Add support for accelerated fixed root background

Source/WebCore/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 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 1216 matching lines @@
 
 void RenderLayerCompositor::frameViewDidLayout()
 {
     RenderLayerBacking* renderViewBacking = m_renderView->layer()->backing();
     if (renderViewBacking)
         renderViewBacking->adjustTiledBackingCoverage();
 }
 
 void RenderLayerCompositor::rootFixedBackgroundsChanged()
 {
-    RenderLayerBacking* renderViewBacking = m_renderView->layer()->backing();
-    if (renderViewBacking && renderViewBacking->usingTiledBacking())
+    if (supportsFixedRootBackgroundCompositing())
         setCompositingLayersNeedRebuild();
 }
 
 void RenderLayerCompositor::scrollingLayerDidChange(RenderLayer* layer)
 {
     if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
         scrollingCoordinator->scrollableAreaScrollLayerDidChange(layer);
 }
 
+void RenderLayerCompositor::fixedRootBackgroundLayerChanged()
+{
+    GraphicsLayer* backgroundLayer = fixedRootBackgroundLayer();
+    if (!backgroundLayer)
+        return;
+
+    // FIXME: there must be a better way to insert this layer into the tree.

[jamesr, 2013/04/09 19:45:48]

yes, please figure out a better way. are the layers you want to be positioned
relative to members of RenderLayerCompositor?

+    // We'll also have to unhook it at some point.
+    GraphicsLayer* root = m_rootContentLayer.get();
+    while (root && root->parent())
+        root = root->parent();
+
+    GraphicsLayer* frameClippingLayer = root->children()[0];
+    GraphicsLayer* frameScrollingLayer = frameClippingLayer->children()[0];
+    GraphicsLayer* nonCompositedContentLayer = frameScrollingLayer->children()[0];
+
+    // ??? Would we ever want to draw in both the NCCH *and* the fixed root bg?
+    // If so, it seems like we're toast. We have to make this layer invisible
+    // so that the fixed root bg can show through.
+    nonCompositedContentLayer->setDrawsContent(false);
+
+    frameClippingLayer->addChildAtIndex(backgroundLayer, 0);
+}
+
 String RenderLayerCompositor::layerTreeAsText(LayerTreeFlags flags)
 {
     updateCompositingLayers(CompositingUpdateAfterLayout);
 
     if (!m_rootContentLayer)
         return String();
 
     flushPendingLayerChanges(true);
 
     LayerTreeAsTextBehavior layerTreeBehavior = LayerTreeAsTextBehaviorNormal;
     if (flags & LayerTreeFlagsIncludeDebugInfo)
         layerTreeBehavior |= LayerTreeAsTextDebug;
     if (flags & LayerTreeFlagsIncludeVisibleRects)
         layerTreeBehavior |= LayerTreeAsTextIncludeVisibleRects;
     if (flags & LayerTreeFlagsIncludeTileCaches)
         layerTreeBehavior |= LayerTreeAsTextIncludeTileCaches;
     if (flags & LayerTreeFlagsIncludeRepaintRects)
         layerTreeBehavior |= LayerTreeAsTextIncludeRepaintRects;
     if (flags & LayerTreeFlagsIncludePaintingPhases)
         layerTreeBehavior |= LayerTreeAsTextIncludePaintingPhases;
 
     // We skip dumping the scroll and clip layers to keep layerTreeAsText output
     // similar between platforms.
-    String layerTreeText = m_rootContentLayer->layerTreeAsText(layerTreeBehavior);
+    GraphicsLayer* layer = m_rootContentLayer.get();
+    while (layer && layer->parent())
+        layer = layer->parent();
+    //String layerTreeText = m_rootContentLayer->layerTreeAsText(layerTreeBehavior);
+    String layerTreeText = layer->layerTreeAsText(layerTreeBehavior);
 
     // The true root layer is not included in the dump, so if we want to report
     // its repaint rects, they must be included here.
     if (flags & LayerTreeFlagsIncludeRepaintRects) {
         String layerTreeTextWithRootRepaintRects = m_renderView->frameView()->trackedRepaintRectsAsText();
         layerTreeTextWithRootRepaintRects.append(layerTreeText);
         return layerTreeTextWithRootRepaintRects;
     }
 
     return layerTreeText;
@@ skipping 948 matching lines @@
 #if PLATFORM(CHROMIUM) && ENABLE(RUBBER_BANDING)
     } else if (graphicsLayer == layerForOverhangAreas()) {
         ScrollView* view = m_renderView->frameView();
         view->calculateAndPaintOverhangAreas(&context, clip);
 #endif
     }
 }
 
 bool RenderLayerCompositor::supportsFixedRootBackgroundCompositing() const
 {
-    RenderLayerBacking* renderViewBacking = m_renderView->layer()->backing();
-    return renderViewBacking && renderViewBacking->usingTiledBacking();
+    return m_renderView->document()->settings() &&
+           m_renderView->document()->settings()->acceleratedCompositingForFixedRootBackgroundEnabled();
 }
 
 bool RenderLayerCompositor::needsFixedRootBackgroundLayer(const RenderLayer* layer) const
 {
     if (layer != m_renderView->layer())
         return false;
 
     return supportsFixedRootBackgroundCompositing() && m_renderView->rootBackgroundIsEntirelyFixed();
 }
 
@@ skipping 791 matching lines @@
     info.addMember(m_layerForBottomOverhangArea, "layerForBottomOverhangArea");
     info.addMember(m_layerForHeader, "layerForHeader");
     info.addMember(m_layerForFooter, "layerForFooter");
 #endif
     info.addMember(m_layerUpdater, "layerUpdater");
 }
 
 } // namespace WebCore
 
 #endif // USE(ACCELERATED_COMPOSITING)