[webkit-reviews] review requested: [Bug 91117] Add support for compositing the contents of overflow:scroll areas : [Attachment 159124] Patch

[bugzilla-daemon at webkit.org]

vollick at chromium.org has asked	for review:
Bug 91117: Add support for compositing the contents of overflow:scroll areas
https://bugs.webkit.org/show_bug.cgi?id=91117

Attachment 159124: Patch
https://bugs.webkit.org/attachment.cgi?id=159124&action=review

------- Additional Comments from vollick at chromium.org
Rebased Sami's patch and hopefully fixed the bug that was causing the layout
test failures. I think the problem is in RenderLayer::calculateRects. In
RenderLayer::calculateClipRects, there is this check:

(renderer()->hasOverflowClip() && (respectOverflowClip == RespectOverflowClip
|| this != rootLayer)

which I interpret as "has an overflow clip, and we should respect it." In
RenderLayer::calculateRects there this check appears three times:

renderer()->hasOverflowClip() && (this != rootLayer || respectOverflowClip ==
IgnoreOverflowClip)

immediately followed by code that clips to the overflow clip rect. So, in
effect, the code is saying "if we have an overflow clip, and we should ignore
it, then clip," but I think this may have been a typo and the same check as we
see in ::calculateClipRects was meant to be used. The result is that the fgRect
is not clipped, so it draws below the overflow scroll controls, breaking the
layout tests.

Still to be done: get the attached tests in working order.