Paint local background colors onto foreground layer.

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintLayerPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutView.h"
@@ skipping 247 matching lines @@
 {
     ASSERT(m_paintLayer.isSelfPaintingLayer() || m_paintLayer.hasSelfPaintingLayerDescendant());
     ASSERT(!(paintFlags & PaintLayerAppliedTransform));
 
     bool isSelfPaintingLayer = m_paintLayer.isSelfPaintingLayer();
     bool isPaintingOverlayScrollbars = paintFlags & PaintLayerPaintingOverlayScrollbars;
     bool isPaintingScrollingContent = paintFlags & PaintLayerPaintingCompositingScrollingPhase;
     bool isPaintingCompositedForeground = paintFlags & PaintLayerPaintingCompositingForegroundPhase;
     bool isPaintingCompositedBackground = paintFlags & PaintLayerPaintingCompositingBackgroundPhase;
     bool isPaintingOverflowContents = paintFlags & PaintLayerPaintingOverflowContents;
+    bool isPaintingBackgroundOntoForeground = paintFlags & PaintLayerPaintingBackgroundOntoForeground;
     // Outline always needs to be painted even if we have no visible content. Also,
     // the outline is painted in the background phase during composited scrolling.
     // If it were painted in the foreground phase, it would move with the scrolled
     // content. When not composited scrolling, the outline is painted in the
     // foreground phase. Since scrolled contents are moved by paint invalidation in this
     // case, the outline won't get 'dragged along'.
     bool shouldPaintSelfOutline = isSelfPaintingLayer && !isPaintingOverlayScrollbars
         && ((isPaintingScrollingContent && isPaintingCompositedBackground)
             || (!isPaintingScrollingContent && isPaintingCompositedForeground))
         && m_paintLayer.layoutObject()->styleRef().hasOutline();
@@ skipping 96 matching lines @@
             ASSERT(objectPaintProperties && objectPaintProperties->localBorderBoxProperties());
             PaintChunkProperties properties(context.getPaintController().currentPaintChunkProperties());
             auto& localBorderBoxProperties = *objectPaintProperties->localBorderBoxProperties();
             properties.transform = localBorderBoxProperties.propertyTreeState.transform;
             properties.clip = localBorderBoxProperties.propertyTreeState.clip;
             properties.effect = localBorderBoxProperties.propertyTreeState.effect;
             properties.backfaceHidden = m_paintLayer.layoutObject()->hasHiddenBackface();
             scopedPaintChunkProperties.emplace(context.getPaintController(), m_paintLayer, properties);
         }
 
-        bool shouldPaintBackground = isPaintingCompositedBackground && shouldPaintContent && !selectionOnly;
+        bool shouldPaintBackground = shouldPaintContent && !selectionOnly
+            && ((isPaintingBackgroundOntoForeground && isPaintingCompositedForeground)
+                || isPaintingCompositedBackground);
         bool shouldPaintNegZOrderList = (isPaintingScrollingContent && isPaintingOverflowContents) || (!isPaintingScrollingContent && isPaintingCompositedBackground);
         bool shouldPaintOwnContents = isPaintingCompositedForeground && shouldPaintContent;
         bool shouldPaintNormalFlowAndPosZOrderLists = isPaintingCompositedForeground;
         bool shouldPaintOverlayScrollbars = isPaintingOverlayScrollbars;
 
         if (shouldPaintBackground) {
             paintBackgroundForFragments(layerFragments, context, paintingInfo.paintDirtyRect,
                 localPaintingInfo, paintFlags);
         }
 
@@ skipping 344 matching lines @@
         clipRecorder.emplace(context, *m_paintLayer.layoutObject(), DisplayItem::ClipLayerForeground, layerFragments[0].foregroundRect, &localPaintingInfo, layerFragments[0].paginationOffset, paintFlags);
         clipState = HasClipped;
     }
 
     // We have to loop through every fragment multiple times, since we have to issue paint invalidations in each specific phase in order for
     // interleaving of the fragments to work properly.
     if (selectionOnly) {
         paintForegroundForFragmentsWithPhase(PaintPhaseSelection, layerFragments, context, localPaintingInfo, paintFlags, clipState);
     } else {
         if (!RuntimeEnabledFeatures::paintOptimizationsEnabled() || m_paintLayer.needsPaintPhaseDescendantBlockBackgrounds())
-            paintForegroundForFragmentsWithPhase(PaintPhaseDescendantBlockBackgroundsOnly, layerFragments, context, localPaintingInfo, paintFlags, clipState);
+            paintForegroundForFragmentsWithPhase(PaintPhaseDescendantBlockBackgroundsOnly, layerFragments, context, localPaintingInfo, paintFlags & ~PaintLayerPaintingBackgroundOntoForeground, clipState);

[flackr, 2016/08/03 15:33:13]

I missed earlier that we don't descend into children from the above paint call,
we paint descendant backgrounds in a separate phase here. We can just remove
PaintLayerPaintingBackgroundOntoForeground here. WDYT?

[chrishtr, 2016/08/03 16:44:48]

Rename to PaintLayerPaintingRootBackgroundOntoForeground then?

[flackr, 2016/08/03 17:47:10]

Done.

         if (!RuntimeEnabledFeatures::paintOptimizationsEnabled() || m_paintLayer.needsPaintPhaseFloat())
             paintForegroundForFragmentsWithPhase(PaintPhaseFloat, layerFragments, context, localPaintingInfo, paintFlags, clipState);
         paintForegroundForFragmentsWithPhase(PaintPhaseForeground, layerFragments, context, localPaintingInfo, paintFlags, clipState);
         if (!RuntimeEnabledFeatures::paintOptimizationsEnabled() || m_paintLayer.needsPaintPhaseDescendantOutlines())
             paintForegroundForFragmentsWithPhase(PaintPhaseDescendantOutlinesOnly, layerFragments, context, localPaintingInfo, paintFlags, clipState);
     }
 }
 
 void PaintLayerPainter::paintForegroundForFragmentsWithPhase(PaintPhase phase,
     const PaintLayerFragments& layerFragments, GraphicsContext& context,
@@ skipping 49 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     PaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize());
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink