0.2.6-dev: impostor review follow-ups (#542) — a skeleton stays in the clip-bounds queue only while an actor uses it (the last one destroyed drops its pending clips, the clip in progress and its scratch skeleton; a later actor queues them again), a clip whose sampling throws is recorded as not measurable and drawn directly while it plays instead of counting as empty, and a frozen model's first update counts as posed only when it succeeded; DESIGN §31.6 updated; golden: unchanged

docs/history/0.2.6.md

@@ -111,62 +111,69 @@ Regression covers normal two-, three- and four-human browser flows, the final tu
 `render/impostor.js`, `render/app.js`.
 
 - **Seen** (GitHub #542 by @ImPQlc; quality 高, usually from round 7 on): 野鬃's flag cut, offset and leaving stray pixels
-  while she idles; 浊心斯卡蒂's head cut in her S3 flight (Skill_3_Begin); 隐现's pistol muzzle cut, offset and leaving
-  stray pixels during her skill.
-- **Cause** (reproduced in headless Chrome: the dev demo's stress crowd, 120 units at impostor interval 4, the three held
-  in their widest poses): a unit's impostor slot was sized once from the pose it showed when it first became an impostor,
-  plus a margin (`_impBox`: the pose's bounds + 30 % / 22 %). A later pose past that box was drawn past the slot's edge:
-  cut in the unit's own sprite and painted into whatever lay beside the slot on the atlas page. A page is cleared on its
-  first flush only and each eraser covers its own slot, so a spill into free space stayed, and a spill into another unit's
-  slot showed on that unit until it was redrawn in a frame without the spill. 浊心斯卡蒂's flight reaches y −704 (skeleton
-  units) against a box top near −516 (54–57 px past her slot in 5 of 5 runs); 野鬃's idle flag reaches x −434, 103 units
-  past a box sized from her setup pose (0–47 px past her slot over 5 runs: it depended on that first pose); after one clean
-  redraw of every impostor the atlas pages held 0–1,405 pixels outside every live slot. 隐现's own poses fit her box (the
-  silencer reaches x 197, her box 225): her muzzle sits at her slot's edge, where a neighbour's spill lands. Of the
-  roster's 681 skeletons, 598 play a clip that leaves a box sized that way from their idle's first frame. No clipping
-  attachment is involved (`spine.js _eyeMaskFallback`, #177, unchanged).
+  while she idles; 浊心斯卡蒂's head cut in her S3 flight (Skill_3_Begin); 隐现's pistol muzzle cut, offset and leaving stray
+  pixels during her skill.
+- **Cause** (reproduced in headless Chrome: the dev demo's stress crowd, 120 units at impostor interval 4, the three
+  held in their widest poses): a unit's impostor slot was sized once from the pose it showed when it first became an
+  impostor, plus a margin (`_impBox`: the pose's bounds + 30 % / 22 %). A later pose past that box was drawn past the
+  slot's edge: cut in the unit's own sprite and painted into whatever lay beside the slot on the atlas page. A page is
+  cleared on its first flush only and each eraser covers its own slot, so a spill into free space stayed, and a spill
+  into another unit's slot showed on that unit until it was redrawn in a frame without the spill. 浊心斯卡蒂's flight reaches
+  y −704 (skeleton units) against a box top near −516 (54–57 px past her slot in 5 of 5 runs); 野鬃's idle flag reaches x
+  −434, 103 units past a box sized from her setup pose (0–47 px past her slot over 5 runs: it depended on that first
+  pose); after one clean redraw of every impostor the atlas pages held 0–1,405 pixels outside every live slot. 隐现's own
+  poses fit her box (the silencer reaches x 197, her box 225): her muzzle sits at her slot's edge, where a neighbour's
+  spill lands. Of the roster's 681 skeletons, 598 play a clip that leaves a box sized that way from their idle's first
+  frame. No clipping attachment is involved (`spine.js _eyeMaskFallback`, #177, unchanged).
 - **Now**: (1) every clip a unit can play (its manifest roles with every skill's set and the Run cycle, its `FORMS` clip
-  sets and change clips) is measured once per skeleton data on a scratch skeleton: 60 poses a second, at most 49 per clip;
-  a region by its attachment rectangle, a mesh by its vertices; slots drawn at alpha 0 skipped. It is queued when the model
-  loads and sampled within 2.5 ms per frame (`stepClipBounds`, called by `render/app.js`), ≈ 9 ms per skeleton on the
-  roster (53 ms at most), shared by every unit of that skeleton; a unit is drawn directly until its box is ready. (2) The
-  box is the idle clip, then each other clip in the order of the area it adds while the box stays within 5 × the idle
-  clip's area (a looping or held clip) or 2 × (a one-off clip: the deploy clip, a skill's, stun's or move's begin and end, a
-  form's change), padded by 3 % + 8 units. A clip that does not fit (`over`: 355 of the roster's 681 deploy clips — the drop
-  from above, up to 1,700 units tall — and the looping or held clips of 13 skeletons with screen-wide effects, among them
-  帕拉斯's skills and 诗怀雅's attack) is drawn directly while it plays; the unit keeps its slot (`_impBypass`). The box is
-  computed once per unit: no bounds work per frame. The setup pose needs no room: a model frozen before its first update —
-  built while its unit is stunned and it has no stun clip (202 of the 210 operators have none), or dead without a death or
-  idle clip — showed its setup pose, which no clip shows (隐现's Back model stands 900 units right of its feet in it);
-  `SpineActor.update` now poses it once at its clip's first frame. (3) The atlas draws each slot's skeleton in a container
-  masked by the slot rectangle, which PIXI draws as a scissor rect (no stencil, no render-pass break): nothing paints
-  outside a slot, and the slot's eraser clears all that an earlier pose can have left in it. Each redrawn slot is a batch
-  flush of its own, and PIXI uploaded its one batch vertex buffer again for every flush, which stalls Apple GPUs (Chrome,
-  ANGLE Metal, Apple M4: the 120-unit crowd at 1920 × 1080 ran at 42–58 fps instead of 60, by the machine's load), so
-  `render/app.js` turns PIXI's `BatchRenderer.canUploadSameBuffer` off: a buffer per flush, PIXI's own setting on iOS.
-  Switched back and forth within one page it gave 60 fps against 42 (DPR 2) and 50 (DPR 1) with the shared buffer —
-  turning it off only around the atlas pass gave 55 — for ≈ 0.3 ms more render CPU per frame; under load it also steadied
-  the 0.2.5 renderer (51 → 59 fps at DPR 2).
-- **Cost**: slot sizes grow with the boxes. On the roster they add up to 1.26 × the old area (the median skeleton
-  1.13 ×). The 120-unit stress crowd at 1600 × 900 (DPR 1) uses 5.5 M px of slots instead of 4.4 M (two of the three atlas
-  pages, no private render target). At DPR 2 a page holds a quarter of the CSS pixels: the crowd at 1280 × 720 keeps 98–108
-  of its units in the atlas instead of 118–120, at 1920 × 1080 59–61 instead of 58–59 (its private render targets 4.4 M px
-  instead of 2.8 M); at 844 × 390, DPR 3, all 120 stay in two pages. 60 fps in every case, before and after (runs on a
-  quiet machine). A unit that finds no slot keeps a private render target, as before; the atlas keeps its ≤ 3 + 2 pages.
-  CPU: `tools/perfbench.mjs` (844 × 390, DPR 2, quality medium / low, where those battles draw through the atlas; four
-  battles at a 4 × CPU throttle, two interleaved runs before and after): the view's JS 4.69 → 5.04 ms per frame, the
-  impostor-redraw stage +21 % (+0.12 ms per frame), all busy JS +0.4 %, 60 fps in every run.
-- [ASSUMED]: the growth limits (5 × / 2 ×), the 3 % + 8 padding, the sampling rate and the 2.5 ms budget. A pose between two
-  samples can still pass the padded box for a frame (42 of the 681 skeletons by a denser 60 Hz check, all in long clips
-  sampled sparser than that); the scissor cuts it and leaves nothing behind.
-- Tests: `test/render/impostor-bounds.test.js` (synthetic Spine 3.8 skeletons: clip bounds, an attachment shown for
-  0.05 s, an alpha-0 slot, the budgeted queue; a model frozen before its first update — stunned without a stun clip, dead
-  without a death or idle clip — posed once at its clip's first frame; `impostorBox` / `playedClips`; every atlas slot's
-  clip box and eraser; UnitView: drawn directly until measured, built while stunned, a skeleton without an Idle clip, the
-  over-clip bypass keeping its slot, the legacy fallback, a pen figure), `test/render/impostor-bounds-models.test.js` (the
-  three operators through the real runtime: every pose of every clip they play, at 30 Hz, inside their box; the old box
-  cut 野鬃 by 103 units and 浊心斯卡蒂 by 188; 隐现's Back model built while stunned shows its Idle's first frame inside
-  the box, its setup pose lies outside it; skips without the assets), `test/render/impostor-bounds.browser.test.js`
-  (`RENDER_E2E=1`: the held stress crowd — inside their slots, no atlas pixel outside a live slot; the scissor on a bare
-  page; 野鬃's deploy drawn directly), `test/render/boardart.test.js` (the allocator's test doubles). Dev:
-  `render-demo.html?scene=stress&ops=<chessId>,…`. Golden: unchanged.
+  sets and change clips) is measured once per skeleton data on a scratch skeleton: 60 poses a second, at most 49 per
+  clip; a region by its attachment rectangle, a mesh by its vertices; slots drawn at alpha 0 skipped. It is queued when
+  the model loads and sampled within 2.5 ms per frame (`stepClipBounds`, called by `render/app.js`), ≈ 9 ms per skeleton
+  on the roster (53 ms at most), shared by every unit of that skeleton; a unit is drawn directly until its box is ready.
+  A skeleton stays queued only while an actor uses it: when the last one is destroyed (a model swap, a battlefield torn
+  down) its pending clips and its scratch skeleton are dropped, so nothing holds a skeleton the Spine store let go or is
+  measured ahead of the next scene's models, and a later actor queues again what was never measured. (2) The box is the
+  idle clip, then each other clip in the order of the area it adds while the box stays within 5 × the idle clip's area
+  (a looping or held clip) or 2 × (a one-off clip: the deploy clip, a skill's, stun's or move's begin and end, a form's
+  change), padded by 3 % + 8 units. A clip that does not fit (`over`: 355 of the roster's 681 deploy clips — the drop
+  from above, up to 1,700 units tall — and the looping or held clips of 13 skeletons with screen-wide effects, among
+  them 帕拉斯's skills and 诗怀雅's attack) is drawn directly while it plays; the unit keeps its slot (`_impBypass`). So is a
+  clip whose sampling threw (recorded as not measurable, never as drawing nothing — the scissor would cut it). The box
+  is computed once per unit: no bounds work per frame. The setup pose needs no room: a model frozen before its first
+  update — built while its unit is stunned and it has no stun clip (202 of the 210 operators have none), or dead without
+  a death or idle clip — showed its setup pose, which no clip shows (隐现's Back model stands 900 units right of its feet
+  in it); `SpineActor.update` now poses it once at its clip's first frame (again on the next frame if that update
+  threw). (3) The atlas draws each slot's skeleton in a container masked by the slot rectangle, which PIXI draws as a
+  scissor rect (no stencil, no render-pass break): nothing paints outside a slot, and the slot's eraser clears all that
+  an earlier pose can have left in it. Each redrawn slot is a batch flush of its own, and PIXI uploaded its one batch
+  vertex buffer again for every flush, which stalls Apple GPUs (Chrome, ANGLE Metal, Apple M4: the 120-unit crowd at
+  1920 × 1080 ran at 42–58 fps instead of 60, by the machine's load), so `render/app.js` turns PIXI's
+  `BatchRenderer.canUploadSameBuffer` off: a buffer per flush, PIXI's own setting on iOS. Switched back and forth within
+  one page it gave 60 fps against 42 (DPR 2) and 50 (DPR 1) with the shared buffer — turning it off only around the
+  atlas pass gave 55 — for ≈ 0.3 ms more render CPU per frame; under load it also steadied the 0.2.5 renderer (51 → 59
+  fps at DPR 2).
+- **Cost**: slot sizes grow with the boxes. On the roster they add up to 1.26 × the old area (the median skeleton 1.13
+  ×). The 120-unit stress crowd at 1600 × 900 (DPR 1) uses 5.5 M px of slots instead of 4.4 M (two of the three atlas
+  pages, no private render target). At DPR 2 a page holds a quarter of the CSS pixels: the crowd at 1280 × 720 keeps
+  98–108 of its units in the atlas instead of 118–120, at 1920 × 1080 59–61 instead of 58–59 (its private render targets
+  4.4 M px instead of 2.8 M); at 844 × 390, DPR 3, all 120 stay in two pages. 60 fps in every case, before and after
+  (runs on a quiet machine). A unit that finds no slot keeps a private render target, as before; the atlas keeps its ≤ 3
+  + 2 pages. CPU: `tools/perfbench.mjs` (844 × 390, DPR 2, quality medium / low, where those battles draw through the
+  atlas; four battles at a 4 × CPU throttle, two interleaved runs before and after): the view's JS 4.69 → 5.04 ms per
+  frame, the impostor-redraw stage +21 % (+0.12 ms per frame), all busy JS +0.4 %, 60 fps in every run.
+- [ASSUMED]: the growth limits (5 × / 2 ×), the 3 % + 8 padding, the sampling rate and the 2.5 ms budget. A pose between
+  two samples can still pass the padded box for a frame (42 of the 681 skeletons by a denser 60 Hz check, all in long
+  clips sampled sparser than that); the scissor cuts it and leaves nothing behind.
+- Tests: `test/render/impostor-bounds.test.js` (synthetic Spine 3.8 skeletons: clip bounds, an attachment shown for 0.05
+  s, an alpha-0 slot, the budgeted queue, a skeleton leaving the queue with its last actor, a clip whose sampling
+  throws; a model frozen before its first update — stunned without a stun clip, dead without a death or idle clip —
+  posed once at its clip's first frame, again after an update that threw; `impostorBox` / `playedClips`; every atlas
+  slot's clip box and eraser; UnitView: drawn directly until measured, built while stunned, a skeleton without an Idle
+  clip, the over-clip bypass keeping its slot, an unmeasurable attack or idle clip drawn directly, the legacy fallback,
+  a pen figure), `test/render/impostor-bounds-models.test.js` (the three operators through the real runtime: every pose
+  of every clip they play, at 30 Hz, inside their box; the old box cut 野鬃 by 103 units and 浊心斯卡蒂 by 188; 隐现's Back model
+  built while stunned shows its Idle's first frame inside the box, its setup pose lies outside it; skips without the
+  assets), `test/render/impostor-bounds.browser.test.js` (`RENDER_E2E=1`: the held stress crowd — inside their slots, no
+  atlas pixel outside a live slot; the scissor on a bare page; 野鬃's deploy drawn directly),
+  `test/render/boardart.test.js` (the allocator's test doubles). Dev: `render-demo.html?scene=stress&ops=<chessId>,…`.
+  Golden: unchanged.

public/js/render/spine.js

@@ -129,12 +129,16 @@ function slotCentre(slot, att, buf, out) {
 // by render/app.js once per frame, samples within that time budget: the clips a unit plays take ≈ 9 ms per skeleton on
 // the current roster (53 ms at most), so a model is measured a few frames after it loads, long before a crowd needs its
 // impostor. [ASSUMED] the rate, the cap and the budget (a pose between two samples is covered by the box's padding,
-// units.js IMP_BOX, and anything past it is cut by the atlas slot's scissor, never left behind).
+// units.js IMP_BOX, and anything past it is cut by the atlas slot's scissor, never left behind). A record is queued only
+// while an actor uses its skeleton data: when the last one is destroyed (a model swap, a battlefield torn down) its pending
+// clips and its scratch skeleton are dropped — nothing holds a skeleton the Spine store let go, and nothing stale is
+// measured ahead of the next scene's models —, and a later actor queues what was never measured again. A clip whose
+// sampling throws is recorded as not measurable (false): units.js draws it directly while it plays, never as empty.
 export const CLIP_SAMPLE_HZ = 60;
 export const CLIP_SAMPLE_MAX = 48;
 export const CLIP_BOUNDS_BUDGET_MS = 2.5;
 const ATT_REGION = 0, ATT_MESH = 2;      // pixi-spine AttachmentType
-const boundsOf = new WeakMap();          // skeleton data → { data, Skeleton, skel, rects: Map<clip, rect|null>, todo, job, failed }
+const boundsOf = new WeakMap();          // skeleton data → { data, Skeleton, skel, rects: Map<clip, rect|null|false>, todo, job, users, failed }
 const boundsQueue = [];                  // records with clips still to sample, oldest request first
 const nowMs = () => (globalThis.performance ? globalThis.performance.now() : Date.now());
 const emptyRect = () => [Infinity, Infinity, -Infinity, -Infinity];
@@ -185,7 +189,7 @@ function scratchSkeleton(rec) {
 function boundsRecord(data, Skeleton) {
   let rec = boundsOf.get(data);
   if (rec) return rec;
-  rec = { data, Skeleton, skel: null, rects: new Map(), todo: [], job: null, failed: false, buf: { v: new Float32Array(256) } };
+  rec = { data, Skeleton, skel: null, rects: new Map(), todo: [], job: null, users: 0, failed: false, buf: { v: new Float32Array(256) } };
   try {
     const skel = scratchSkeleton(rec);
     skel.setToSetupPose();
@@ -223,9 +227,25 @@ export function requestClipBounds(data, Skeleton, names) {
     if (typeof n === 'string' && !rec.rects.has(n) && !rec.todo.includes(n) && !(rec.job && rec.job.name === n)) { rec.todo.push(n); added = true; }
   }
   if (added && !boundsQueue.includes(rec)) boundsQueue.push(rec);
+  else if (!boundsQueue.includes(rec)) rec.skel = null;   // nothing to sample: no scratch skeleton kept
   return rec;
 }
 
+/**
+ * One actor more (+1, SpineActor.clipBounds) or less (−1, SpineActor.destroy) measures record `rec`; with none left, the
+ * record leaves the queue with its pending clips (todo and the clip in progress) and its scratch skeleton — a later actor
+ * queues what was never measured again (a todo left behind would read as queued and never be measured).
+ */
+function useBounds(rec, delta) {
+  rec.users = Math.max(0, rec.users + delta);
+  if (rec.users > 0) return;
+  const i = boundsQueue.indexOf(rec);
+  if (i >= 0) boundsQueue.splice(i, 1);
+  rec.todo.length = 0;
+  rec.job = null;
+  rec.skel = null;
+}
+
 /**
  * Sample queued clips for up to `budgetMs` (render/app.js calls it once per frame): pose after pose, a clip resumed on the
  * next call when the budget runs out inside it; at least one pose per call.
@@ -240,8 +260,10 @@ export function stepClipBounds(budgetMs = CLIP_BOUNDS_BUDGET_MS) {
     if (!rec.job) {
       const name = rec.todo.shift();
       if (name === undefined) { boundsQueue.shift(); rec.skel = null; continue; }
-      try { rec.job = startClip(rec, name); } catch { rec.job = null; }
-      if (!rec.job) { rec.rects.set(name, null); finished++; continue; }
+      let broken = false;
+      try { rec.job = startClip(rec, name); } catch { rec.job = null; broken = true; }
+      // no such clip: it never plays (null); a clip that could not be set up: not measurable (false)
+      if (!rec.job) { rec.rects.set(name, broken ? false : null); finished++; continue; }
     }
     const j = rec.job;
     try {
@@ -255,9 +277,10 @@ export function stepClipBounds(budgetMs = CLIP_BOUNDS_BUDGET_MS) {
         posed++;
         if (nowMs() >= end) break;
       }
-    } catch { j.i = j.n + 1; j.r = emptyRect(); }
+    } catch { j.i = j.n + 1; j.broken = true; }
     if (j.i > j.n) {
-      rec.rects.set(j.name, rectOk(j.r) ? j.r : null);
+      // a pose that threw: the clip is not measurable (false) — drawn directly while it plays, not taken as empty
+      rec.rects.set(j.name, j.broken ? false : rectOk(j.r) ? j.r : null);
       rec.job = null;
       finished++;
     }
@@ -804,8 +827,10 @@ export class SpineActor {
     // left in its setup pose, which no clip shows and the impostor box does not cover (GitHub #542: 隐现's Back model
     // stands 900 units to the right of its feet in the setup pose)
     if (!this.frozen || !this._posed) {
-      try { this.spine.update(this.frozen ? 0 : dt); } catch { /* a broken skeleton must not stop the frame */ }
-      this._posed = true;
+      try {
+        this.spine.update(this.frozen ? 0 : dt);
+        this._posed = true;               // (a first update that threw is tried again: no setup pose left on screen)
+      } catch { /* a broken skeleton must not stop the frame */ }
     }
     if (this.clipped && !this.clipOn) this._eyeMaskFallback();
     this._applied = true;
@@ -863,8 +888,9 @@ export class SpineActor {
 
   /**
    * Skeleton-space bounds of clips `names` ("clip bounds" above; render/units.js _impBox): a Map name → rect (null: draws
-   * nothing / no such clip) once every clip is sampled; null while some still wait — they are queued here and
-   * render/app.js samples them (stepClipBounds); false when this runtime cannot be posed off-screen (a test double).
+   * nothing / no such clip; false: its sampling threw, not measurable) once every clip is sampled; null while some still
+   * wait — they are queued here and render/app.js samples them (stepClipBounds); false when this runtime cannot be posed
+   * off-screen (a test double). The actor counts as a user of its skeleton's record until it is destroyed.
    * @param {string[]} names
    */
   clipBounds(names) {
@@ -874,6 +900,11 @@ export class SpineActor {
     let rec = boundsOf.get(data);
     if (!rec || names.some((n) => !rec.rects.has(n))) rec = requestClipBounds(data, sp.skeleton && sp.skeleton.constructor, names);
     if (rec.failed) return false;
+    if (this._bounds !== rec) {
+      if (this._bounds) useBounds(this._bounds, -1);
+      this._bounds = rec;
+      useBounds(rec, 1);
+    }
     const clips = new Map();
     for (const n of names) {
       if (!rec.rects.has(n)) return null;
@@ -890,6 +921,7 @@ export class SpineActor {
   }
 
   destroy() {
+    if (this._bounds) { useBounds(this._bounds, -1); this._bounds = null; }   // the last user gone: its queue entry goes
     try { this.spine.destroy({ children: true, texture: false, baseTexture: false }); } catch { /* ignore */ }
     this.spine = null;
   }

public/js/render/units.js

@@ -469,8 +469,9 @@ export const IMP_BOX = Object.freeze({ steady: 5, transient: 2, pad: 0.03, padMi
  * one-off clip). A clip that does not fit and is not inside the box anyway is `over`: its unit is drawn directly while it
  * plays (units.js _updateImpostor), so a rare huge clip (a deploy drop from above, a screen-wide sweep) does not grow every
  * refresh of the unit's slot. Padded by IMP_BOX.pad. The setup pose needs no room: no model shows it (spine.js
- * SpineActor.update poses one frozen before its first update at its clip's first frame). Without an idle clip that draws
- * anything, the looping clips make the core. null when nothing is drawn.
+ * SpineActor.update poses one frozen before its first update at its clip's first frame). A clip whose rect is `false`
+ * (its sampling threw, spine.js clipBounds) is `over` as well — drawn directly, never taken as drawing nothing. Without an
+ * idle clip that draws anything, the looping clips make the core. null when nothing is drawn.
  * @returns {{ x0: number, y0: number, w: number, h: number, over: Set<string> } | null}
  */
 export function impostorBox(idle, clips = []) {
@@ -490,7 +491,7 @@ export function impostorBox(idle, clips = []) {
     if (area(u) <= (c.once ? IMP_BOX.transient : IMP_BOX.steady) * limit) box = u;
     else left.push(c);
   }
-  const over = new Set();
+  const over = new Set(clips.filter(([, r]) => r === false).map(([name]) => name));
   for (const c of left) if (c.r[0] < box[0] || c.r[1] < box[1] || c.r[2] > box[2] || c.r[3] > box[3]) over.add(c.name);
   const pad = IMP_BOX.pad * Math.max(box[2] - box[0], box[3] - box[1]) + IMP_BOX.padMin;
   return { x0: box[0] - pad, y0: box[1] - pad, w: box[2] - box[0] + 2 * pad, h: box[3] - box[1] + 2 * pad, over };
@@ -1745,13 +1746,19 @@ export class UnitView {
     const rects = typeof a.clipBounds === 'function' ? a.clipBounds([...names.keys()]) : false;
     if (rects === null) return null;
     let box = null;
+    const unmeasured = new Set();   // clips whose sampling threw (false): drawn directly while they play
     if (rects) {
       const idle = this._idleClip();
+      const rect = (name) => (rects.has(name) ? rects.get(name) : null);
       const rest = [];
-      for (const [name, once] of names) if (name !== idle) rest.push([name, rects.get(name) || null, once]);
-      box = impostorBox(idle ? rects.get(idle) || null : null, rest);
+      for (const [name, once] of names) {
+        if (rect(name) === false) unmeasured.add(name);
+        if (name !== idle) rest.push([name, rect(name), once]);
+      }
+      box = impostorBox(idle && rect(idle) !== false ? rect(idle) : null, rest);
+      if (box && idle && unmeasured.has(idle)) box.over.add(idle);
     }
-    this._box = box || this._legacyBox();
+    this._box = box || this._legacyBox(unmeasured);
     return this._box;
   }
 
@@ -1789,8 +1796,11 @@ export class UnitView {
     return out;
   }
 
-  /** The box sized from the pose drawn now, for a runtime whose clips cannot be measured (the pre-#542 rule). */
-  _legacyBox() {
+  /**
+   * The box sized from the pose drawn now, for a runtime whose clips cannot be measured (the pre-#542 rule); `over` =
+   * clips that could not be measured (drawn directly while they play).
+   */
+  _legacyBox(over = NO_CLIPS) {
     let b = null;
     try { b = this.actor.spine.getLocalBounds(); } catch { b = null; }
     let x0 = -220, y0 = -420, x1 = 220, y1 = 40;
@@ -1799,7 +1809,7 @@ export class UnitView {
       x0 = Math.min(b.x - padX, -140); x1 = Math.max(b.x + b.width + padX, 140);
       y0 = Math.min(b.y - padY, -260); y1 = Math.max(b.y + b.height + padY * 0.4, 30);
     }
-    return { x0, y0, w: x1 - x0, h: y1 - y0, over: NO_CLIPS };
+    return { x0, y0, w: x1 - x0, h: y1 - y0, over: over && over.size ? over : NO_CLIPS };
   }
 
   /** Is a clip outside the box (`over`) on screen — the track's clip or one it is still mixing out of? */

test/render/impostor-bounds.test.js

@@ -104,6 +104,43 @@ describe('clip bounds (render/spine.js): what a skeleton draws, measured once pe
     assert.equal(spine.stepClipBounds(), 0, 'an empty queue costs nothing');
   });
 
+  test('a record leaves the queue when its last actor is destroyed — pending clips, the clip in progress and its scratch skeleton —; a later actor queues them again', () => {
+    const data = skeleton();
+    /** A SpineActor stand-in on the real runtime skeleton (clipBounds / destroy are the real methods). */
+    const actor = () => Object.assign(Object.create(spine.SpineActor.prototype), { spine: { spineData: data, skeleton: new rt.Skeleton(data), destroy() {} } });
+    const a = actor(), b = actor();
+    assert.equal(a.clipBounds(['Wave', 'Flash']), null, 'queued');
+    assert.equal(b.clipBounds(['Wave', 'Flash']), null);
+    spine.stepClipBounds(0);                            // one pose of Wave: a clip in progress
+    const rec = spine.requestClipBounds(data, rt.Skeleton, []);
+    assert.ok(rec.job && rec.skel, 'sampling Wave on its scratch skeleton');
+    a.destroy();
+    assert.equal(spine.pendingClipBounds(), 2, 'b still uses the skeleton: still queued');
+    b.destroy();                                        // e.g. the battlefield torn down with its units
+    assert.equal(spine.pendingClipBounds(), 0, 'nothing left to sample');
+    assert.ok(rec.job === null && rec.todo.length === 0 && rec.skel === null, 'no clip in progress, no todo, no scratch skeleton held');
+    const c = actor();                                  // the same skeleton in the next scene
+    assert.equal(c.clipBounds(['Wave', 'Flash']), null, 'queued again (no todo left behind to block it)');
+    assert.equal(spine.pendingClipBounds(), 2);
+    drain();
+    near(c.clipBounds(['Wave', 'Flash']).get('Wave'), [-50, -200, 425, 25], 'measured');
+    c.destroy();
+  });
+
+  test('a clip whose sampling throws is recorded as not measurable (false), never as drawing nothing', () => {
+    const data = skeleton();
+    const wave = data.findAnimation('Wave');
+    const apply = wave.apply.bind(wave);
+    wave.apply = (skel, last, t, ...rest) => { if (t > 0.5) throw new Error('a broken timeline'); return apply(skel, last, t, ...rest); };
+    const rec = spine.requestClipBounds(data, rt.Skeleton, ['Wave', 'Still']);
+    drain();
+    assert.equal(rec.rects.get('Wave'), false, 'not measurable');
+    near(rec.rects.get('Still'), [-50, -200, 125, 25], 'the other clip is measured');
+    assert.equal(rec.rects.get('Nope'), undefined);
+    const b = units.impostorBox([-50, -200, 125, 25], [['Wave', false, false], ['Still', rec.rects.get('Still'), false]]);
+    assert.deepEqual([...b.over], ['Wave'], 'drawn directly while it plays');
+  });
+
   test('SpineActor.clipBounds: null while queued, then a Map clip → rect; false for a runtime that cannot be posed', () => {
     const data = skeleton();
     const stand = { spine: { spineData: data, skeleton: new rt.Skeleton(data) } };
@@ -144,6 +181,17 @@ describe('a model frozen before its first update shows its clip\'s first frame,
     assert.deepEqual(posed, [0, 0.1]);
   });
 
+  test('a first update that throws is tried again: the frozen model is posed once an update succeeds', () => {
+    const { a, posed } = actor({ animations: [{ name: 'Idle' }, { name: 'Die' }] }, ENTRY);
+    let broken = true;
+    a.spine.update = (dt) => { posed.push(dt); if (broken) { broken = false; throw new Error('a broken skeleton'); } };
+    a.setBase('stun');
+    a.update(0.1);                                      // throws inside pixi-spine (caught): not posed yet
+    a.update(0.1);                                      // tried again at the clip's first frame: posed
+    a.update(0.1);                                      // held
+    assert.deepEqual(posed, [0, 0]);
+  });
+
   test('stunned after it was posed: the pose it had holds (unchanged)', () => {
     const { a, posed } = actor({ animations: [{ name: 'Idle' }, { name: 'Die' }] }, ENTRY);
     a.update(0.2);
@@ -355,6 +403,28 @@ describe('UnitView impostor mode (render/units.js)', () => {
     assert.equal(log.alloc, c0.alloc, 'the same slot');
   });
 
+  test('a clip whose sampling threw is drawn directly while it plays — the attack, or even the idle clip —, never cut by the slot', async () => {
+    const broken = new Map(MEASURED).set('Attack', false);
+    const { v, step, log } = await operator(() => broken);
+    step(3);
+    assert.ok(v.imp && v._box.over.has('Attack'));
+    const draws = log.draw;
+    v.actor._play('Attack', false, { mix: 0 });
+    step(2);
+    assert.equal(v.imp.bypass, true, 'the attack is drawn directly');
+    assert.equal(log.draw, draws, 'not into the slot');
+    const idleBroken = new Map(MEASURED).set('Idle', false);
+    const w = (await operator(() => idleBroken)).v;
+    w.update(1 / 60, cam(), 0);
+    assert.ok(w._box.over.has('Idle'), 'an unmeasurable idle clip: drawn directly while it idles');
+    const b = w._box, c = MEASURED.get('Attack');
+    assert.ok(b.x0 <= c[0] && b.x0 + b.w >= c[2], 'the box built from the clips that were measured');
+    const none = new Map([...MEASURED.keys()].map((n) => [n, false]));
+    const z = (await operator(() => none)).v;
+    z.update(1 / 60, cam(), 0);
+    assert.deepEqual([...z._box.over].sort(), ['Attack', 'Die', 'Idle', 'Start'], 'nothing measurable: every clip drawn directly');
+  });
+
   test('a runtime whose clips cannot be measured keeps the box from the pose shown (the pre-#542 rule)', async () => {
     const { v, step } = await operator(() => false);
     step(3);