile
+/// `assets/<ns>/.../<name>.png`, whose `<name><suffix>.png` sits beside it, the overlay is loaded
+/// too and paired with it, blocks first, then tiles, each by name, at most [`MAX`] - [`NATIVE`]
+/// (native mods keep their share of the table). A pack without such files adds nothing.
+pub fn load_overlays(root: &Path, suffix: &str, sprites: &mut Sprites) -> Vec<(String, String)> {
     // Blocks with identical pixels share a layer (and the shader pairs by layer): a shared
     // base would glow on every block that shares it, so it gets no overlay.
     let mut sharing: BTreeMap<u32, usize> = BTreeMap::new();
@@ -56,8 +55,8 @@ pub fn load_optifine(root: &Path, sprites: &mut Sprites) -> Vec<(String, String)
             sharing[layer] == 1
                 && (name
                     .split_once(':')
-                    .is_some_and(|(_, p)| p.starts_with("block/") && !p.ends_with(&suffix))
-                    || tile_file(name).is_some_and(|stem| !stem.ends_with(&suffix)))
+                    .is_some_and(|(_, p)| p.starts_with("block/") && !p.ends_with(suffix))
+                    || tile_file(name).is_some_and(|stem| !stem.ends_with(suffix)))
         })
         .map(|(name, _)| name.clone())
         .collect();
@@ -110,7 +109,7 @@ pub fn load_optifine(root: &Path, sprites: &mut Sprites) -> Vec<(String, String)
 pub const CUTOUT: u32 = 1 << 31;
 
 /// The frame's overlay table: native mods' pairs (at most [`NATIVE`] requested), then the packs'
-/// OptiFine pairs flagged [`CUTOUT`] (at most [`MAX`] - [`NATIVE`], as [`load_optifine`] loads),
+/// OptiFine pairs flagged [`CUTOUT`] (at most [`MAX`] - [`NATIVE`], as [`load_overlays`] loads),
 /// one per base layer with native mods' first, sorted by base layer for the shader's early exit.
 pub fn table<'a>(
     layers: &BTreeMap<String, u32>,
@@ -204,7 +203,7 @@ mod tests {
         // Items draw from the HUD atlas, not the terrain: no pair.
         sprites.insert(&root, "minecraft:item/stick").unwrap();
         // glowstone isn't loaded: its overlay pairs with nothing.
-        let pairs = load_optifine(&root, &mut sprites);
+        let pairs = load_overlays(&root, "_e", &mut sprites);
         assert_eq!(
             pairs,
             [(
@@ -215,9 +214,6 @@ mod tests {
         assert!(sprites.layers.contains_key("minecraft:block/stone_e"));
         assert!(!sprites.layers.contains_key("minecraft:block/granite_e"));
         // The pack's own suffix.
-        let props = root.join("assets/minecraft/optifine/emissive.properties");
-        std::fs::create_dir_all(props.parent().unwrap()).unwrap();
-        std::fs::write(&props, "suffix.emissive=_glow").unwrap();
         // Connected-texture tiles pair with the overlay beside them.
         let tiles = root.join("assets/minecraft/optifine/ctm/lamp");
         png(&tiles.join("0.png"), 230);
@@ -234,7 +230,7 @@ mod tests {
                 .insert_file(&root, &format!("assets/minecraft/optifine/{tile}.png"))
                 .unwrap();
         }
-        let pairs = load_optifine(&root, &mut sprites);
+        let pairs = load_overlays(&root, "_glow", &mut sprites);
         assert_eq!(
             pairs,
             // Blocks first, then tiles.

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

@@ -162,10 +162,38 @@ impl OptionsUi {
         };
         let mut rows = Vec::new();
         registered.rows(&mut rows);
-        rows.into_iter()
-            .enumerate()
-            .map(|(r, row)| self.added_row(page, r, row))
-            .collect()
+        let mut out = Vec::new();
+        // The row a half-width button started, waiting for the next to sit beside it.
+        let mut half_open = false;
+        for (r, row) in rows.into_iter().enumerate() {
+            match row {
+                // Wrapped as the engine's own notes; space is for pages drawn as a screen.
+                added::Row::Text { text, .. } => {
+                    out.extend(wrap(&text, 64).into_iter().map(Row::Note))
+                }
+                added::Row::Space(_) => continue,
+                added::Row::Button {
+                    label,
+                    active,
+                    half: true,
+                    ..
+                } => {
+                    let mut half = button(0.0, 0.0, 150.0, tr(label), Act::PageRow(page, r));
+                    if !active {
+                        half = inactive(half);
+                    }
+                    match out.last_mut() {
+                        Some(Row::Buttons(_, second @ None)) if half_open => *second = Some(half),
+                        _ => out.push(Row::Buttons(half, None)),
+                    }
+                    half_open = !half_open;
+                    continue;
+                }
+                row => out.push(self.added_row(page, r, row)),
+            }
+            half_open = false;
+        }
+        out
     }
 
     fn added_row(&self, page: usize, r: usize, row: added::Row) -> Row {
@@ -177,7 +205,10 @@ impl OptionsUi {
             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::Button { label, active, .. } => {
+                let wide = button(0.0, 0.0, 310.0, tr(label), act);
+                Row::Buttons(if active { wide } else { inactive(wide) }, None)
+            }
             added::Row::Key { label, key } => {
                 let mut message = keybinds::display_name(&key);
                 if self.selected_key == Some(PAGE_KEY)
@@ -461,4 +492,84 @@ mod tests {
             Some(tr("test.sample.switch.tooltip").plain())
         );
     }
+
+    /// Text, a grey note, space, two half buttons (the second inactive) and a footer button.
+    struct Shaped(Mutex<Vec<usize>>);
+
+    impl added::Page for Shaped {
+        fn id(&self) -> &'static str {
+            "test.shaped"
+        }
+        fn title(&self) -> &'static str {
+            "test.shaped.title"
+        }
+        fn place(&self) -> added::Place {
+            added::Place::HorizonSettings
+        }
+        fn rows(&self, rows: &mut Vec<added::Row>) {
+            rows.push(added::Row::text("ABCDE-FGHIJ").groups());
+            rows.push(added::Row::text("grey").quiet());
+            rows.push(added::Row::Space(6));
+            rows.push(added::Row::button("test.shaped.copy").half());
+            rows.push(added::Row::button("test.shaped.stop").half().active(false));
+            rows.push(added::Row::button("test.shaped.help").footer());
+        }
+        fn act(&self, row: usize, _: added::Act) {
+            self.0.lock().unwrap().push(row);
+        }
+    }
+
+    static SHAPED: Shaped = Shaped(Mutex::new(Vec::new()));
+    static SHAPED_PAGES: [&dyn added::Page; 1] = [&SHAPED];
+
+    #[test]
+    fn half_buttons_share_a_row_and_an_inactive_one_is_never_pressed() {
+        let mut s = Settings::default();
+        TEST_PAGES.set(Some(&SHAPED_PAGES));
+        let ui = OptionsUi::default();
+        let rows = ui.added_rows(0);
+        // The two texts as notes (space shows nothing here), the halves on one row, the
+        // footer button below them (the settings shell has no footer of its own).
+        assert!(matches!(&rows[0], Row::Note(t) if t == "ABCDE-FGHIJ"));
+        assert!(matches!(&rows[1], Row::Note(t) if t == "grey"));
+        let Row::Buttons(copy, Some(stop)) = &rows[2] else {
+            panic!("the halves sit side by side: {:?}", rows.len());
+        };
+        assert_eq!((copy.w, stop.w), (150.0, 150.0));
+        assert!(matches!(&rows[3], Row::Buttons(help, None) if help.w == 310.0));
+        assert_eq!(rows.len(), 4);
+        let mut ui = ui;
+        ui.show(Page::Added(0));
+        press(&mut ui, &mut s, Act::PageRow(0, 3), false);
+        press(&mut ui, &mut s, Act::PageRow(0, 5), false);
+        let (widgets, ..) = ui.layout(&s, 480.0, 240.0);
+        let stop = widgets
+            .iter()
+            .find(|w| {
+                matches!(
+                    &w.kind,
+                    WKind::Button {
+                        act: Act::PageRow(0, 4),
+                        ..
+                    }
+                )
+            })
+            .expect("Stop is drawn");
+        let atlas = super::super::tests::atlas();
+        ui.click(
+            &mut s,
+            &atlas,
+            stop.x + 1.0,
+            stop.y + 1.0,
+            (480.0, 240.0),
+            [480, 240],
+            false,
+            false,
+        );
+        assert_eq!(
+            *SHAPED.0.lock().unwrap(),
+            [3, 5],
+            "the inactive half heard nothing"
+        );
+    }
 }

crates/horizon-client-render/src/pack_formats/mod.rs

@@ -20,6 +20,10 @@ impl PackFormats for Formats {
         Some(colors::read(root))
     }
 
+    fn emissive_suffix(&self, root: &Path) -> Option<String> {
+        Some(horizon_optifine::emissive::suffix(root))
+    }
+
     fn custom_sky(&self, root: &Path) -> Option<Arc<dyn crate::custom_sky::SkyLayers>> {
         let sky = custom_sky::CustomSky::load(root);
         (!sky.is_empty()).then(|| Arc::new(sky) as _)

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

@@ -15,6 +15,12 @@ pub trait PackFormats: Send + Sync {
         None
     }
 
+    /// The name ending of the overlay's emissive textures (`stone_e.png` beside `stone.png`),
+    /// if its format has them.
+    fn emissive_suffix(&self, _root: &Path) -> Option<String> {
+        None
+    }
+
     /// The sky layers the overlay draws over the vanilla sky, if it has any.
     fn custom_sky(&self, _root: &Path) -> Option<Arc<dyn crate::custom_sky::SkyLayers>> {
         None

crates/horizon-client/Cargo.toml

@@ -119,10 +119,11 @@ 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, Discord and Play with Friends, and ray
+# tracing on request (`HORIZON_RAY_TRACING=1`). 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 = ["horizon-client-lib/horizon-extras", "discord", "friends"]
+horizon-extras = ["horizon-client-lib/horizon-extras", "horizon-client-render/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"]

crates/horizon-client/src/entry.rs

@@ -23,6 +23,13 @@ pub fn main_with(mods: crate::mod_api::Mods) {
     horizon_client::telemetry::mark_start();
     // Opt-in telemetry keeps each crash report (docs/telemetry.md), whatever the mode.
     crash::on_report(horizon_client::telemetry::keep_crash);
+    // Crates' text in the player's language (`horizon_hooks::tr`).
+    horizon_hooks::engine::set_language(|key| {
+        horizon_client::lang::has(key).then(|| horizon_client::lang::get(key))
+    });
+    // Play with Friends' host side, until it moves to horizon-friends (spec #14167).
+    #[cfg(feature = "friends")]
+    game::register_friends();
     // Crates above the engine registered their hooks before this (horizon-official's `main`);
     // none registers after this point.
     horizon_hooks::engine::seal();

crates/horizon-client/src/game.rs

@@ -143,6 +143,8 @@ mod enderman_hurt_teleport_tests;
 mod enderman_placement_tests;
 mod entity;
 mod entity_culling;
+#[cfg(test)]
+mod entity_inside_tests;
 mod entity_sounds;
 mod event_loop;
 mod events;
@@ -162,15 +164,6 @@ mod frame_geometry;
 mod frames;
 #[cfg(feature = "friends")]
 mod friends;
-mod held_items;
-#[cfg(test)]
-mod setblock_order_tests;
-// Without Play with Friends: nothing shared, no Friends button (game/friends_off.rs).
-#[cfg(test)]
-mod entity_inside_tests;
-#[cfg(not(feature = "friends"))]
-#[path = "game/friends_off.rs"]
-mod friends;
 mod functions;
 mod game_mode;
 mod game_tests;
@@ -181,6 +174,7 @@ mod golems;
 mod growth;
 mod hand;
 mod headless;
+mod held_items;
 mod hud_editor;
 mod hud_room;
 mod ime;
@@ -357,6 +351,7 @@ mod pad;
 mod pad_actions;
 mod pad_craft;
 mod pad_menu;
+mod page_screen;
 mod paintings;
 mod pandas;
 mod particle_culling;
@@ -420,7 +415,10 @@ mod seats;
 mod server_links;
 mod server_packs;
 mod server_travel;
+#[cfg(test)]
+mod setblock_order_tests;
 mod shader_packs;
+mod share_view;
 mod sheep_dye;
 mod shelf;
 mod shield;
@@ -597,6 +595,8 @@ use resource_loader::{
     EntityModels, GameCpuResources, Loaded, LoaderMsg, PendingWorldEntry, WorldRestLoader,
     run_loading, write_report,
 };
+#[cfg(feature = "friends")]
+pub(crate) use share_view::register_friends;
 use std::{
     cell::RefCell,
     collections::{HashMap, HashSet},
@@ -649,9 +649,9 @@ enum Screen {
     Advancements,
     /// WorldOptionsScreen (game/lan_screen.rs).
     WorldOptions,
-    /// Play with Friends, from the pause menu's Friends button
-    /// (game/friends.rs, game/friends/screen.rs).
-    Friends,
+    /// The page a crate registered at `Place::PauseFriends` (Play with Friends in the official
+    /// build), from the pause menu's Friends icon, drawn as its own screen (game/page_screen.rs).
+    AddedPage,
     /// `SocialInteractionsScreen` (`social_screen`, game/social.rs).
     Social,
     /// CommandBlockEditScreen (game/command_blocks.rs).
@@ -695,7 +695,7 @@ impl Screen {
             Screen::Stats => "stats",
             Screen::Advancements => "advancements",
             Screen::WorldOptions => "world_options",
-            Screen::Friends => "friends",
+            Screen::AddedPage => "friends",
             Screen::Social => "social",
             Screen::CommandBlock => "command_block",
             Screen::BlockEditor => "block_editor",
@@ -2903,9 +2903,6 @@ struct Game<'a> {
     level_shapes: horizon_client::chunk::LevelShapes,
     /// This game is that server thread's (game/integrated.rs).
     serving: Option<integrated::Serving>,
-    /// The open world is shared behind an invite code (game/friends.rs).
-    #[cfg(feature = "friends")]
-    friends: Option<friends::Sharing>,
     /// The Social Interactions screen and the players whose chat is hidden (game/social.rs).
     social: social::Social,
     world_options: Option<lan_screen::WorldOptions>,
@@ -5737,7 +5734,6 @@ impl Game<'_> {
         if let Some(log) = self.world.block_log.as_mut() {
             log.extend(held);
         }
-        self.tick_friends();
         horizon_client::spans::time("tick_hand", || self.tick_hand());
         horizon_client::spans::time("tick_sleep", || self.tick_sleep());
         self.announce_sleep_status();
@@ -6241,7 +6237,7 @@ impl Game<'_> {
             Screen::Advancements => self.draw_advancements(&mut batch),
             Screen::Mod => {}
             Screen::WorldOptions => self.draw_world_options(&mut batch),
-            Screen::Friends => self.draw_friends_screen(&mut batch),
+            Screen::AddedPage => self.draw_added_page(&mut batch),
             Screen::Social => self.draw_social_screen(&mut batch),
             Screen::ServerLinks => self.draw_server_links(&mut batch),
             Screen::ConfirmLink => self.draw_confirm_link(&mut batch),
@@ -11014,8 +11010,8 @@ impl Game<'_> {
                         Screen::WorldOptions if button == MouseButton::Left => {
                             self.world_options_release()
                         }
-                        Screen::Friends if pressed && button == MouseButton::Left => {
-                            self.friends_screen_click()
+                        Screen::AddedPage if pressed && button == MouseButton::Left => {
+                            self.added_page_click()
                         }
                         Screen::Social if pressed && button == MouseButton::Left => {
                             self.social_click()
@@ -11413,6 +11409,7 @@ impl Game<'_> {
                         // the world's own ticks.
                         horizon_client::social::set_presence_status(self.presence_status());
                         horizon_client::social::tick();
+                        self.share_tick();
                         // Minecraft.tick: ClientTickEvent.Pre before any of it.
                         self.native_client_tick_pre();
                         if self.title.is_none() && !self.pause {
@@ -12180,8 +12177,6 @@ impl<'a> Game<'a> {
             test_defs_snapshot: false,
             test_highlights: HashMap::new(),
             game_tests: game_tests::GameTests::default(),
-            #[cfg(feature = "friends")]
-            friends: None,
             social: Default::default(),
             debug_keys: Default::default(),
             debug_charts: Default::default(),

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

@@ -479,7 +479,7 @@ impl Game<'_> {
             Screen::Stats => "stats",
             Screen::Advancements => "advancements",
             Screen::WorldOptions => "world-options",
-            Screen::Friends => "friends",
+            Screen::AddedPage => "friends",
             Screen::Social => "social",
             Screen::ServerLinks => "server-links",
             Screen::ConfirmLink => "confirm-link",

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

@@ -17,16 +17,19 @@ const PROTOCOL: &str = "0.1.0";
 
 /// The command groups the game serves, as `help` chains them: what `hello` reports as its features.
 const FEATURES: &[&str] = &[
-    "game", "station", "blocks", "lan", "friends", "render", "sculk", "agent", "ui", "options",
-    "events", "saves", "pad", "studio",
+    "game", "station", "blocks", "lan", "render", "sculk", "agent", "ui", "options", "events",
+    "saves", "pad", "studio",
 ];
 
-/// `hello`: the protocol the socket speaks, the game's release and the command groups it serves.
+/// `hello`: the protocol the socket speaks, the game's release and the command groups it serves
+/// (the engine's, then those of the crates that answer commands, `Hooks::control_commands`).
 fn hello() -> Value {
+    let groups = horizon_hooks::engine::control_commands().map(|(group, _)| group);
+    let features: Vec<&str> = FEATURES.iter().copied().chain(groups).collect();
     json!({
         "protocol": PROTOCOL,
         "release": horizon_core::release::VERSION,
-        "features": FEATURES,
+        "features": features,
     })
 }
 
@@ -400,7 +403,7 @@ impl Game<'_> {
         if let Some(value) = self.lan_control(&words)? {
             return Ok(Some(value));
         }
-        if let Some(value) = self.friends_control(&words)? {
+        if let Some(value) = self.hooks_control(&words)? {
             return Ok(Some(value));
         }
         if let Some(value) = self.studio_control(&words)? {
@@ -417,7 +420,7 @@ impl Game<'_> {
                 .chain(super::station_control::HELP)
                 .chain(super::blockctl::HELP)
                 .chain(super::lan::HELP)
-                .chain(super::friends::HELP)
+                .chain(horizon_hooks::engine::control_commands().flat_map(|(_, help)| help))
                 .chain(super::render_control::HELP)
                 .chain(super::sculk::HELP)
                 .chain(super::agent::HELP)
@@ -1370,7 +1373,7 @@ impl Game<'_> {
             Screen::Stats => "stats",
             Screen::Advancements => "advancements",
             Screen::WorldOptions => "world-options",
-            Screen::Friends => "friends",
+            Screen::AddedPage => "friends",
             Screen::Social => "social",
             Screen::ServerLinks => "server-links",
             Screen::ConfirmLink => "confirm-link",

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

@@ -123,7 +123,7 @@ fn screen_ids_are_distinct_and_stable() {
         Screen::Stats,
         Screen::Advancements,
         Screen::WorldOptions,
-        Screen::Friends,
+        Screen::AddedPage,
         Screen::Social,
         Screen::CommandBlock,
         Screen::BlockEditor,

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

@@ -523,7 +523,7 @@ fn debug_options_interrupts(screen: Screen, playing_overlay: bool) -> bool {
         | Screen::EmoteWheel
         | Screen::Stats
         | Screen::Advancements
-        | Screen::Friends
+        | Screen::AddedPage
         | Screen::Social
         | Screen::ServerLinks
         | Screen::ConfirmLink
@@ -584,7 +584,7 @@ mod tests {
             Screen::GameModeSwitcher,
             Screen::Stats,
             Screen::Advancements,
-            Screen::Friends,
+            Screen::AddedPage,
             Screen::Social,
             Screen::ServerLinks,
             Screen::ConfirmLink,

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

@@ -1,5 +1,5 @@
 //! Play with friends, host side: "Start Sharing" on the Play with Friends
-//! screen (`screen`, the pause menu's Friends button) opens the world to LAN if
+//! page (`PAGE`, what the pause menu's Friends icon opens) 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
@@ -7,18 +7,23 @@
 //! LAN one, unchanged: tunnelled guests are LAN guests that connect from the
 //! loopback address. The joining side is horizon-friends' (`game`), registered by
 //! horizon-official.
-use super::{Game, lan::LanSettings};
-use horizon_client::{Result, hud::HudBatch, lang, text::Text};
+//!
+//! It sees the game only through `horizon_hooks` (the `ShareView` its `Hooks::share` tick
+//! gets, `Hooks::lan_closed`, its page, `tr`) and keeps what it shares in its own statics, so
+//! it can leave the engine for horizon-friends (spec #14167). `horizon-ctl friends` reaches it
+//! through `Hooks::control`.
 use horizon_friends::{Host, HostConfig, HostEvent, PathMode, host::DEFAULT_PORT, reach, stun};
+use horizon_hooks::{
+    Hooks,
+    pages::{Act, Page, Place, Row},
+    share::{LanOptions, ShareView},
+};
 use horizon_protocol::{GAME_VERSION, PROTOCOL_VERSION};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Mutex, MutexGuard, PoisonError};
 use std::time::{Duration, Instant};
 
-mod screen;
-
-use screen::{self as friends_screen, Action, FriendsView};
-pub use screen::{TITLE, title};
-
-pub(super) struct Sharing {
+struct Sharing {
     host: Host,
     /// Sharing opened the world to LAN, so stopping closes it again.
     opened_lan: bool,
@@ -31,12 +36,126 @@ pub(super) struct Sharing {
     paths: (u32, u32),
 }
 
+/// The world shared, if one is. The game has one window player who can share (the engine
+/// calls the hooks for it only), so one is all there is.
+static SHARING: Mutex<Option<Sharing>> = Mutex::new(None);
+/// Whether [`SHARING`] holds one: a tick with nothing shared is this one load.
+static ON: AtomicBool = AtomicBool::new(false);
+
+/// What the page left for the next [`Hooks::share`] tick, which has the game's view.
+#[derive(Default)]
+struct PageState {
+    /// Chat lines (new codes, the relay stopping), said in order.
+    chat: Vec<String>,
+    /// A button pressed on the page.
+    pressed: Option<Action>,
+    /// The page was drawn since the last tick: its guests are read again.
+    open: bool,
+    /// The other players, as the last tick while the page was open read them.
+    guests: Vec<String>,
+    /// The action of each row the page last showed.
+    acts: Vec<Option<Action>>,
+}
+static PAGE_STATE: Mutex<PageState> = Mutex::new(PageState {
+    chat: Vec::new(),
+    pressed: None,
+    open: false,
+    guests: Vec::new(),
+    acts: Vec::new(),
+});
+/// Whether [`PAGE_STATE`] has something for the tick.
+static WORK: AtomicBool = AtomicBool::new(false);
+
+fn page() -> MutexGuard<'static, PageState> {
+    PAGE_STATE.lock().unwrap_or_else(PoisonError::into_inner)
+}
+
+/// A button of the page.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum Action {
+    Share,
+    Copy,
+    Stop,
+    /// Open the troubleshooting page.
+    Help,
+}
+
+fn sharing() -> MutexGuard<'static, Option<Sharing>> {
+    SHARING.lock().unwrap_or_else(PoisonError::into_inner)
+}
+
+/// Ends the sharing, if there is one. The lock is let go before the caller touches the
+/// game: closing LAN calls [`Hooks::lan_closed`], which takes it again.
+fn take() -> Option<Sharing> {
+    let taken = sharing().take();
+    ON.store(false, Ordering::Relaxed);
+    taken
+}
+
+/// Registered by the engine's entry while this module is part of it.
+pub struct Friends;
+pub static HOOKS: Friends = Friends;
+
+impl Hooks for Friends {
+    fn control_commands(&self) -> Option<(&'static str, &'static [&'static str])> {
+        Some(("friends", HELP))
+    }
+
+    /// `horizon-ctl friends host|stop|status`.
+    fn control(
+        &self,
+        words: &[&str],
+        world: &mut dyn ShareView,
+    ) -> Option<std::result::Result<String, String>> {
+        (words.first() == Some(&"friends"))
+            .then(|| control(words.get(1).copied(), world).map(|answer| answer.to_string()))
+    }
+
+    /// What the page left for the game: chat lines, a button's press, the guests while it is
+    /// open. With nothing left, one relaxed load.
+    fn share(&self, world: &mut dyn ShareView) {
+        if !WORK.swap(false, Ordering::Relaxed) {
+            return;
+        }
+        let (lines, pressed, open) = {
+            let mut page = page();
+            let open = std::mem::take(&mut page.open);
+            (std::mem::take(&mut page.chat), page.pressed.take(), open)
+        };
+        for line in lines {
+            world.chat(&line);
+        }
+        if let Some(action) = pressed {
+            press(action, world);
+        }
+        if open {
+            let mut guests = Vec::new();
+            world.players(&mut |name| guests.push(name.to_owned()));
+            page().guests = guests;
+        }
+    }
+
+    /// The LAN server is closing: the code goes with it.
+    fn lan_closed(&self) {
+        if ON.load(Ordering::Relaxed)
+            && let Some(mut sharing) = take()
+        {
+            sharing.host.stop();
+        }
+    }
+}
+
 pub const HELP: &[&str] = &[
     "friends host                   share the open world behind an invite code",
     "friends stop                   stop sharing",
     "friends status                 the code, how friends reach this host, the guests",
 ];
 
+/// A string in the player's language, or the English one.
+fn tr(key: &str, english: &str) -> String {
+    horizon_hooks::tr(key).unwrap_or_else(|| english.to_owned())
+}
+
 /// `HORIZON_STUN_SERVERS`, else `friendsStun` in horizon.txt, else the defaults.
 fn stun_servers() -> Vec<String> {
     if std::env::var_os("HORIZON_STUN_SERVERS").is_some() {
@@ -53,101 +172,98 @@ fn env_flag(name: &str, default: bool) -> bool {
     std::env::var(name).map_or(default, |v| v != "0")
 }
 
-impl Game<'_> {
-    /// Start sharing the open world.
-    pub(super) fn friends_start(&mut self) -> Result<()> {
-        if self.friends.is_some() {
-            return Ok(());
-        }
-        // Single player on its server thread shares that server, as Open to
-        // LAN publishes it; another server can't be shared.
-        if self.title.is_some() || (self.remote.is_some() && self.integrated.is_none()) {
-            return Err("open a singleplayer world first".into());
-        }
-        let opened_lan = self.lan_port().is_none();
-        if opened_lan {
-            // ShareToLanScreen's defaults, as the world options screen offers them.
-            self.lan_open(LanSettings {
-                port: horizon_client::lan::available_port(),
-                guest_commands: false,
-                force_game_mode: true,
-            })?;
-        }
-        let port = self.lan_port().ok_or("the world isn't open to LAN")?;
-        let host = match Host::start(HostConfig {
-            lan: std::net::SocketAddr::from(([127, 0, 0, 1], port)),
-            protocol: PROTOCOL_VERSION,
-            game: GAME_VERSION.to_owned(),
-            relay: horizon_client::net::friends_relay_setting(),
-            path: PathMode::from_env(),
-            port: std::env::var("HORIZON_FRIENDS_PORT")
-                .ok()
-                .and_then(|p| p.parse().ok())
-                .unwrap_or(DEFAULT_PORT),
-            reach: reach::Options {
-                // HORIZON_FRIENDS_UPNP=0 leaves the router alone.
-                map_port: env_flag("HORIZON_FRIENDS_UPNP", true),
-                stun: stun_servers(),
-                // Both ends on one machine (tests).
-                loopback: env_flag("HORIZON_FRIENDS_LOOPBACK", false),
-            },
-        }) {
-            Ok(h) => h,
-            Err(e) => {
-                if opened_lan {
-                    self.lan_close(true);
-                }
-                return Err(e.into());
+/// Start sharing the open world.
+fn start(world: &mut dyn ShareView) -> std::result::Result<(), String> {
+    if ON.load(Ordering::Relaxed) {
+        return Ok(());
+    }
+    if !world.can_share() {
+        return Err("open a singleplayer world first".into());
+    }
+    let (port, opened_lan) = match world.lan_port() {
+        Some(port) => (port, false),
+        // ShareToLanScreen's defaults, as the world options screen offers them.
+        None => (world.open_lan(LanOptions::default())?, true),
+    };
+    let host = Host::start(HostConfig {
+        lan: std::net::SocketAddr::from(([127, 0, 0, 1], port)),
+        protocol: PROTOCOL_VERSION,
+        game: GAME_VERSION.to_owned(),
+        relay: horizon_client::net::friends_relay_setting(),
+        path: PathMode::from_env(),
+        port: std::env::var("HORIZON_FRIENDS_PORT")
+            .ok()
+            .and_then(|p| p.parse().ok())
+            .unwrap_or(DEFAULT_PORT),
+        reach: reach::Options {
+            // HORIZON_FRIENDS_UPNP=0 leaves the router alone.
+            map_port: env_flag("HORIZON_FRIENDS_UPNP", true),
+            stun: stun_servers(),
+            // Both ends on one machine (tests).
+            loopback: env_flag("HORIZON_FRIENDS_LOOPBACK", false),
+        },
+    });
+    let host = match host {
+        Ok(h) => h,
+        Err(e) => {
+            if opened_lan {
+                world.close_lan();
             }
-        };
-        self.friends = Some(Sharing {
-            host,
-            opened_lan,
-            code: None,
-            wrong: 0,
-            notice: None,
-            copied: None,
-            paths: (0, 0),
-        });
-        Ok(())
-    }
+            return Err(e.to_string());
+        }
+    };
+    *sharing() = Some(Sharing {
+        host,
+        opened_lan,
+        code: None,
+        wrong: 0,
+        notice: None,
+        copied: None,
+        paths: (0, 0),
+    });
+    ON.store(true, Ordering::Relaxed);
+    Ok(())
+}
 
-    /// Stop sharing: the code ends (direct port closed, router mapping
-    /// deleted); the world closes to LAN again if sharing opened it.
-    pub(super) fn friends_stop(&mut self) {
-        let Some(mut sharing) = self.friends.take() else {
+/// Stop sharing: the code ends (direct port closed, router mapping
+/// deleted); the world closes to LAN again if sharing opened it.
+fn stop(world: &mut dyn ShareView) {
+    if !world.can_share() {
+        return;
+    }
+    let Some(mut sharing) = take() else {
+        return;
+    };
+    sharing.host.stop();
+    if sharing.opened_lan {
+        world.close_lan();
+    } else {
+        let text = tr(
+            "horizon.friends.stopped",
+            "Stopped sharing the invite code.",
+        );
+        world.chat(&text);
+    }
+}
+
+/// New codes and sessions, while the page is drawn and when `friends status` asks. Its chat
+/// lines wait for the next tick ([`Hooks::share`]), or for [`say`].
+fn poll() {
+    if !ON.load(Ordering::Relaxed) {
+        return;
+    }
+    let mut announce = false;
+    let mut stopped = None;
+    {
+        let mut guard = sharing();
+        let Some(sharing) = guard.as_mut() else {
             return;
         };
-        sharing.host.stop();
-        if sharing.opened_lan {
-            self.lan_close(true);
-        } else {
-            self.system_message(Text::literal(lang::get_or(
-                "horizon.friends.stopped",
-                "Stopped sharing the invite code.",
-            )));
-        }
-    }
-
-    /// The LAN server is closing: the code goes with it.
-    pub(super) fn friends_lan_closed(&mut self) {
-        if let Some(mut sharing) = self.friends.take() {
-            sharing.host.stop();
-        }
-    }
-
-    /// New codes and sessions, once a tick and while the pause menu is drawn.
-    pub(super) fn tick_friends(&mut self) {
-        let Some(sharing) = self.friends.as_mut() else {
-            return;
-        };
-        let mut announce = false;
-        let mut stopped = None;
         for event in sharing.host.poll() {
             match event {
                 HostEvent::Code(code) => {
                     if sharing.code.is_some() && sharing.wrong >= horizon_friends::host::MAX_WRONG {
-                        sharing.notice = Some(lang::get_or(
+                        sharing.notice = Some(tr(
                             "horizon.friends.short_code_changed",
                             "Someone kept trying a wrong short code, so it changed.",
                         ));
@@ -158,7 +274,7 @@ impl Game<'_> {
                 }
                 HostEvent::WrongCode { count } => {
                     sharing.wrong = count;
-                    sharing.notice = Some(lang::get_or(
+                    sharing.notice = Some(tr(
                         "horizon.friends.wrong_code",
                         "Someone tried a wrong code.",
                     ));
@@ -167,7 +283,7 @@ impl Game<'_> {
                 HostEvent::Connected { direct: false, .. } => sharing.paths.1 += 1,
                 HostEvent::Disconnected { .. } => {}
                 HostEvent::RelayStopped => {
-                    let text = lang::get_or(
+                    let text = tr(
                         "horizon.friends.relay_stopped",
                         "Too many wrong short codes, so the relay is off until you share again. Friends can still join with the full code.",
                     );
@@ -176,164 +292,481 @@ impl Game<'_> {
                 }
             }
         }
-        if let Some(text) = stopped {
-            self.system_message(Text::literal(text));
-        }
-        if announce {
-            self.system_message(Text::literal(lang::get_or(
-                "horizon.friends.code_ready",
-                "Your invite code is ready: Game Menu, Play with Friends. Copy it and send it to your friends.",
-            )));
-        }
     }
+    let mut page = page();
+    page.chat.extend(stopped);
+    if announce {
+        page.chat.push(tr(
+            "horizon.friends.code_ready",
+            "Your invite code is ready: Game Menu, Play with Friends. Copy it and send it to your friends.",
+        ));
+    }
+    if !page.chat.is_empty() {
+        WORK.store(true, Ordering::Relaxed);
+    }
+}
 
-    pub(super) fn friends_copy(&mut self) {
-        let Some(code) = self.friends.as_ref().and_then(|s| s.code.clone()) else {
-            return;
-        };
-        use horizon_client::clipboard::Clipboard;
-        self.clipboard.set(&code);
-        if let Some(s) = self.friends.as_mut() {
-            s.copied = Some(Instant::now());
-        }
+/// The chat lines waiting, said now.
+fn say(world: &mut dyn ShareView) {
+    let lines = std::mem::take(&mut page().chat);
+    for line in lines {
+        world.chat(&line);
     }
+}
 
-    /// Play with Friends. The world is paused under it in singleplayer, so
-    /// new codes and sessions are read while it is drawn.
-    pub(super) fn draw_friends_screen(&mut self, batch: &mut HudBatch) {
-        self.tick_friends();
-        let view = self.friends_view();
-        horizon_client::widgets::begin_screen(|| {
-            horizon_client::widgets::ScreenInfo::new("friends", friends_screen::TITLE)
-        });
-        friends_screen::draw(batch, &self.gui.atlas, self.cursor, &view, true);
-    }
-    pub(super) fn friends_screen_click(&mut self) {
-        let view = self.friends_view();
-        let Some(action) =
-            friends_screen::click(&self.gui.atlas, self.gui_size(), self.cursor, &view)
-        else {
-            return;
-        };
-        self.audio.play_button_click();
-        match action {
-            Action::Share => {
-                if let Err(e) = self.friends_start() {
-                    self.system_message(Text::literal(
-                        lang::get_or(
-                            "horizon.friends.share_failed",
-                            "Couldn't share the world: %s",
-                        )
-                        .replacen("%s", &e.to_string(), 1),
-                    ));
-                }
+/// A button of the page, on the tick after its press.
+fn press(action: Action, world: &mut dyn ShareView) {
+    match action {
+        Action::Share => {
+            if let Err(e) = start(world) {
+                let text = tr(
+                    "horizon.friends.share_failed",
+                    "Couldn't share the world: %s",
+                )
+                .replacen("%s", &e, 1);
+                world.chat(&text);
             }
-            Action::Copy => self.friends_copy(),
-            Action::Stop => self.friends_stop(),
-            // The system browser, as the folder buttons open their folders.
-            Action::Help => {
-                if let Some(url) = &view.help {
-                    super::packs::open_uri(url);
-                }
-            }
-            Action::Done => self.screen = super::Screen::Paused,
         }
+        Action::Copy => copy(world),
+        Action::Stop => stop(world),
+        // The system browser, as the folder buttons open their folders.
+        Action::Help => world.open_url(reach::HELP_URL),
     }
+}
 
-    /// Whether the pause menu offers Play with Friends (a singleplayer world).
-    pub(super) fn friends_shown(&self) -> bool {
-        self.friends_view().shown
+fn copy(world: &mut dyn ShareView) {
+    if !world.can_share() {
+        return;
     }
-
-    /// What Play with Friends shows.
-    pub(super) fn friends_view(&self) -> FriendsView {
-        let guests = match &self.lan {
-            Some(h) => h.hub.guests.iter().map(|g| g.name.clone()).collect(),
-            // On the server thread: the other players the server lists.
-            None if self.integrated.is_some() => {
-                let me = self.options.player_name();
-                let mut names = self.remote_online_names().unwrap_or_default();
-                names.retain(|n| *n != me);
-                names
-            }
-            None => Vec::new(),
-        };
-        let Some(s) = &self.friends else {
-            return FriendsView {
-                shown: self.remote.is_none() || self.integrated.is_some(),
-                ..FriendsView::default()
-            };
-        };
-        let state = s.host.state();
-        let mut status = if s.code.is_none() {
-            lang::get_or(
-                "horizon.friends.finding_route",
-                "Finding how friends can reach you…",
-            )
-        } else {
-            state.summary.clone()
-        };
-        if let Some(short) = &state.short {
-            status.push_str(&format!(" Short code for the relay: {short}."));
-        }
-        if let Some(problem) = &state.relay_problem {
-            status.push(' ');
-            status.push_str(problem);
-        }
-        let reachable = matches!(
-            state.verdict,
-            Some(reach::Verdict::Mapped(_) | reach::Verdict::Public)
-        ) || state.short.is_some();
-        FriendsView {
-            shown: true,
-            sharing: true,
-            code: s.code.clone(),
-            status,
-            reachable,
-            help: (!reachable && s.code.is_some()).then(|| reach::HELP_URL.to_owned()),
-            guests,
-            notice: s.notice.clone(),
-            copied: s
-                .copied
-                .is_some_and(|t| t.elapsed() < Duration::from_secs(2)),
-        }
+    let Some(code) = sharing().as_ref().and_then(|s| s.code.clone()) else {
+        return;
+    };
+    world.copy(&code);
+    if let Some(s) = sharing().as_mut() {
+        s.copied = Some(Instant::now());
     }
+}
 
-    /// `horizon-ctl friends ...`.
-    pub(super) fn friends_control(&mut self, words: &[&str]) -> Result<Option<serde_json::Value>> {
-        use serde_json::json;
-        if words[0] != "friends" {
-            return Ok(None);
-        }
-        match words.get(1).copied() {
-            Some("host") => {
-                self.friends_start()?;
-                Ok(Some(json!({ "ok": true, "lan_port": self.lan_port() })))
-            }
-            Some("stop") => {
-                self.friends_stop();
-                Ok(Some(json!({ "ok": true })))
-            }
-            Some("status") => {
-                self.tick_friends();
-                let view = self.friends_view();
-                let state = self.friends.as_ref().map(|s| s.host.state());
-                Ok(Some(json!({
-                    "sharing": view.sharing,
-                    "code": view.code,
-                    "short": state.as_ref().and_then(|s| s.short.as_ref().map(ToString::to_string)),
-                    "summary": view.status,
-                    "reachable": view.reachable,
-                    "verdict": state.as_ref().and_then(|s| s.verdict.as_ref().map(|v| format!("{v:?}"))),
-                    "direct_port": state.as_ref().map(|s| s.port),
-                    "sessions": self.friends.as_ref().map_or(0, |s| s.host.sessions()),
-                    "direct": self.friends.as_ref().map_or(0, |s| s.paths.0),
-                    "relayed": self.friends.as_ref().map_or(0, |s| s.paths.1),
-                    "guests": view.guests,
-                    "lan_port": self.lan_port(),
-                })))
-            }
-            _ => Err("friends host|stop|status".into()),
+/// What Play with Friends shows.
+#[derive(Clone, Debug, Default)]
+struct View {
+    sharing: bool,
+    code: Option<String>,
+    /// Who can join and what to do when friends on the internet can't (or,
+    /// before the code, what the game is doing).
+    status: String,
+    /// Friends on the internet can reach the host.
+    reachable: bool,
+    /// The players in the world besides the host.
+    guests: Vec<String>,
+    notice: Option<String>,
+    /// The code was just copied.
+    copied: bool,
+}
+
+/// What Play with Friends shows; `guests` is asked only while sharing.
+fn view(guests: impl FnOnce() -> Vec<String>) -> View {
+    let guard = sharing();
+    let Some(s) = guard.as_ref() else {
+        return View::default();
+    };
+    let state = s.host.state();
+    let mut status = if s.code.is_none() {
+        tr(
+            "horizon.friends.finding_route",
+            "Finding how friends can reach you…",
+        )
+    } else {
+        state.summary.clone()
+    };
+    if let Some(short) = &state.short {
+        status.push_str(&format!(" Short code for the relay: {short}."));
+    }
+    if let Some(problem) = &state.relay_problem {
+        status.push(' ');
+        status.push_str(problem);
+    }
+    let reachable = matches!(
+        state.verdict,
+        Some(reach::Verdict::Mapped(_) | reach::Verdict::Public)
+    ) || state.short.is_some();
+    View {
+        sharing: true,
+        code: s.code.clone(),
+        status,
+        reachable,
+        guests: guests(),
+        notice: s.notice.clone(),
+        copied: s
+            .copied
+            .is_some_and(|t| t.elapsed() < Duration::from_secs(2)),
+    }
+}
+
+/// The page's rows for `view`, each with the button's action: the layout today's Friends
+/// screen had (the engine draws it, `game/page_screen.rs`).
+fn rows(view: &View, rows: &mut Vec<Row>, acts: &mut Vec<Option<Action>>) {
+    let mut row = |row: Row, act: Option<Action>| {
+        rows.push(row);
+        acts.push(act);
+    };
+    let hint = || {
+        tr(
+            "horizon.friends.hint",
+            "Friends paste the code after the title screen's Friends button, in Direct Connection, or on the launcher's Play page.",
+        )
+    };
+    if !view.sharing {
+        row(
+            Row::text(tr(
+                "horizon.friends.share_intro",
+                "Share this world behind an invite code: it opens to LAN, and friends on the internet join with the code. No server of ours is involved.",
+            )),
+            None,
+        );
+        row(Row::Space(4), None);
+        row(Row::text(hint()).quiet(), None);
+        row(Row::Space(8), None);
+        row(
+            Row::button("horizon.friends.start_sharing"),
+            Some(Action::Share),
+        );
+        return;
+    }
+    row(
+        Row::text(tr("horizon.multiplayer.invite_code", "Invite Code")).quiet(),
+        None,
+    );
+    row(Row::Space(2), None);
+    match &view.code {
+        Some(code) => row(Row::text(code.clone()).groups(), None),
+        None => row(Row::text(view.status.clone()), None),
+    }
+    row(Row::Space(6), None);
+    let copy = if view.copied {
+        "horizon.friends.copied"
+    } else {
+        "horizon.friends.copy_code"
+    };
+    row(
+        Row::button(copy).half().active(view.code.is_some()),
+        Some(Action::Copy),
+    );
+    row(
+        Row::button("horizon.friends.stop_sharing").half(),
+        Some(Action::Stop),
+    );
+    if view.code.is_some() {
+        // Who can join: grey when friends anywhere can, white (it asks
+        // for something) when only the LAN and VPNs can.
+        let status = Row::text(view.status.clone());
+        row(
+            if view.reachable {
+                status.quiet()
+            } else {
+                status
+            },
+            None,
+        );
+        row(Row::Space(4), None);
+    }
+    let here = if view.guests.is_empty() {
+        tr("horizon.friends.none_yet", "No friends here yet.")
+    } else {
+        tr("horizon.friends.here_now", "Here now: %s").replacen("%s", &view.guests.join(", "), 1)
+    };
+    row(Row::text(here).quiet(), None);
+    if let Some(notice) = &view.notice {
+        row(Row::text(notice.clone()), None);
+    }
+    // Where friends paste the code, while it fits above the footer.
+    row(Row::text(hint()).quiet(), None);
+    // Troubleshooting beside Done when friends on the internet can't reach the host.
+    if !view.reachable && view.code.is_some() {
+        row(
+            Row::button("horizon.friends.troubleshooting").footer(),
+            Some(Action::Help),
+        );
+    }
+}
+
+/// Play with Friends' page: what the pause menu's Friends icon opens. Its rows are read when
+/// it is drawn; a press waits for the next tick, which has the game's view.
+pub struct FriendsPage;
+pub static PAGE: FriendsPage = FriendsPage;
+
+impl Page for FriendsPage {
+    fn id(&self) -> &'static str {
+        "horizon_friends.share"
+    }
+    fn title(&self) -> &'static str {
+        "horizon.friends.title"
+    }
+    fn place(&self) -> Place {
+        Place::PauseFriends
+    }
+    fn rows(&self, out: &mut Vec<Row>) {
+        // The world is paused under the page in singleplayer, so new codes and sessions are
+        // read while it is drawn.
+        poll();
+        let guests = std::mem::take(&mut page().guests);
+        let view = view(|| guests);
+        let mut acts = Vec::new();
+        rows(&view, out, &mut acts);
+        let mut page = page();
+        page.guests = view.guests;
+        page.acts = acts;
+        page.open = true;
+        WORK.store(true, Ordering::Relaxed);
+    }
+    fn act(&self, row: usize, act: Act) {
+        let mut page = page();
+        if act == Act::Press
+            && let Some(Some(action)) = page.acts.get(row).copied()
+        {
+            page.pressed = Some(action);
+            WORK.store(true, Ordering::Relaxed);
         }
     }
 }
+
+/// `horizon-ctl friends host|stop|status`.
+fn control(
+    word: Option<&str>,
+    world: &mut dyn ShareView,
+) -> std::result::Result<serde_json::Value, String> {
+    use serde_json::json;
+    match word {
+        Some("host") => {
+            start(world)?;
+            Ok(json!({ "ok": true, "lan_port": world.lan_port() }))
+        }
+        Some("stop") => {
+            stop(world);
+            Ok(json!({ "ok": true }))
+        }
+        Some("status") => {
+            // A splitscreen guest asking hears nothing of P1's sharing, and its chat stays its own.
+            let view = if world.can_share() {
+                poll();
+                say(world);
+                view(|| {
+                    let mut guests = Vec::new();
+                    world.players(&mut |name| guests.push(name.to_owned()));
+                    guests
+                })
+            } else {
+                View::default()
+            };
+            let guard = sharing();
+            let sharing = guard.as_ref().filter(|_| view.sharing);
+            let state = sharing.map(|s| s.host.state());
+            Ok(json!({
+                "sharing": view.sharing,
+                "code": view.code,
+                "short": state.as_ref().and_then(|s| s.short.as_ref().map(ToString::to_string)),
+                "summary": view.status,
+                "reachable": view.reachable,
+                "verdict": state.as_ref().and_then(|s| s.verdict.as_ref().map(|v| format!("{v:?}"))),
+                "direct_port": state.as_ref().map(|s| s.port),
+                "sessions": sharing.map_or(0, |s| s.host.sessions()),
+                "direct": sharing.map_or(0, |s| s.paths.0),
+                "relayed": sharing.map_or(0, |s| s.paths.1),
+                "guests": view.guests,
+                "lan_port": world.lan_port(),
+            }))
+        }
+        _ => Err("friends host|stop|status".into()),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// A world as the engine shows it, recording what the crate did to it.
+    #[derive(Default)]
+    struct Fake {
+        can_share: bool,
+        lan: Option<u16>,
+        refuse_lan: bool,
+        did: Vec<String>,
+    }
+
+    impl ShareView for Fake {
+        fn can_share(&self) -> bool {
+            self.can_share
+        }
+        fn lan_port(&self) -> Option<u16> {
+            self.lan
+        }
+        fn open_lan(&mut self, options: LanOptions) -> std::result::Result<u16, String> {
+            self.did.push(format!("open_lan {options:?}"));
+            if self.refuse_lan {
+                return Err("no free port".into());
+            }
+            self.lan = Some(25565);
+            Ok(25565)
+        }
+        fn close_lan(&mut self) {
+            self.did.push("close_lan".into());
+            self.lan = None;
+        }
+        fn players(&self, each: &mut dyn FnMut(&str)) {
+            each("Alex");
+        }
+        fn chat(&mut self, text: &str) {
+            self.did.push(format!("chat {text}"));
+        }
+        fn copy(&mut self, text: &str) {
+            self.did.push(format!("copy {text}"));
+        }
+        fn open_url(&mut self, url: &str) {
+            self.did.push(format!("open_url {url}"));
+        }
+        fn tr(&self, _key: &str) -> Option<String> {
+            None
+        }
+    }
+
+    #[test]
+    fn a_world_that_cannot_be_shared_is_left_alone() {
+        // Another server, or a splitscreen guest in P1's world.
+        let mut guest = Fake {
+            lan: Some(25565),
+            ..Fake::default()
+        };
+        assert_eq!(
+            control(Some("host"), &mut guest).unwrap_err(),
+            "open a singleplayer world first"
+        );
+        stop(&mut guest);
+        copy(&mut guest);
+        assert!(guest.did.is_empty(), "{:?}", guest.did);
+        // horizon-ctl reaches the same through the hook; other commands aren't its.
+        let status = HOOKS
+            .control(&["friends", "status"], &mut guest)
+            .unwrap()
+            .unwrap();
+        let status: serde_json::Value = serde_json::from_str(&status).unwrap();
+        assert_eq!(status["sharing"], false);
+        assert!(HOOKS.control(&["lan", "status"], &mut guest).is_none());
+        assert!(guest.did.is_empty(), "{:?}", guest.did);
+        assert!(!ON.load(Ordering::Relaxed));
+    }
+
+    #[test]
+    fn sharing_opens_lan_as_open_to_lan_does_and_a_refusal_shares_nothing() {
+        let mut world = Fake {
+            can_share: true,
+            refuse_lan: true,
+            ..Fake::default()
+        };
+        assert_eq!(start(&mut world).unwrap_err(), "no free port");
+        assert_eq!(
+            world.did,
+            ["open_lan LanOptions { guest_commands: false, force_game_mode: true }"]
+        );
+        // Offered, not shared: the guests aren't asked for.
+        let view = view(|| unreachable!("the guests of a world not shared"));
+        assert!(!view.sharing && view.guests.is_empty());
+        assert!(!ON.load(Ordering::Relaxed));
+    }
+
+    #[test]
+    fn the_page_shows_todays_screen_and_a_press_runs_on_the_next_tick() {
+        // Sharing, with a code friends on the internet can't reach yet.
+        let shared = View {
+            sharing: true,
+            code: Some("K7QM2-AAAAA".into()),
+            status: "Friends on your network can join.".into(),
+            ..View::default()
+        };
+        let (mut out, mut acts) = (Vec::new(), Vec::new());
+        rows(&shared, &mut out, &mut acts);
+        let buttons: Vec<_> = out
+            .iter()
+            .zip(&acts)
+            .filter_map(|(row, act)| match row {
+                Row::Button {
+                    label,
+                    active,
+                    half,
+                    footer,
+                    ..
+                } => Some((*label, *active, *half, *footer, *act)),
+                _ => None,
+            })
+            .collect();
+        assert_eq!(
+            buttons,
+            [
+                (
+                    "horizon.friends.copy_code",
+                    true,
+                    true,
+                    false,
+                    Some(Action::Copy)
+                ),
+                (
+                    "horizon.friends.stop_sharing",
+                    true,
+                    true,
+                    false,
+                    Some(Action::Stop)
+                ),
+                (
+                    "horizon.friends.troubleshooting",
+                    true,
+                    false,
+                    true,
+                    Some(Action::Help)
+                ),
+            ]
+        );
+        assert!(out.iter().any(
+            |row| matches!(row, Row::Text { text, groups: true, .. } if text == "K7QM2-AAAAA")
+        ));
+        // Before the code there is nothing to copy.
+        let (mut out, mut acts) = (Vec::new(), Vec::new());
+        rows(
+            &View {
+                code: None,
+                ..shared
+            },
+            &mut out,
+            &mut acts,
+        );
+        assert!(out.iter().any(|row| matches!(
+            row,
+            Row::Button {
+                label: "horizon.friends.copy_code",
+                active: false,
+                ..
+            }
+        )));
+
+        // Not sharing: Start Sharing. Its press waits for the tick, which has the world.
+        let (mut out, mut acts) = (Vec::new(), Vec::new());
+        rows(&View::default(), &mut out, &mut acts);
+        let share = acts.iter().position(|a| *a == Some(Action::Share)).unwrap();
+        page().acts = acts;
+        PAGE.act(share, Act::Press);
+        let mut world = Fake {
+            can_share: true,
+            refuse_lan: true,
+            ..Fake::default()
+        };
+        HOOKS.share(&mut world);
+        assert_eq!(
+            world.did,
+            [
+                "open_lan LanOptions { guest_commands: false, force_game_mode: true }",
+                "chat Couldn't share the world: no free port",
+            ]
+        );
+        // Pressed once, run once.
+        HOOKS.share(&mut world);
+        assert_eq!(world.did.len(), 2);
+    }
+}

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

@@ -1,340 +0,0 @@
-//! Play with Friends: Horizon's own sharing of the open world behind an
-//! 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 horizon_client::{
-    hud::{HudAtlas, HudBatch, rgba},
-    multiplayer::wrap,
-    text::Text,
-    ui,
-};
-
-/// The English title: the fallback of [`title`], and what the screen's widgets are named by.
-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 {
-    horizon_client::lang::get_or(key, english)
-}
-/// The title in the current language.
-pub fn title() -> String {
-    tr("horizon.friends.title", TITLE)
-}
-/// What the screen shows (game/friends.rs fills it).
-#[derive(Clone, Debug, Default)]
-pub struct FriendsView {
-    /// A singleplayer world (not a server): sharing is offered.
-    pub shown: bool,
-    pub sharing: bool,
-    pub code: Option<String>,
-    /// Who can join and what to do when friends on the internet can't (or,
-    /// before the code, what the game is doing).
-    pub status: String,
-    /// Friends on the internet can reach the host.
-    pub reachable: bool,
-    /// Where the troubleshooting is, when they can't.
-    pub help: Option<String>,
-    /// The players in the world besides the host.
-    pub guests: Vec<String>,
-    pub notice: Option<String>,
-    /// The code was just copied.
-    pub copied: bool,
-}
-
-/// A button's action.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Action {
-    Share,
-    Copy,
-    Stop,
-    /// Open the troubleshooting page.
-    Help,
-    Done,
-}
-
-fn grey() -> u32 {
-    rgba(160, 160, 160, 255)
-}
-const WHITE: u32 = u32::MAX;
-fn hint() -> String {
-    tr(
-        "horizon.friends.hint",
-        "Friends paste the code after the title screen's Friends button, in Direct Connection, or on the launcher's Play page.",
-    )
-}
-
-struct Button {
-    x: f32,
-    y: f32,
-    w: f32,
-    label: String,
-    action: Action,
-    active: bool,
-}
-
-/// The centred lines (text, colour, y) and the buttons.
-fn layout(
-    atlas: &HudAtlas,
-    (w, h): (f32, f32),
-    view: &FriendsView,
-) -> (Vec<(String, u32, f32)>, Vec<Button>) {
-    let width = (w - 40.0).min(310.0);
-    let cx = (w / 2.0).floor();
-    let mut lines = Vec::new();
-    let mut y = 40.0;
-    let add = |lines: &mut Vec<(String, u32, f32)>, text: &str, color: u32, y: &mut f32| {
-        for line in wrap(text, width, atlas) {
-            lines.push((line, color, *y));
-            *y += 10.0;
-        }
-    };
-    let mut buttons = Vec::new();
-    if view.sharing {
-        lines.push((
-            tr("horizon.multiplayer.invite_code", "Invite Code"),
-            grey(),
-            y,
-        ));
-        y += 12.0;
-        match &view.code {
-            Some(code) => {
-                for line in code_lines(atlas, code, width) {
-                    lines.push((line, WHITE, y));
-                    y += 10.0;
-                }
-            }
-            None => add(&mut lines, &view.status, WHITE, &mut y),
-        }
-        y += 6.0;
-        buttons.push(Button {
-            x: cx - 154.0,
-            y,
-            w: 150.0,
-            label: if view.copied {
-                tr("horizon.friends.copied", "Copied")
-            } else {
-                tr("horizon.friends.copy_code", "Copy Code")
-            },
-            action: Action::Copy,
-            active: view.code.is_some(),
-        });
-        buttons.push(Button {
-            x: cx + 4.0,
-            y,
-            w: 150.0,
-            label: tr("horizon.friends.stop_sharing", "Stop Sharing"),
-            action: Action::Stop,
-            active: true,
-        });
-        y += 30.0;
-        if view.code.is_some() {
-            // Who can join: grey when friends anywhere can, white (it asks
-            // for something) when only the LAN and VPNs can.
-            let tint = if view.reachable { grey() } else { WHITE };
-            add(&mut lines, &view.status, tint, &mut y);
-            y += 4.0;
-        }
-        let here = if view.guests.is_empty() {
-            tr("horizon.friends.none_yet", "No friends here yet.")
-        } else {
-            tr("horizon.friends.here_now", "Here now: %s").replacen(
-                "%s",
-                &view.guests.join(", "),
-                1,
-            )
-        };
-        add(&mut lines, &here, grey(), &mut y);
-        if let Some(notice) = &view.notice {
-            add(&mut lines, notice, WHITE, &mut y);
-        }
-        // Where friends paste the code, while it fits above the footer.
-        let hint = hint();
-        if y + 10.0 * wrap(&hint, width, atlas).len() as f32 <= h - 33.0 {
-            add(&mut lines, &hint, grey(), &mut y);
-        }
-    } else {
-        add(
-            &mut lines,
-            &tr(
-                "horizon.friends.share_intro",
-                "Share this world behind an invite code: it opens to LAN, and friends on the internet join with the code. No server of ours is involved.",
-            ),
-            WHITE,
-            &mut y,
-        );
-        y += 4.0;
-        add(&mut lines, &hint(), grey(), &mut y);
-        buttons.push(Button {
-            x: cx - 100.0,
-            y: y + 8.0,
-            w: 200.0,
-            label: tr("horizon.friends.start_sharing", "Start Sharing"),
-            action: Action::Share,
-            active: view.shown,
-        });
-    }
-    // HeaderAndFooterLayout's footer: Done, beside Troubleshooting when
-    // friends on the internet can't reach the host.
-    if view.sharing && view.help.is_some() {
-        buttons.push(Button {
-            x: cx - 154.0,
-            y: h - 27.0,
-            w: 150.0,
-            label: tr("horizon.friends.troubleshooting", "Troubleshooting..."),
-            action: Action::Help,
-            active: true,
-        });
-        buttons.push(Button {
-            x: cx + 4.0,
-            y: h - 27.0,
-            w: 150.0,
-            label: "gui.done".to_owned(),
-            action: Action::Done,
-            active: true,
-        });
-    } else {
-        buttons.push(Button {
-            x: cx - 100.0,
-            y: h - 27.0,
-            w: 200.0,
-            label: "gui.done".to_owned(),
-            action: Action::Done,
-            active: true,
-        });
-    }
-    (lines, buttons)
-}
-/// The code's groups packed into lines of at most `width`.
-fn code_lines(atlas: &HudAtlas, code: &str, width: f32) -> Vec<String> {
-    let mut lines: Vec<String> = Vec::new();
-    for group in code.split('-') {
-        match lines.last_mut() {
-            Some(l) if HudBatch::text_width(atlas, &format!("{l}-{group}")) <= width => {
-                l.push('-');
-                l.push_str(group);
-            }
-            _ => lines.push(group.to_owned()),
-        }
-    }
-    lines
-}
-fn label(key: &str) -> Text {
-    if key.starts_with("gui.") {
-        Text::translate(key, &[])
-    } else {
-        Text::literal(key)
-    }
-}
-pub fn draw(
-    batch: &mut HudBatch,
-    atlas: &HudAtlas,
-    cursor: (f32, f32),
-    view: &FriendsView,
-    in_world: bool,
-) {
-    let (w, h) = (batch.width, batch.height);
-    ui::menu_background(batch, atlas, 0.0, 0.0, w, h, in_world);
-    let title = Text::literal(title());
-    let tw = atlas.font.width_text(&title);
-    batch.text_styled(atlas, &title, ((w - tw) / 2.0).floor(), 15.0, WHITE, true);
-    let (lines, buttons) = layout(atlas, (w, h), view);
-    for (line, color, y) in lines {
-        let lw = HudBatch::text_width(atlas, &line);
-        batch.text(atlas, &line, ((w - lw) / 2.0).floor(), y, color, true);
-    }
-    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) {
-            horizon_client::widgets::declare_action(
-                horizon_client::widgets::Action::Done,
-                [b.x, b.y, b.w, 20.0],
-                b.active,
-            );
-        }
-        ui::button(
-            batch,
-            atlas,
-            b.x,
-            b.y,
-            b.w,
-            20.0,
-            &label(&b.label),
-            b.active,
-            hover,
-        );
-    }
-}
-/// The button under a click, if it is active.
-pub fn click(
-    atlas: &HudAtlas,
-    size: (f32, f32),
-    cursor: (f32, f32),
-    view: &FriendsView,
-) -> Option<Action> {
-    layout(atlas, size, view)
-        .1
-        .into_iter()
-        .find(|b| b.active && ui::hovered(cursor, b.x, b.y, b.w, 20.0))
-        .map(|b| b.action)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    fn atlas() -> HudAtlas {
-        HudAtlas::build(std::path::Path::new("/nonexistent/horizon-test-assets")).unwrap()
-    }
-
-    #[test]
-    fn share_then_copy_and_stop() {
-        let atlas = atlas();
-        let size = (427.0, 240.0);
-        let idle = FriendsView {
-            shown: true,
-            ..FriendsView::default()
-        };
-        let (_, buttons) = layout(&atlas, size, &idle);
-        let share = buttons.iter().find(|b| b.action == Action::Share).unwrap();
-        assert_eq!(
-            click(&atlas, size, (share.x + 1.0, share.y + 1.0), &idle),
-            Some(Action::Share)
-        );
-        let sharing = FriendsView {
-            shown: true,
-            sharing: true,
-            status: "Finding how friends can reach you…".into(),
-            ..FriendsView::default()
-        };
-        let (_, buttons) = layout(&atlas, size, &sharing);
-        let copy = buttons.iter().find(|b| b.action == Action::Copy).unwrap();
-        assert!(!copy.active, "nothing to copy before the code");
-        let with_code = FriendsView {
-            code: Some("0B33K-Q405Q-1Z5CV-X6NHY-R12N0-VK8T1-60N00-RA134-952PE-1HA08-910P0-K5M01-ST1NB-JDTB6-K4W1P-0".into()),
-            status: "Friends on your network or VPN can join. For friends on the internet: turn on UPnP on your router, or forward TCP port 25580 to 10.0.0.2, or use a relay, or a VPN such as Tailscale or ZeroTier (the code already holds your VPN address).".into(),
-            help: Some("https://example.invalid/help".into()),
-            ..sharing
-        };
-        let (lines, buttons) = layout(&atlas, size, &with_code);
-        assert!(
-            lines.iter().all(|(_, _, y)| y + 9.0 <= size.1 - 27.0),
-            "the text stays above the footer"
-        );
-        for action in [Action::Copy, Action::Stop, Action::Help, Action::Done] {
-            let b = buttons.iter().find(|b| b.action == action).unwrap();
-            assert_eq!(
-                click(&atlas, size, (b.x + 1.0, b.y + 1.0), &with_code),
-                Some(action)
-            );
-        }
-    }
-
-    #[test]
-    fn a_server_offers_no_sharing() {
-        let atlas = atlas();
-        let view = FriendsView::default();
-        let (_, buttons) = layout(&atlas, (427.0, 240.0), &view);
-        let share = buttons.iter().find(|b| b.action == Action::Share).unwrap();
-        assert!(!share.active);
-    }
-}

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

@@ -1,38 +0,0 @@
-//! 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 (`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, 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) {}
-
-    pub(super) fn tick_friends(&mut self) {}
-
-    /// Only reached by naming the screen (`horizon-ctl`): back to the pause menu.
-    pub(super) fn draw_friends_screen(&mut self, _batch: &mut HudBatch) {
-        self.screen = Screen::Paused;
-    }
-
-    pub(super) fn friends_screen_click(&mut self) {}
-
-    pub(super) fn friends_shown(&self) -> bool {
-        false
-    }
-
-    /// `horizon-ctl friends ...`.
-    pub(super) fn friends_control(&mut self, words: &[&str]) -> Result<Option<serde_json::Value>> {
-        if words[0] != "friends" {
-            return Ok(None);
-        }
-        Err("this build has no Play with Friends (the `friends` feature)".into())
-    }
-}

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

@@ -1489,7 +1489,7 @@ impl Game<'_> {
                 None => self.unpublish(),
             };
             if closed {
-                self.friends_lan_closed();
+                self.lan_closed_hooks();
             }
             if closed && announce && self.integrated.is_some() {
                 self.system_message(Text::translate(
@@ -1499,7 +1499,7 @@ impl Game<'_> {
             }
             return;
         }
-        self.friends_lan_closed();
+        self.lan_closed_hooks();
         self.native_players_leaving();
         let Some(mut host) = self.lan.take() else {
             return;

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

@@ -0,0 +1,330 @@
+//! A page drawn as its own screen (`horizon_hooks::pages::Place::PauseFriends`, what the pause
+//! menu's vanilla Friends icon opens), the way a mod adds a screen to vanilla: the menu
+//! background over the paused world, the title centred at the top, the rows centred down the
+//! middle, footer buttons beside Done at the bottom (`HeaderAndFooterLayout`).
+use super::{Game, Screen};
+use horizon_client::{
+    hud::{HudAtlas, HudBatch, rgba},
+    multiplayer::wrap,
+    text::Text,
+    ui,
+};
+use horizon_hooks::pages::{self, Act, Page, Place, Row};
+
+/// What a click on the screen hit.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum Hit {
+    /// The page's row with this index.
+    Row(usize),
+    Done,
+}
+
+struct Button {
+    x: f32,
+    y: f32,
+    w: f32,
+    label: &'static str,
+    hit: Hit,
+    active: bool,
+}
+
+fn grey() -> u32 {
+    rgba(160, 160, 160, 255)
+}
+const WHITE: u32 = u32::MAX;
+
+/// The centred lines (text, colour, y) and the buttons.
+fn layout(
+    atlas: &HudAtlas,
+    (w, h): (f32, f32),
+    rows: &[Row],
+) -> (Vec<(String, u32, f32)>, Vec<Button>) {
+    let width = (w - 40.0).min(310.0);
+    let cx = (w / 2.0).floor();
+    let mut lines = Vec::new();
+    let mut buttons = Vec::new();
+    let mut footer = Vec::new();
+    let mut y = 40.0;
+    // A half-width button waiting for the next to sit beside it.
+    let mut half_open = false;
+    for (r, row) in rows.iter().enumerate() {
+        let beside = std::mem::take(&mut half_open);
+        let (text, quiet, groups) = match row {
+            Row::Text {
+                text,
+                quiet,
+                groups,
+                ..
+            } => (text.clone(), *quiet, *groups),
+            Row::Note(text) => (text.clone(), true, false),
+            Row::Heading(key) => (horizon_client::lang::get(key), true, false),
+            Row::Space(px) => {
+                y += f32::from(*px);
+                continue;
+            }
+            Row::Button {
+                label,
+                active,
+                footer: true,
+                ..
+            } => {
+                footer.push((r, *label, *active));
+                continue;
+            }
+            Row::Button {
+                label,
+                active,
+                half,
+                ..
+            } => {
+                let (x, w) = match (*half, beside) {
+                    (true, true) => {
+                        y -= 30.0;
+                        (cx + 4.0, 150.0)
+                    }
+                    (true, false) => {
+                        half_open = true;
+                        (cx - 154.0, 150.0)
+                    }
+                    (false, _) => (cx - 100.0, 200.0),
+                };
+                buttons.push(Button {
+                    x,
+                    y,
+                    w,
+                    label,
+                    hit: Hit::Row(r),
+                    active: *active,
+                });
+                y += 30.0;
+                continue;
+            }
+            // Settings rows belong in the options shell.
+            _ => continue,
+        };
+        let wrapped = if groups {
+            groups_lines(atlas, &text, width)
+        } else {
+            wrap(&text, width, atlas)
+        };
+        // Text that would run into the footer is left out.
+        if y + 10.0 * wrapped.len() as f32 > h - 33.0 {
+            continue;
+        }
+        let color = if quiet { grey() } else { WHITE };
+        for line in wrapped {
+            lines.push((line, color, y));
+            y += 10.0;
+        }
+    }
+    // The footer: the page's buttons, then Done; Done alone is wider.
+    footer.push((usize::MAX, "gui.done", true));
+    let (each, gap) = if footer.len() == 1 {
+        (200.0, 0.0)
+    } else {
+        (150.0, 8.0)
+    };
+    let total = footer.len() as f32 * (each + gap) - gap;
+    let mut x = cx - total / 2.0;
+    for (r, label, active) in footer {
+        let hit = if r == usize::MAX {
+            Hit::Done
+        } else {
+            Hit::Row(r)
+        };
+        buttons.push(Button {
+            x,
+            y: h - 27.0,
+            w: each,
+            label,
+            hit,
+            active,
+        });
+        x += each + gap;
+    }
+    (lines, buttons)
+}
+
+/// `-`-separated groups packed into lines of at most `width`, never broken inside a group.
+fn groups_lines(atlas: &HudAtlas, text: &str, width: f32) -> Vec<String> {
+    let mut lines: Vec<String> = Vec::new();
+    for group in text.split('-') {
+        match lines.last_mut() {
+            Some(l) if HudBatch::text_width(atlas, &format!("{l}-{group}")) <= width => {
+                l.push('-');
+                l.push_str(group);
+            }
+            _ => lines.push(group.to_owned()),
+        }
+    }
+    lines
+}
+
+fn draw(batch: &mut HudBatch, atlas: &HudAtlas, cursor: (f32, f32), title: &str, rows: &[Row]) {
+    let (w, h) = (batch.width, batch.height);
+    ui::menu_background(batch, atlas, 0.0, 0.0, w, h, true);
+    let title = Text::translate(title, &[]);
+    let tw = atlas.font.width_text(&title);
+    batch.text_styled(atlas, &title, ((w - tw) / 2.0).floor(), 15.0, WHITE, true);
+    let (lines, buttons) = layout(atlas, (w, h), rows);
+    for (line, color, y) in lines {
+        let lw = HudBatch::text_width(atlas, &line);
+        batch.text(atlas, &line, ((w - lw) / 2.0).floor(), y, color, true);
+    }
+    for b in buttons {
+        let hover = b.active && ui::hovered(cursor, b.x, b.y, b.w, 20.0);
+        if b.hit == Hit::Done {
+            horizon_client::widgets::declare_action(
+                horizon_client::widgets::Action::Done,
+                [b.x, b.y, b.w, 20.0],
+                b.active,
+            );
+        }
+        let label = Text::translate(b.label, &[]);
+        ui::button(batch, atlas, b.x, b.y, b.w, 20.0, &label, b.active, hover);
+    }
+}
+
+/// The active button under a click.
+fn click(atlas: &HudAtlas, size: (f32, f32), cursor: (f32, f32), rows: &[Row]) -> Option<Hit> {
+    layout(atlas, size, rows)
+        .1
+        .into_iter()
+        .find(|b| b.active && ui::hovered(cursor, b.x, b.y, b.w, 20.0))
+        .map(|b| b.hit)
+}
+
+/// The page the Friends icon opens: the first registered there.
+fn friends_page() -> Option<&'static dyn Page> {
+    pages::engine::all()
+        .iter()
+        .copied()
+        .find(|page| page.place() == Place::PauseFriends)
+}
+
+/// What the Friends icon and its screen are named, for its tooltip, the narrator, controller
+/// focus and the control socket's widget tree: the page's title, else vanilla's tooltip.
+pub(super) fn friends_name() -> String {
+    friends_page().map_or_else(
+        || horizon_client::lang::get("gui.friends.open"),
+        |page| horizon_client::lang::get(page.title()),
+    )
+}
+
+impl Game<'_> {
+    /// Whether the pause menu's Friends icon is active: a page is registered for it and this
+    /// window plays a singleplayer world (another server's world can't be shared).
+    pub(super) fn friends_shown(&self) -> bool {
+        self.can_share() && friends_page().is_some()
+    }
+
+    /// The Friends icon's page. Its rows are asked each time it is drawn.
+    pub(super) fn draw_added_page(&mut self, batch: &mut HudBatch) {
+        let Some(page) = friends_page() else {
+            // Only reached by naming the screen (`horizon-ctl`): back to the pause menu.
+            self.screen = Screen::Paused;
+            return;
+        };
+        let mut rows = Vec::new();
+        page.rows(&mut rows);
+        horizon_client::widgets::begin_screen(|| {
+            horizon_client::widgets::ScreenInfo::new("friends", friends_name())
+        });
+        draw(batch, &self.gui.atlas, self.cursor, page.title(), &rows);
+    }
+
+    pub(super) fn added_page_click(&mut self) {
+        let Some(page) = friends_page() else {
+            return;
+        };
+        let mut rows = Vec::new();
+        page.rows(&mut rows);
+        let Some(hit) = click(&self.gui.atlas, self.gui_size(), self.cursor, &rows) else {
+            return;
+        };
+        self.audio.play_button_click();
+        match hit {
+            Hit::Row(r) => page.act(r, Act::Press),
+            Hit::Done => self.screen = Screen::Paused,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn atlas() -> HudAtlas {
+        HudAtlas::build(std::path::Path::new("/nonexistent/horizon-test-assets")).unwrap()
+    }
+
+    fn at(buttons: &[Button], hit: Hit) -> &Button {
+        buttons.iter().find(|b| b.hit == hit).unwrap()
+    }
+
+    #[test]
+    fn halves_sit_side_by_side_and_footer_buttons_beside_done() {
+        let atlas = atlas();
+        let size = (427.0, 240.0);
+        let rows = [
+            Row::text("Invite Code").quiet(),
+            Row::Space(2),
+            Row::text("0B33K-Q405Q-1Z5CV-X6NHY-R12N0-VK8T1-60N00-RA134-952PE-1HA08-910P0-K5M01-ST1NB-JDTB6-K4W1P-0").groups(),
+            Row::Space(6),
+            Row::button("copy").half().active(false),
+            Row::button("stop").half(),
+            Row::text("Friends on your network or VPN can join. For friends on the internet: turn on UPnP on your router, or forward TCP port 25580 to 10.0.0.2, or use a relay, or a VPN such as Tailscale or ZeroTier (the code already holds your VPN address)."),
+            Row::button("help").footer(),
+        ];
+        let (lines, buttons) = layout(&atlas, size, &rows);
+        let (copy, stop) = (at(&buttons, Hit::Row(4)), at(&buttons, Hit::Row(5)));
+        // 213 is the middle: two 150-wide halves 8 apart around it, as vanilla's pairs.
+        assert_eq!(
+            (copy.x, copy.w, stop.x, stop.w),
+            (59.0, 150.0, 217.0, 150.0)
+        );
+        assert_eq!(copy.y, stop.y);
+        let (help, done) = (at(&buttons, Hit::Row(7)), at(&buttons, Hit::Done));
+        assert_eq!(
+            (help.x, done.x, help.y, done.y),
+            (59.0, 217.0, 213.0, 213.0)
+        );
+        // The code breaks between its groups only.
+        let code: Vec<_> = lines
+            .iter()
+            .filter(|(_, c, _)| *c == WHITE)
+            .map(|(l, ..)| l)
+            .collect();
+        assert!(code[0].starts_with("0B33K-") && code.iter().all(|l| !l.ends_with('-')));
+        assert!(
+            lines.iter().all(|(_, _, y)| y + 9.0 <= size.1 - 27.0),
+            "above the footer"
+        );
+        // An inactive button takes no click; Done alone is 200 wide.
+        assert_eq!(
+            click(&atlas, size, (copy.x + 1.0, copy.y + 1.0), &rows),
+            None
+        );
+        assert_eq!(
+            click(&atlas, size, (stop.x + 1.0, stop.y + 1.0), &rows),
+            Some(Hit::Row(5))
+        );
+        let (_, alone) = layout(&atlas, size, &[Row::button("share")]);
+        assert_eq!(at(&alone, Hit::Done).w, 200.0);
+        assert_eq!(at(&alone, Hit::Row(0)).x, 113.0);
+    }
+
+    #[test]
+    fn text_that_would_reach_the_footer_is_left_out() {
+        let atlas = atlas();
+        let rows = [
+            Row::Space(150),
+            Row::text("first"),
+            Row::text("too low").quiet(),
+        ];
+        let (lines, _) = layout(&atlas, (427.0, 240.0), &rows);
+        // 40 + 150 = 190: one line fits above 207, the next (200..210) doesn't.
+        assert_eq!(lines.len(), 1);
+        assert_eq!(lines[0].0, "first");
+    }
+}

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

@@ -108,7 +108,7 @@ impl Game<'_> {
                         self.death_confirm_answer(false)?;
                     }
                 }
-                Screen::Stats | Screen::Friends => self.screen = Screen::Paused,
+                Screen::Stats | Screen::AddedPage => self.screen = Screen::Paused,
                 Screen::Social => self.close_social(),
                 Screen::ServerLinks => self.screen = Screen::Paused,
                 // ConfirmScreen.keyPressed: Escape answers no; both return to

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

@@ -1569,7 +1569,7 @@ impl Game<'_> {
         self.left = false;
         self.right = false;
         // The shared world is closing: its invite code ends with it.
-        self.friends_lan_closed();
+        self.lan_closed_hooks();
         // Single player's server thread saves the world before the title shows.
         let single_player = match self.integrated.take() {
             Some(server) => {

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

@@ -73,7 +73,7 @@ impl Screen {
             | Self::Stats
             | Self::Advancements
             | Self::WorldOptions
-            | Self::Friends
+            | Self::AddedPage
             | Self::ServerLinks
             | Self::ConfirmLink
             | Self::DialogWarning
@@ -92,7 +92,7 @@ impl Screen {
             | Self::Stats
             | Self::Advancements
             | Self::WorldOptions
-            | Self::Friends
+            | Self::AddedPage
             | Self::Social
             | Self::ServerLinks
             | Self::ConfirmLink
@@ -191,8 +191,8 @@ fn pause_buttons(
 }
 
 /// The icon row: report bugs, feedback, friends, player reporting.
-/// `FRIENDS_ICON` (vanilla's `CommonButtons.friends`) opens Horizon's
-/// Play with Friends; the first two open their link through
+/// `FRIENDS_ICON` (vanilla's `CommonButtons.friends`) opens the page registered at
+/// `Place::PauseFriends` (Play with Friends in the official build); the first two open their link through
 /// `ConfirmLinkScreen`; player reporting opens `SocialInteractionsScreen`.
 const FRIENDS_ICON: usize = 2;
 /// `CommonLinks.SNAPSHOT_BUGS_FEEDBACK`, behind `PauseScreen.REPORT_BUGS`.
@@ -312,6 +312,7 @@ impl Game<'_> {
     }
     pub(super) fn draw_pause_menu(&mut self, batch: &mut HudBatch) {
         let friends = self.friends_shown();
+        let friends_name = super::page_screen::friends_name();
         let atlas = &self.gui.atlas;
         let (w, h) = (batch.width, batch.height);
         ui::menu_background(batch, atlas, 0.0, 0.0, w, h, true);
@@ -373,7 +374,7 @@ 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(super::friends::TITLE, [x, y, 20.0, 20.0], active);
+                horizon_client::widgets::record(&friends_name, [x, y, 20.0, 20.0], active);
             }
             ui::button(
                 batch,
@@ -410,7 +411,7 @@ 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(super::friends::title())
+                    Text::literal(friends_name.clone())
                 } else {
                     Text::translate(ICON_LABELS[i], &[])
                 });
@@ -438,7 +439,7 @@ impl Game<'_> {
             3 => self.open_stats(),
             4 => self.open_advancements(true),
             9 => self.open_world_options(),
-            10 => self.screen = Screen::Friends,
+            10 => self.screen = Screen::AddedPage,
             // DialogConnectionAccess.openDialog(Dialogs.SERVER_LINKS).
             11 => {
                 self.links_ui.scroll = 0.0;
@@ -993,7 +994,7 @@ mod tests {
             Screen::Stats,
             Screen::Advancements,
             Screen::WorldOptions,
-            Screen::Friends,
+            Screen::AddedPage,
             Screen::ServerLinks,
             Screen::ConfirmLink,
             Screen::DialogWarning,

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

@@ -0,0 +1,120 @@
+//! The window's world as `horizon_hooks::share` shows it to the crates that share it past the
+//! LAN (Play with Friends), and where the engine calls `Hooks::share` and `Hooks::lan_closed`.
+use super::{Game, lan::LanSettings};
+use horizon_client::text::Text;
+use horizon_hooks::share::{LanOptions, ShareView};
+
+/// The window's own player: not the integrated server's thread, not a splitscreen guest (it
+/// plays P1's world and can't share it; its leaving doesn't close it).
+fn shares(game: &Game<'_>) -> bool {
+    !game.serving() && !game.options.split_guest
+}
+
+/// Play with Friends' host side (game/friends.rs) hears the hooks, until it moves to
+/// horizon-friends (spec #14167). Before the hooks are sealed.
+#[cfg(feature = "friends")]
+pub(crate) fn register_friends() {
+    if horizon_hooks::register(&super::friends::HOOKS).is_err()
+        || horizon_hooks::pages::register(&super::friends::PAGE).is_err()
+    {
+        log::warn!("Play with Friends registered after the game started: sharing is off");
+    }
+}
+
+impl Game<'_> {
+    /// `Hooks::share`, once a client tick (`Minecraft.runTick`, so also while paused).
+    pub(super) fn share_tick(&mut self) {
+        if shares(self) {
+            horizon_hooks::engine::share(&mut World(self));
+        }
+    }
+
+    /// `Hooks::lan_closed`: the world stopped being open to LAN, or the player left it.
+    pub(super) fn lan_closed_hooks(&self) {
+        if shares(self) {
+            horizon_hooks::engine::lan_closed();
+        }
+    }
+
+    /// `Hooks::control`: a `horizon-ctl` command a crate answers, with this window's world.
+    pub(super) fn hooks_control(
+        &mut self,
+        words: &[&str],
+    ) -> horizon_client::Result<Option<serde_json::Value>> {
+        match horizon_hooks::engine::control(words, &mut World(self)) {
+            None => Ok(None),
+            Some(Ok(json)) => Ok(Some(serde_json::from_str(&json)?)),
+            Some(Err(why)) => Err(why.into()),
+        }
+    }
+
+    /// A singleplayer world runs on this window's server thread, so it can be shared, as Open
+    /// to LAN publishes it; another server can't be.
+    pub(super) fn can_share(&self) -> bool {
+        self.title.is_none() && (self.remote.is_none() || self.integrated.is_some())
+    }
+}
+
+pub(super) struct World<'a, 'g>(&'a mut Game<'g>);
+
+impl ShareView for World<'_, '_> {
+    fn can_share(&self) -> bool {
+        self.0.can_share()
+    }
+
+    fn lan_port(&self) -> Option<u16> {
+        self.0.lan_port()
+    }
+
+    fn open_lan(&mut self, options: LanOptions) -> Result<u16, String> {
+        self.0
+            .lan_open(LanSettings {
+                port: horizon_client::lan::available_port(),
+                guest_commands: options.guest_commands,
+                force_game_mode: options.force_game_mode,
+            })
+            .map_err(|e| e.to_string())?;
+        self.0
+            .lan_port()
+            .ok_or_else(|| "the world isn't open to LAN".to_owned())
+    }
+
+    fn close_lan(&mut self) {
+        self.0.lan_close(true);
+    }
+
+    fn players(&self, each: &mut dyn FnMut(&str)) {
+        let g = &self.0;
+        if let Some(host) = &g.lan {
+            for guest in &host.hub.guests {
+                each(&guest.name);
+            }
+        } else if g.integrated.is_some() {
+            // On the server thread: the other players the server lists.
+            let me = g.options.player_name();
+            for name in g.remote_online_names().unwrap_or_default() {
+                if name != me {
+                    each(&name);
+                }
+            }
+        }
+    }
+
+    fn chat(&mut self, text: &str) {
+        self.0.system_message(Text::literal(text));
+    }
+
+    fn copy(&mut self, text: &str) {
+        use horizon_client::clipboard::Clipboard;
+        self.0.clipboard.set(text);
+    }
+
+    fn open_url(&mut self, url: &str) {
+        // The system browser, as the folder buttons open their folders.
+        super::packs::open_uri(url);
+    }
+
+    fn tr(&self, key: &str) -> Option<String> {
+        horizon_client::lang::has(key).then(|| horizon_client::lang::get(key))
+    }
+}

crates/horizon-hdr/src/lib.rs

@@ -47,6 +47,15 @@ pub fn open_vulkan_device(
     Some(unsafe { adapter.create_device_from_hal(open, desc) })
 }
 
+/// wgpu's opt-in to its `EXPERIMENTAL_*` features, which the crates that forbid unsafe code
+/// can't give: hardware ray queries, asked for only when the player turns ray tracing on
+/// (`gfx/ray_query.rs` in horizon-client-render).
+pub fn experimental_features() -> wgpu::ExperimentalFeatures {
+    // Safety: wgpu warns that its experimental features may have bugs that reach undefined
+    // behaviour through safe calls. Horizon accepts that only on request, for ray queries.
+    unsafe { wgpu::ExperimentalFeatures::enabled() }
+}
+
 /// Tells the compositor, through `VK_EXT_hdr_metadata`, that the swapchain's
 /// content is BT.709, peaks at `peak` nits and is no darker than `black`. Needs a
 /// device from `open_vulkan_device` and a configured surface; does nothing otherwise.

crates/horizon-hooks/src/lib.rs

@@ -21,6 +21,7 @@ pub mod hud;
 pub mod pages;
 mod registry;
 pub mod settings;
+pub mod share;
 pub mod tunnel;
 
 use registry::Registry;
@@ -48,6 +49,31 @@ pub trait Hooks: Sync {
     fn tunnel(&self) -> Option<&dyn tunnel::Resolver> {
         None
     }
+
+    /// Once a client tick (20 a second, also while the game is paused or on the title screen),
+    /// with the window's world ([`share`]). Only the window's own player calls it.
+    fn share(&self, _world: &mut dyn share::ShareView) {}
+
+    /// The window's world stopped being open to LAN: Open to LAN's stop, or the player left the
+    /// world. Called at that moment, by the window's own player only.
+    fn lan_closed(&self) {}
+
+    /// The `horizon-ctl` commands this crate answers in the game: their group, as `hello` lists
+    /// it, and the lines `help` adds for them.
+    fn control_commands(&self) -> Option<(&'static str, &'static [&'static str])> {
+        None
+    }
+
+    /// A `horizon-ctl` command (its words) on the window's game: `Some` with the answer as JSON
+    /// text, or why it failed, when it is this crate's. The first hook that answers wins; the
+    /// hooks are asked before most of the engine's own commands.
+    fn control(
+        &self,
+        _words: &[&str],
+        _world: &mut dyn share::ShareView,
+    ) -> Option<Result<String, String>> {
+        None
+    }
 }
 
 /// What [`Hooks::started`] gets.
@@ -85,6 +111,15 @@ pub fn register(hooks: &'static dyn Hooks) -> Result<(), TooLate> {
 }
 
 /// The registered hooks, sealing the list on the first call.
+/// The game's translations, which it installs at start ([`engine::set_language`]).
+static LANGUAGE: std::sync::OnceLock<fn(&str) -> Option<String>> = std::sync::OnceLock::new();
+
+/// The text of a translation key in the player's language, if the game has it. For text a crate
+/// makes outside a view, such as a page's rows. None before the game installs its languages.
+pub fn tr(key: &str) -> Option<String> {
+    LANGUAGE.get().and_then(|language| language(key))
+}
+
 fn all() -> &'static [&'static dyn Hooks] {
     HOOKS.all()
 }
@@ -102,6 +137,11 @@ pub mod engine {
         crate::hud::engine::all();
     }
 
+    /// Where [`crate::tr`] reads translations from; the first call wins.
+    pub fn set_language(language: fn(&str) -> Option<String>) {
+        let _ = LANGUAGE.set(language);
+    }
+
     /// [`Hooks::started`].
     pub fn started(game: &Started<'_>) {
         for hooks in all() {
@@ -130,6 +170,33 @@ pub mod engine {
         }
     }
 
+    /// [`Hooks::share`].
+    pub fn share(world: &mut dyn share::ShareView) {
+        for hooks in all() {
+            hooks.share(world);
+        }
+    }
+
+    /// [`Hooks::lan_closed`].
+    pub fn lan_closed() {
+        for hooks in all() {
+            hooks.lan_closed();
+        }
+    }
+
+    /// [`Hooks::control`]: the first hook's answer.
+    pub fn control(
+        words: &[&str],
+        world: &mut dyn share::ShareView,
+    ) -> Option<Result<String, String>> {
+        all().iter().find_map(|hooks| hooks.control(words, world))
+    }
+
+    /// [`Hooks::control_commands`] of every hook, in registration order.
+    pub fn control_commands() -> impl Iterator<Item = (&'static str, &'static [&'static str])> {
+        all().iter().filter_map(|hooks| hooks.control_commands())
+    }
+
     /// [`Hooks::tunnel`]: the first registered hook's resolver.
     pub fn tunnel() -> Option<&'static dyn tunnel::Resolver> {
         all().iter().find_map(|hooks| hooks.tunnel())

crates/horizon-hooks/src/pages.rs

@@ -19,6 +19,12 @@ pub enum Place {
     /// 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,
+    /// What the pause menu's Friends icon opens (vanilla's `CommonButtons.friends`): the icon is
+    /// active while a page is registered here and the world can be shared (singleplayer). The
+    /// first page registered here is drawn as its own screen over the paused world, as a mod's
+    /// screen is: the title at the top, the rows centred down the middle, footer buttons beside
+    /// Done at the bottom. Text that would reach the footer is left out.
+    PauseFriends,
 }
 
 /// One page. Its values live in the crate (statics, often its settings [`crate::settings::Store`]);
@@ -61,13 +67,93 @@ pub enum Row {
         value: f32,
         text: Label,
     },
-    /// A button that does something.
-    Button { label: &'static str },
+    /// A button that does something ([`Row::button`]). An inactive one is drawn greyed and
+    /// never pressed; two half-width ones in a row sit side by side; a footer one sits at the
+    /// bottom beside Done on a page drawn as its own screen, and with the others elsewhere.
+    /// Horizon Settings' Extras shows only active ones.
+    #[non_exhaustive]
+    Button {
+        label: &'static str,
+        active: bool,
+        half: bool,
+        footer: bool,
+    },
+    /// Text shown as it is, wrapped to the page's width ([`Row::text`]): white, or grey when
+    /// `quiet` (secondary); `groups` breaks it only between its `-`-separated groups (a code).
+    #[non_exhaustive]
+    Text {
+        text: String,
+        quiet: bool,
+        groups: bool,
+    },
+    /// Empty space, in GUI pixels, on a page drawn as its own screen; nothing elsewhere.
+    Space(u8),
     /// 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 },
 }
 
+impl Row {
+    /// An active, full-width button in the page's body.
+    pub fn button(label: &'static str) -> Self {
+        Self::Button {
+            label,
+            active: true,
+            half: false,
+            footer: false,
+        }
+    }
+
+    /// White text in the page's body, wrapped at spaces.
+    pub fn text(text: impl Into<String>) -> Self {
+        Self::Text {
+            text: text.into(),
+            quiet: false,
+            groups: false,
+        }
+    }
+
+    /// A button greyed out (`false`): drawn, never pressed.
+    pub fn active(mut self, on: bool) -> Self {
+        if let Self::Button { active, .. } = &mut self {
+            *active = on;
+        }
+        self
+    }
+
+    /// A button half as wide: two in a row sit side by side.
+    pub fn half(mut self) -> Self {
+        if let Self::Button { half, .. } = &mut self {
+            *half = true;
+        }
+        self
+    }
+
+    /// A button in the footer, beside Done, on a page drawn as its own screen.
+    pub fn footer(mut self) -> Self {
+        if let Self::Button { footer, .. } = &mut self {
+            *footer = true;
+        }
+        self
+    }
+
+    /// Text in grey: secondary.
+    pub fn quiet(mut self) -> Self {
+        if let Self::Text { quiet, .. } = &mut self {
+            *quiet = true;
+        }
+        self
+    }
+
+    /// Text broken only between its `-`-separated groups, never inside one (a code).
+    pub fn groups(mut self) -> Self {
+        if let Self::Text { groups, .. } = &mut self {
+            *groups = true;
+        }
+        self
+    }
+}
+
 /// 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 {

crates/horizon-hooks/src/share.rs

@@ -0,0 +1,53 @@
+//! Sharing the open world past the LAN (Play with Friends' host side): what the engine lets a
+//! crate do with the world a window plays. The engine implements [`ShareView`] and hands it to
+//! [`Hooks::share`](crate::Hooks::share) once a client tick; [`Hooks::lan_closed`](crate::Hooks::lan_closed)
+//! says the world stopped being open to LAN.
+//!
+//! Only the window's own player calls them (a splitscreen guest can't share P1's world, and
+//! its leaving doesn't close it), never the integrated server's thread or a dedicated server.
+
+/// How [`ShareView::open_lan`] opens the world, as Open to LAN's screen does. The default is
+/// what `ShareToLanScreen` offers: no commands for guests, the world's game mode forced on them.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[non_exhaustive]
+pub struct LanOptions {
+    /// Guests may run commands (`ShareToLanScreen`'s "Allow Cheats").
+    pub guest_commands: bool,
+    /// Guests play in the world's game mode.
+    pub force_game_mode: bool,
+}
+
+impl Default for LanOptions {
+    fn default() -> Self {
+        Self {
+            guest_commands: false,
+            force_game_mode: true,
+        }
+    }
+}
+
+/// The window's world, as a crate sharing it sees it. Nothing here allocates per call unless a
+/// method says so.
+pub trait ShareView {
+    /// A singleplayer world runs on this window's server thread, so it can be shared. False on
+    /// the title screen and on another server.
+    fn can_share(&self) -> bool;
+    /// The port the world is open to LAN on, if it is.
+    fn lan_port(&self) -> Option<u16>;
+    /// Opens the world to LAN on a free port, as Open to LAN does; the port, or why not.
+    fn open_lan(&mut self, options: LanOptions) -> Result<u16, String>;
+    /// Closes the world to LAN, saying so in chat as Open to LAN's stop does.
+    fn close_lan(&mut self);
+    /// The names of the other players in the world (not this one's). For a screen or a command,
+    /// not every tick.
+    fn players(&self, each: &mut dyn FnMut(&str));
+    /// A line in this player's chat, as the game's own system messages; `text` is already in
+    /// the player's language ([`ShareView::tr`]).
+    fn chat(&mut self, text: &str);
+    /// Puts `text` on the system clipboard.
+    fn copy(&mut self, text: &str);
+    /// Opens `url` in the system's browser.
+    fn open_url(&mut self, url: &str);
+    /// The translation of `key` in the player's language, if the game has one.
+    fn tr(&self, key: &str) -> Option<String>;
+}

crates/horizon-platform/src/lib.rs

@@ -46,7 +46,7 @@ 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, tunnel};
+    pub use horizon_hooks::{Hooks, Started, TooLate, register, share, tr, tunnel};
 }
 
 /// The settings store (`horizon_hooks::settings`): a crate's own `key:value` lines in the game

docs/forking.md

@@ -25,7 +25,7 @@ What changes in that build:
 | The official server added to the server list, the withdrawn partner server taken out | `official_servers.rs` | the module and its call at startup (`game.rs`, `fn run`) |
 | Horizon Settings (Extras, PvP & HUD, Splitscreen, Studio, AI Agent, Discord) and Mods (with the registry browser) | `options_ui.rs` (`Page::Horizon` and below), `extras_ui.rs`, `extras.rs`, `pvp.rs`, `game/extras.rs`, `game/tweaks.rs`, `extras_hud.rs` | the Options screen shows vanilla's greyed Telemetry Data instead (`options_ui::HORIZON_EXTRAS`, set in `entry.rs`) |
 | Discord Rich Presence | `discord_presence.rs`, `game/discord.rs` | the `discord` feature, which `horizon-extras` turns on |
-| Play with Friends | hosting: `game/friends.rs`, `game/friends/screen.rs`; joining: crate `horizon-friends` (`game`) | hosting: the `friends` feature (`game/friends_off.rs` stands in); joining: only the official executable registers it ([layers.md](layers.md#how-a-horizon-crate-plugs-in)) |
+| Play with Friends | hosting: `game/friends.rs` (its page, drawn by `game/page_screen.rs`); joining: crate `horizon-friends` (`game`) | hosting: the `friends` feature (`game/friends_off.rs` stands in); joining: only the official executable registers it ([layers.md](layers.md#how-a-horizon-crate-plugs-in)) |
 | The anonymous "I'm playing" ping | crate `horizon-heartbeat` | not in horizon-client at all: only the official executable (`horizon-official`) registers it ([layers.md](layers.md#how-a-horizon-crate-plugs-in)) |
 
 Credits & Attribution then says where the official build is (`horizon.plain.official`).

docs/layers.md

@@ -288,7 +288,10 @@ build pays nothing.
 
 The hooks today: `started` (once, when someone plays: not a dedicated server, a benchmark or an automated run),
 `published` (the world opened to or closed from LAN or friends, on change), `shutdown` (the window closed, the
-world saved) and `tunnel` (the resolver of `friend:` addresses, Play with Friends'). **A hook you need and don't find:** add a method with an empty default to `Hooks` and a function in
+world saved), `tunnel` (the resolver of `friend:` addresses, Play with Friends'), `share` (each client tick, the window's world
+through `share::ShareView`: open it to LAN, its players, chat, the clipboard) and `lan_closed` (it stopped being open
+to LAN), `control_commands` and `control` (the `horizon-ctl` commands a crate answers in the game, with that view).
+**A hook you need and don't find:** add a method with an empty default to `Hooks` and a function in
 `horizon_hooks::engine` that the engine calls where vanilla does the matching thing; give it plain data or a type
 the engine owns, never one from above. A hook that needs engine types the platform doesn't expose yet (a draw
 context for HUD and chat overlays, a settings page) comes with that type's platform API (M6). An extension point
@@ -364,7 +367,7 @@ pub trait Store: Sync {
 A page lives in the options screen's shell, and its entry sits on one of the game's menus.
 
 ```rust
-pub enum Place { HorizonSettings, Title, Pause }
+pub enum Place { HorizonSettings, Title, Pause, Extras, PauseFriends }
 pub trait Page: Sync {
     fn id(&self) -> &'static str;            // stable, for horizon-ctl and the page stack
     fn title(&self) -> &'static str;         // translation key
@@ -379,8 +382,10 @@ pub enum Row {
     Toggle { label: &'static str, on: bool },
     Cycle { label: &'static str, value: Label },
     Slider { label: &'static str, value: f32, text: Label },   // value in 0..=1
-    Button { label: &'static str },
+    Button { label: &'static str, active: bool, half: bool, footer: bool },  // Row::button(..).half()...
     Key { label: &'static str, key: String },                 // a binding: `key.keyboard.z`
+    Text { text: String, quiet: bool, groups: bool },         // Row::text(..): white or grey, wrapped
+    Space(u8),                                                // GUI pixels, on a page drawn as a screen
 }
 pub enum Label { Key(&'static str), Value(String) }
 pub enum Act { Press, PressBack, Slide(f32), Bind(String) }
@@ -390,6 +395,13 @@ pub enum Act { Press, PressBack, Slide(f32), Bind(String) }
   button on the title screen or the pause menu that opens the page. These buttons exist only when something
   registered, so the vanilla menus keep vanilla's look. The page is drawn with the same widgets, tooltips,
   narration, controller focus and `horizon-ctl` ids as the engine's pages.
+- `PauseFriends`: what the pause menu's vanilla Friends icon opens. The icon is active while a page is registered
+  there and the world can be shared; the page is drawn as its own screen over the paused world (title, rows down the
+  middle, footer buttons beside Done), the way Play with Friends' screen always looked.
+- `Button` and `Text` are built with `Row::button` and `Row::text` and their options: `.active(false)` greys a
+  button, `.half()` puts two side by side, `.footer()` sets one beside Done on a page drawn as its own screen,
+  `.quiet()` greys text, `.groups()` breaks it only between `-`-separated groups (an invite code). In the options
+  shell, text is notes and space is nothing.
 - Rows are rebuilt when the page is drawn or acted on, like the engine's own pages: no cost while no page is
   open.
 - The engine keeps native mods' pages (`Page::NativeMod`) as they are. Both kinds sit in one module that

docs/play-with-friends.md

@@ -26,7 +26,7 @@ that finds the port takes the session.
 ## How it works
 
 **Hosting.** The pause menu's Friends button (vanilla's icon, beside Player Reporting) opens **Play
-with Friends** (`game/friends/screen.rs`); its **Start Sharing** opens the world to LAN if it isn't (Open to
+with Friends** (game/friends.rs's page at `Place::PauseFriends`, drawn by `game/page_screen.rs`); its **Start Sharing** opens the world to LAN if it isn't (Open to
 LAN's defaults), then the host's game, on its own:
 
 1. listens on its **direct port**, TCP 25580 by default (the same port every time, so a port forwarded
@@ -54,9 +54,13 @@ router that opened the port, or with a forwarded port, that's it: no server took
 reads codes and opens the tunnel, which the join (`net.rs`) then reaches on a loopback port like any server.
 horizon-friends' `game` side offers it, and the official executable (`horizon-official`) registers it;
 horizon-client's own executable has none, so there a `friend:` address is refused. Hosting needs no hook: the
-host end connects to the world's LAN port over loopback, so tunnelled guests are LAN guests. It still lives in
-horizon-client (`game/friends.rs`, `game/friends/screen.rs`, the `friends` feature, which comes with
-`horizon-extras`) until the pause menu and `horizon-ctl` offer entries to crates above the engine.
+host end connects to the world's LAN port over loopback, so tunnelled guests are LAN guests. Hosting sees the
+game only through `horizon_hooks`: `Hooks::share` each client tick with a `share::ShareView` (open the world to
+LAN, its players, chat, the clipboard, a link), `Hooks::lan_closed`, its page (`pages::Place::PauseFriends`, what
+the pause menu's Friends icon opens; a press runs on the next tick) and `tr`. It keeps what it shares in its own
+statics. It still lives in horizon-client (`game/friends.rs`, the `friends` feature, which comes with
+`horizon-extras`), and answers `horizon-ctl friends` through `Hooks::control`, until it moves to horizon-friends
+(#14167).
 
 **Codes.** Crockford base32 (`0-9 A-Z` without `I L O U`; input ignores case, spaces and dashes and reads
 `O` as `0`, `I`/`L` as `1`) in groups of five, with a 16-bit checksum so a typo is caught before