Changeset 183970 in webkit

Timestamp:

May 7, 2015, 6:46:59 PM (10 years ago)

Author:

Simon Fraser

Message:

REGRESSION (r183300): Fixed elements flash when scrolling
​https://bugs.webkit.org/show_bug.cgi?id=144778
rdar://problem/20769741

Reviewed by Dean Jackson.

After r183300 we can detached layer backing store when outside the coverage region.
However, position:fixed layers are moved around by the ScrollingCoordinator behind
GraphicsLayer's back, so we can do layer flushes with stale information about layer
geometry.

To avoid dropping backing store for layers in this situation, prevent backing
store detachment on layers registered with the ScrollingCoordinator as viewport-constrained
layers. Preventing detachment on a layer also prevents detachment on all descendant
layers.

• platform/graphics/GraphicsLayer.h:

(WebCore::GraphicsLayer::setAllowsBackingStoreDetachment):
(WebCore::GraphicsLayer::allowsBackingStoreDetachment):

• platform/graphics/ca/GraphicsLayerCA.cpp:

(WebCore::GraphicsLayerCA::GraphicsLayerCA):
(WebCore::GraphicsLayerCA::setVisibleAndCoverageRects): Set m_intersectsCoverageRect to true
if backing store detachment is prevented.
(WebCore::GraphicsLayerCA::recursiveCommitChanges): Set a bit in the CommitState to
communicate to descendants that detachment is prevented.

• platform/graphics/ca/GraphicsLayerCA.h:

(WebCore::GraphicsLayerCA::CommitState::CommitState): Deleted.

• rendering/RenderLayerBacking.cpp:

(WebCore::RenderLayerBacking::setIsScrollCoordinatedWithViewportConstrainedRole):

• rendering/RenderLayerBacking.h:

(WebCore::RenderLayerBacking::setScrollingNodeIDForRole): If registering with a non-zero
nodeID for the ViewportConstrained role, turn off backing store detachment.

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/graphics/GraphicsLayer.h (modified) (1 diff)
• platform/graphics/ca/GraphicsLayerCA.cpp (modified) (6 diffs)
• platform/graphics/ca/GraphicsLayerCA.h (modified) (4 diffs)
• rendering/RenderLayerBacking.cpp (modified) (1 diff)
• rendering/RenderLayerBacking.h (modified) (2 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2015-05-07  Simon Fraser  <simon.fraser@apple.com>
+
+        REGRESSION (r183300): Fixed elements flash when scrolling
+        https://bugs.webkit.org/show_bug.cgi?id=144778
+        rdar://problem/20769741
+
+        Reviewed by Dean Jackson.
+
+        After r183300 we can detached layer backing store when outside the coverage region.
+        However, position:fixed layers are moved around by the ScrollingCoordinator behind
+        GraphicsLayer's back, so we can do layer flushes with stale information about layer
+        geometry.
+        
+        To avoid dropping backing store for layers in this situation, prevent backing
+        store detachment on layers registered with the ScrollingCoordinator as viewport-constrained
+        layers. Preventing detachment on a layer also prevents detachment on all descendant
+        layers.
+
+        * platform/graphics/GraphicsLayer.h:
+        (WebCore::GraphicsLayer::setAllowsBackingStoreDetachment):
+        (WebCore::GraphicsLayer::allowsBackingStoreDetachment):
+        * platform/graphics/ca/GraphicsLayerCA.cpp:
+        (WebCore::GraphicsLayerCA::GraphicsLayerCA):
+        (WebCore::GraphicsLayerCA::setVisibleAndCoverageRects): Set m_intersectsCoverageRect to true
+        if backing store detachment is prevented.
+        (WebCore::GraphicsLayerCA::recursiveCommitChanges): Set a bit in the CommitState to 
+        communicate to descendants that detachment is prevented.
+        * platform/graphics/ca/GraphicsLayerCA.h:
+        (WebCore::GraphicsLayerCA::CommitState::CommitState): Deleted.
+        * rendering/RenderLayerBacking.cpp:
+        (WebCore::RenderLayerBacking::setIsScrollCoordinatedWithViewportConstrainedRole):
+        * rendering/RenderLayerBacking.h:
+        (WebCore::RenderLayerBacking::setScrollingNodeIDForRole): If registering with a non-zero
+        nodeID for the ViewportConstrained role, turn off backing store detachment.
+
 2015-05-07  Sam Weinig  <sam@webkit.org>
 

trunk/Source/WebCore/platform/graphics/GraphicsLayer.h

@@ -491 +491 @@
     float pageScaleFactor() const { return m_client.pageScaleFactor(); }
     float deviceScaleFactor() const { return m_client.deviceScaleFactor(); }
+    
+    // Whether this layer (and descendants) can detach backing store when outside the coverage area.
+    virtual void setAllowsBackingStoreDetachment(bool) { }
+    virtual bool allowsBackingStoreDetachment() const { return true; }
 
     virtual void deviceOrPageScaleFactorChanged() { }

trunk/Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp

@@ -354 +354 @@
     , m_needsFullRepaint(false)
     , m_usingBackdropLayerType(false)
+    , m_allowsBackingStoreDetachment(true)
     , m_intersectsCoverageRect(true)
 {
@@ -1253 +1254 @@
 }
 
-void GraphicsLayerCA::setVisibleAndCoverageRects(const VisibleAndCoverageRects& rects)
+void GraphicsLayerCA::setVisibleAndCoverageRects(const VisibleAndCoverageRects& rects, bool allowBackingStoreDetachment)
 {
     bool visibleRectChanged = rects.visibleRect != m_visibleRect;
@@ -1276 +1277 @@
 
         // FIXME: we need to take reflections into account when determining whether this layer intersects the coverage rect.
-        m_intersectsCoverageRect = m_coverageRect.intersects(FloatRect(m_boundsOrigin, size()));
+        m_intersectsCoverageRect = !allowBackingStoreDetachment || m_coverageRect.intersects(FloatRect(m_boundsOrigin, size()));
 
         if (GraphicsLayerCA* maskLayer = downcast<GraphicsLayerCA>(m_maskLayer)) {
@@ -1301 +1302 @@
         }
     }
-    setVisibleAndCoverageRects(rects);
+    setVisibleAndCoverageRects(rects, m_allowsBackingStoreDetachment && commitState.ancestorsAllowBackingStoreDetachment);
 
 #ifdef VISIBLE_TILE_WASH
@@ -1344 +1345 @@
         affectedByTransformAnimation = true;
     }
+    
+    childCommitState.ancestorsAllowBackingStoreDetachment &= m_allowsBackingStoreDetachment;
 
     if (GraphicsLayerCA* maskLayer = downcast<GraphicsLayerCA>(m_maskLayer))
@@ -3626 +3629 @@
 }
 
+void GraphicsLayerCA::setAllowsBackingStoreDetachment(bool allowDetachment)
+{
+    if (allowDetachment == m_allowsBackingStoreDetachment)
+        return;
+
+    m_allowsBackingStoreDetachment = allowDetachment;
+    noteLayerPropertyChanged(CoverageRectChanged);
+}
+
 void GraphicsLayerCA::deviceOrPageScaleFactorChanged()
 {

trunk/Source/WebCore/platform/graphics/ca/GraphicsLayerCA.h

@@ -149 +149 @@
 
     struct CommitState {
-        bool ancestorHasTransformAnimation;
-        int treeDepth;
-        CommitState()
-            : ancestorHasTransformAnimation(false)
-            , treeDepth(0)
-        { }
+        int treeDepth { 0 };
+        bool ancestorHasTransformAnimation { false };
+        bool ancestorsAllowBackingStoreDetachment { true };
     };
     void recursiveCommitChanges(const CommitState&, const TransformState&, float pageScaleFactor = 1, const FloatPoint& positionRelativeToBase = FloatPoint(), bool affectedByPageScale = false);
@@ -197 +194 @@
 
     virtual bool isCommittingChanges() const override { return m_isCommittingChanges; }
+
+    WEBCORE_EXPORT virtual void setAllowsBackingStoreDetachment(bool) override;
+    WEBCORE_EXPORT virtual bool allowsBackingStoreDetachment() const override { return m_allowsBackingStoreDetachment; }
 
     WEBCORE_EXPORT virtual double backingStoreMemoryEstimate() const override;
@@ -294 +294 @@
     const FloatRect& coverageRect() const { return m_coverageRect; }
 
-    void setVisibleAndCoverageRects(const VisibleAndCoverageRects&);
+    void setVisibleAndCoverageRects(const VisibleAndCoverageRects&, bool allowBackingStoreDetachment);
     
     static FloatRect adjustTiledLayerVisibleRect(TiledBacking*, const FloatRect& oldVisibleRect, const FloatRect& newVisibleRect, const FloatSize& oldSize, const FloatSize& newSize);
@@ -511 +511 @@
     bool m_needsFullRepaint : 1;
     bool m_usingBackdropLayerType : 1;
+    bool m_allowsBackingStoreDetachment : 1;
     bool m_intersectsCoverageRect : 1;
 

trunk/Source/WebCore/rendering/RenderLayerBacking.cpp

@@ -1570 +1570 @@
 }
 
+void RenderLayerBacking::setIsScrollCoordinatedWithViewportConstrainedRole(bool viewportCoordinated)
+{
+    m_graphicsLayer->setAllowsBackingStoreDetachment(!viewportCoordinated);
+}
+
 GraphicsLayerPaintingPhase RenderLayerBacking::paintingPhaseForPrimaryLayer() const
 {

trunk/Source/WebCore/rendering/RenderLayerBacking.h

@@ -127 +127 @@
         case ViewportConstrained:
             m_viewportConstrainedNodeID = nodeID;
+            setIsScrollCoordinatedWithViewportConstrainedRole(nodeID);
             break;
         }
@@ -132 +133 @@
     
     ScrollingNodeID scrollingNodeIDForChildren() const { return m_scrollingNodeID ? m_scrollingNodeID : m_viewportConstrainedNodeID; }
+
+    void setIsScrollCoordinatedWithViewportConstrainedRole(bool);
 
     bool hasMaskLayer() const { return m_maskLayer != 0; }