perf(hover): stop scanning every wire on hover for large drawings

Two per-hover O(N) costs on big drawings, both keyed off the cursor:

- The selection/hover xray overlay rebuilt by scanning ALL wires and
  string-parsing each `name` into a handle on every hover change. Index
  handle → wire slots once per wire upload instead, so the overlay gathers
  only the highlighted entity's wires (O(highlighted)).

- click_hit (runs on every mouse move) projected every vertex of every
  wire to screen. In the flat top-down ortho view it now pre-rejects a
  wire by its world-space AABB (four corners projected, so a Z-rotated
  plan view is still correct) and only projects points for wires actually
  near the cursor. Tilted/orbit views fall back to the full test, so no
  pick is ever missed; covered by a unit test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/hit_test.rs

@@ -32,8 +32,40 @@ pub fn click_hit<'a>(
     let mut best_dist = CLICK_THRESHOLD_PX;
     let mut best: Option<&str> = None;
 
+    // World z only shifts the *screen* x/y when the view is tilted (orbit /
+    // perspective). In the flat top-down ortho view — the case where hover lag
+    // on large drawings actually bites — a wire's screen position depends only
+    // on its world x/y, so its world-space AABB projects exactly and we can
+    // reject wires nowhere near the cursor without projecting any of their
+    // points (the dominant per-move cost on 100 k-wire drawings).
+    let z_flat = view_proj.z_axis.x.abs() < 1e-9 && view_proj.z_axis.y.abs() < 1e-9;
+
     // Q: lazy projection — no Vec allocation per wire; NaN resets the segment chain.
     for wire in wires {
+        // Cheap AABB pre-reject (flat view only; never for the unbounded
+        // sentinel used by previews / greeked text).
+        if z_flat && wire.aabb != WireModel::UNBOUNDED_AABB {
+            let [minx, miny, maxx, maxy] = wire.aabb;
+            // Project all four corners — a plan view can be rotated about Z, so
+            // the screen footprint isn't axis-aligned and the two diagonal
+            // corners alone wouldn't bound it.
+            let mut sx0 = f32::MAX;
+            let mut sy0 = f32::MAX;
+            let mut sx1 = f32::MIN;
+            let mut sy1 = f32::MIN;
+            for (cx, cy) in [(minx, miny), (maxx, miny), (maxx, maxy), (minx, maxy)] {
+                let s = world_to_screen(Vec3::new(cx, cy, 0.0), view_proj, bounds);
+                sx0 = sx0.min(s.x);
+                sx1 = sx1.max(s.x);
+                sy0 = sy0.min(s.y);
+                sy1 = sy1.max(s.y);
+            }
+            let t = CLICK_THRESHOLD_PX;
+            if cursor.x < sx0 - t || cursor.x > sx1 + t || cursor.y < sy0 - t || cursor.y > sy1 + t
+            {
+                continue;
+            }
+        }
         let mut prev: Option<Point> = None;
         for &[px, py, pz] in &wire.points {
             if px.is_nan() {
@@ -590,3 +622,32 @@ fn dist_point_to_segment(p: Point, a: Point, b: Point) -> f32 {
     let dy = p.y - cy;
     (dx * dx + dy * dy).sqrt()
 }
+
+#[cfg(test)]
+mod aabb_reject_tests {
+    use super::*;
+
+    fn wire(name: &str, pts: Vec<[f32; 3]>, aabb: [f32; 4]) -> WireModel {
+        let mut w = WireModel::solid(name.to_string(), pts, [1.0; 4], false);
+        w.aabb = aabb;
+        w
+    }
+
+    // Identity ortho view: world (x,y) → screen ((x+1)*100, (1-y)*100) for a
+    // 200×200 viewport. The view is flat (z_axis.xy == 0) so the AABB pre-reject
+    // is active — these tests guard it against false negatives.
+    #[test]
+    fn aabb_reject_keeps_near_wire_drops_far() {
+        let vp = Mat4::IDENTITY;
+        let bounds = Rectangle { x: 0.0, y: 0.0, width: 200.0, height: 200.0 };
+        let cursor = Point::new(100.0, 100.0); // world origin
+
+        let near = wire("5", vec![[-0.02, 0.0, 0.0], [0.02, 0.0, 0.0]], [-0.02, 0.0, 0.02, 0.0]);
+        let far = wire("9", vec![[0.9, 0.9, 0.0], [0.95, 0.9, 0.0]], [0.9, 0.9, 0.95, 0.9]);
+
+        assert_eq!(click_hit(cursor, std::slice::from_ref(&near), vp, bounds), Some("5"));
+        assert_eq!(click_hit(cursor, std::slice::from_ref(&far), vp, bounds), None);
+        // The far wire must be rejected without hiding the near one.
+        assert_eq!(click_hit(cursor, &[far, near], vp, bounds), Some("5"));
+    }
+}

src/scene/pipeline/mod.rs

@@ -134,6 +134,11 @@ pub struct Pipeline {
     /// a pick bumps only `selection_generation`, refreshing the overlay without
     /// touching the main wire buffers.
     pub cached_selection: (u64, u64),
+    /// Handle → indices into the resident wire set, built once per wire upload
+    /// (when `cached_wire_id` changes). Lets the selection/hover xray overlay
+    /// gather just the highlighted entity's wires (`O(highlighted)`) instead of
+    /// scanning and string-parsing every wire on each hover change.
+    wire_handle_index: rustc_hash::FxHashMap<u64, Vec<u32>>,
 }
 
 impl Pipeline {
@@ -905,6 +910,7 @@ impl Pipeline {
             cached_epoch: (u64::MAX, u64::MAX, u64::MAX),
             cached_wire_id: u64::MAX,
             cached_selection: (u64::MAX, u64::MAX),
+            wire_handle_index: rustc_hash::FxHashMap::default(),
         }
     }
 
@@ -939,6 +945,17 @@ impl Pipeline {
             i = j;
         }
         self.gpu_wires = batches;
+
+        // Index handle → wire slots once, here, so the per-hover selection
+        // overlay can gather just the highlighted wires instead of scanning +
+        // string-parsing the whole set every time the hovered entity changes.
+        self.wire_handle_index.clear();
+        self.wire_handle_index.reserve(wires.len());
+        for (idx, w) in wires.iter().enumerate() {
+            if let Ok(h) = w.name.parse::<u64>() {
+                self.wire_handle_index.entry(h).or_default().push(idx as u32);
+            }
+        }
     }
 
     /// Build the selection xray overlay: full-brightness copies of the wires
@@ -960,19 +977,23 @@ impl Pipeline {
             self.gpu_selected_wires = vec![];
             return;
         }
+        // Gather only the highlighted entities' wires via the prebuilt index —
+        // O(highlighted), no per-wire string parse / full-set scan. Indices are
+        // collected then sorted so the xray run keeps the original draw order.
+        let mut slots: Vec<u32> = Vec::new();
+        for h in highlight {
+            if let Some(idxs) = self.wire_handle_index.get(&h.value()) {
+                slots.extend_from_slice(idxs);
+            }
+        }
+        slots.sort_unstable();
         // Recolor to the selection highlight: the xray pass uses the normal
         // wire shader (no forced colour), so the highlight now lives here
         // instead of being baked into the tessellation. Drawn on top with
         // depth-compare Always, so it overrides the base-coloured main pass.
-        let selected: Vec<WireModel> = wires
+        let selected: Vec<WireModel> = slots
             .iter()
-            .filter(|w| {
-                w.name
-                    .parse::<u64>()
-                    .ok()
-                    .map(acadrust::Handle::new)
-                    .is_some_and(|h| highlight.contains(&h))
-            })
+            .filter_map(|&i| wires.get(i as usize))
             .map(|w| {
                 let mut c = w.clone();
                 c.color = WireModel::SELECTED;