Bug 238648 – intersectsWithAncestor doesn't take fragmented boxes into account

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Matt Woodrow]

intersectsWithAncestor uses overlapBounds(), which doesn't take into account the boxes of other fragments, and can incorrectly determine that we don't intersect if only the first fragment intersects.

<rdar://90589355>

[Matt Woodrow]

Created attachment 456311 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 456311 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=456311&action=review

> Source/WebCore/rendering/RenderLayerBacking.cpp:2813
> -    auto overlap = child.overlapBounds();
> -    overlap.moveBy(offset);
> +    auto overlap = child.boundingBox(&ancestor, child.offsetFromAncestor(&ancestor), RenderLayer::UseFragmentBoxesExcludingCompositing);

Is child.overlapBounds() just wrong in this case? That implies there are other cases where overlap is broken?

[Matt Woodrow]

Comment on attachment 456311 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=456311&action=review

>> Source/WebCore/rendering/RenderLayerBacking.cpp:2813
>> +    auto overlap = child.boundingBox(&ancestor, child.offsetFromAncestor(&ancestor), RenderLayer::UseFragmentBoxesExcludingCompositing);
> 
> Is child.overlapBounds() just wrong in this case? That implies there are other cases where overlap is broken?

It looks like the only other caller overlapBounds is within RenderLayerCompositor, and RenderLayerCompositor::canBeComposited returns false for RenderFragmentedFlow, so I think it shouldn't ever be called for this case.

[EWS]

Committed r292350 (249215@main): <https://commits.webkit.org/249215@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 456311 [details].