Event region generation needs to know about backing-sharing

[Simon Fraser (smfr)]

When we use backing-store sharing for composting, event region generation also needs to run code to get shared layers to produce event regions.

This will fix fast/scrolling/ios/overflow-scroll-overlap-4.html

[Simon Fraser (smfr)]

For now I'll mark this as a test failure in TestExpectations.

[Radar WebKit Bug Importer]

<rdar://problem/50584991>

[Radar WebKit Bug Importer]

<rdar://problem/50584994>

[Antti Koivisto]

Created attachment 369547 [details]
patch

[Antti Koivisto]

Created attachment 369548 [details]
patch

[Anders Carlsson]

Comment on attachment 369548 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=369548&action=review

> Source/WebCore/rendering/RenderLayerBacking.cpp:1497
> +    for (auto& layerWeakPtr : m_backingSharingLayers)
> +        layerWeakPtr->paintLayerContents(nullContext, paintingInfo, paintFlags);

Do you need to null check layerWeakPtr here?

[Antti Koivisto]

> Do you need to null check layerWeakPtr here?

Nah, weakptrs in this code are just for safety, the logic should guarantee they won't be null here.

[Simon Fraser (smfr)]

Comment on attachment 369548 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=369548&action=review

>> Source/WebCore/rendering/RenderLayerBacking.cpp:1497
>> +        layerWeakPtr->paintLayerContents(nullContext, paintingInfo, paintFlags);
> 
> Do you need to null check layerWeakPtr here?

No, we think that's a correctness bug and are OK with a null-deref crash.

However, this code will be wrong when the sharing layers have transforms. Please file a follow-up bug to fix that. You'll need to use something like I'm adding in bug 197692.

[WebKit Commit Bot]

Comment on attachment 369548 [details]
patch

Clearing flags on attachment: 369548

Committed r245175: <https://trac.webkit.org/changeset/245175>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.