Paint solid color background into both scrolling contents layer and graphics layer.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 158 matching lines @@
   return (!page) ? nullptr : page->scrollingCoordinator();
 }
 
 CompositedLayerMapping::CompositedLayerMapping(PaintLayer& layer)
     : m_owningLayer(layer),
       m_contentOffsetInCompositingLayerDirty(false),
       m_pendingUpdateScope(GraphicsLayerUpdateNone),
       m_isMainFrameLayoutViewLayer(false),
       m_backgroundLayerPaintsFixedRootBackground(false),
       m_scrollingContentsAreEmpty(false),
-      m_backgroundPaintsOntoScrollingContentsLayer(false) {
+      m_backgroundPaintsOntoScrollingContentsLayer(false),
+      m_backgroundPaintsOntoGraphicsLayer(true) {

[chrishtr, 2016/11/17 20:55:39]

false

[flackr, 2016/11/17 23:38:00]

Done.

   if (layer.isRootLayer() && layoutObject()->frame()->isMainFrame())
     m_isMainFrameLayoutViewLayer = true;
 
   createPrimaryGraphicsLayer();
 }
 
 CompositedLayerMapping::~CompositedLayerMapping() {
   // Hits in compositing/squashing/squash-onto-nephew.html.
   DisableCompositingQueryAsserts disabler;
 
@@ skipping 164 matching lines @@
   ASSERT(m_owningLayer.stackingNode()->isStackingContext() || !isolate);
 
   m_graphicsLayer->setIsRootForIsolatedGroup(isolate);
 }
 
 void CompositedLayerMapping::
     updateBackgroundPaintsOntoScrollingContentsLayer() {
   // We can only paint the background onto the scrolling contents layer if
   // it would be visually correct and we are using composited scrolling meaning
   // we have a scrolling contents layer to paint it into.
+  BackgroundPaintLocation paintLocation =
+      m_owningLayer.backgroundPaintLocation();
   bool shouldPaintOntoScrollingContentsLayer =
-      m_owningLayer.canPaintBackgroundOntoScrollingContentsLayer() &&
+      paintLocation & BackgroundPaintInScrollingContents &&
       m_owningLayer.getScrollableArea()->usesCompositedScrolling();
   if (shouldPaintOntoScrollingContentsLayer !=
       backgroundPaintsOntoScrollingContentsLayer()) {
     m_backgroundPaintsOntoScrollingContentsLayer =
         shouldPaintOntoScrollingContentsLayer;
     // If the background is no longer painted onto the scrolling contents layer
     // the scrolling contents layer needs to be updated. If it is going to be
     // painted onto the scrolling contents layer this update will be triggered
     // by LayoutBoxModelObject::setBackingNeedsPaintInvalidationInRect
     if (hasScrollingLayer() && !shouldPaintOntoScrollingContentsLayer)
       m_scrollingContentsLayer->setNeedsDisplay();
   }
+  m_backgroundPaintsOntoGraphicsLayer =
+      !m_backgroundPaintsOntoScrollingContentsLayer ||
+      paintLocation & BackgroundPaintInGraphicsLayer;
 }
 
 void CompositedLayerMapping::updateContentsOpaque() {
   if (isAcceleratedCanvas(layoutObject())) {
     // Determine whether the rendering context's external texture layer is
     // opaque.
     CanvasRenderingContext* context =
         toHTMLCanvasElement(layoutObject()->node())->renderingContext();
     if (!context->creationAttributes().alpha())
       m_graphicsLayer->setContentsOpaque(true);
@@ skipping 13 matching lines @@
     if (hasScrollingLayer() && m_backgroundPaintsOntoScrollingContentsLayer) {
       // Backgrounds painted onto the foreground are clipped by the padding box
       // rect.
       // TODO(flackr): This should actually check the entire overflow rect
       // within the scrolling contents layer but since we currently only trigger
       // this for solid color backgrounds the answer will be the same.
       m_scrollingContentsLayer->setContentsOpaque(
           m_owningLayer.backgroundIsKnownToBeOpaqueInRect(
               toLayoutBox(layoutObject())->paddingBoxRect()));
 
-      // When we paint the background onto the scrolling contents layer we are
-      // going to leave a hole in the m_graphicsLayer where the background is so
-      // it is not opaque.
-      m_graphicsLayer->setContentsOpaque(false);
+      if (m_owningLayer.backgroundPaintLocation() &
+          BackgroundPaintInGraphicsLayer) {
+        m_graphicsLayer->setContentsOpaque(
+            m_owningLayer.backgroundIsKnownToBeOpaqueInRect(
+                compositedBounds()));
+      } else {
+        // If we only paint the background onto the scrolling contents layer we
+        // are going to leave a hole in the m_graphicsLayer where the background
+        // is so it is not opaque.
+        m_graphicsLayer->setContentsOpaque(false);
+      }
     } else {
       if (hasScrollingLayer())
         m_scrollingContentsLayer->setContentsOpaque(false);
       m_graphicsLayer->setContentsOpaque(
           m_owningLayer.backgroundIsKnownToBeOpaqueInRect(compositedBounds()));
     }
   }
 }
 
 void CompositedLayerMapping::updateCompositedBounds() {
@@ skipping 2545 matching lines @@
       graphicsLayer == m_maskLayer.get() ||
       graphicsLayer == m_childClippingMaskLayer.get() ||
       graphicsLayer == m_scrollingContentsLayer.get()) {
     bool paintRootBackgroundOntoScrollingContentsLayer =
         m_backgroundPaintsOntoScrollingContentsLayer;
     DCHECK(!paintRootBackgroundOntoScrollingContentsLayer ||
            (!m_backgroundLayer && !m_foregroundLayer));
     if (paintRootBackgroundOntoScrollingContentsLayer) {
       if (graphicsLayer == m_scrollingContentsLayer.get())
         paintLayerFlags &= ~PaintLayerPaintingSkipRootBackground;
-      else
+      else if (!m_backgroundPaintsOntoGraphicsLayer)
         paintLayerFlags |= PaintLayerPaintingSkipRootBackground;
     }
     GraphicsLayerPaintInfo paintInfo;
     paintInfo.paintLayer = &m_owningLayer;
     paintInfo.compositedBounds = compositedBounds();
     paintInfo.offsetFromLayoutObject = graphicsLayer->offsetFromLayoutObject();
     adjustForCompositedScrolling(graphicsLayer,
                                  paintInfo.offsetFromLayoutObject);
 
     // We have to use the same root as for hit testing, because both methods can
@@ skipping 260 matching lines @@
   } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
     name = "Scrolling Contents Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink