Changeset 281913 in webkit

Timestamp:

Sep 2, 2021, 2:11:58 AM (4 years ago)

Author:

commit-queue@webkit.org

Message:

Absolutely positioned and negative z-index div with canvas child gets drawn with wrong stacking order
​https://bugs.webkit.org/show_bug.cgi?id=217154

Patch by Rob Buis <​rbuis@igalia.com> on 2021-09-02
Reviewed by Simon Fraser.

Source/WebCore:

Keep overlap map accurate.

Test: compositing/subtree-div-overlaps-multiple-negative-z-divs.html

• rendering/RenderLayerCompositor.cpp:

(WebCore::RenderLayerCompositor::computeCompositingRequirements):

LayoutTests:

Add test based on bug report test case.

• compositing/subtree-div-overlaps-multiple-negative-z-divs-expected.html: Added.
• compositing/subtree-div-overlaps-multiple-negative-z-divs.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/compositing/subtree-div-overlaps-multiple-negative-z-divs-expected.html (added)
• LayoutTests/compositing/subtree-div-overlaps-multiple-negative-z-divs.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderLayerCompositor.cpp (modified) (2 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2021-09-02  Rob Buis  <rbuis@igalia.com>
+
+        Absolutely positioned and negative z-index div with canvas child gets drawn with wrong stacking order
+        https://bugs.webkit.org/show_bug.cgi?id=217154
+
+        Reviewed by Simon Fraser.
+
+        Add test based on bug report test case.
+
+        * compositing/subtree-div-overlaps-multiple-negative-z-divs-expected.html: Added.
+        * compositing/subtree-div-overlaps-multiple-negative-z-divs.html: Added.
+
 2021-09-01  Sonia Singla  <ssingla@igalia.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2021-09-02  Rob Buis  <rbuis@igalia.com>
+
+        Absolutely positioned and negative z-index div with canvas child gets drawn with wrong stacking order
+        https://bugs.webkit.org/show_bug.cgi?id=217154
+
+        Reviewed by Simon Fraser.
+
+        Keep overlap map accurate.
+
+        Test: compositing/subtree-div-overlaps-multiple-negative-z-divs.html
+
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::computeCompositingRequirements):
+
 2021-09-02  Mark Lam  <mark.lam@apple.com>
 

trunk/Source/WebCore/rendering/RenderLayerCompositor.cpp

@@ -1099 +1099 @@
     bool descendantsAddedToOverlap = currentState.hasNonRootCompositedAncestor();
 
+    unsigned newlyCompositedChildLayerCount = 0;
     for (auto* childLayer : layer.negativeZOrderLayers()) {
         computeCompositingRequirements(&layer, *childLayer, overlapMap, currentState, backingSharingState, anyDescendantHas3DTransform);
@@ -1104 +1105 @@
         // If we have to make a layer for this child, make one now so we can have a contents layer
         // (since we need to ensure that the -ve z-order child renders underneath our contents).
-        if (!willBeComposited && currentState.subtreeIsCompositing) {
-            layer.setIndirectCompositingReason(IndirectCompositingReason::BackgroundLayer);
-            layerWillComposite();
-        }
+        if (!willBeComposited && currentState.subtreeIsCompositing)
+            ++newlyCompositedChildLayerCount;
+    }
+    while (newlyCompositedChildLayerCount--) {
+        layer.setIndirectCompositingReason(IndirectCompositingReason::BackgroundLayer);
+        layerWillComposite();
     }