Bug 260370 – AX: Relations updates thrash between dirty and clean when multiple deferred id attribute changes are processed

• Status: RESOLVED
• Resolution: FIXED
• Component: Accessibility

[Tyler Wilcock]

...

[Radar WebKit Bug Importer]

<rdar://problem/114052085>

[Tyler Wilcock]

Created attachment 467317 [details]
Patch

[Andres Gonzalez]

(In reply to Tyler Wilcock from comment #2)
> Created attachment 467317 [details]
> Patch

AX: Relations updates thrash between dirty and clean when
 multiple deferred id attribute changes are processed
 https://bugs.webkit.org/show_bug.cgi?id=260370 rdar://problem/114052085

Reviewed by NOBODY (OOPS!).

In AXObjectCache::handleAttributeChange, any change to the `id`
attribute causes AXObjectCache::m_relationsNeedUpdate to become true.

This is problematic when `m_deferredAttributeChange` contains multiple
`id` attribute changes, as we thrash between dirtying m_relationsNeedUpdate,
immediately clearing it as a result of a random `parentObject` call, and
then re-dirtying it.

AG: why paretObject is dirtying the flag?

With this patch, we introduce a mechanism to suppress relations updates
within a defined scope to avoid needlessly re-computing it over and
over.

AG: If the problem is caused by multiple id changes being queued, we can just set a local flag in the method that processes the queue to signal that the relations were already updated. But it sounds like the real cause is the dirtying of the flag when it shouldn't be.

[Tyler Wilcock]

Created attachment 467334 [details]
Patch

[Andres Gonzalez]

(In reply to Tyler Wilcock from comment #4)
> Created attachment 467334 [details]
> Patch

"""
This is problematic when `m_deferredAttributeChange` contains multiple
`id` attribute changes, as we thrash between setting m_relationsNeedUpdate to true,
immediately resetting it to false as a result of a random `parentObject` call, and
then re-dirtying it with the next id attribute change.
"""

Is it worth clarifying why parentObject() is called? The "random" term here is inaccurate. The re-calculation of the relations occur because parentObject() now calls ownerParentObject(), which forces the relations to be computed. I think parentObject() is called in this context because of accessibilityIsIgnored().

[Tyler Wilcock]

Created attachment 467367 [details]
Patch

[Tyler Wilcock]

Created attachment 467381 [details]
Patch

[EWS]

Found 1 new test failure: media/video-remove-insert-repaints.html

[Tyler Wilcock]

I really don't think that's related to this patch. Going to try cq+ again.

[EWS]

Found 1 new test failure: media/video-remove-insert-repaints.html

[EWS]

Committed 267190@main (f8ef167b97d5): <https://commits.webkit.org/267190@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 467381 [details].