Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: d8f6ca541f56a048e8d292e862d5cc3249957ccd
https://github.com/WebKit/WebKit/commit/d8f6ca541f56a048e8d292e862d5cc3249957ccd
Author: Ahmad Saleem <[email protected]>
Date: 2026-06-19 (Fri, 19 Jun 2026)
Changed paths:
M
LayoutTests/imported/w3c/web-platform-tests/css/css-scroll-snap/input/paged-expected.txt
M
LayoutTests/imported/w3c/web-platform-tests/css/css-scroll-snap/scroll-snap-stop-002-expected.txt
M LayoutTests/platform/mac/TestExpectations
M Source/WebCore/page/scrolling/ScrollSnapOffsetsInfo.cpp
Log Message:
-----------
Scroll snapping selects a snap point that overshoots the destination instead
of the closest one in the scroll direction
https://bugs.webkit.org/show_bug.cgi?id=317064
rdar://179549119
Reviewed by Simon Fraser.
When two snap offsets bracket a scroll destination,
closestSnapOffsetWithInfoAndAxis()
picked the one in the scroll direction unconditionally instead of the closest
one, so a
snap point between the origin and the destination could be skipped in favor of
one that
overshoots it (e.g. offsets 0/95/120, scrolling from 0 to 100, snapped to 120
instead of 95).
The fix is twofold. First, make the directional trap-escape filter decide which
side to
discard from the actual scroll direction (velocity) rather than from the
predicted
destination: the predicted destination can collapse onto the original offset
(e.g. when
momentum scrolling prediction is disabled), in which case the strict
origin-vs-destination
comparison failed to drop the candidate sitting at the origin. Only fall back
to the
destination for non-directional scrolls where velocity is 0. With that filter
now reliably
discarding any candidate at or behind the origin, both remaining candidates are
valid
forward targets, so pick whichever is closest to the destination, using scroll
direction
only to break an exact tie.
*
LayoutTests/imported/w3c/web-platform-tests/css/css-scroll-snap/input/paged-expected.txt:
Progressions
*
LayoutTests/imported/w3c/web-platform-tests/css/css-scroll-snap/scroll-snap-stop-002-expected.txt:
Ditto
* LayoutTests/platform/mac/TestExpectations: Unskip now passing test
* Source/WebCore/page/scrolling/ScrollSnapOffsetsInfo.cpp:
(WebCore::closestSnapOffsetWithInfoAndAxis):
Canonical link: https://commits.webkit.org/315522@main
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