Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: c223637aad47dceef3291a95636ceb9fc10ee1ab
https://github.com/WebKit/WebKit/commit/c223637aad47dceef3291a95636ceb9fc10ee1ab
Author: Tyler Wilcock <tyle...@apple.com>
Date: 2024-07-10 (Wed, 10 Jul 2024)
Changed paths:
A LayoutTests/accessibility/mac/role-img-selection-hang-expected.txt
A LayoutTests/accessibility/mac/role-img-selection-hang.html
M Source/WebCore/accessibility/AXObjectCache.cpp
Log Message:
-----------
AXObjectCache::characterOffsetFromVisiblePosition can iterate infinitely when
moving through role="img" container
https://bugs.webkit.org/show_bug.cgi?id=276464
rdar://problem/131502510
Reviewed by Ryosuke Niwa.
Given this markup:
<div role="img">
<span style="position:absolute">X</span>
<span>Y</span>
</div>
When we create a VisiblePosition from this Position:
(Position
(anchor node: #text 0x159003ec0 length=1 "Y")
(offset: 0)
(anchor type: offset in anchor))
We get its `canonicalPosition` in the VisiblePosition constructor, which
computes:
(Position
(anchor node: DIV 0x159003c40)
(offset: 0)
(anchor type: before anchor))
This starts iteration for `nextVisuallyDistinctCandidate` back at the beginning
of the div, repeating until we get back
to the "Y" position, in turn computing the before-anchor-div position,
repeating forever.
This happens because the div is role="img", which was special cased to be
`Element::canContainRangeEndPoint()` in:
https://bugs.webkit.org/attachment.cgi?id=229259&action=prettypatch (Find on
Page can get stuck in a loop when the search string occurs in an input in a
fieldset).
Making it `canContainRangeEndPoint` also makes it `editingIgnoresContent ==
true`, in turn making it `Position::isCandidate() == true`.
I tried to solve the core editing bug in
https://github.com/WebKit/WebKit/pull/30614, but my approach (removing this
special role="img" logic in Element::canContainRangeEndPoint()) caused other
undesirable effects (more details in
https://github.com/WebKit/WebKit/pull/30614#issuecomment-2221064954), so some
other fix is needed (tracked by
https://bugs.webkit.org/show_bug.cgi?id=276460).
For now, this commit works around this foundational bug by changing
`AXObjectCache::characterOffsetFromVisiblePosition`
to detect we've moved back to the start position, and breaking to prevent an
infinite loop.
* LayoutTests/accessibility/mac/role-img-selection-hang-expected.txt: Added.
* LayoutTests/accessibility/mac/role-img-selection-hang.html: Added.
* Source/WebCore/accessibility/AXObjectCache.cpp:
(WebCore::AXObjectCache::characterOffsetFromVisiblePosition):
Canonical link: https://commits.webkit.org/280847@main
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