tree c4c8153efb58fb35b4670c7b930fd5720be22c89
parent f8265763ef28bcaccdd9f40f37ee5988dcf2dcff
author simon.fraser@apple.com <simon.fraser@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1558143123 +0000
committer simon.fraser@apple.com <simon.fraser@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1558143123 +0000

REGRESSION (r245170): gmail.com inbox table header flickers
https://bugs.webkit.org/show_bug.cgi?id=198005
<rdar://problem/50907718>

Reviewed by Antti Koivisto.

Source/WebCore:

When a layer started as painting into shared backing, but then became independently
composited (e.g. by having to clip composited children), it wouldn't have the "overlap"
indirect compositing reason. This allowed requiresOwnBackingStore() to say that it
could paint into some ancestor, but this breaks overlap. So in this code path,
put IndirectCompositingReason::Overlap back on the layer which restores the previous
behavior.

Make some logging changes to help diagnose things like this.

Test: compositing/shared-backing/overlap-after-end-sharing.html

* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::calculateClipRects const):
(WebCore::outputPaintOrderTreeLegend):
(WebCore::outputPaintOrderTreeRecursive):
* rendering/RenderLayer.h:
* rendering/RenderLayerCompositor.cpp:
(WebCore::RenderLayerCompositor::computeCompositingRequirements):
(WebCore::RenderLayerCompositor::updateBacking):
(WebCore::RenderLayerCompositor::requiresOwnBackingStore const):
(WebCore::RenderLayerCompositor::reasonsForCompositing const):
(WebCore::RenderLayerCompositor::requiresCompositingForIndirectReason const):
* rendering/RenderLayerCompositor.h:

LayoutTests:

* compositing/shared-backing/overlap-after-end-sharing-expected.html: Added.
* compositing/shared-backing/overlap-after-end-sharing.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@245490 268f45cc-cd09-0410-ab3c-d52691b4dbfc