feat(mods): allow cancelling targeted block highlights

Co-Authored-By: Codex <[email protected]>

crates/horizon-client/src/game.rs

@@ -14529,6 +14529,12 @@ impl Game<'_> {
                         || !self.block_action_restricted(h.pos)
                         || self.can_place_on_in_adventure(h.pos)
                 })
+                .filter(|h| {
+                    let state = self.world.block(h.pos[0], h.pos[1], h.pos[2]);
+                    let mut canceled = false;
+                    self.native_block_highlight(h.pos, state, alpha as f32, &mut canceled);
+                    !canceled
+                })
                 .map(|h| {
                     let state = self.world.block(h.pos[0], h.pos[1], h.pos[2]);
                     let f = self.res.facts().get(state);

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

@@ -1084,6 +1084,17 @@ impl Game<'_> {
     /// and on servers), and the server's own (`native_window` is false
     /// there: the single player server thread, a dedicated server).
     pub(super) fn native_tick(&mut self) {}
+    /// Before an eligible targeted block's selection outline is built.
+    /// Cancel skips only the default block highlight, after normal HUD and game-mode gates.
+    pub(super) fn native_block_highlight(
+        &self,
+        pos: [i32; 3],
+        state: BlockStateId,
+        partial: f32,
+        canceled: &mut bool,
+    ) {
+        let _ = (pos, state, partial, canceled);
+    }
     /// The world frame's local visual sources. Push requests; Horizon validates
     /// and limits them before rendering. Called only while a world is visible.
     pub(super) fn native_visuals(

tests/test_block_highlight_hook.py

@@ -0,0 +1,51 @@
+"""Run the actual outline filter with a fake mod, without a renderer."""
+from pathlib import Path
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+class BlockHighlightHookTests(unittest.TestCase):
+    @unittest.skipUnless(shutil.which("rustc"), "requires Rust")
+    def test_cancel_filters_only_the_target_outline(self):
+        source = (ROOT / "crates/horizon-client/src/game.rs").read_text()
+        call = source.index("self.native_block_highlight(")
+        start = source.rindex(".filter(|h| {", 0, call)
+        end = source.index(".map(|h| {", call)
+        self.assertLess(source.index("let outline = if !self.ui.hide_gui"), start)
+        self.assertLess(source.index("self.can_place_on_in_adventure(h.pos)"), start)
+        fixture = r"""
+use std::cell::Cell;
+#[derive(Clone, Copy, Debug, PartialEq)]
+struct Hit { pos: [i32; 3] }
+#[derive(Clone, Copy, Debug, PartialEq)]
+struct BlockStateId(u32);
+struct World;
+impl World { fn block(&self, x: i32, y: i32, z: i32) -> BlockStateId { assert_eq!([x,y,z], [1,2,3]); BlockStateId(42) } }
+struct Game { world: World, cancel: bool, calls: Cell<usize> }
+impl Game {
+    fn native_block_highlight(&self, pos: [i32; 3], state: BlockStateId, partial: f32, canceled: &mut bool) {
+        assert_eq!(pos, [1,2,3]); assert_eq!(state, BlockStateId(42)); assert_eq!(partial, 0.5);
+        self.calls.set(self.calls.get()+1); *canceled = self.cancel;
+    }
+    fn filter(&self, hit: Option<Hit>) -> Option<Hit> { let alpha = 0.5; hit FILTER }
+}
+#[test]
+fn cancelled_default_and_missing_target() {
+    for cancel in [false, true] {
+        let game = Game { world: World, cancel, calls: Cell::new(0) };
+        let hit = Hit { pos: [1,2,3] };
+        assert_eq!(game.filter(Some(hit)), if cancel { None } else { Some(hit) });
+        assert_eq!(game.filter(None), None);
+        assert_eq!(game.calls.get(), 1);
+    }
+}
+""".replace("FILTER", source[start:end])
+        with tempfile.TemporaryDirectory() as folder:
+            src, exe = Path(folder) / "outline.rs", Path(folder) / "outline.exe"
+            src.write_text(fixture)
+            subprocess.run(["rustc", "--edition=2024", "--test", str(src), "-o", str(exe)], check=True)
+            subprocess.run([str(exe)], check=True)

tools/native-hook-fragments/block_highlight.json

@@ -0,0 +1,12 @@
+{
+  "hooks": [
+    {
+      "name": "block_highlight",
+      "target": "horizon_client::game::native_hooks::Game<'_>::native_block_highlight",
+      "side": "client",
+      "cancellable": true
+    }
+  ],
+  "rust_summary": "a cancellable targeted-block highlight hook (`native_block_highlight`).",
+  "doc_summary": "`native_block_highlight(pos, state, partial, canceled)` runs before building the eligible targeted block's selection outline, after hidden-HUD and game-mode restrictions. Set `canceled` to suppress only that outline; default behavior is unchanged otherwise. Position is block coordinates and state is the current block state ID. No entity outlines are affected. Bundles need \"hooks\": @API:block_highlight@."
+}