Changeset 245375 in webkit

Timestamp:

May 15, 2019 10:41:08 PM (5 years ago)

Author:

Simon Fraser

Message:

Avoid a recursive descendants layer walk sometimes
​https://bugs.webkit.org/show_bug.cgi?id=197939

Reviewed by Zalan Bujtas.

If a layer got composited post-descendants because it needs to clip, for example, we'd do a recursive
descendant tree walk to add layers to the overlap map. However, all the descendants would already
have contributed to the overlap map if some non-root ancestor was already composited. So we can
skip the addDescendantsToOverlapMapRecursive() if we know, before descendants, whether there's
a non-root composited ancestor.

• rendering/RenderLayerCompositor.cpp:

(WebCore::RenderLayerCompositor::CompositingState::hasNonRootCompositedAncestor const):
(WebCore::RenderLayerCompositor::computeCompositingRequirements):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• rendering/RenderLayerCompositor.cpp (modified) (4 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-05-15  Simon Fraser  <simon.fraser@apple.com>
+
+        Avoid a recursive descendants layer walk sometimes
+        https://bugs.webkit.org/show_bug.cgi?id=197939
+
+        Reviewed by Zalan Bujtas.
+
+        If a layer got composited post-descendants because it needs to clip, for example, we'd do a recursive
+        descendant tree walk to add layers to the overlap map. However, all the descendants would already
+        have contributed to the overlap map if some non-root ancestor was already composited. So we can
+        skip the addDescendantsToOverlapMapRecursive() if we know, before descendants, whether there's
+        a non-root composited ancestor.
+
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::CompositingState::hasNonRootCompositedAncestor const):
+        (WebCore::RenderLayerCompositor::computeCompositingRequirements):
+
 2019-05-15  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebCore/rendering/RenderLayerCompositor.cpp

@@ -176 +176 @@
     }
 
+    bool hasNonRootCompositedAncestor() const
+    {
+        return compositingAncestor && !compositingAncestor->isRenderViewLayer();
+    }
+
     RenderLayer* compositingAncestor;
     RenderLayer* backingSharingAncestor { nullptr };
@@ -856 +861 @@
     bool willBeComposited = layer.isComposited();
     bool becameCompositedAfterDescendantTraversal = false;
+
     if (layer.needsPostLayoutCompositingUpdate() || compositingState.fullPaintOrderTraversalRequired || compositingState.descendantsRequireCompositingUpdate) {
         layer.setIndirectCompositingReason(RenderLayer::IndirectCompositingReason::None);
@@ -952 +958 @@
 
     bool anyDescendantHas3DTransform = false;
+    bool descendantsAddedToOverlap = currentState.hasNonRootCompositedAncestor();
 
     for (auto* childLayer : layer.negativeZOrderLayers()) {
@@ -1049 +1056 @@
 
     bool layerContributesToOverlap = currentState.compositingAncestor && !currentState.compositingAncestor->isRenderViewLayer();
-    updateOverlapMap(overlapMap, layer, layerExtent, layerContributesToOverlap, becameCompositedAfterDescendantTraversal);
+    updateOverlapMap(overlapMap, layer, layerExtent, layerContributesToOverlap, becameCompositedAfterDescendantTraversal && !descendantsAddedToOverlap);
 
     // Pop backing/overlap sharing state.