GraphicsContext culling support.

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 46 matching lines @@
 #include "core/rendering/RenderTableCell.h"
 #include "core/rendering/RenderTextControl.h"
 #include "core/rendering/RenderTextFragment.h"
 #include "core/rendering/RenderTheme.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/shapes/ShapeOutsideInfo.h"
 #include "core/rendering/style/ContentData.h"
 #include "core/rendering/style/RenderStyle.h"
 #include "platform/geometry/FloatQuad.h"
 #include "platform/geometry/TransformState.h"
+#include "platform/graphics/GraphicsContextCullSaver.h"
 #include "platform/graphics/GraphicsContextStateSaver.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/TemporaryChange.h"
 
 using namespace std;
 using namespace WTF;
 using namespace Unicode;
 
 namespace WebCore {
 
@@ skipping 1748 matching lines @@
 }
 
 void RenderBlock::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     ANNOTATE_GRAPHICS_CONTEXT(paintInfo, this);
 
     LayoutPoint adjustedPaintOffset = paintOffset + location();
 
     PaintPhase phase = paintInfo.phase;
 
+    LayoutRect overflowBox;
     // Check if we need to do anything at all.
     // FIXME: Could eliminate the isRoot() check if we fix background painting so that the RenderView
     // paints the root's background.
     if (!isRoot()) {
-        LayoutRect overflowBox = overflowRectForPaintRejection();
+        overflowBox = overflowRectForPaintRejection();
         flipForWritingMode(overflowBox);
         overflowBox.moveBy(adjustedPaintOffset);
         if (!overflowBox.intersects(paintInfo.rect))
             return;
     }
 
     // There are some cases where not all clipped visual overflow is accounted for.
     // FIXME: reduce the number of such cases.
     ContentsClipBehavior contentsClipBehavior = ForceContentsClip;
     if (hasOverflowClip() && !hasControlClip() && !(shouldPaintSelectionGaps() && phase == PaintPhaseForeground) && !hasCaret())
         contentsClipBehavior = SkipContentsClipIfPossible;
 
     bool pushedClip = pushContentsClip(paintInfo, adjustedPaintOffset, contentsClipBehavior);
-    paintObject(paintInfo, adjustedPaintOffset);
+    {
+        GraphicsContextCullSaver cullSaver(*paintInfo.context);
+        // Cull if we have more than one child and we didn't already clip.
+        bool shouldCull = document().settings()->containerCullingEnabled() && !pushedClip && !isRoot()
+            && firstChild() && lastChild() && firstChild() != lastChild();
+        if (shouldCull)
+            cullSaver.cull(overflowBox);
+
+        paintObject(paintInfo, adjustedPaintOffset);
+    }
     if (pushedClip)
         popContentsClip(paintInfo, phase, adjustedPaintOffset);
 
     // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
     // z-index.  We paint after we painted the background/border, so that the scrollbars will
     // sit above the background/border.
     if (hasOverflowClip() && style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && paintInfo.shouldPaintWithinRoot(this) && !paintInfo.paintRootBackgroundOnly())
         layer()->scrollableArea()->paintOverflowControls(paintInfo.context, roundedIntPoint(adjustedPaintOffset), paintInfo.rect, false /* paintingOverlayControls */);
 }
 
@@ skipping 3161 matching lines @@
 void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
 {
     showRenderObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace WebCore