Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: efd075461ed0d76cd9e6697e469674fa0577bf79
https://github.com/WebKit/WebKit/commit/efd075461ed0d76cd9e6697e469674fa0577bf79
Author: Lily Spiniolas <[email protected]>
Date: 2026-05-05 (Tue, 05 May 2026)
Changed paths:
A
LayoutTests/fast/scrolling/latching/mainframe-stretch-snaps-back-after-hold-over-subscroller-expected.txt
A
LayoutTests/fast/scrolling/latching/mainframe-stretch-snaps-back-after-hold-over-subscroller.html
M Source/WebCore/page/scrolling/ScrollingTreeLatchingController.cpp
M Source/WebCore/page/scrolling/ScrollingTreeLatchingController.h
Log Message:
-----------
Main frame scroll stretching may get stuck when gesture is initiated above
subscroller and held
https://bugs.webkit.org/show_bug.cgi?id=314055
rdar://173104821
Reviewed by Wenson Hsieh and Abrar Rahman Protyasha.
If the the mainframe and a subscroller are both scrolled to the top of the page,
the user initiates a scroll gesture above the subscroller which causes the main
frame to enter a scroll stretch, and the user then holds the gesture for more
than 100ms, the stretch gets stuck if the cursor is still above the subscroller.
This bug is caused by an issue with scroll latching. If a scroll gesture begins
over a subscroller and neither that subscroller nor any of its parent scrollers
can scroll in the direction of the gesture without going out of bounds, then the
main frame's root scrolling node becomes the latched node, and the main frame
correctly enters a scroll stretch. However, when the gesture is held longer than
100ms, the latched node (main frame's root scrolling node in this case)
is no longer considered relevant, so it stops automatically receiving wheel
events.
When the gesture is finally released, instead of dispatching the ending event to
the latched node, a hit-test is performed. If the cursor is above the
subscroller
still when this happens, the ending wheel event is sent there instead of the
main
frame's root scrolling node. Since the main frame does not receive an ending
wheel
event, it does not rubberband back.
To resolve this, we now also consider the latched node relevant if the wheel
event
phase is not `Began` so that the latched node remains relevant for the entirety
of a continuous scroll gesture.
Test:
fast/scrolling/latching/mainframe-stretch-snaps-back-after-hold-over-subscroller.html
*
LayoutTests/fast/scrolling/latching/mainframe-stretch-snaps-back-after-hold-over-subscroller-expected.txt:
Added.
*
LayoutTests/fast/scrolling/latching/mainframe-stretch-snaps-back-after-hold-over-subscroller.html:
Added.
* Source/WebCore/page/scrolling/ScrollingTreeLatchingController.cpp:
(WebCore::ScrollingTreeLatchingController::receivedWheelEvent):
(WebCore::ScrollingTreeLatchingController::latchingDataForEvent const):
(WebCore::ScrollingTreeLatchingController::latchedNodeHasRecentInteraction
const):
(WebCore::ScrollingTreeLatchingController::latchedNodeIsRelevant const):
Deleted.
* Source/WebCore/page/scrolling/ScrollingTreeLatchingController.h:
Canonical link: https://commits.webkit.org/312628@main
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