https://bugs.webkit.org/show_bug.cgi?id=228891
<rdar://81640239>
Reviewed by Antti Koivisto.
Source/WebCore:
If a page has a horizontal scrolling carousel with a non-passive wheel event handler, and a
user with a clicky scroll wheel mouse tries to vertically scroll over that carousel, then
we'd fail to propagate the scroll to the page. This affects apple.com/store.
This happened because we don't do latching for legacy mouse wheel events, so we hit the code
in EventHandler::handleWheelEventInAppropriateEnclosingBox(); this finds the carousel and
calls handleWheelEventInScrollableArea(), but that dispatches to the scrolling thread in way
that does not propagate the event to the nearest ancestor that can handle it.
The fix is to check that the ScrollableArea can handle the event, sharing some code that
already exists and was used by findEnclosingScrollableContainer(). This is a conservative
fix; it's possible that scrollableAreaCanHandleEvent() could be called down in
handleWheelEventInScrollableArea() but that will affect other call sites.
Test: fast/scrolling/mac/vertical-scroll-in-horizontal-scroller.html
* page/EventHandler.cpp:
(WebCore::EventHandler::handleWheelEventInAppropriateEnclosingBox):
(WebCore::EventHandler::scrollableAreaCanHandleEvent):
* page/EventHandler.h:
* page/mac/EventHandlerMac.mm:
(WebCore::findEnclosingScrollableContainer):
LayoutTests:
* fast/scrolling/mac/vertical-scroll-in-horizontal-scroller-expected.txt: Added.
* fast/scrolling/mac/vertical-scroll-in-horizontal-scroller.html: Added.
* tiled-drawing/scrolling/overflow-scroll-reduced-content.html: Convert this test to use
async scrolling. webkit.org/b/228898 tracks an existing problem that caused the test
to fail with non-async scrolling.
Canonical link: https://commits.webkit.org/240377@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@280807 268f45cc-cd09-0410-ab3c-d52691b4dbfc
