Defer timing animation start through JS Animated (#57003)#57003
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Summary: Wire `animatedDeferStartOfTimingAnimations` through the JS Animated layer: `AnimatedValue` arms a one-shot `__deferAnimationStart`, and `TimingAnimation` forwards `deferredStart` in the native animation config so the native `FrameAnimationDriver` defers its start to the first rendered frame. Gated behind the runtime flag (default off). Adds Fantom integration tests asserting the behavior with the flag on and off. ## Changelog: [Internal] [Changed] - Defer timing animation start through JS Animated Differential Revision: D106825746
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Summary: Wire `animatedDeferStartOfTimingAnimations` through the JS Animated layer: `AnimatedValue` arms a one-shot `__deferAnimationStart`, and `TimingAnimation` forwards `deferredStart` in the native animation config so the native `FrameAnimationDriver` defers its start to the first rendered frame. Gated behind the runtime flag (default off). Adds Fantom integration tests asserting the behavior with the flag on and off. ## Changelog: [Internal] [Changed] - Defer timing animation start through JS Animated Differential Revision: D106825746
Summary: ## Changelog: [Internal] [Changed] - Revisit timing to capture old/new nodes Previously, when `applyViewTransitionName` is called from react reconciler, if there is active viewtransition, we decide it's applying to new node. This was incorrect because `applyViewTransitionName(old)` for next transition can be called when the previous transition is still ongoing. In fact `applyViewTransitionName(old)` is guaranteed to be called before mutationCallback in a transition while `applyViewTransitionName(new)` is inside mutationCallback. So that is a better criteria to separate old and new cases. Given mutationCallback is synchronous on JS thread we can just use a boolean flag to tell the timing. Given this interleaved situation, when we clean up resources (for new/old nodes) of a transition at its end, we should also avoid removing those for a pending transition. Introducing transitionId for this case. Reviewed By: Abbondanzo Differential Revision: D105214322
Summary: ## Changelog: [Internal] [Changed] - Add trace markers in ViewTransitionModule Reviewed By: rubennorte Differential Revision: D105214325
Summary: Add the `animatedDeferStartOfTimingAnimations` JS feature flag (default off). On its own this is a no-op; it gates deferring the start of native-driven timing animations to the first rendered frame, implemented in the following diffs. Includes the regenerated `ReactNativeFeatureFlags.js`. ## Changelog: [Internal] [Changed] - Add animatedDeferStartOfTimingAnimations feature flag Differential Revision: D106825629
Summary: ## Changelog: [Internal] [Fixed] - Defer animation start time in FrameAnimationDriver **Problem**: In complex apps, if animation is started in commit phase (the case if animation starts in useLayoutEffect, or from ViewTransition event handlers), it'll skip initial frames — the user sees the animation snap to an intermediate position. This happens because `FrameAnimationDriver` anchors its start time on the first `runAnimationStep` call, but the UI thread may be busy with layout/mount work for several frames before the view actually composites. The elapsed wall-clock time advances, causing `frameIndex` to jump ahead. **Why**: `startFrameTimeMs_` is set to the Choreographer frame time on the first tick. If the UI thread is blocked processing a heavy tree (many views mounting), subsequent ticks arrive much later — `timeDeltaMs` jumps and the animation skips to a mid-point. - Every major framework solves this: Flutter uses lazy start (`_startTime ??= timeStamp` on first actual tick), Android native uses `CALLBACK_COMMIT` to adjust post-traversal, and CSS View Transitions spec defers start until post-composite. **Fix**: On the very first `update()` call, output the starting value (frame 0) and reset `startFrameTimeMs_ = -1`. This causes the base class to re-anchor on the next `runAnimationStep`, so elapsed time is measured from the first frame that has actually been rendered — not from when `startAnimatingNode` was dispatched. The flag disables itself after one use, so all subsequent frames use pure elapsed-time with no behavioral change. Differential Revision: D106007152
Summary: Wire `animatedDeferStartOfTimingAnimations` through the JS Animated layer: `AnimatedValue` arms a one-shot `__deferAnimationStart`, and `TimingAnimation` forwards `deferredStart` in the native animation config so the native `FrameAnimationDriver` defers its start to the first rendered frame. Gated behind the runtime flag (default off). Adds Fantom integration tests asserting the behavior with the flag on and off. ## Changelog: [Internal] [Changed] - Defer timing animation start through JS Animated Differential Revision: D106825746
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Summary:
Wire
animatedDeferStartOfTimingAnimationsthrough the JS Animated layer:AnimatedValuearms a one-shot__deferAnimationStart, andTimingAnimationforwardsdeferredStartin the native animation config so the nativeFrameAnimationDriverdefers its start to the first rendered frame. Gated behind the runtime flag (default off). Adds Fantom integration tests asserting the behavior with the flag on and off.Changelog:
[Internal] [Changed] - Defer timing animation start through JS Animated
Differential Revision: D106825746