Factor painting code out of RenderBox into a new class called BoxPainter.

Source/core/paint/BoxPainter.cpp

Index: Source/core/paint/BoxPainter.cpp
diff --git a/Source/core/paint/BoxPainter.cpp b/Source/core/paint/BoxPainter.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..c495937249fbb70ca7cc2725ccd5053d76e5a642
--- /dev/null
+++ b/Source/core/paint/BoxPainter.cpp
@@ -0,0 +1,241 @@
+// 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 "config.h"
+#include "core/paint/BoxPainter.h"
+
+#include "core/rendering/BoxDecorationData.h"
+#include "core/rendering/PaintInfo.h"
+#include "core/rendering/RenderBox.h"
+#include "core/rendering/RenderLayer.h"
+#include "core/rendering/RenderTable.h"
+#include "core/rendering/RenderTheme.h"
+#include "core/rendering/RenderView.h"
+#include "platform/geometry/LayoutPoint.h"
+#include "platform/graphics/GraphicsContextStateSaver.h"
+
+namespace blink {
+
+void BoxPainter::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    LayoutPoint adjustedPaintOffset = paintOffset + m_renderBox.location();
+    // default implementation. Just pass paint through to the children
+    PaintInfo childInfo(paintInfo);
+    childInfo.updatePaintingRootForChildren(&m_renderBox);
+    for (RenderObject* child = m_renderBox.slowFirstChild(); child; child = child->nextSibling())
+        child->paint(childInfo, adjustedPaintOffset);
+}
+
+void BoxPainter::paintBoxDecorationBackground(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    if (!paintInfo.shouldPaintWithinRoot(&m_renderBox))
+        return;
+
+    LayoutRect paintRect = m_renderBox.borderBoxRect();
+    paintRect.moveBy(paintOffset);
+    paintBoxDecorationBackgroundWithRect(paintInfo, paintOffset, paintRect);
+}
+
+void BoxPainter::paintBoxDecorationBackgroundWithRect(PaintInfo& paintInfo, const LayoutPoint& paintOffset, const LayoutRect& paintRect)
+{
+    RenderStyle* style = m_renderBox.style();
+    BoxDecorationData boxDecorationData(*style, m_renderBox.canRenderBorderImage(), m_renderBox.backgroundHasOpaqueTopLayer(), paintInfo.context);
+
+    // FIXME: Should eventually give the theme control over whether the box shadow should paint, since controls could have
+    // custom shadows of their own.
+    if (!m_renderBox.boxShadowShouldBeAppliedToBackground(boxDecorationData.bleedAvoidance))
+        m_renderBox.paintBoxShadow(paintInfo, paintRect, style, Normal);
+
+    GraphicsContextStateSaver stateSaver(*paintInfo.context, false);
+    if (boxDecorationData.bleedAvoidance == BackgroundBleedClipBackground) {
+        stateSaver.save();
+        RoundedRect border = style->getRoundedBorderFor(paintRect);
+        paintInfo.context->clipRoundedRect(border);
+    }
+
+    // If we have a native theme appearance, paint that before painting our background.
+    // The theme will tell us whether or not we should also paint the CSS background.
+    IntRect snappedPaintRect(pixelSnappedIntRect(paintRect));
+    bool themePainted = boxDecorationData.hasAppearance && !RenderTheme::theme().paint(&m_renderBox, paintInfo, snappedPaintRect);
+    if (!themePainted) {
+        if (boxDecorationData.bleedAvoidance == BackgroundBleedBackgroundOverBorder)
+            m_renderBox.paintBorder(paintInfo, paintRect, style, boxDecorationData.bleedAvoidance);
+
+        paintBackground(paintInfo, paintRect, boxDecorationData.backgroundColor, boxDecorationData.bleedAvoidance);
+
+        if (boxDecorationData.hasAppearance)
+            RenderTheme::theme().paintDecorations(&m_renderBox, paintInfo, snappedPaintRect);
+    }
+    m_renderBox.paintBoxShadow(paintInfo, paintRect, style, Inset);
+
+    // The theme will tell us whether or not we should also paint the CSS border.
+    if (boxDecorationData.hasBorder && boxDecorationData.bleedAvoidance != BackgroundBleedBackgroundOverBorder
+        && (!boxDecorationData.hasAppearance || (!themePainted && RenderTheme::theme().paintBorderOnly(&m_renderBox, paintInfo, snappedPaintRect)))
+        && !(m_renderBox.isTable() && toRenderTable(&m_renderBox)->collapseBorders()))
+        m_renderBox.paintBorder(paintInfo, paintRect, style, boxDecorationData.bleedAvoidance);
+}
+
+static bool skipBodyBackground(const RenderBox* bodyElementRenderer)
+{
+    ASSERT(bodyElementRenderer->isBody());
+    // The <body> only paints its background if the root element has defined a background independent of the body,
+    // or if the <body>'s parent is not the document element's renderer (e.g. inside SVG foreignObject).
+    RenderObject* documentElementRenderer = bodyElementRenderer->document().documentElement()->renderer();
+    return documentElementRenderer
+        && !documentElementRenderer->hasBackground()
+        && (documentElementRenderer == bodyElementRenderer->parent());
+}
+
+void BoxPainter::paintBackground(const PaintInfo& paintInfo, const LayoutRect& paintRect, const Color& backgroundColor, BackgroundBleedAvoidance bleedAvoidance)
+{
+    if (m_renderBox.isDocumentElement()) {
+        paintRootBoxFillLayers(paintInfo);
+        return;
+    }
+    if (m_renderBox.isBody() && skipBodyBackground(&m_renderBox))
+        return;
+    if (m_renderBox.boxDecorationBackgroundIsKnownToBeObscured())
+        return;
+    paintFillLayers(paintInfo, backgroundColor, m_renderBox.style()->backgroundLayers(), paintRect, bleedAvoidance);
+}
+
+void BoxPainter::paintRootBoxFillLayers(const PaintInfo& paintInfo)
+{
+    if (paintInfo.skipRootBackground())
+        return;
+
+    RenderObject* rootBackgroundRenderer = m_renderBox.rendererForRootBackground();
+
+    const FillLayer& bgLayer = rootBackgroundRenderer->style()->backgroundLayers();
+    Color bgColor = rootBackgroundRenderer->resolveColor(CSSPropertyBackgroundColor);
+
+    paintFillLayers(paintInfo, bgColor, bgLayer, m_renderBox.view()->backgroundRect(&m_renderBox), BackgroundBleedNone, CompositeSourceOver, rootBackgroundRenderer);
+}
+
+void BoxPainter::paintFillLayers(const PaintInfo& paintInfo, const Color& c, const FillLayer& fillLayer, const LayoutRect& rect,
+    BackgroundBleedAvoidance bleedAvoidance, CompositeOperator op, RenderObject* backgroundObject)
+{
+    Vector<const FillLayer*, 8> layers;
+    const FillLayer* curLayer = &fillLayer;
+    bool shouldDrawBackgroundInSeparateBuffer = false;
+    bool isBottomLayerOccluded = false;
+    while (curLayer) {
+        layers.append(curLayer);
+        // Stop traversal when an opaque layer is encountered.
+        // FIXME : It would be possible for the following occlusion culling test to be more aggressive
+        // on layers with no repeat by testing whether the image covers the layout rect.
+        // Testing that here would imply duplicating a lot of calculations that are currently done in
+        // RenderBoxModelObject::paintFillLayerExtended. A more efficient solution might be to move
+        // the layer recursion into paintFillLayerExtended, or to compute the layer geometry here
+        // and pass it down.
+
+        if (!shouldDrawBackgroundInSeparateBuffer && curLayer->blendMode() != WebBlendModeNormal)
+            shouldDrawBackgroundInSeparateBuffer = true;
+
+        // The clipOccludesNextLayers condition must be evaluated first to avoid short-circuiting.
+        if (curLayer->clipOccludesNextLayers(curLayer == &fillLayer)
+            && curLayer->hasOpaqueImage(&m_renderBox)
+            && curLayer->image()->canRender(m_renderBox, m_renderBox.style()->effectiveZoom())
+            && curLayer->hasRepeatXY()
+            && curLayer->blendMode() == WebBlendModeNormal
+            && !m_renderBox.boxShadowShouldBeAppliedToBackground(bleedAvoidance))
+            break;
+        curLayer = curLayer->next();
+    }
+
+    if (layers.size() > 0  && (**layers.rbegin()).next())
+        isBottomLayerOccluded = true;
+
+    GraphicsContext* context = paintInfo.context;
+    if (!context)
+        shouldDrawBackgroundInSeparateBuffer = false;
+
+    bool skipBaseColor = false;
+    if (shouldDrawBackgroundInSeparateBuffer) {
+        bool isBaseColorVisible = !isBottomLayerOccluded && c.hasAlpha();
+
+        // Paint the document's base background color outside the transparency layer,
+        // so that the background images don't blend with this color: http://crbug.com/389039.
+        if (isBaseColorVisible && m_renderBox.isDocumentElementWithOpaqueBackground()) {
+            m_renderBox.paintRootBackgroundColor(paintInfo, rect, Color());
+            skipBaseColor = true;
+        }
+        context->beginTransparencyLayer(1);
+    }
+
+    Vector<const FillLayer*>::const_reverse_iterator topLayer = layers.rend();
+    for (Vector<const FillLayer*>::const_reverse_iterator it = layers.rbegin(); it != topLayer; ++it)
+        paintFillLayer(paintInfo, c, **it, rect, bleedAvoidance, op, backgroundObject, skipBaseColor);
+
+    if (shouldDrawBackgroundInSeparateBuffer)
+        context->endLayer();
+}
+
+void BoxPainter::paintFillLayer(const PaintInfo& paintInfo, const Color& c, const FillLayer& fillLayer, const LayoutRect& rect,
+    BackgroundBleedAvoidance bleedAvoidance, CompositeOperator op, RenderObject* backgroundObject, bool skipBaseColor)
+{
+    m_renderBox.paintFillLayerExtended(paintInfo, c, fillLayer, rect, bleedAvoidance, 0, LayoutSize(), op, backgroundObject, skipBaseColor);
+}
+
+void BoxPainter::paintMask(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    if (!paintInfo.shouldPaintWithinRoot(&m_renderBox) || m_renderBox.style()->visibility() != VISIBLE || paintInfo.phase != PaintPhaseMask)
+        return;
+
+    LayoutRect paintRect = LayoutRect(paintOffset, m_renderBox.size());
+    paintMaskImages(paintInfo, paintRect);
+}
+
+void BoxPainter::paintMaskImages(const PaintInfo& paintInfo, const LayoutRect& paintRect)
+{
+    // Figure out if we need to push a transparency layer to render our mask.
+    bool pushTransparencyLayer = false;
+    bool compositedMask = m_renderBox.hasLayer() && m_renderBox.layer()->hasCompositedMask();
+    bool flattenCompositingLayers = m_renderBox.view()->frameView() && m_renderBox.view()->frameView()->paintBehavior() & PaintBehaviorFlattenCompositingLayers;
+    CompositeOperator compositeOp = CompositeSourceOver;
+
+    bool allMaskImagesLoaded = true;
+
+    if (!compositedMask || flattenCompositingLayers) {
+        pushTransparencyLayer = true;
+        StyleImage* maskBoxImage = m_renderBox.style()->maskBoxImage().image();
+        const FillLayer& maskLayers = m_renderBox.style()->maskLayers();
+
+        // Don't render a masked element until all the mask images have loaded, to prevent a flash of unmasked content.
+        if (maskBoxImage)
+            allMaskImagesLoaded &= maskBoxImage->isLoaded();
+
+        allMaskImagesLoaded &= maskLayers.imagesAreLoaded();
+
+        paintInfo.context->setCompositeOperation(CompositeDestinationIn);
+        paintInfo.context->beginTransparencyLayer(1);
+        compositeOp = CompositeSourceOver;
+    }
+
+    if (allMaskImagesLoaded) {
+        paintFillLayers(paintInfo, Color::transparent, m_renderBox.style()->maskLayers(), paintRect, BackgroundBleedNone, compositeOp);
+        m_renderBox.paintNinePieceImage(paintInfo.context, paintRect, m_renderBox.style(), m_renderBox.style()->maskBoxImage(), compositeOp);
+    }
+
+    if (pushTransparencyLayer)
+        paintInfo.context->endLayer();
+}
+
+void BoxPainter::paintClippingMask(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    if (!paintInfo.shouldPaintWithinRoot(&m_renderBox) || m_renderBox.style()->visibility() != VISIBLE || paintInfo.phase != PaintPhaseClippingMask)
+        return;
+
+    if (!m_renderBox.layer() || m_renderBox.layer()->compositingState() != PaintsIntoOwnBacking)
+        return;
+
+    // We should never have this state in this function. A layer with a mask
+    // should have always created its own backing if it became composited.
+    ASSERT(layer()->compositingState() != HasOwnBackingButPaintsIntoAncestor);
+
+    LayoutRect paintRect = LayoutRect(paintOffset, m_renderBox.size());
+    paintInfo.context->fillRect(pixelSnappedIntRect(paintRect), Color::black);
+}
+
+} // namespace blink