Event region collection should take clipping into account

• Component: Scrolling
• Status: RESOLVED FIXED

[Antti Koivisto]

Similar to paint.

[Antti Koivisto]

<rdar://problem/53826561>

[Antti Koivisto]

Created attachment 376161 [details]
patch

[Simon Fraser (smfr)]

Comment on attachment 376161 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=376161&action=review

> Source/WebCore/rendering/EventRegion.cpp:63
> +    m_clipStack.removeLast();

If we have mismatched push/pop, this will do shrink(size() - 1); which will underflow and create a huge vector and probably crash. I think we should be defensive here and check for m_clipStack not being empty.

This is especially true since we don't have save/restore, so you're doing manual push/pop.

> Source/WebCore/rendering/RenderBox.cpp:1821
> +    if (paintInfo.phase == PaintPhase::EventRegion)
> +        paintInfo.eventRegionContext->popClip();
> +
>      paintInfo.context().restore();

This is a manual pop, but the painting code is doing a save/restore. Maybe in future it would be better to implement save/restore for the event region context.

If I'm changing painting code in future, it's going to be really hard to know how to change the event region code.

Also, there may be other code paths that save/clip/restore that need to also do something with the event region.

[Antti Koivisto]

Created attachment 376185 [details]
patch

[WebKit Commit Bot]

Comment on attachment 376185 [details]
patch

Clearing flags on attachment: 376185

Committed r248604: <https://trac.webkit.org/changeset/248604>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.