Changeset 243309 in webkit

Timestamp:

Mar 21, 2019, 11:58:09 AM (7 years ago)

Author:

Simon Fraser

Message:

Absolute in stacking-context scroller jiggles when scrolled
​https://bugs.webkit.org/show_bug.cgi?id=196010

Reviewed by Zalan Bujtas.

Source/WebCore:

Updating compositing layers after a scroll (in a compositing update on the main thread)
failed to traverse to an absolute layer inside a stacking-context overflow:scroll,
because the overflow's layer didn't have the "hasCompositingAncestor" bit set on it.

This happened because childState.subtreeIsCompositing wasn't being set when indirect
reasons trigger compositing. So clean up RenderLayerCompositor::computeCompositingRequirements()
to set childState.subtreeIsCompositing for "late" compositing decisions, and move the
"Subsequent layers in the parent stacking context also need to composite" chunk
down to after the last compositing decision has been made.

Test: compositing/overflow/absolute-in-overflow.html

• page/scrolling/ScrollingTreeScrollingNode.cpp:

(WebCore::ScrollingTreeScrollingNode::scrollTo):

• page/scrolling/cocoa/ScrollingTreePositionedNode.mm:

(WebCore::ScrollingTreePositionedNode::applyLayerPositions):

• rendering/RenderLayerCompositor.cpp:

(WebCore::RenderLayerCompositor::computeCompositingRequirements):

LayoutTests:

• compositing/overflow/absolute-in-overflow-expected.html: Added.
• compositing/overflow/absolute-in-overflow.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/compositing/overflow/absolute-in-overflow-expected.html (added)
• LayoutTests/compositing/overflow/absolute-in-overflow.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.cpp (modified) (1 diff)
• Source/WebCore/page/scrolling/cocoa/ScrollingTreePositionedNode.mm (modified) (2 diffs)
• Source/WebCore/rendering/RenderLayerCompositor.cpp (modified) (5 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2019-03-21  Simon Fraser  <simon.fraser@apple.com>
+
+        Absolute in stacking-context scroller jiggles when scrolled
+        https://bugs.webkit.org/show_bug.cgi?id=196010
+
+        Reviewed by Zalan Bujtas.
+
+        * compositing/overflow/absolute-in-overflow-expected.html: Added.
+        * compositing/overflow/absolute-in-overflow.html: Added.
+
 2019-03-21  Zalan Bujtas  <zalan@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-03-21  Simon Fraser  <simon.fraser@apple.com>
+
+        Absolute in stacking-context scroller jiggles when scrolled
+        https://bugs.webkit.org/show_bug.cgi?id=196010
+
+        Reviewed by Zalan Bujtas.
+
+        Updating compositing layers after a scroll (in a compositing update on the main thread)
+        failed to traverse to an absolute layer inside a stacking-context overflow:scroll,
+        because the overflow's layer didn't have the "hasCompositingAncestor" bit set on it.
+
+        This happened because childState.subtreeIsCompositing wasn't being set when indirect
+        reasons trigger compositing. So clean up RenderLayerCompositor::computeCompositingRequirements()
+        to set childState.subtreeIsCompositing for "late" compositing decisions, and move the
+        "Subsequent layers in the parent stacking context also need to composite" chunk
+        down to after the last compositing decision has been made.
+
+        Test: compositing/overflow/absolute-in-overflow.html
+
+        * page/scrolling/ScrollingTreeScrollingNode.cpp:
+        (WebCore::ScrollingTreeScrollingNode::scrollTo):
+        * page/scrolling/cocoa/ScrollingTreePositionedNode.mm:
+        (WebCore::ScrollingTreePositionedNode::applyLayerPositions):
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::computeCompositingRequirements):
+
 2019-03-21  Zalan Bujtas  <zalan@apple.com>
 

trunk/Source/WebCore/page/scrolling/ScrollingTreeScrollingNode.cpp

@@ -162 +162 @@
 
     m_currentScrollPosition = adjustedScrollPosition(position, clamp);
+    
+    LOG_WITH_STREAM(Scrolling, stream << "ScrollingTreeScrollingNode " << scrollingNodeID() << " scrollTo " << position << " (delta from last committed position " << (m_lastCommittedScrollPosition - m_currentScrollPosition) << ")");
+
     updateViewportForCurrentScrollPosition();
     currentScrollPositionChanged();

trunk/Source/WebCore/page/scrolling/cocoa/ScrollingTreePositionedNode.mm

@@ -88 +88 @@
         }
     }
-    LOG_WITH_STREAM(Scrolling, stream << "ScrollingTreePositionedNode " << scrollingNodeID() << " applyLayerPositions: overflow delta " << scrollOffsetSinceLastCommit);
-
     auto layerOffset = -scrollOffsetSinceLastCommit;
     if (m_constraints.scrollPositioningBehavior() == ScrollPositioningBehavior::Stationary) {
@@ -97 +95 @@
 
     FloatPoint layerPosition = m_constraints.layerPositionAtLastLayout() - layerOffset;
+
+    LOG_WITH_STREAM(Scrolling, stream << "ScrollingTreePositionedNode " << scrollingNodeID() << " applyLayerPositions: overflow delta " << scrollOffsetSinceLastCommit << " moving layer to " << layerPosition);
+
     [m_layer _web_setLayerTopLeftPosition:layerPosition - m_constraints.alignmentOffset()];
 

trunk/Source/WebCore/rendering/RenderLayerCompositor.cpp

@@ -959 +959 @@
         layer.setIndirectCompositingReason(indirectCompositingReason);
         childState.compositingAncestor = &layer;
+        childState.subtreeIsCompositing = true;
         overlapMap.pushCompositingContainer();
         addToOverlapMapRecursive(overlapMap, layer);
@@ -968 +969 @@
         layer.reflectionLayer()->setIndirectCompositingReason(willBeComposited ? RenderLayer::IndirectCompositingReason::Stacking : RenderLayer::IndirectCompositingReason::None);
     }
-
-    // Subsequent layers in the parent stacking context also need to composite.
-    compositingState.subtreeIsCompositing |= childState.subtreeIsCompositing;
-    compositingState.fullPaintOrderTraversalRequired |= childState.fullPaintOrderTraversalRequired;
 
     // Set the flag to say that this layer has compositing children.
@@ -988 +985 @@
         if (!willBeComposited) {
             childState.compositingAncestor = &layer;
+            childState.subtreeIsCompositing = true;
             overlapMap.pushCompositingContainer();
             addToOverlapMapRecursive(overlapMap, layer);
@@ -995 +993 @@
 
 #if ENABLE(CSS_COMPOSITING)
-    if ((willBeComposited && layer.hasBlendMode())
-        || (layer.hasNotIsolatedCompositedBlendingDescendants() && !layer.isolatesCompositedBlending()))
+    if ((willBeComposited && layer.hasBlendMode()) || (layer.hasNotIsolatedCompositedBlendingDescendants() && !layer.isolatesCompositedBlending()))
         compositingState.hasNotIsolatedCompositedBlendingDescendants = true;
 #endif
@@ -1014 +1011 @@
 #endif
     }
-    
+
+    // Subsequent layers in the parent stacking context also need to composite.
+    compositingState.subtreeIsCompositing |= childState.subtreeIsCompositing;
+    compositingState.fullPaintOrderTraversalRequired |= childState.fullPaintOrderTraversalRequired;
+
     ASSERT(willBeComposited == needsToBeComposited(layer, queryData));