[tomekzaw]

Summary:

Motivation. Native-driven animations apply non-layout props straight to the mounted views, without a ShadowTree commit (synchronouslyUpdateViewOnUIThread): Animated with useNativeDriver, the shared Animation Backend, sticky headers, and libraries like Reanimated's synchronous-props path. While a transform animates, the committed tree lags behind the screen. Native hit-testing uses the live view hierarchy, but the layout queries (measure, measureInWindow, getBoundingClientRect, UIManager::getRelativeLayoutMetrics) read the committed transform. Pressability mixes the two — it measure()s the responder region on grant and compares it with native touch coordinates on every move — so a press with slight finger drift on a moving view fires onPressIn but silently drops onPress. This reproduces with plain Animated on a device and is the root cause behind #51621, #36504, #44768 and the passthroughAnimatedPropExplicitValues workaround in createAnimatedComponent.js.

Approaches considered.

• Measure the mounted view instead of the ShadowTree (fix: pressability issues new arch #51835, measureAsyncOnUI): fixes Pressability only, adds a UI→JS hop per press, and leaves every other geometry query stale (measure, getBoundingClientRect, pointer-capture retargeting, libraries measuring on the UI thread).
• Commit on every animation frame: exactly the cost the fast path exists to avoid.
• Change Pressability to not use a measured rect: changes pressRetentionOffset semantics and helps no other consumer.

Chosen solution: a synchronous transform overlay. UIManager keeps a small thread-safe map from view tag to the last transform / transformOrigin written synchronously, parsed with the same conversions as ShadowNode props. It implements a new LayoutableShadowNode::TransformOverrideProvider; computeRelativeLayoutMetrics asks the provider (via LayoutInspectingPolicy) for a node's transform before falling back to getTransform(), so the result composes through nested and committed ancestor transforms, transformOrigin and percentages like committed props would. Recording happens at the platform funnel every synchronous write goes through (FabricUIManager.synchronouslyUpdateViewOnUIThread on Android, RCTSurfacePresenter on iOS, SchedulerDelegateImpl on ReactCxxPlatform); libraries that bypass them can call UIManager::recordSynchronousTransform. Only transform is tracked: it is the only synchronously written prop that affects geometry (opacity goes to layer.opacity, which neither UIKit's nor the ShadowTree's hit-testing consults). Entries live until the view is deleted (lazy pruning with a doubling threshold) or until the writer removes them (the Animation Backend does after its AnimationEndSync commit), mirroring the lifetime of the platforms' own view-level overrides. When nothing was written synchronously the provider is nullptr and the hot path is unchanged.

Behind the new enableSynchronousTransformOverlay feature flag (default off). Design notes: ReactCommon/react/renderer/uimanager/__docs__/SynchronousTransformOverlay.md. Not covered yet, as follow-ups: findNodeAtPoint (only used by the DevTools inspector) and the batched AnimatedProps path behind optimizedAnimatedPropUpdates.

Changelog:

[GENERAL] [FIXED] - Layout queries (measure, getBoundingClientRect, ...) and Pressable now account for natively-driven transform animations, behind enableSynchronousTransformOverlay

Test Plan:

• yarn fantom packages/react-native/Libraries/Animated/__tests__/AnimatedSynchronousTransformOverlay-itest.js: 32/32 (4 tests × flag on/off × useSharedAnimatedBackend × animatedDeferStartOfTimingAnimations): mid-animation measure/measureInWindow/getBoundingClientRect of the animated view and its descendants, two nested natively-animated levels, a committed scale ancestor, pruning across a commit that deletes views, and the committed final values after the animation. Animated-itest.js still passes.
• gtest: LayoutableShadowNodeTest.relativeLayoutMetricsWithTransformOverride and the new SynchronousTransformOverlayTest (parsing, transformOrigin merging, remove/prune/threshold). Not run locally (no OSS gtest runner).
• yarn flow-check, yarn test for the feature flags, yarn format, yarn featureflags --update, C++ API snapshots regenerated.
• Manual, flag force-enabled in RNTester: a Pressable inside an Animated.View with a 2-minute native-driven translateY, pressed 60 s in with finger drift, on a Samsung Galaxy A16 (Android 16) and the iPhone 18 Pro simulator. main: onPressIn: 1 | onPress: 0; this PR: 1 | 1, and measure() reports the live position instead of the committed one.

Android (Galaxy A16) on main	Android (Galaxy A16) with the overlay	iOS simulator with the overlay

Recording (Android, overlay on): the 2-minute animation, a mid-animation press with finger drift, then measure():

android-overlay-on.mp4

🤖 Generated with Claude Code

[github-actions]

Visual regression

1 visual difference(s) at eed2d8661a8d. Visual differences need maintainer approval. Review the report, then apply visual-change-approved.

android: no capture

ios switch/custom-colors/toggled: Changed, 11804 px (0.474%)

Expected and Captured

Expected	Captured