RESOLVED FIXED304189
[threaded-animations] scroll-driven animations don't update in sync with scroll updates on iOS 
https://bugs.webkit.org/show_bug.cgi?id=304189
Summary [threaded-animations] scroll-driven animations don't update in sync with scro...
Antoine Quint
Reported 2025-12-15 09:25:06 PST
We only update scroll-driven animations at 60Hz on iOS, because we only run updates under `RemoteScrollingCoordinatorProxyIOS::displayDidRefresh()` which only runs at 60Hz. We do however update the remote timelines as scroll updates come in at 120Hz under `RemoteScrollingTreeIOS::scrollingTreeNodeDidScroll()`. On macOS we update at 120Hz because `RemoteLayerTreeEventDispatcher::didRefreshDisplay()` already updates at 120Hz, which explains why this issue is not visible on macOS. This is quite visible on demos where transforms fight with scroll updates, for instance https://scroll-driven-animations.style/demos/reverse-scroll/css/.
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Radar WebKit Bug Importer
Comment 1 2025-12-15 09:25:28 PST
<rdar://problem/166546662>
Antoine Quint
Comment 2 2025-12-17 03:54:20 PST
Pull request: https://github.com/WebKit/WebKit/pull/55551
EWS
Comment 3 2025-12-17 13:21:02 PST
Committed 304619@main (230a3fd2ec73): <https://commits.webkit.org/304619@main> Reviewed commits have been landed. Closing PR #55551 and removing active labels.
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