Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: d8184230a66a6f34ff32f0bcbbb6318a60231b14
https://github.com/WebKit/WebKit/commit/d8184230a66a6f34ff32f0bcbbb6318a60231b14
Author: Tyler Wilcock <[email protected]>
Date: 2025-05-27 (Tue, 27 May 2025)
Changed paths:
A LayoutTests/accessibility/editable-svg-arrow-movement-expected.txt
A LayoutTests/accessibility/editable-svg-arrow-movement.html
M Source/WebCore/accessibility/AXObjectCache.cpp
Log Message:
-----------
AX: AXObjectCache::characterOffsetFromVisiblePosition iterates over the
result of VisiblePosition::canonicalPosition(const Position&), which can return
previous positions, resulting in infinite loops
https://bugs.webkit.org/show_bug.cgi?id=293619
rdar://152094332
Reviewed by Joshua Hoffman.
Over time, we've added various attempts to catch infinite loops in
AXObjectCache::characterOffsetFromVisiblePosition
that result from getting the "next" position actually returning previous
positions, thus resulting in us looping forever.
This commit removes all of these workarounds, and eliminates the root cause for
getting any previous positions in the
first place. This happened because we maintained `currentPosition` by
constructing a `VisiblePosition` from the
`nextVisuallyDistinctCandidate`, then extracting the `deepEquivalent` from the
`VisiblePosition`. The problem with that
is that the VisiblePosition constructor calls `canonicalPosition` on the passed
`Position`, which critically can return
a previous `Position`. When this happens, we will loop forever.
There is no code comment or layout test proving why we need to canonicalize the
positions we use, so this commit stops
doing it. Instead, we solely loop over `nextVisuallyDistinctCandidate`, which
should guarantee forward progress.
New test added that exhibited a full hang before this change.
* LayoutTests/accessibility/editable-svg-arrow-movement-expected.txt: Added.
* LayoutTests/accessibility/editable-svg-arrow-movement.html: Added.
* Source/WebCore/accessibility/AXObjectCache.cpp:
(WebCore::AXObjectCache::characterOffsetFromVisiblePosition):
Canonical link: https://commits.webkit.org/295486@main
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