Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 00e6ceb5249da6496d9fd8ab58530bc2ea047abb
https://github.com/WebKit/WebKit/commit/00e6ceb5249da6496d9fd8ab58530bc2ea047abb
Author: Ahmad Saleem <[email protected]>
Date: 2026-10-07 (Wed, 07 Oct 2026)
Changed paths:
A
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-expected.txt
A
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-horizontal-expected.txt
A
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-horizontal.html
A
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly.html
M
Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeScrollingNodeDelegateIOS.h
M
Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeScrollingNodeDelegateIOS.mm
Log Message:
-----------
scroll snap animation taking extremely long to settle
https://bugs.webkit.org/show_bug.cgi?id=321127
rdar://184176304
Reviewed by Frédéric Wang Nélar and Simon Fraser.
On iOS, flicking an overflow scroller with `scroll-snap-type: mandatory` past
its last snap
position could take multiple seconds to settle back onto that snap position.
With `overscroll-behavior: none`, a fast flick pins the scroller at its maximum
scroll offset
while the finger still has a large velocity.
-scrollViewWillEndDragging:withVelocity:targetContentOffset:
then replaced UIKit's target with the closest snap offset, which lies behind
the current offset,
against the direction of the velocity. UIKit decelerates very slowly towards a
target like this.
Detect this case after computing the snap target. Stop the momentum by setting
the target to the
current offset, and once dragging ends, animate to the snap offset with
-setContentOffset:animated:.
The scroll stays a user interaction until the animation ends, so it still ends
with exactly one
scrollDidEnd() call (and one scrollend event).
Flicks in either direction past the first or last snap position, on either
axis, go through this
same check, so neither the vertical nor the horizontal case needs special
handling. The tests cover
both directions on both axes.
Tests:
fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-horizontal.html
fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly.html
*
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-expected.txt:
Added.
*
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-horizontal-expected.txt:
Added.
*
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly-horizontal.html:
Added.
*
LayoutTests/fast/scrolling/ios/scroll-snap-momentum-against-snap-direction-settles-quickly.html:
Added.
*
Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeScrollingNodeDelegateIOS.h:
*
Source/WebKit/UIProcess/RemoteLayerTree/ios/ScrollingTreeScrollingNodeDelegateIOS.mm:
(-[WKScrollingNodeScrollViewDelegate scrollViewWillBeginDragging:]):
(-[WKScrollingNodeScrollViewDelegate
scrollViewWillEndDragging:withVelocity:targetContentOffset:]):
(-[WKScrollingNodeScrollViewDelegate scrollViewDidEndDragging:willDecelerate:]):
(-[WKScrollingNodeScrollViewDelegate scrollViewDidEndScrollingAnimation:]):
Canonical link: https://commits.webkit.org/323056@main
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