Use polyfill from "animation-timelines" package

Author: sebmarkbage

fixtures/view-transition/package.json

@@ -14,7 +14,7 @@
     "ignore-styles": "^5.0.1",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
-    "animation-timelines": "^0.0.1"
+    "animation-timelines": "^0.0.4"
   },
   "eslintConfig": {
     "extends": [

fixtures/view-transition/src/components/SwipeRecognizer.js

@@ -5,6 +5,8 @@ import React, {
   unstable_startGestureTransition as startGestureTransition,
 } from 'react';
 
+import ScrollTimelinePolyfill from 'animation-timelines/scroll-timeline';
+
 // Example of a Component that can recognize swipe gestures using a ScrollTimeline
 // without scrolling its own content. Allowing it to be used as an inert gesture
 // recognizer to drive a View Transition.
@@ -25,14 +27,20 @@ export default function SwipeRecognizer({
     if (activeGesture.current !== null) {
       return;
     }
-    if (typeof ScrollTimeline !== 'function') {
-      return;
+
+    let scrollTimeline;
+    if (typeof ScrollTimeline === 'function') {
+      // eslint-disable-next-line no-undef
+      scrollTimeline = new ScrollTimeline({
+        source: scrollRef.current,
+        axis: axis,
+      });
+    } else {
+      scrollTimeline = new ScrollTimelinePolyfill({
+        source: scrollRef.current,
+        axis: axis,
+      });
     }
-    // eslint-disable-next-line no-undef
-    const scrollTimeline = new ScrollTimeline({
-      source: scrollRef.current,
-      axis: axis,
-    });
     activeGesture.current = startGestureTransition(
       scrollTimeline,
       () => {

fixtures/view-transition/yarn.lock

@@ -2427,6 +2427,11 @@ ajv@^8.0.0, ajv@^8.6.0, ajv@^8.9.0:
     json-schema-traverse "^1.0.0"
     require-from-string "^2.0.2"
 
+animation-timelines@^0.0.4:
+  version "0.0.4"
+  resolved "https://registry.yarnpkg.com/animation-timelines/-/animation-timelines-0.0.4.tgz#7ac4614bae73c4d1ea2ff18d5d87a518793258af"
+  integrity sha512-HwCE3m1nM8ZdLbwDwD1j5ZNKmY+3J2CliXJNIsf3y1Si927SIaWpfxkycTg5nWLJSHgjsYxrmOy2Jbo4JR1e9A==
+
 ansi-escapes@^4.2.1, ansi-escapes@^4.3.1:
   version "4.3.2"
   resolved "https://registry.yarnpkg.com/ansi-escapes/-/ansi-escapes-4.3.2.tgz#6b2291d1db7d98b6521d5f1efa42d0f3a9feb65e"