NEW252454
[UI-side compositing] css3/scroll-snap/scroll-snap-drag-scrollbar-thumb-with-sticky.html fails 
https://bugs.webkit.org/show_bug.cgi?id=252454
Summary [UI-side compositing] css3/scroll-snap/scroll-snap-drag-scrollbar-thumb-with-...
Simon Fraser (smfr)
Reported 2023-02-16 20:56:17 PST
css3/scroll-snap/scroll-snap-drag-scrollbar-thumb-with-sticky.html fails with UI-side compositing.
Attachments
Add attachment proposed patch, testcase, etc.
Radar WebKit Bug Importer
Comment 1 2023-02-16 20:56:44 PST
<rdar://problem/105579303>
Simon Fraser (smfr)
Comment 2 2023-02-16 21:00:19 PST
This test drags a scrollbar thumb with mouse events, and then tests to see if the scroller scrolled to a snap point. This mouse handling happens on the webcontent main thread (ScrollableArea::doPostThumbMoveSnapping()) which does: newOffset.setX(scrollAnimator->scrollOffsetAdjustedForSnapping(ScrollEventAxis::Horizontal, currentOffset, ScrollSnapPointSelectionMethod::Closest)); Without UI-side compositing, newOffset.setX.x ends up with 748. With UI-side compositing, it's zero. The issue with UI-side compositing here is that doPostThumbMoveSnapping() runs before the web process has actually updated the ScrollableArea's X offset to 748, because this involves a round-trip through the UI process (via RenderLayer::requestScrollPositionUpdate(), coming back through AsyncScrollingCoordinator::updateScrollPositionAfterAsyncScroll().
Note You need to log in before you can comment on or make changes to this bug.