Bug 212534

Summary:	Event regions are wrong in the scrolled contents layer
Product:	WebKit	Reporter:	Simon Fraser (smfr) <simon.fraser>
Component:	UI Events	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	dbates, koivisto, simon.fraser
Priority:	P2
Version:	Safari Technology Preview
Hardware:	Unspecified
OS:	Unspecified
See Also:	https://bugs.webkit.org/show_bug.cgi?id=212545

Description Simon Fraser (smfr) 2020-05-29 11:08:01 PDT

The event region in the scrolled contents layer covers only the visible part, meaning that if you swipe then tap before we've done layout/rendering update, you get the wrong region types.

RenderBlock::paintObject() uses:
auto borderRect = LayoutRect(paintOffset, size());
which is obviously wrong for the contents of scrolled overflow.