perf(core): a video edit with no animation timeline stops rewriting every clip each frame

packages/core/src/runtime/init.test.ts

@@ -612,6 +612,25 @@ describe("initSandboxRuntimeModular", () => {
       }
     });
 
+    it("leaves hidden clips alone on every jump when the page has no timeline", () => {
+      document.body.innerHTML =
+        `<div data-composition-id="main" data-root="true" data-start="0" data-duration="10" data-width="1920" data-height="1080">` +
+        `<video id="first" src="a.mp4" data-start="0" data-duration="2" data-track-index="0"></video>` +
+        `<video id="second" src="a.mp4" data-start="2" data-duration="8" data-track-index="0"></video>` +
+        `</div>`;
+      window.__timelines = {};
+      initSandboxRuntimeModular();
+      const query = vi.spyOn(document, "querySelectorAll");
+      const looked = () =>
+        query.mock.calls.filter(([selector]) => selector === "[data-hf-clip-hidden]").length;
+      try {
+        for (const t of [0.5, 1, 1.5, 3, 6]) window.__player?.seek(t);
+        expect(looked()).toBe(0);
+      } finally {
+        query.mockRestore();
+      }
+    });
+
     it("styles a hidden clip visible once while playing toward its start, far scene included", () => {
       document.body.innerHTML =
         `<div data-composition-id="main" data-root="true" data-start="0" data-duration="10" data-width="1920" data-height="1080">` +

packages/core/src/runtime/init.ts

@@ -5163,6 +5163,16 @@ export function initSandboxRuntimeModular(): void {
       return false;
     }
   };
+  // Registered timelines other than the root composition's: each scene's own clock.
+  const sceneTimelines = () => {
+    const timelines = (window.__timelines ?? {}) as Record<string, RuntimeTimelineLike | undefined>;
+    const rootCompositionId =
+      resolveRootCompositionElement()?.getAttribute("data-composition-id") ?? null;
+    return Object.entries(timelines).filter(
+      (entry): entry is [string, RuntimeTimelineLike] =>
+        !!entry[1] && typeof entry[1] === "object" && entry[0] !== rootCompositionId,
+    );
+  };
   const seekStandaloneRegisteredTimelines = (
     timeSeconds: number,
     revision: number,
@@ -5172,12 +5182,7 @@ export function initSandboxRuntimeModular(): void {
       sceneClocks = new WeakMap();
       sceneClocksRevision = revision;
     }
-    const timelines = (window.__timelines ?? {}) as Record<string, RuntimeTimelineLike | undefined>;
-    const rootCompositionId =
-      resolveRootCompositionElement()?.getAttribute("data-composition-id") ?? null;
-    for (const [compositionId, timeline] of Object.entries(timelines)) {
-      if (!timeline || typeof timeline !== "object" || compositionId === rootCompositionId)
-        continue;
+    for (const [compositionId, timeline] of sceneTimelines()) {
       const scene = sceneClockOf(compositionId, timeline);
       if (!scene) continue;
       const sourceTime =
@@ -5291,9 +5296,10 @@ export function initSandboxRuntimeModular(): void {
     // Only clips holding a tween that renders for the first time on this seek need their authored style read.
     const firstRendered =
       firstRenders && tl ? clipsFirstRenderedIn(tl, tweensRenderedThrough.time, t) : null;
-    // An empty set means no tween draws for the first time: nothing to show, so no page-wide query.
+    // An empty set means no tween draws for the first time, and a page with no timeline has no tween:
+    // nothing to show, so no page-wide query.
     const hideClipsAgain =
-      firstRenders && firstRendered?.size !== 0
+      firstRenders && firstRendered?.size !== 0 && (tl || sceneTimelines().length > 0)
         ? showHiddenClips(firstRendered ? (el) => firstRendered.has(el) : undefined)
         : null;
     // Scenes first, each paused on its own clock, so the root's pass skips them and its later