Bug 201330

Summary: On the first compositing update, "drawsContent" can be wrong
Product: WebKit Reporter: Simon Fraser (smfr) <simon.fraser>
Component: CompositingAssignee: Simon Fraser (smfr) <simon.fraser>
Status: NEW    
Severity: Normal CC: ap, koivisto, simon.fraser, zalan
Priority: P2    
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Bug Depends on:    
Bug Blocks: 84393    
Attachments:
Description Flags
Patch koivisto: review+

Simon Fraser (smfr)
Reported 2019-08-29 21:40:28 PDT
There's an ordering dependency in computing "requiresOwnBackingStore" that causes us to set drawsContent on the GrpahicsLayer when we don't need to, causing test failures: (bounds 342.00 240.00) + (drawsContent 1) (childrenTransform [1.00 0.00 0.00 0.00] [0.00 1.00 0.00 0.00] [0.00 0.00 1.00 -0.00] [0.00 0.00 0.00 1.00]) The issue is that updateDrawsContent(contentsInfo); happens in RenderLayerBacking::updateAfterDescendants(), but RenderLayerCompositor::requiresOwnBackingStore() on descendants runs before this, and consults compositingAncestorLayer->backing()->graphicsLayer()->drawsContent()
Attachments
Patch (31.99 KB, patch)
2019-09-03 21:44 PDT, Simon Fraser (smfr) 		koivisto: review+
DetailsFormatted DiffDiff
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Simon Fraser (smfr)
Comment 1 2019-08-30 18:28:30 PDT
I need to tease apart "requires own backing store" from "paints into ancestor". RenderLayerBacking::paintsContent() currently checks isPaintDestinationForDescendantLayers(), which walks descendants without their own backing store.
Simon Fraser (smfr)
Comment 2 2019-09-03 21:44:44 PDT
Created attachment 377955 [details] Patch
Antti Koivisto
Comment 3 2019-09-04 11:01:13 PDT
Comment on attachment 377955 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=377955&action=review > Source/WebCore/rendering/RenderLayerBacking.h:87 > + void updateGeometry(const RenderLayer* compositingAncestor, const RenderLayer* compositedAncestorWithBackingStore); Can we start passing the traversal state like I suggested before? > Source/WebCore/rendering/RenderLayerCompositor.cpp:1238 > + layerBacking->updateGeometry(traversalState.compositingAncestor, traversalStateForDescendants.paintDestinationAncestor); It seems wrong this is consulting traversalStateForDescendants while calling into backing of the current layer.
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