Bug 304189

Summary: [threaded-animations] scroll-driven animations don't update in sync with scroll updates on iOS
Product: WebKit Reporter: Antoine Quint <graouts>
Component: AnimationsAssignee: Antoine Quint <graouts>
Status: RESOLVED FIXED    
Severity: Normal CC: graouts, mattwoodrow, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   

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/.
Attachments
Radar WebKit Bug Importer
Comment 1 2025-12-15 09:25:28 PST
Antoine Quint
Comment 2 2025-12-17 03:54:20 PST
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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