root/Source/core/rendering/compositing/CompositedLayerMapping.cpp

DEFINITIONS

1. contentsRect
2. backgroundRect
3. isAcceleratedCanvas
4. hasBoxDecorations
5. hasBoxDecorationsOrBackgroundImage
6. contentLayerSupportsDirectBackgroundComposition
7. platformLayerForPlugin
8. isAcceleratedContents
9. scrollingCoordinatorFromLayer
10. m_needToUpdateGraphicsLayerOfAllDecendants
11. createGraphicsLayer
12. createPrimaryGraphicsLayer
13. destroyGraphicsLayers
14. updateOpacity
15. updateTransform
16. updateFilters
17. updateLayerBlendMode
18. updateIsRootForIsolatedGroup
19. updateHasGpuRasterizationHint
20. updateContentsOpaque
21. hasNonZeroTransformOrigin
22. layerOrAncestorIsTransformedOrUsingCompositedScrolling
23. shouldClipCompositedBounds
24. updateCompositedBounds
25. updateAfterWidgetResize
26. updateCompositingReasons
27. updateGraphicsLayerConfiguration
28. clipBox
29. computeOffsetFromCompositedAncestor
30. adjustBoundsForSubPixelAccumulation
31. updateSquashingLayerGeometry
32. updateGraphicsLayerGeometry
33. registerScrollingLayers
34. updateInternalHierarchy
35. updateContentsRect
36. updateDrawsContent
37. updateChildrenTransform
38. updateClippingLayers
39. updateChildTransformLayer
40. setBackgroundLayerPaintsFixedRootBackground
41. toggleScrollbarLayerIfNeeded
42. updateOverflowControlsLayers
43. positionOverflowControlsLayers
44. hasUnpositionedOverflowControlsLayers
45. ApplyToGraphicsLayers
46. updateRenderingContext
47. updateShouldFlattenTransform
48. updateForegroundLayer
49. updateBackgroundLayer
50. updateMaskLayer
51. updateClippingMaskLayers
52. updateScrollingLayers
53. updateScrollParentForGraphicsLayer
54. updateScrollParent
55. updateClipParent
56. updateSquashingLayers
57. paintingPhaseForPrimaryLayer
58. compositingOpacity
59. rendererBackgroundColor
60. updateBackgroundColor
61. paintsChildren
62. isCompositedPlugin
63. hasVisibleNonCompositingDescendant
64. hasVisibleNonCompositingDescendantLayers
65. containsPaintedContent
66. isDirectlyCompositedImage
67. contentChanged
68. updateImageContents
69. computeTransformOrigin
70. computePerspectiveOrigin
71. contentOffsetInCompostingLayer
72. contentsBox
73. parentForSublayers
74. localRootForOwningLayer
75. childForSuperlayers
76. layerForChildrenTransform
77. updateRequiresOwnBackingStoreForAncestorReasons
78. updateRequiresOwnBackingStoreForIntrinsicReasons
79. paintsIntoCompositedAncestorChanged
80. setBlendMode
81. setNeedsGraphicsLayerUpdate
82. updateTypeForChildren
83. clearNeedsGraphicsLayerUpdate
84. assertNeedsToUpdateGraphicsLayerBitsCleared
85. setContentsNeedDisplay
86. setContentsNeedDisplayInRect
87. doPaintTask
88. paintScrollbar
89. paintContents
90. isTrackingRepaints
91. collectTrackedRepaintRects
92. verifyNotPainting
93. notifyAnimationStarted
94. pixelSnappedCompositedBounds
95. updateSquashingLayerAssignment
96. removeRenderLayerFromSquashingGraphicsLayer
97. finishAccumulatingSquashingLayers
98. debugName

/*
 * 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
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"

#include "core/rendering/compositing/CompositedLayerMapping.h"

#include "CSSPropertyNames.h"
#include "HTMLNames.h"
#include "RuntimeEnabledFeatures.h"
#include "core/animation/ActiveAnimations.h"
#include "core/fetch/ImageResource.h"
#include "core/html/HTMLIFrameElement.h"
#include "core/html/HTMLMediaElement.h"
#include "core/html/canvas/CanvasRenderingContext.h"
#include "core/inspector/InspectorInstrumentation.h"
#include "core/page/Chrome.h"
#include "core/frame/FrameView.h"
#include "core/frame/Settings.h"
#include "core/page/scrolling/ScrollingCoordinator.h"
#include "core/plugins/PluginView.h"
#include "core/rendering/FilterEffectRenderer.h"
#include "core/rendering/RenderApplet.h"
#include "core/rendering/RenderEmbeddedObject.h"
#include "core/rendering/RenderIFrame.h"
#include "core/rendering/RenderImage.h"
#include "core/rendering/RenderLayerStackingNodeIterator.h"
#include "core/rendering/RenderVideo.h"
#include "core/rendering/RenderView.h"
#include "core/rendering/compositing/GraphicsLayerUpdater.h"
#include "core/rendering/compositing/RenderLayerCompositor.h"
#include "core/rendering/style/KeyframeList.h"
#include "platform/LengthFunctions.h"
#include "platform/fonts/FontCache.h"
#include "platform/graphics/GraphicsContext.h"
#include "wtf/CurrentTime.h"
#include "wtf/text/StringBuilder.h"

using namespace std;

namespace WebCore {

using namespace HTMLNames;

static IntRect clipBox(RenderBox* renderer);

static IntRect contentsRect(const RenderObject* renderer)
{
    if (!renderer->isBox())
        return IntRect();

    return renderer->isVideo() ?
        toRenderVideo(renderer)->videoBox() :
        pixelSnappedIntRect(toRenderBox(renderer)->contentBoxRect());
}

static IntRect backgroundRect(const RenderObject* renderer)
{
    if (!renderer->isBox())
        return IntRect();

    LayoutRect rect;
    const RenderBox* box = toRenderBox(renderer);
    EFillBox clip = box->style()->backgroundClip();
    switch (clip) {
    case BorderFillBox:
        rect = box->borderBoxRect();
        break;
    case PaddingFillBox:
        rect = box->paddingBoxRect();
        break;
    case ContentFillBox:
        rect = box->contentBoxRect();
        break;
    case TextFillBox:
        break;
    }

    return pixelSnappedIntRect(rect);
}

static inline bool isAcceleratedCanvas(const RenderObject* renderer)
{
    if (renderer->isCanvas()) {
        HTMLCanvasElement* canvas = toHTMLCanvasElement(renderer->node());
        if (CanvasRenderingContext* context = canvas->renderingContext())
            return context->isAccelerated();
    }
    return false;
}

static bool hasBoxDecorations(const RenderStyle* style)
{
    return style->hasBorder() || style->hasBorderRadius() || style->hasOutline() || style->hasAppearance() || style->boxShadow() || style->hasFilter();
}

static bool hasBoxDecorationsOrBackgroundImage(const RenderStyle* style)
{
    return hasBoxDecorations(style) || style->hasBackgroundImage();
}

static bool contentLayerSupportsDirectBackgroundComposition(const RenderObject* renderer)
{
    // No support for decorations - border, border-radius or outline.
    // Only simple background - solid color or transparent.
    if (hasBoxDecorationsOrBackgroundImage(renderer->style()))
        return false;

    // If there is no background, there is nothing to support.
    if (!renderer->style()->hasBackground())
        return true;

    // Simple background that is contained within the contents rect.
    return contentsRect(renderer).contains(backgroundRect(renderer));
}

static blink::WebLayer* platformLayerForPlugin(RenderObject* renderer)
{
    if (!renderer->isEmbeddedObject())
        return 0;
    Widget* widget = toRenderEmbeddedObject(renderer)->widget();
    if (!widget || !widget->isPluginView())
        return 0;
    return toPluginView(widget)->platformLayer();

}

static inline bool isAcceleratedContents(RenderObject* renderer)
{
    return isAcceleratedCanvas(renderer)
        || (renderer->isEmbeddedObject() && toRenderEmbeddedObject(renderer)->requiresAcceleratedCompositing())
        || renderer->isVideo();
}

// Get the scrolling coordinator in a way that works inside CompositedLayerMapping's destructor.
static ScrollingCoordinator* scrollingCoordinatorFromLayer(RenderLayer& layer)
{
    Page* page = layer.renderer()->frame()->page();
    if (!page)
        return 0;

    return page->scrollingCoordinator();
}

CompositedLayerMapping::CompositedLayerMapping(RenderLayer& layer)
    : m_owningLayer(layer)
    , m_artificiallyInflatedBounds(false)
    , m_isMainFrameRenderViewLayer(false)
    , m_requiresOwnBackingStoreForIntrinsicReasons(true)
    , m_requiresOwnBackingStoreForAncestorReasons(true)
    , m_canCompositeFilters(false)
    , m_backgroundLayerPaintsFixedRootBackground(false)
    , m_needToUpdateGraphicsLayer(false)
    , m_needToUpdateGraphicsLayerOfAllDecendants(false)
{
    if (layer.isRootLayer() && renderer()->frame()->isMainFrame())
        m_isMainFrameRenderViewLayer = true;

    createPrimaryGraphicsLayer();
}

CompositedLayerMapping::~CompositedLayerMapping()
{
    // Do not leave the destroyed pointer dangling on any RenderLayers that painted to this mapping's squashing layer.
    for (size_t i = 0; i < m_squashedLayers.size(); ++i) {
        RenderLayer* oldSquashedLayer = m_squashedLayers[i].renderLayer;
        if (oldSquashedLayer->groupedMapping() == this) {
            oldSquashedLayer->setGroupedMapping(0, true);
            oldSquashedLayer->setLostGroupedMapping(true);
        }
    }

    updateClippingLayers(false, false);
    updateOverflowControlsLayers(false, false, false);
    updateChildTransformLayer(false);
    updateForegroundLayer(false);
    updateBackgroundLayer(false);
    updateMaskLayer(false);
    updateClippingMaskLayers(false);
    updateScrollingLayers(false);
    updateSquashingLayers(false);
    destroyGraphicsLayers();
}

PassOwnPtr<GraphicsLayer> CompositedLayerMapping::createGraphicsLayer(CompositingReasons reasons)
{
    GraphicsLayerFactory* graphicsLayerFactory = 0;
    if (Page* page = renderer()->frame()->page())
        graphicsLayerFactory = page->chrome().client().graphicsLayerFactory();

    OwnPtr<GraphicsLayer> graphicsLayer = GraphicsLayer::create(graphicsLayerFactory, this);

    graphicsLayer->setCompositingReasons(reasons);

    return graphicsLayer.release();
}

void CompositedLayerMapping::createPrimaryGraphicsLayer()
{
    m_graphicsLayer = createGraphicsLayer(m_owningLayer.compositingReasons());

#if !OS(ANDROID)
    if (m_isMainFrameRenderViewLayer)
        m_graphicsLayer->contentLayer()->setDrawCheckerboardForMissingTiles(true);
#endif

    updateOpacity(renderer()->style());
    updateTransform(renderer()->style());
    updateFilters(renderer()->style());
    updateHasGpuRasterizationHint(renderer()->style());

    if (RuntimeEnabledFeatures::cssCompositingEnabled()) {
        updateLayerBlendMode(renderer()->style());
        updateIsRootForIsolatedGroup();
    }
}

void CompositedLayerMapping::destroyGraphicsLayers()
{
    if (m_graphicsLayer)
        m_graphicsLayer->removeFromParent();

    m_ancestorClippingLayer = nullptr;
    m_graphicsLayer = nullptr;
    m_foregroundLayer = nullptr;
    m_backgroundLayer = nullptr;
    m_childContainmentLayer = nullptr;
    m_childTransformLayer = nullptr;
    m_maskLayer = nullptr;
    m_childClippingMaskLayer = nullptr;

    m_scrollingLayer = nullptr;
    m_scrollingContentsLayer = nullptr;
}

void CompositedLayerMapping::updateOpacity(const RenderStyle* style)
{
    m_graphicsLayer->setOpacity(compositingOpacity(style->opacity()));
}

void CompositedLayerMapping::updateTransform(const RenderStyle* style)
{
    // FIXME: This could use m_owningLayer.transform(), but that currently has transform-origin
    // baked into it, and we don't want that.
    TransformationMatrix t;
    if (m_owningLayer.hasTransform()) {
        style->applyTransform(t, toRenderBox(renderer())->pixelSnappedBorderBoxRect().size(), RenderStyle::ExcludeTransformOrigin);
        makeMatrixRenderable(t, compositor()->canRender3DTransforms());
    }

    m_graphicsLayer->setTransform(t);
}

void CompositedLayerMapping::updateFilters(const RenderStyle* style)
{
    bool didCompositeFilters = m_canCompositeFilters;
    m_canCompositeFilters = m_graphicsLayer->setFilters(owningLayer().computeFilterOperations(style));
    if (didCompositeFilters != m_canCompositeFilters) {
        //
        // If filters used to be painted in software and are now painted in the compositor, we need to:
        // (1) Remove the FilterEffectRenderer, which was used for painting filters in software.
        // (2) Repaint the layer contents to remove the software-applied filter because the compositor will apply it.
        //
        // Similarly, if filters used to be painted in the compositor and are now painted in software, we need to:
        // (1) Create a FilterEffectRenderer.
        // (2) Repaint the layer contents to apply a software filter because the compositor won't apply it.
        //
        m_owningLayer.updateOrRemoveFilterEffectRenderer();
        setContentsNeedDisplay();
    }
}

void CompositedLayerMapping::updateLayerBlendMode(const RenderStyle* style)
{
    setBlendMode(style->blendMode());
}

void CompositedLayerMapping::updateIsRootForIsolatedGroup()
{
    bool isolate = m_owningLayer.shouldIsolateCompositedDescendants();

    // non stacking context layers should never isolate
    ASSERT(m_owningLayer.stackingNode()->isStackingContext() || !isolate);

    m_graphicsLayer->setIsRootForIsolatedGroup(isolate);
}

void CompositedLayerMapping::updateHasGpuRasterizationHint(const RenderStyle* style)
{
    m_graphicsLayer->setHasGpuRasterizationHint(style->hasWillChangeGpuRasterizationHint());
}

void CompositedLayerMapping::updateContentsOpaque()
{
    // For non-root layers, background is always painted by the primary graphics layer.
    ASSERT(m_isMainFrameRenderViewLayer || !m_backgroundLayer);
    if (m_backgroundLayer) {
        m_graphicsLayer->setContentsOpaque(false);
        m_backgroundLayer->setContentsOpaque(m_owningLayer.backgroundIsKnownToBeOpaqueInRect(compositedBounds()));
    } else {
        m_graphicsLayer->setContentsOpaque(m_owningLayer.backgroundIsKnownToBeOpaqueInRect(compositedBounds()));
    }
}

static bool hasNonZeroTransformOrigin(const RenderObject* renderer)
{
    RenderStyle* style = renderer->style();
    return (style->transformOriginX().type() == Fixed && style->transformOriginX().value())
        || (style->transformOriginY().type() == Fixed && style->transformOriginY().value());
}

static bool layerOrAncestorIsTransformedOrUsingCompositedScrolling(RenderLayer* layer)
{
    for (RenderLayer* curr = layer; curr; curr = curr->parent()) {
        if (curr->hasTransform() || curr->needsCompositedScrolling())
            return true;
    }

    return false;
}

bool CompositedLayerMapping::shouldClipCompositedBounds() const
{
    // Scrollbar layers use this layer for relative positioning, so don't clip.
    if (layerForHorizontalScrollbar() || layerForVerticalScrollbar())
        return false;

    if (layerOrAncestorIsTransformedOrUsingCompositedScrolling(&m_owningLayer))
        return false;

    // Scrolled composited layers are clipped by their ancestor clipping layer,
    // so don't clip these, either.
    if (!compositor()->clippedByAncestor(&m_owningLayer))
        return true;

    if (m_owningLayer.renderer()->containingBlock()->enclosingLayer() != m_owningLayer.ancestorScrollingLayer())
        return true;

    return false;
}

void CompositedLayerMapping::updateCompositedBounds(GraphicsLayerUpdater::UpdateType updateType)
{
    if (!shouldUpdateGraphicsLayer(updateType))
        return;

    // We need to know if we draw content in order to update our bounds (this has an effect
    // on whether or not descendands will paint into our backing). Update this value now.
    updateDrawsContent();

    LayoutRect layerBounds = compositor()->calculateCompositedBounds(&m_owningLayer, &m_owningLayer);

    // Clip to the size of the document or enclosing overflow-scroll layer.
    // If this or an ancestor is transformed, we can't currently compute the correct rect to intersect with.
    // We'd need RenderObject::convertContainerToLocalQuad(), which doesn't yet exist.
    if (shouldClipCompositedBounds()) {
        RenderView* view = m_owningLayer.renderer()->view();
        RenderLayer* rootLayer = view->layer();

        LayoutRect clippingBounds;
        if (renderer()->style()->position() == FixedPosition && renderer()->container() == view)
            clippingBounds = view->frameView()->viewportConstrainedVisibleContentRect();
        else
            clippingBounds = view->unscaledDocumentRect();

        if (&m_owningLayer != rootLayer)
            clippingBounds.intersect(m_owningLayer.clipper().backgroundClipRect(ClipRectsContext(rootLayer, AbsoluteClipRects)).rect());

        LayoutPoint delta;
        m_owningLayer.convertToLayerCoords(rootLayer, delta);
        clippingBounds.move(-delta.x(), -delta.y());

        layerBounds.intersect(clippingBounds);
    }

    // If the element has a transform-origin that has fixed lengths, and the renderer has zero size,
    // then we need to ensure that the compositing layer has non-zero size so that we can apply
    // the transform-origin via the GraphicsLayer anchorPoint (which is expressed as a fractional value).
    if (layerBounds.isEmpty() && hasNonZeroTransformOrigin(renderer())) {
        layerBounds.setWidth(1);
        layerBounds.setHeight(1);
        m_artificiallyInflatedBounds = true;
    } else {
        m_artificiallyInflatedBounds = false;
    }

    m_compositedBounds = layerBounds;
}

void CompositedLayerMapping::updateAfterWidgetResize()
{
    if (renderer()->isRenderPart()) {
        if (RenderLayerCompositor* innerCompositor = RenderLayerCompositor::frameContentsCompositor(toRenderPart(renderer()))) {
            innerCompositor->frameViewDidChangeSize();
            // We can floor this point because our frameviews are always aligned to pixel boundaries.
            ASSERT(contentsBox().location() == flooredIntPoint(contentsBox().location()));
            innerCompositor->frameViewDidChangeLocation(flooredIntPoint(contentsBox().location()));
        }
    }
}

void CompositedLayerMapping::updateCompositingReasons()
{
    // All other layers owned by this mapping will have the same compositing reason
    // for their lifetime, so they are initialized only when created.
    m_graphicsLayer->setCompositingReasons(m_owningLayer.compositingReasons());
}

bool CompositedLayerMapping::updateGraphicsLayerConfiguration(GraphicsLayerUpdater::UpdateType updateType)
{
    if (!shouldUpdateGraphicsLayer(updateType))
        return false;

    RenderLayerCompositor* compositor = this->compositor();
    RenderObject* renderer = this->renderer();

    m_owningLayer.updateDescendantDependentFlags();
    m_owningLayer.stackingNode()->updateZOrderLists();

    bool layerConfigChanged = false;
    setBackgroundLayerPaintsFixedRootBackground(compositor->needsFixedRootBackgroundLayer(&m_owningLayer));

    // The background layer is currently only used for fixed root backgrounds.
    if (updateBackgroundLayer(m_backgroundLayerPaintsFixedRootBackground))
        layerConfigChanged = true;

    if (updateForegroundLayer(compositor->needsContentsCompositingLayer(&m_owningLayer)))
        layerConfigChanged = true;

    bool needsDescendantsClippingLayer = compositor->clipsCompositingDescendants(&m_owningLayer);

    // Our scrolling layer will clip.
    if (m_owningLayer.needsCompositedScrolling())
        needsDescendantsClippingLayer = false;

    RenderLayer* scrollParent = renderer->compositorDrivenAcceleratedScrollingEnabled() ? m_owningLayer.scrollParent() : 0;
    bool needsAncestorClip = compositor->clippedByAncestor(&m_owningLayer);
    if (scrollParent) {
        // If our containing block is our ancestor scrolling layer, then we'll already be clipped
        // to it via our scroll parent and we don't need an ancestor clipping layer.
        if (m_owningLayer.renderer()->containingBlock()->enclosingLayer() == m_owningLayer.ancestorCompositedScrollingLayer())
            needsAncestorClip = false;
    }

    if (updateClippingLayers(needsAncestorClip, needsDescendantsClippingLayer))
        layerConfigChanged = true;

    if (updateOverflowControlsLayers(requiresHorizontalScrollbarLayer(), requiresVerticalScrollbarLayer(), requiresScrollCornerLayer()))
        layerConfigChanged = true;

    if (updateScrollingLayers(m_owningLayer.needsCompositedScrolling()))
        layerConfigChanged = true;

    bool hasPerspective = false;
    if (RenderStyle* style = renderer->style())
        hasPerspective = style->hasPerspective();
    bool needsChildTransformLayer = hasPerspective && (layerForChildrenTransform() == m_childTransformLayer.get());
    if (updateChildTransformLayer(needsChildTransformLayer))
        layerConfigChanged = true;

    updateScrollParent(scrollParent);
    updateClipParent(m_owningLayer.clipParent());

    if (updateSquashingLayers(!m_squashedLayers.isEmpty()))
        layerConfigChanged = true;

    if (layerConfigChanged)
        updateInternalHierarchy();

    if (updateMaskLayer(renderer->hasMask()))
        m_graphicsLayer->setMaskLayer(m_maskLayer.get());

    bool hasChildClippingLayer = compositor->clipsCompositingDescendants(&m_owningLayer) && (hasClippingLayer() || hasScrollingLayer());
    bool needsChildClippingMask = (renderer->style()->clipPath() || renderer->style()->hasBorderRadius()) && (hasChildClippingLayer || isAcceleratedContents(renderer));
    if (updateClippingMaskLayers(needsChildClippingMask)) {
        if (hasClippingLayer())
            clippingLayer()->setMaskLayer(m_childClippingMaskLayer.get());
        else if (hasScrollingLayer())
            scrollingLayer()->setMaskLayer(m_childClippingMaskLayer.get());
        else if (isAcceleratedContents(renderer))
            m_graphicsLayer->setContentsClippingMaskLayer(m_childClippingMaskLayer.get());
    }

    if (m_owningLayer.reflectionInfo()) {
        if (m_owningLayer.reflectionInfo()->reflectionLayer()->hasCompositedLayerMapping()) {
            GraphicsLayer* reflectionLayer = m_owningLayer.reflectionInfo()->reflectionLayer()->compositedLayerMapping()->mainGraphicsLayer();
            m_graphicsLayer->setReplicatedByLayer(reflectionLayer);
        }
    } else {
        m_graphicsLayer->setReplicatedByLayer(0);
    }

    updateBackgroundColor();

    if (isDirectlyCompositedImage())
        updateImageContents();

    if (blink::WebLayer* layer = platformLayerForPlugin(renderer)) {
        m_graphicsLayer->setContentsToPlatformLayer(layer);
    } else if (renderer->node() && renderer->node()->isFrameOwnerElement() && toHTMLFrameOwnerElement(renderer->node())->contentFrame()) {
        blink::WebLayer* layer = toHTMLFrameOwnerElement(renderer->node())->contentFrame()->remotePlatformLayer();
        if (layer)
            m_graphicsLayer->setContentsToPlatformLayer(layer);
    } else if (renderer->isVideo()) {
        HTMLMediaElement* mediaElement = toHTMLMediaElement(renderer->node());
        m_graphicsLayer->setContentsToPlatformLayer(mediaElement->platformLayer());
    } else if (isAcceleratedCanvas(renderer)) {
        HTMLCanvasElement* canvas = toHTMLCanvasElement(renderer->node());
        if (CanvasRenderingContext* context = canvas->renderingContext())
            m_graphicsLayer->setContentsToPlatformLayer(context->platformLayer());
        layerConfigChanged = true;
    }
    if (renderer->isRenderPart())
        layerConfigChanged = RenderLayerCompositor::parentFrameContentLayers(toRenderPart(renderer));

    return layerConfigChanged;
}

static IntRect clipBox(RenderBox* renderer)
{
    LayoutRect result = PaintInfo::infiniteRect();
    if (renderer->hasOverflowClip())
        result = renderer->overflowClipRect(LayoutPoint());

    if (renderer->hasClip())
        result.intersect(renderer->clipRect(LayoutPoint()));

    return pixelSnappedIntRect(result);
}

static LayoutPoint computeOffsetFromCompositedAncestor(const RenderLayer* layer, const RenderLayer* compositedAncestor)
{
    LayoutPoint offset;
    layer->convertToLayerCoords(compositedAncestor, offset);
    if (compositedAncestor)
        offset.move(compositedAncestor->compositedLayerMapping()->owningLayer().subpixelAccumulation());
    return offset;
}

void CompositedLayerMapping::adjustBoundsForSubPixelAccumulation(const RenderLayer* compositedAncestor, IntRect& localBounds, IntRect& relativeBounds, IntPoint& delta)
{
    LayoutRect localRawCompositingBounds = compositedBounds();
    LayoutPoint rawDelta = computeOffsetFromCompositedAncestor(&m_owningLayer, compositedAncestor);
    delta = flooredIntPoint(rawDelta);
    LayoutSize subpixelAccumulation = toLayoutSize(rawDelta).fraction();
    m_owningLayer.setSubpixelAccumulation(subpixelAccumulation);

    // Move the bounds by the subpixel accumulation so that it pixel-snaps relative to absolute pixels instead of local coordinates.
    localRawCompositingBounds.move(subpixelAccumulation);
    localBounds = pixelSnappedIntRect(localRawCompositingBounds);

    relativeBounds = localBounds;
    relativeBounds.moveBy(delta);
}

void CompositedLayerMapping::updateSquashingLayerGeometry(const IntPoint& delta)
{
    if (!m_squashingLayer)
        return;

    ASSERT(compositor()->layerSquashingEnabled());

    LayoutRect totalSquashBounds;
    for (size_t i = 0; i < m_squashedLayers.size(); ++i) {
        LayoutRect squashedBounds = compositor()->calculateCompositedBounds(m_squashedLayers[i].renderLayer, m_squashedLayers[i].renderLayer);

        // Store the local bounds of the RenderLayer subtree before applying the offset.
        m_squashedLayers[i].compositedBounds = squashedBounds;

        squashedBounds.move(m_squashedLayers[i].offsetFromSquashingCLM);
        totalSquashBounds.unite(squashedBounds);
    }

    // The totalSquashBounds is positioned with respect to m_owningLayer of this CompositedLayerMapping.
    // But the squashingLayer needs to be positioned with respect to the ancestor CompositedLayerMapping.
    // The conversion between m_owningLayer and the ancestor CLM is already computed in the caller as
    // |delta| + |subpixelAccumulation|.
    LayoutPoint rawDelta = delta + m_owningLayer.subpixelAccumulation();
    totalSquashBounds.moveBy(rawDelta);
    IntRect squashLayerBounds = enclosingIntRect(totalSquashBounds);
    IntPoint squashLayerOrigin = squashLayerBounds.location();
    LayoutPoint squashLayerOriginInOwningLayerSpace = LayoutPoint(squashLayerOrigin - rawDelta);

    m_squashingLayer->setPosition(squashLayerBounds.location());
    m_squashingLayer->setSize(squashLayerBounds.size());

    // Now that the squashing bounds are known, we can convert the RenderLayer painting offsets
    // from CLM owning layer space to the squashing layer space.
    //
    // The painting offset we want to compute for each squashed RenderLayer is essentially the position of
    // the squashed RenderLayer described w.r.t. m_squashingLayer's origin. For this purpose we already cached
    // offsetFromSquashingCLM before, which describes where the squashed RenderLayer is located w.r.t.
    // m_owningLayer. So we just need to convert that point from m_owningLayer space to m_squashingLayer
    // space. This is simply done by subtracing squashLayerOriginInOwningLayerSpace, but then the offset
    // overall needs to be negated because that's the direction that the painting code expects the
    // offset to be.
    for (size_t i = 0; i < m_squashedLayers.size(); ++i) {
        LayoutSize offsetFromSquashLayerOrigin = LayoutPoint(m_squashedLayers[i].offsetFromSquashingCLM) - squashLayerOriginInOwningLayerSpace;
        m_squashedLayers[i].offsetFromRenderer = -flooredIntSize(offsetFromSquashLayerOrigin);

        m_squashedLayers[i].renderLayer->setSubpixelAccumulation(offsetFromSquashLayerOrigin.fraction());
        ASSERT(m_squashedLayers[i].renderLayer->subpixelAccumulation() ==
            toLayoutSize(computeOffsetFromCompositedAncestor(m_squashedLayers[i].renderLayer, m_squashedLayers[i].renderLayer->ancestorCompositingLayer())).fraction());

        // FIXME: find a better design to avoid this redundant value - most likely it will make
        // sense to move the paint task info into RenderLayer's m_compositingProperties.
        m_squashedLayers[i].renderLayer->setOffsetFromSquashingLayerOrigin(m_squashedLayers[i].offsetFromRenderer);
    }
}

void CompositedLayerMapping::updateGraphicsLayerGeometry(GraphicsLayerUpdater::UpdateType updateType)
{
    // If we haven't built z-order lists yet, wait until later.
    if (m_owningLayer.stackingNode()->isStackingContainer() && m_owningLayer.stackingNode()->zOrderListsDirty())
        return;

    if (!shouldUpdateGraphicsLayer(updateType))
        return;

    // Set transform property, if it is not animating. We have to do this here because the transform
    // is affected by the layer dimensions.
    if (!hasActiveAnimationsOnCompositor(*renderer(), CSSPropertyTransform))
        updateTransform(renderer()->style());

    // Set opacity, if it is not animating.
    if (!hasActiveAnimationsOnCompositor(*renderer(), CSSPropertyOpacity))
        updateOpacity(renderer()->style());

    m_owningLayer.updateDescendantDependentFlags();

    // m_graphicsLayer is the corresponding GraphicsLayer for this RenderLayer and its non-compositing
    // descendants. So, the visibility flag for m_graphicsLayer should be true if there are any
    // non-compositing visible layers.
    bool contentsVisible = m_owningLayer.hasVisibleContent() || hasVisibleNonCompositingDescendantLayers();
    if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && renderer()->isVideo()) {
        HTMLMediaElement* mediaElement = toHTMLMediaElement(renderer()->node());
        if (mediaElement->isFullscreen())
            contentsVisible = false;
    }
    m_graphicsLayer->setContentsVisible(contentsVisible);

    RenderStyle* style = renderer()->style();
    m_graphicsLayer->setBackfaceVisibility(style->backfaceVisibility() == BackfaceVisibilityVisible);

    RenderLayer* compAncestor = m_owningLayer.ancestorCompositingLayer();

    // We compute everything relative to the enclosing compositing layer.
    IntRect ancestorCompositingBounds;
    if (compAncestor) {
        ASSERT(compAncestor->hasCompositedLayerMapping());
        ancestorCompositingBounds = compAncestor->compositedLayerMapping()->pixelSnappedCompositedBounds();
    }

    IntRect localCompositingBounds;
    IntRect relativeCompositingBounds;
    IntPoint delta;
    adjustBoundsForSubPixelAccumulation(compAncestor, localCompositingBounds, relativeCompositingBounds, delta);

    IntPoint graphicsLayerParentLocation;
    if (compAncestor && compAncestor->compositedLayerMapping()->hasClippingLayer()) {
        // If the compositing ancestor has a layer to clip children, we parent in that, and therefore
        // position relative to it.
        IntRect clippingBox = clipBox(toRenderBox(compAncestor->renderer()));
        graphicsLayerParentLocation = clippingBox.location() + roundedIntSize(compAncestor->subpixelAccumulation());
    } else if (compAncestor) {
        graphicsLayerParentLocation = ancestorCompositingBounds.location();
    } else {
        graphicsLayerParentLocation = renderer()->view()->documentRect().location();
    }

    if (compAncestor && compAncestor->needsCompositedScrolling()) {
        RenderBox* renderBox = toRenderBox(compAncestor->renderer());
        IntSize scrollOffset = renderBox->scrolledContentOffset();
        IntPoint scrollOrigin(renderBox->borderLeft(), renderBox->borderTop());
        graphicsLayerParentLocation = scrollOrigin - scrollOffset;
    }

    if (compAncestor && m_ancestorClippingLayer) {
        ClipRectsContext clipRectsContext(compAncestor, CompositingClipRects, IgnoreOverlayScrollbarSize, IgnoreOverflowClip);
        IntRect parentClipRect = pixelSnappedIntRect(m_owningLayer.clipper().backgroundClipRect(clipRectsContext).rect());
        ASSERT(parentClipRect != PaintInfo::infiniteRect());
        m_ancestorClippingLayer->setPosition(FloatPoint(parentClipRect.location() - graphicsLayerParentLocation));
        m_ancestorClippingLayer->setSize(parentClipRect.size());

        // backgroundRect is relative to compAncestor, so subtract deltaX/deltaY to get back to local coords.
        m_ancestorClippingLayer->setOffsetFromRenderer(parentClipRect.location() - delta);

        // The primary layer is then parented in, and positioned relative to this clipping layer.
        graphicsLayerParentLocation = parentClipRect.location();
    }

    FloatSize contentsSize = relativeCompositingBounds.size();

    m_graphicsLayer->setPosition(FloatPoint(relativeCompositingBounds.location() - graphicsLayerParentLocation));
    m_graphicsLayer->setOffsetFromRenderer(toIntSize(localCompositingBounds.location()));

    FloatSize oldSize = m_graphicsLayer->size();
    if (oldSize != contentsSize)
        m_graphicsLayer->setSize(contentsSize);

    // If we have a layer that clips children, position it.
    IntRect clippingBox;
    if (GraphicsLayer* clipLayer = clippingLayer()) {
        clippingBox = clipBox(toRenderBox(renderer()));
        clipLayer->setPosition(FloatPoint(clippingBox.location() - localCompositingBounds.location() + roundedIntSize(m_owningLayer.subpixelAccumulation())));
        clipLayer->setSize(clippingBox.size());
        clipLayer->setOffsetFromRenderer(toIntSize(clippingBox.location()));
        if (m_childClippingMaskLayer && !m_scrollingLayer) {
            m_childClippingMaskLayer->setPosition(clipLayer->position());
            m_childClippingMaskLayer->setSize(clipLayer->size());
            m_childClippingMaskLayer->setOffsetFromRenderer(clipLayer->offsetFromRenderer());
        }
    } else if (m_childTransformLayer) {
        m_childTransformLayer->setSize(contentsSize);
    }

    if (m_maskLayer) {
        if (m_maskLayer->size() != m_graphicsLayer->size()) {
            m_maskLayer->setSize(m_graphicsLayer->size());
            m_maskLayer->setNeedsDisplay();
        }
        m_maskLayer->setPosition(FloatPoint());
        m_maskLayer->setOffsetFromRenderer(m_graphicsLayer->offsetFromRenderer());
    }

    if (m_owningLayer.hasTransform()) {
        const LayoutRect borderBox = toRenderBox(renderer())->borderBoxRect();

        // Get layout bounds in the coords of compAncestor to match relativeCompositingBounds.
        IntRect layerBounds = pixelSnappedIntRect(toLayoutPoint(m_owningLayer.subpixelAccumulation()), borderBox.size());
        layerBounds.moveBy(delta);

        // Update properties that depend on layer dimensions
        FloatPoint3D transformOrigin = computeTransformOrigin(IntRect(IntPoint(), layerBounds.size()));
        // Compute the anchor point, which is in the center of the renderer box unless transform-origin is set.
        FloatPoint3D anchor(
            relativeCompositingBounds.width() ? (layerBounds.x() - relativeCompositingBounds.x() + transformOrigin.x()) / relativeCompositingBounds.width()  : 0.5f,
            relativeCompositingBounds.height() ? (layerBounds.y() - relativeCompositingBounds.y() + transformOrigin.y()) / relativeCompositingBounds.height() : 0.5f,
            transformOrigin.z());
        m_graphicsLayer->setAnchorPoint(anchor);
    } else {
        m_graphicsLayer->setAnchorPoint(FloatPoint3D(0.5f, 0.5f, 0));
    }

    if (GraphicsLayer* childrenTransformLayer = layerForChildrenTransform())
        childrenTransformLayer->setAnchorPoint(m_graphicsLayer->anchorPoint());

    if (m_foregroundLayer) {
        FloatSize foregroundSize = contentsSize;
        IntSize foregroundOffset = m_graphicsLayer->offsetFromRenderer();
        if (hasClippingLayer()) {
            // If we have a clipping layer (which clips descendants), then the foreground layer is a child of it,
            // so that it gets correctly sorted with children. In that case, position relative to the clipping layer.
            foregroundSize = FloatSize(clippingBox.size());
            foregroundOffset = toIntSize(clippingBox.location());
        }

        m_foregroundLayer->setPosition(FloatPoint());
        if (foregroundSize != m_foregroundLayer->size()) {
            m_foregroundLayer->setSize(foregroundSize);
            m_foregroundLayer->setNeedsDisplay();
        }
        m_foregroundLayer->setOffsetFromRenderer(foregroundOffset);
    }

    if (m_backgroundLayer) {
        FloatSize backgroundSize = contentsSize;
        if (backgroundLayerPaintsFixedRootBackground()) {
            FrameView* frameView = toRenderView(renderer())->frameView();
            backgroundSize = frameView->visibleContentRect().size();
        }
        m_backgroundLayer->setPosition(FloatPoint());
        if (backgroundSize != m_backgroundLayer->size()) {
            m_backgroundLayer->setSize(backgroundSize);
            m_backgroundLayer->setNeedsDisplay();
        }
        m_backgroundLayer->setOffsetFromRenderer(m_graphicsLayer->offsetFromRenderer());
    }

    if (m_owningLayer.reflectionInfo() && m_owningLayer.reflectionInfo()->reflectionLayer()->hasCompositedLayerMapping()) {
        CompositedLayerMappingPtr reflectionCompositedLayerMapping = m_owningLayer.reflectionInfo()->reflectionLayer()->compositedLayerMapping();
        reflectionCompositedLayerMapping->updateGraphicsLayerGeometry(GraphicsLayerUpdater::ForceUpdate);

        // The reflection layer has the bounds of m_owningLayer.reflectionLayer(),
        // but the reflected layer is the bounds of this layer, so we need to position it appropriately.
        FloatRect layerBounds = compositedBounds();
        FloatRect reflectionLayerBounds = reflectionCompositedLayerMapping->compositedBounds();
        reflectionCompositedLayerMapping->mainGraphicsLayer()->setReplicatedLayerPosition(FloatPoint(layerBounds.location() - reflectionLayerBounds.location()));
    }

    if (m_scrollingLayer) {
        ASSERT(m_scrollingContentsLayer);
        RenderBox* renderBox = toRenderBox(renderer());
        IntRect clientBox = enclosingIntRect(renderBox->clientBoxRect());

        IntSize adjustedScrollOffset = m_owningLayer.scrollableArea()->adjustedScrollOffset();
        m_scrollingLayer->setPosition(FloatPoint(clientBox.location() - localCompositingBounds.location() + roundedIntSize(m_owningLayer.subpixelAccumulation())));
        m_scrollingLayer->setSize(clientBox.size());

        IntSize oldScrollingLayerOffset = m_scrollingLayer->offsetFromRenderer();
        m_scrollingLayer->setOffsetFromRenderer(-toIntSize(clientBox.location()));

        if (m_childClippingMaskLayer) {
            m_childClippingMaskLayer->setPosition(m_scrollingLayer->position());
            m_childClippingMaskLayer->setSize(m_scrollingLayer->size());
            m_childClippingMaskLayer->setOffsetFromRenderer(toIntSize(clientBox.location()));
        }

        bool clientBoxOffsetChanged = oldScrollingLayerOffset != m_scrollingLayer->offsetFromRenderer();

        IntSize scrollSize(renderBox->scrollWidth(), renderBox->scrollHeight());
        if (scrollSize != m_scrollingContentsLayer->size() || clientBoxOffsetChanged)
            m_scrollingContentsLayer->setNeedsDisplay();

        IntSize scrollingContentsOffset = toIntSize(clientBox.location() - adjustedScrollOffset);
        if (scrollingContentsOffset != m_scrollingContentsLayer->offsetFromRenderer() || scrollSize != m_scrollingContentsLayer->size()) {
            bool coordinatorHandlesOffset = compositor()->scrollingLayerDidChange(&m_owningLayer);
            m_scrollingContentsLayer->setPosition(coordinatorHandlesOffset ? FloatPoint() : FloatPoint(-adjustedScrollOffset));
        }

        m_scrollingContentsLayer->setSize(scrollSize);
        // FIXME: The paint offset and the scroll offset should really be separate concepts.
        m_scrollingContentsLayer->setOffsetFromRenderer(scrollingContentsOffset, GraphicsLayer::DontSetNeedsDisplay);

        if (m_foregroundLayer) {
            if (m_foregroundLayer->size() != m_scrollingContentsLayer->size())
                m_foregroundLayer->setSize(m_scrollingContentsLayer->size());
            m_foregroundLayer->setNeedsDisplay();
            m_foregroundLayer->setOffsetFromRenderer(m_scrollingContentsLayer->offsetFromRenderer());
        }
    }

    {
        IntPoint squashingDelta(delta);
        squashingDelta.moveBy(-graphicsLayerParentLocation);
        updateSquashingLayerGeometry(squashingDelta);
    }

    if (m_owningLayer.scrollableArea() && m_owningLayer.scrollableArea()->scrollsOverflow())
        m_owningLayer.scrollableArea()->positionOverflowControls();

    // We can't make this call in RenderLayerCompositor::allocateOrClearCompositedLayerMapping
    // since it depends on whether compAncestor draws content, which gets updated later.
    updateRequiresOwnBackingStoreForAncestorReasons(compAncestor);

    if (RuntimeEnabledFeatures::cssCompositingEnabled()) {
        updateLayerBlendMode(style);
        updateIsRootForIsolatedGroup();
    }

    updateHasGpuRasterizationHint(renderer()->style());
    updateContentsRect();
    updateBackgroundColor();
    updateDrawsContent();
    updateContentsOpaque();
    updateAfterWidgetResize();
    updateRenderingContext();
    updateShouldFlattenTransform();
    updateChildrenTransform();
    updateScrollParent(renderer()->compositorDrivenAcceleratedScrollingEnabled() ? m_owningLayer.scrollParent() : 0);
    registerScrollingLayers();

    updateCompositingReasons();
}

void CompositedLayerMapping::registerScrollingLayers()
{
    // Register fixed position layers and their containers with the scrolling coordinator.
    ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer);
    if (!scrollingCoordinator)
        return;

    compositor()->updateViewportConstraintStatus(&m_owningLayer);

    scrollingCoordinator->updateLayerPositionConstraint(&m_owningLayer);

    // Page scale is applied as a transform on the root render view layer. Because the scroll
    // layer is further up in the hierarchy, we need to avoid marking the root render view
    // layer as a container.
    bool isContainer = m_owningLayer.hasTransform() && !m_owningLayer.isRootLayer();
    // FIXME: we should make certain that childForSuperLayers will never be the m_squashingContainmentLayer here
    scrollingCoordinator->setLayerIsContainerForFixedPositionLayers(localRootForOwningLayer(), isContainer);
}

void CompositedLayerMapping::updateInternalHierarchy()
{
    // m_foregroundLayer has to be inserted in the correct order with child layers,
    // so it's not inserted here.
    if (m_ancestorClippingLayer)
        m_ancestorClippingLayer->removeAllChildren();

    m_graphicsLayer->removeFromParent();

    if (m_ancestorClippingLayer)
        m_ancestorClippingLayer->addChild(m_graphicsLayer.get());

    if (m_childContainmentLayer)
        m_graphicsLayer->addChild(m_childContainmentLayer.get());
    else if (m_childTransformLayer)
        m_graphicsLayer->addChild(m_childTransformLayer.get());

    if (m_scrollingLayer) {
        GraphicsLayer* superLayer = m_graphicsLayer.get();

        if (m_childContainmentLayer)
            superLayer = m_childContainmentLayer.get();

        if (m_childTransformLayer)
            superLayer = m_childTransformLayer.get();

        superLayer->addChild(m_scrollingLayer.get());
    }

    // The clip for child layers does not include space for overflow controls, so they exist as
    // siblings of the clipping layer if we have one. Normal children of this layer are set as
    // children of the clipping layer.
    if (m_layerForHorizontalScrollbar)
        m_graphicsLayer->addChild(m_layerForHorizontalScrollbar.get());
    if (m_layerForVerticalScrollbar)
        m_graphicsLayer->addChild(m_layerForVerticalScrollbar.get());
    if (m_layerForScrollCorner)
        m_graphicsLayer->addChild(m_layerForScrollCorner.get());

    // The squashing containment layer, if it exists, becomes a no-op parent.
    if (m_squashingLayer) {
        ASSERT(compositor()->layerSquashingEnabled());
        ASSERT((m_ancestorClippingLayer && !m_squashingContainmentLayer) || (!m_ancestorClippingLayer && m_squashingContainmentLayer));

        if (m_squashingContainmentLayer) {
            m_squashingContainmentLayer->removeAllChildren();
            m_squashingContainmentLayer->addChild(m_graphicsLayer.get());
            m_squashingContainmentLayer->addChild(m_squashingLayer.get());
        } else {
            // The ancestor clipping layer is already set up and has m_graphicsLayer under it.
            m_ancestorClippingLayer->addChild(m_squashingLayer.get());
        }
    }
}

void CompositedLayerMapping::updateContentsRect()
{
    m_graphicsLayer->setContentsRect(pixelSnappedIntRect(contentsBox()));
}

void CompositedLayerMapping::updateDrawsContent()
{
    if (m_scrollingLayer) {
        // We don't have to consider overflow controls, because we know that the scrollbars are drawn elsewhere.
        // m_graphicsLayer only needs backing store if the non-scrolling parts (background, outlines, borders, shadows etc) need to paint.
        // m_scrollingLayer never has backing store.
        // m_scrollingContentsLayer only needs backing store if the scrolled contents need to paint.
        bool hasNonScrollingPaintedContent = m_owningLayer.hasVisibleContent() && m_owningLayer.hasBoxDecorationsOrBackground();
        m_graphicsLayer->setDrawsContent(hasNonScrollingPaintedContent);

        bool hasScrollingPaintedContent = m_owningLayer.hasVisibleContent() && (renderer()->hasBackground() || paintsChildren());
        m_scrollingContentsLayer->setDrawsContent(hasScrollingPaintedContent);
        return;
    }

    bool hasPaintedContent = containsPaintedContent();
    if (hasPaintedContent && isAcceleratedCanvas(renderer())) {
        CanvasRenderingContext* context = toHTMLCanvasElement(renderer()->node())->renderingContext();
        // Content layer may be null if context is lost.
        if (blink::WebLayer* contentLayer = context->platformLayer()) {
            Color bgColor(Color::transparent);
            if (contentLayerSupportsDirectBackgroundComposition(renderer())) {
                bgColor = rendererBackgroundColor();
                hasPaintedContent = false;
            }
            contentLayer->setBackgroundColor(bgColor.rgb());
        }
    }

    // FIXME: we could refine this to only allocate backings for one of these layers if possible.
    m_graphicsLayer->setDrawsContent(hasPaintedContent);
    if (m_foregroundLayer)
        m_foregroundLayer->setDrawsContent(hasPaintedContent);

    if (m_backgroundLayer)
        m_backgroundLayer->setDrawsContent(hasPaintedContent);
}

void CompositedLayerMapping::updateChildrenTransform()
{
    if (GraphicsLayer* childTransformLayer = layerForChildrenTransform()) {
        childTransformLayer->setTransform(owningLayer().perspectiveTransform());
        bool hasPerspective = false;
        if (RenderStyle* style = m_owningLayer.renderer()->style())
            hasPerspective = style->hasPerspective();
        if (hasPerspective)
            childTransformLayer->setShouldFlattenTransform(false);

        // Note, if the target is the scrolling layer, we need to ensure that the
        // scrolling content layer doesn't flatten the transform. (It would be nice
        // if we could apply transform to the scrolling content layer, but that's
        // too late, we need the children transform to be applied _before_ the
        // scrolling offset.)
        if (childTransformLayer == m_scrollingLayer.get())
            m_scrollingContentsLayer->setShouldFlattenTransform(false);
    }
}

// Return true if the layers changed.
bool CompositedLayerMapping::updateClippingLayers(bool needsAncestorClip, bool needsDescendantClip)
{
    bool layersChanged = false;

    if (needsAncestorClip) {
        if (!m_ancestorClippingLayer) {
            m_ancestorClippingLayer = createGraphicsLayer(CompositingReasonLayerForAncestorClip);
            m_ancestorClippingLayer->setMasksToBounds(true);
            layersChanged = true;
        }
    } else if (m_ancestorClippingLayer) {
        m_ancestorClippingLayer->removeFromParent();
        m_ancestorClippingLayer = nullptr;
        layersChanged = true;
    }

    if (needsDescendantClip) {
        // We don't need a child containment layer if we're the main frame render view
        // layer. It's redundant as the frame clip above us will handle this clipping.
        if (!m_childContainmentLayer && !m_isMainFrameRenderViewLayer) {
            m_childContainmentLayer = createGraphicsLayer(CompositingReasonLayerForDescendantClip);
            m_childContainmentLayer->setMasksToBounds(true);
            layersChanged = true;
        }
    } else if (hasClippingLayer()) {
        m_childContainmentLayer->removeFromParent();
        m_childContainmentLayer = nullptr;
        layersChanged = true;
    }

    return layersChanged;
}

bool CompositedLayerMapping::updateChildTransformLayer(bool needsChildTransformLayer)
{
    bool layersChanged = false;

    if (needsChildTransformLayer) {
        if (!m_childTransformLayer) {
            m_childTransformLayer = createGraphicsLayer(CompositingReasonLayerForPerspective);
            m_childTransformLayer->setDrawsContent(false);
            m_childTransformLayer->setShouldFlattenTransform(false);
            layersChanged = true;
        }
    } else if (m_childTransformLayer) {
        m_childTransformLayer->removeFromParent();
        m_childTransformLayer = nullptr;
        layersChanged = true;
    }

    return layersChanged;
}

void CompositedLayerMapping::setBackgroundLayerPaintsFixedRootBackground(bool backgroundLayerPaintsFixedRootBackground)
{
    m_backgroundLayerPaintsFixedRootBackground = backgroundLayerPaintsFixedRootBackground;
}

// Only a member function so it can call createGraphicsLayer.
bool CompositedLayerMapping::toggleScrollbarLayerIfNeeded(OwnPtr<GraphicsLayer>& layer, bool needsLayer, CompositingReasons reason)
{
    if (needsLayer == !!layer)
        return false;
    layer = needsLayer ? createGraphicsLayer(reason) : nullptr;
    return true;
}

bool CompositedLayerMapping::updateOverflowControlsLayers(bool needsHorizontalScrollbarLayer, bool needsVerticalScrollbarLayer, bool needsScrollCornerLayer)
{
    bool horizontalScrollbarLayerChanged = toggleScrollbarLayerIfNeeded(m_layerForHorizontalScrollbar, needsHorizontalScrollbarLayer, CompositingReasonLayerForHorizontalScrollbar);
    bool verticalScrollbarLayerChanged = toggleScrollbarLayerIfNeeded(m_layerForVerticalScrollbar, needsVerticalScrollbarLayer, CompositingReasonLayerForVerticalScrollbar);
    bool scrollCornerLayerChanged = toggleScrollbarLayerIfNeeded(m_layerForScrollCorner, needsScrollCornerLayer, CompositingReasonLayerForScrollCorner);

    if (ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer)) {
        if (horizontalScrollbarLayerChanged)
            scrollingCoordinator->scrollableAreaScrollbarLayerDidChange(m_owningLayer.scrollableArea(), HorizontalScrollbar);
        if (verticalScrollbarLayerChanged)
            scrollingCoordinator->scrollableAreaScrollbarLayerDidChange(m_owningLayer.scrollableArea(), VerticalScrollbar);
    }

    return horizontalScrollbarLayerChanged || verticalScrollbarLayerChanged || scrollCornerLayerChanged;
}

void CompositedLayerMapping::positionOverflowControlsLayers(const IntSize& offsetFromRoot)
{
    IntSize offsetFromRenderer = m_graphicsLayer->offsetFromRenderer() - roundedIntSize(m_owningLayer.subpixelAccumulation());
    if (GraphicsLayer* layer = layerForHorizontalScrollbar()) {
        Scrollbar* hBar = m_owningLayer.scrollableArea()->horizontalScrollbar();
        if (hBar) {
            layer->setPosition(hBar->frameRect().location() - offsetFromRoot - offsetFromRenderer);
            layer->setSize(hBar->frameRect().size());
            if (layer->hasContentsLayer())
                layer->setContentsRect(IntRect(IntPoint(), hBar->frameRect().size()));
        }
        layer->setDrawsContent(hBar && !layer->hasContentsLayer());
    }

    if (GraphicsLayer* layer = layerForVerticalScrollbar()) {
        Scrollbar* vBar = m_owningLayer.scrollableArea()->verticalScrollbar();
        if (vBar) {
            layer->setPosition(vBar->frameRect().location() - offsetFromRoot - offsetFromRenderer);
            layer->setSize(vBar->frameRect().size());
            if (layer->hasContentsLayer())
                layer->setContentsRect(IntRect(IntPoint(), vBar->frameRect().size()));
        }
        layer->setDrawsContent(vBar && !layer->hasContentsLayer());
    }

    if (GraphicsLayer* layer = layerForScrollCorner()) {
        const LayoutRect& scrollCornerAndResizer = m_owningLayer.scrollableArea()->scrollCornerAndResizerRect();
        layer->setPosition(scrollCornerAndResizer.location() - offsetFromRenderer);
        layer->setSize(scrollCornerAndResizer.size());
        layer->setDrawsContent(!scrollCornerAndResizer.isEmpty());
    }
}

bool CompositedLayerMapping::hasUnpositionedOverflowControlsLayers() const
{
    if (GraphicsLayer* layer = layerForHorizontalScrollbar()) {
        if (!layer->drawsContent())
            return true;
    }

    if (GraphicsLayer* layer = layerForVerticalScrollbar()) {
        if (!layer->drawsContent())
            return true;
    }

    if (GraphicsLayer* layer = layerForScrollCorner()) {
        if (!layer->drawsContent())
            return true;
    }

    return false;
}

enum ApplyToGraphicsLayersModeFlags {
    ApplyToCoreLayers = (1 << 0),
    ApplyToSquashingLayer = (1 << 1),
    ApplyToScrollbarLayers = (1 << 2),
    ApplyToBackgroundLayer = (1 << 3),
    ApplyToMaskLayers = (1 << 4),
    ApplyToContentLayers = (1 << 5),
    ApplyToAllGraphicsLayers = (ApplyToSquashingLayer | ApplyToScrollbarLayers | ApplyToBackgroundLayer | ApplyToMaskLayers | ApplyToCoreLayers | ApplyToContentLayers)
};
typedef unsigned ApplyToGraphicsLayersMode;

template <typename Func>
static void ApplyToGraphicsLayers(const CompositedLayerMapping* mapping, const Func& f, ApplyToGraphicsLayersMode mode)
{
    ASSERT(mode);

    if ((mode & ApplyToCoreLayers) && mapping->squashingContainmentLayer())
        f(mapping->squashingContainmentLayer());
    if ((mode & ApplyToCoreLayers) && mapping->childTransformLayer())
        f(mapping->childTransformLayer());
    if ((mode & ApplyToCoreLayers) && mapping->ancestorClippingLayer())
        f(mapping->ancestorClippingLayer());
    if (((mode & ApplyToCoreLayers) || (mode & ApplyToContentLayers)) && mapping->mainGraphicsLayer())
        f(mapping->mainGraphicsLayer());
    if ((mode & ApplyToCoreLayers) && mapping->clippingLayer())
        f(mapping->clippingLayer());
    if ((mode & ApplyToCoreLayers) && mapping->scrollingLayer())
        f(mapping->scrollingLayer());
    if (((mode & ApplyToCoreLayers) || (mode & ApplyToContentLayers)) && mapping->scrollingContentsLayer())
        f(mapping->scrollingContentsLayer());
    if (((mode & ApplyToCoreLayers) || (mode & ApplyToContentLayers)) && mapping->foregroundLayer())
        f(mapping->foregroundLayer());

    if ((mode & ApplyToSquashingLayer) && mapping->squashingLayer())
        f(mapping->squashingLayer());

    if (((mode & ApplyToMaskLayers) || (mode & ApplyToContentLayers)) && mapping->maskLayer())
        f(mapping->maskLayer());
    if (((mode & ApplyToMaskLayers) || (mode & ApplyToContentLayers)) && mapping->childClippingMaskLayer())
        f(mapping->childClippingMaskLayer());

    if (((mode & ApplyToBackgroundLayer) || (mode & ApplyToContentLayers)) && mapping->backgroundLayer())
        f(mapping->backgroundLayer());

    if ((mode & ApplyToScrollbarLayers) && mapping->layerForHorizontalScrollbar())
        f(mapping->layerForHorizontalScrollbar());
    if ((mode & ApplyToScrollbarLayers) && mapping->layerForVerticalScrollbar())
        f(mapping->layerForVerticalScrollbar());
    if ((mode & ApplyToScrollbarLayers) && mapping->layerForScrollCorner())
        f(mapping->layerForScrollCorner());
}

struct UpdateRenderingContextFunctor {
    void operator() (GraphicsLayer* layer) const { layer->setRenderingContext(renderingContext); }
    int renderingContext;
};

void CompositedLayerMapping::updateRenderingContext()
{
    // All layers but the squashing layer (which contains 'alien' content) should be included in this
    // rendering context.
    int id = 0;

    // NB, it is illegal at this point to query an ancestor's compositing state. Some compositing
    // reasons depend on the compositing state of ancestors. So if we want a rendering context id
    // for the context root, we cannot ask for the id of its associated WebLayer now; it may not have
    // one yet. We could do a second past after doing the compositing updates to get these ids,
    // but this would actually be harmful. We do not want to attach any semantic meaning to
    // the context id other than the fact that they group a number of layers together for the
    // sake of 3d sorting. So instead we will ask the compositor to vend us an arbitrary, but
    // consistent id.
    if (RenderLayer* root = m_owningLayer.renderingContextRoot()) {
        if (Node* node = root->renderer()->node())
            id = static_cast<int>(WTF::PtrHash<Node*>::hash(node));
    }

    UpdateRenderingContextFunctor functor = { id };
    ApplyToGraphicsLayersMode mode = ApplyToAllGraphicsLayers & ~ApplyToSquashingLayer;
    ApplyToGraphicsLayers<UpdateRenderingContextFunctor>(this, functor, mode);
}

struct UpdateShouldFlattenTransformFunctor {
    void operator() (GraphicsLayer* layer) const { layer->setShouldFlattenTransform(shouldFlatten); }
    bool shouldFlatten;
};

void CompositedLayerMapping::updateShouldFlattenTransform()
{
    // All CLM-managed layers that could affect a descendant layer should update their
    // should-flatten-transform value (the other layers' transforms don't matter here).
    UpdateShouldFlattenTransformFunctor functor = { !m_owningLayer.shouldPreserve3D() };
    ApplyToGraphicsLayersMode mode = ApplyToCoreLayers;
    ApplyToGraphicsLayers(this, functor, mode);
}

bool CompositedLayerMapping::updateForegroundLayer(bool needsForegroundLayer)
{
    bool layerChanged = false;
    if (needsForegroundLayer) {
        if (!m_foregroundLayer) {
            m_foregroundLayer = createGraphicsLayer(CompositingReasonLayerForForeground);
            m_foregroundLayer->setDrawsContent(true);
            m_foregroundLayer->setPaintingPhase(GraphicsLayerPaintForeground);
            layerChanged = true;
        }
    } else if (m_foregroundLayer) {
        m_foregroundLayer->removeFromParent();
        m_foregroundLayer = nullptr;
        layerChanged = true;
    }

    if (layerChanged)
        m_graphicsLayer->setPaintingPhase(paintingPhaseForPrimaryLayer());

    return layerChanged;
}

bool CompositedLayerMapping::updateBackgroundLayer(bool needsBackgroundLayer)
{
    bool layerChanged = false;
    if (needsBackgroundLayer) {
        if (!m_backgroundLayer) {
            m_backgroundLayer = createGraphicsLayer(CompositingReasonLayerForBackground);
            m_backgroundLayer->setDrawsContent(true);
            m_backgroundLayer->setAnchorPoint(FloatPoint3D());
            m_backgroundLayer->setPaintingPhase(GraphicsLayerPaintBackground);
#if !OS(ANDROID)
            m_backgroundLayer->contentLayer()->setDrawCheckerboardForMissingTiles(true);
            m_graphicsLayer->contentLayer()->setDrawCheckerboardForMissingTiles(false);
#endif
            layerChanged = true;
        }
    } else {
        if (m_backgroundLayer) {
            m_backgroundLayer->removeFromParent();
            m_backgroundLayer = nullptr;
#if !OS(ANDROID)
            m_graphicsLayer->contentLayer()->setDrawCheckerboardForMissingTiles(true);
#endif
            layerChanged = true;
        }
    }

    if (layerChanged && !m_owningLayer.renderer()->documentBeingDestroyed())
        compositor()->rootFixedBackgroundsChanged();

    return layerChanged;
}

bool CompositedLayerMapping::updateMaskLayer(bool needsMaskLayer)
{
    bool layerChanged = false;
    if (needsMaskLayer) {
        if (!m_maskLayer) {
            m_maskLayer = createGraphicsLayer(CompositingReasonLayerForMask);
            m_maskLayer->setDrawsContent(true);
            m_maskLayer->setPaintingPhase(GraphicsLayerPaintMask);
            layerChanged = true;
        }
    } else if (m_maskLayer) {
        m_maskLayer = nullptr;
        layerChanged = true;
    }

    if (layerChanged)
        m_graphicsLayer->setPaintingPhase(paintingPhaseForPrimaryLayer());

    return layerChanged;
}

bool CompositedLayerMapping::updateClippingMaskLayers(bool needsChildClippingMaskLayer)
{
    bool layerChanged = false;
    if (needsChildClippingMaskLayer) {
        if (!m_childClippingMaskLayer) {
            m_childClippingMaskLayer = createGraphicsLayer(CompositingReasonLayerForClippingMask);
            m_childClippingMaskLayer->setDrawsContent(true);
            m_childClippingMaskLayer->setPaintingPhase(GraphicsLayerPaintChildClippingMask);
            layerChanged = true;
        }
    } else if (m_childClippingMaskLayer) {
        m_childClippingMaskLayer = nullptr;
        layerChanged = true;
    }
    return layerChanged;
}

bool CompositedLayerMapping::updateScrollingLayers(bool needsScrollingLayers)
{
    ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer);

    bool layerChanged = false;
    if (needsScrollingLayers) {
        if (!m_scrollingLayer) {
            // Outer layer which corresponds with the scroll view.
            m_scrollingLayer = createGraphicsLayer(CompositingReasonLayerForScrollingContainer);
            m_scrollingLayer->setDrawsContent(false);
            m_scrollingLayer->setMasksToBounds(true);

            // Inner layer which renders the content that scrolls.
            m_scrollingContentsLayer = createGraphicsLayer(CompositingReasonLayerForScrollingContents);
            m_scrollingContentsLayer->setDrawsContent(true);
            GraphicsLayerPaintingPhase paintPhase = GraphicsLayerPaintOverflowContents | GraphicsLayerPaintCompositedScroll;
            if (!m_foregroundLayer)
                paintPhase |= GraphicsLayerPaintForeground;
            m_scrollingContentsLayer->setPaintingPhase(paintPhase);
            m_scrollingLayer->addChild(m_scrollingContentsLayer.get());

            layerChanged = true;
            if (scrollingCoordinator)
                scrollingCoordinator->scrollableAreaScrollLayerDidChange(m_owningLayer.scrollableArea());
        }
    } else if (m_scrollingLayer) {
        m_scrollingLayer = nullptr;
        m_scrollingContentsLayer = nullptr;
        layerChanged = true;
        if (scrollingCoordinator)
            scrollingCoordinator->scrollableAreaScrollLayerDidChange(m_owningLayer.scrollableArea());
    }

    if (layerChanged) {
        updateInternalHierarchy();
        m_graphicsLayer->setPaintingPhase(paintingPhaseForPrimaryLayer());
        m_graphicsLayer->setNeedsDisplay();
        if (renderer()->view())
            compositor()->scrollingLayerDidChange(&m_owningLayer);
    }

    return layerChanged;
}

static void updateScrollParentForGraphicsLayer(GraphicsLayer* layer, GraphicsLayer* topmostLayer, RenderLayer* scrollParent, ScrollingCoordinator* scrollingCoordinator)
{
    if (!layer)
        return;

    // Only the topmost layer has a scroll parent. All other layers have a null scroll parent.
    if (layer != topmostLayer)
        scrollParent = 0;

    scrollingCoordinator->updateScrollParentForGraphicsLayer(layer, scrollParent);
}

void CompositedLayerMapping::updateScrollParent(RenderLayer* scrollParent)
{
    if (!scrollParent && m_squashedLayers.size() && renderer()->compositorDrivenAcceleratedScrollingEnabled())
        scrollParent = m_squashedLayers[0].renderLayer->scrollParent();

    if (ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer)) {
        GraphicsLayer* topmostLayer = childForSuperlayers();
        updateScrollParentForGraphicsLayer(m_squashingContainmentLayer.get(), topmostLayer, scrollParent, scrollingCoordinator);
        updateScrollParentForGraphicsLayer(m_ancestorClippingLayer.get(), topmostLayer, scrollParent, scrollingCoordinator);
        updateScrollParentForGraphicsLayer(m_graphicsLayer.get(), topmostLayer, scrollParent, scrollingCoordinator);
    }
}

void CompositedLayerMapping::updateClipParent(RenderLayer* clipParent)
{
    if (ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer))
        scrollingCoordinator->updateClipParentForGraphicsLayer(m_graphicsLayer.get(), clipParent);
}

bool CompositedLayerMapping::updateSquashingLayers(bool needsSquashingLayers)
{
    bool layersChanged = false;

    if (needsSquashingLayers) {
        ASSERT(compositor()->layerSquashingEnabled());

        if (!m_squashingLayer) {
            ASSERT(!m_squashingContainmentLayer);

            m_squashingLayer = createGraphicsLayer(CompositingReasonLayerForSquashingContents);
            m_squashingLayer->setDrawsContent(true);

            // FIXME: containment layer needs a new CompositingReason, CompositingReasonOverlap is not appropriate.
            if (!m_ancestorClippingLayer)
                m_squashingContainmentLayer = createGraphicsLayer(CompositingReasonLayerForSquashingContainer);
            layersChanged = true;
        }

        ASSERT(m_squashingLayer);
    } else {
        if (m_squashingLayer) {
            m_squashingLayer->removeFromParent();
            m_squashingLayer = nullptr;
            layersChanged = true;
        }
        if (m_squashingContainmentLayer) {
            m_squashingContainmentLayer->removeFromParent();
            m_squashingContainmentLayer = nullptr;
            layersChanged = true;
        }
        ASSERT(!m_squashingLayer && !m_squashingContainmentLayer);
    }

    return layersChanged;
}

GraphicsLayerPaintingPhase CompositedLayerMapping::paintingPhaseForPrimaryLayer() const
{
    unsigned phase = 0;
    if (!m_backgroundLayer)
        phase |= GraphicsLayerPaintBackground;
    if (!m_foregroundLayer)
        phase |= GraphicsLayerPaintForeground;
    if (!m_maskLayer)
        phase |= GraphicsLayerPaintMask;

    if (m_scrollingContentsLayer) {
        phase &= ~GraphicsLayerPaintForeground;
        phase |= GraphicsLayerPaintCompositedScroll;
    }

    if (m_owningLayer.compositingReasons() & CompositingReasonOverflowScrollingParent)
        phase |= GraphicsLayerPaintCompositedScroll;

    return static_cast<GraphicsLayerPaintingPhase>(phase);
}

float CompositedLayerMapping::compositingOpacity(float rendererOpacity) const
{
    float finalOpacity = rendererOpacity;

    for (RenderLayer* curr = m_owningLayer.parent(); curr; curr = curr->parent()) {
        // We only care about parents that are stacking contexts.
        // Recall that opacity creates stacking context.
        if (!curr->stackingNode()->isStackingContainer())
            continue;

        // If we found a composited layer, regardless of whether it actually
        // paints into it, we want to compute opacity relative to it. So we can
        // break here.
        //
        // FIXME: with grouped backings, a composited descendant will have to
        // continue past the grouped (squashed) layers that its parents may
        // contribute to. This whole confusion can be avoided by specifying
        // explicitly the composited ancestor where we would stop accumulating
        // opacity.
        if (curr->compositingState() == PaintsIntoOwnBacking || curr->compositingState() == HasOwnBackingButPaintsIntoAncestor)
            break;

        finalOpacity *= curr->renderer()->opacity();
    }

    return finalOpacity;
}

Color CompositedLayerMapping::rendererBackgroundColor() const
{
    RenderObject* backgroundRenderer = renderer();
    if (backgroundRenderer->isRoot())
        backgroundRenderer = backgroundRenderer->rendererForRootBackground();

    return backgroundRenderer->resolveColor(CSSPropertyBackgroundColor);
}

void CompositedLayerMapping::updateBackgroundColor()
{
    m_graphicsLayer->setBackgroundColor(rendererBackgroundColor());
}

bool CompositedLayerMapping::paintsChildren() const
{
    if (m_owningLayer.hasVisibleContent() && m_owningLayer.hasNonEmptyChildRenderers())
        return true;

    if (hasVisibleNonCompositingDescendantLayers())
        return true;

    return false;
}

static bool isCompositedPlugin(RenderObject* renderer)
{
    return renderer->isEmbeddedObject() && toRenderEmbeddedObject(renderer)->requiresAcceleratedCompositing();
}

static bool hasVisibleNonCompositingDescendant(RenderLayer* parent)
{
    if (!parent->hasVisibleDescendant())
        return false;

    // FIXME: We shouldn't be called with a stale z-order lists. See bug 85512.
    parent->stackingNode()->updateLayerListsIfNeeded();

#if !ASSERT_DISABLED
    LayerListMutationDetector mutationChecker(parent->stackingNode());
#endif

    RenderLayerStackingNodeIterator normalFlowIterator(*parent->stackingNode(), AllChildren);
    while (RenderLayerStackingNode* curNode = normalFlowIterator.next()) {
        RenderLayer* curLayer = curNode->layer();
        if (curLayer->hasCompositedLayerMapping())
            continue;
        if (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer))
            return true;
    }

    return false;
}

// FIXME: By name the implementation is correct. But the code that uses this function means something
// very slightly different - the implementation needs to also include composited descendants that
// don't paint into their own backing, and instead paint into this backing.
bool CompositedLayerMapping::hasVisibleNonCompositingDescendantLayers() const
{
    return hasVisibleNonCompositingDescendant(&m_owningLayer);
}

bool CompositedLayerMapping::containsPaintedContent() const
{
    if (paintsIntoCompositedAncestor() || m_artificiallyInflatedBounds || m_owningLayer.isReflection())
        return false;

    if (isDirectlyCompositedImage())
        return false;

    RenderObject* renderObject = renderer();
    // FIXME: we could optimize cases where the image, video or canvas is known to fill the border box entirely,
    // and set background color on the layer in that case, instead of allocating backing store and painting.
    if (renderObject->isVideo() && toRenderVideo(renderer())->shouldDisplayVideo())
        return m_owningLayer.hasBoxDecorationsOrBackground();

    if (m_owningLayer.hasVisibleBoxDecorations())
        return true;

    if (renderObject->hasMask()) // masks require special treatment
        return true;

    if (renderObject->isReplaced() && !isCompositedPlugin(renderObject))
        return true;

    if (renderObject->isRenderRegion())
        return true;

    if (renderObject->node() && renderObject->node()->isDocumentNode()) {
        // Look to see if the root object has a non-simple background
        RenderObject* rootObject = renderObject->document().documentElement() ? renderObject->document().documentElement()->renderer() : 0;
        // Reject anything that has a border, a border-radius or outline,
        // or is not a simple background (no background, or solid color).
        if (rootObject && hasBoxDecorationsOrBackgroundImage(rootObject->style()))
            return true;

        // Now look at the body's renderer.
        HTMLElement* body = renderObject->document().body();
        RenderObject* bodyObject = (body && body->hasLocalName(bodyTag)) ? body->renderer() : 0;
        if (bodyObject && hasBoxDecorationsOrBackgroundImage(bodyObject->style()))
            return true;
    }

    // FIXME: it's O(n^2). A better solution is needed.
    return paintsChildren();
}

// An image can be directly compositing if it's the sole content of the layer, and has no box decorations
// that require painting. Direct compositing saves backing store.
bool CompositedLayerMapping::isDirectlyCompositedImage() const
{
    RenderObject* renderObject = renderer();

    if (!renderObject->isImage() || m_owningLayer.hasBoxDecorationsOrBackground() || renderObject->hasClip())
        return false;

    RenderImage* imageRenderer = toRenderImage(renderObject);
    if (ImageResource* cachedImage = imageRenderer->cachedImage()) {
        if (!cachedImage->hasImage())
            return false;

        Image* image = cachedImage->imageForRenderer(imageRenderer);
        return image->isBitmapImage();
    }

    return false;
}

void CompositedLayerMapping::contentChanged(ContentChangeType changeType)
{
    if ((changeType == ImageChanged) && isDirectlyCompositedImage()) {
        updateImageContents();
        return;
    }

    if ((changeType == CanvasChanged || changeType == CanvasPixelsChanged) && isAcceleratedCanvas(renderer())) {
        m_graphicsLayer->setContentsNeedsDisplay();
        return;
    }
}

void CompositedLayerMapping::updateImageContents()
{
    ASSERT(renderer()->isImage());
    RenderImage* imageRenderer = toRenderImage(renderer());

    ImageResource* cachedImage = imageRenderer->cachedImage();
    if (!cachedImage)
        return;

    Image* image = cachedImage->imageForRenderer(imageRenderer);
    if (!image)
        return;

    // We have to wait until the image is fully loaded before setting it on the layer.
    if (!cachedImage->isLoaded())
        return;

    // This is a no-op if the layer doesn't have an inner layer for the image.
    m_graphicsLayer->setContentsToImage(image);
    updateDrawsContent();

    // Image animation is "lazy", in that it automatically stops unless someone is drawing
    // the image. So we have to kick the animation each time; this has the downside that the
    // image will keep animating, even if its layer is not visible.
    image->startAnimation();
}

FloatPoint3D CompositedLayerMapping::computeTransformOrigin(const IntRect& borderBox) const
{
    RenderStyle* style = renderer()->style();

    FloatPoint3D origin;
    origin.setX(floatValueForLength(style->transformOriginX(), borderBox.width()));
    origin.setY(floatValueForLength(style->transformOriginY(), borderBox.height()));
    origin.setZ(style->transformOriginZ());

    return origin;
}

FloatPoint CompositedLayerMapping::computePerspectiveOrigin(const IntRect& borderBox) const
{
    RenderStyle* style = renderer()->style();

    float boxWidth = borderBox.width();
    float boxHeight = borderBox.height();

    FloatPoint origin;
    origin.setX(floatValueForLength(style->perspectiveOriginX(), boxWidth));
    origin.setY(floatValueForLength(style->perspectiveOriginY(), boxHeight));

    return origin;
}

// Return the offset from the top-left of this compositing layer at which the renderer's contents are painted.
LayoutSize CompositedLayerMapping::contentOffsetInCompostingLayer() const
{
    return LayoutSize(-m_compositedBounds.x(), -m_compositedBounds.y());
}

LayoutRect CompositedLayerMapping::contentsBox() const
{
    LayoutRect contentsBox = contentsRect(renderer());
    contentsBox.move(contentOffsetInCompostingLayer());
    return contentsBox;
}

GraphicsLayer* CompositedLayerMapping::parentForSublayers() const
{
    if (m_scrollingContentsLayer)
        return m_scrollingContentsLayer.get();

    if (m_childContainmentLayer)
        return m_childContainmentLayer.get();

    if (m_childTransformLayer)
        return m_childTransformLayer.get();

    return m_graphicsLayer.get();
}

GraphicsLayer* CompositedLayerMapping::localRootForOwningLayer() const
{
    if (m_ancestorClippingLayer)
        return m_ancestorClippingLayer.get();

    return m_graphicsLayer.get();
}

GraphicsLayer* CompositedLayerMapping::childForSuperlayers() const
{
    if (m_squashingContainmentLayer)
        return m_squashingContainmentLayer.get();

    return localRootForOwningLayer();
}

GraphicsLayer* CompositedLayerMapping::layerForChildrenTransform() const
{
    if (GraphicsLayer* clipLayer = clippingLayer())
        return clipLayer;
    if (m_scrollingLayer)
        return m_scrollingLayer.get();
    return m_childTransformLayer.get();
}

bool CompositedLayerMapping::updateRequiresOwnBackingStoreForAncestorReasons(const RenderLayer* compositingAncestorLayer)
{
    bool previousRequiresOwnBackingStoreForAncestorReasons = m_requiresOwnBackingStoreForAncestorReasons;
    bool previousPaintsIntoCompositedAncestor = paintsIntoCompositedAncestor();
    bool canPaintIntoAncestor = compositingAncestorLayer
        && (compositingAncestorLayer->compositedLayerMapping()->mainGraphicsLayer()->drawsContent()
            || compositingAncestorLayer->compositedLayerMapping()->paintsIntoCompositedAncestor());
    m_requiresOwnBackingStoreForAncestorReasons = !canPaintIntoAncestor;

    if (paintsIntoCompositedAncestor() != previousPaintsIntoCompositedAncestor)
        paintsIntoCompositedAncestorChanged();
    return m_requiresOwnBackingStoreForAncestorReasons != previousRequiresOwnBackingStoreForAncestorReasons;
}

bool CompositedLayerMapping::updateRequiresOwnBackingStoreForIntrinsicReasons()
{
    bool previousRequiresOwnBackingStoreForIntrinsicReasons = m_requiresOwnBackingStoreForIntrinsicReasons;
    bool previousPaintsIntoCompositedAncestor = paintsIntoCompositedAncestor();
    RenderObject* renderer = m_owningLayer.renderer();
    m_requiresOwnBackingStoreForIntrinsicReasons = m_owningLayer.isRootLayer()
        || (m_owningLayer.compositingReasons() & CompositingReasonComboReasonsThatRequireOwnBacking)
        || m_owningLayer.transform()
        || m_owningLayer.clipsCompositingDescendantsWithBorderRadius() // FIXME: Revisit this if the paintsIntoCompositedAncestor state is removed.
        || renderer->isTransparent()
        || renderer->hasMask()
        || renderer->hasReflection()
        || renderer->hasFilter();

    if (paintsIntoCompositedAncestor() != previousPaintsIntoCompositedAncestor)
        paintsIntoCompositedAncestorChanged();
    return m_requiresOwnBackingStoreForIntrinsicReasons != previousRequiresOwnBackingStoreForIntrinsicReasons;
}

void CompositedLayerMapping::paintsIntoCompositedAncestorChanged()
{
    // The answer to paintsIntoCompositedAncestor() affects cached clip rects, so when
    // it changes we have to clear clip rects on descendants.
    m_owningLayer.clipper().clearClipRectsIncludingDescendants(PaintingClipRects);
    m_owningLayer.repainter().computeRepaintRectsIncludingDescendants();

    compositor()->repaintInCompositedAncestor(&m_owningLayer, compositedBounds());
}

void CompositedLayerMapping::setBlendMode(blink::WebBlendMode blendMode)
{
    if (m_ancestorClippingLayer) {
        m_ancestorClippingLayer->setBlendMode(blendMode);
        m_graphicsLayer->setBlendMode(blink::WebBlendModeNormal);
    } else {
        m_graphicsLayer->setBlendMode(blendMode);
    }
}

void CompositedLayerMapping::setNeedsGraphicsLayerUpdate()
{
    m_needToUpdateGraphicsLayerOfAllDecendants = true;

    for (RenderLayer* current = &m_owningLayer; current; current = current->ancestorCompositingLayer()) {
        ASSERT(current->hasCompositedLayerMapping());
        CompositedLayerMappingPtr mapping = current->compositedLayerMapping();
        if (mapping->m_needToUpdateGraphicsLayer)
            return;
        mapping->m_needToUpdateGraphicsLayer = true;
    }
}

GraphicsLayerUpdater::UpdateType CompositedLayerMapping::updateTypeForChildren(GraphicsLayerUpdater::UpdateType updateType) const
{
    if (m_needToUpdateGraphicsLayerOfAllDecendants)
        return GraphicsLayerUpdater::ForceUpdate;
    return updateType;
}

void CompositedLayerMapping::clearNeedsGraphicsLayerUpdate()
{
    m_needToUpdateGraphicsLayer = false;
    m_needToUpdateGraphicsLayerOfAllDecendants = false;
}

#if !ASSERT_DISABLED

void CompositedLayerMapping::assertNeedsToUpdateGraphicsLayerBitsCleared()
{
    ASSERT(!m_needToUpdateGraphicsLayer);
    ASSERT(!m_needToUpdateGraphicsLayerOfAllDecendants);
}

#endif

struct SetContentsNeedsDisplayFunctor {
    void operator() (GraphicsLayer* layer) const
    {
        if (layer->drawsContent())
            layer->setNeedsDisplay();
    }
};

void CompositedLayerMapping::setContentsNeedDisplay()
{
    // FIXME: need to split out repaints for the background.
    ASSERT(!paintsIntoCompositedAncestor());
    ApplyToGraphicsLayers(this, SetContentsNeedsDisplayFunctor(), ApplyToContentLayers);
}

struct SetContentsNeedsDisplayInRectFunctor {
    void operator() (GraphicsLayer* layer) const
    {
        if (layer->drawsContent()) {
            IntRect layerDirtyRect = r;
            layerDirtyRect.move(-layer->offsetFromRenderer());
            layer->setNeedsDisplayInRect(layerDirtyRect);
        }
    }

    IntRect r;
};

// r is in the coordinate space of the layer's render object
void CompositedLayerMapping::setContentsNeedDisplayInRect(const IntRect& r)
{
    // FIXME: need to split out repaints for the background.
    ASSERT(!paintsIntoCompositedAncestor());
    SetContentsNeedsDisplayInRectFunctor functor = { r };
    ApplyToGraphicsLayers(this, functor, ApplyToContentLayers);
}

void CompositedLayerMapping::doPaintTask(GraphicsLayerPaintInfo& paintInfo, GraphicsContext* context,
    const IntRect& clip) // In the coords of rootLayer.
{
    if (paintsIntoCompositedAncestor()) {
        ASSERT_NOT_REACHED();
        return;
    }

    FontCachePurgePreventer fontCachePurgePreventer;

    PaintLayerFlags paintFlags = 0;
    if (paintInfo.paintingPhase & GraphicsLayerPaintBackground)
        paintFlags |= PaintLayerPaintingCompositingBackgroundPhase;
    if (paintInfo.paintingPhase & GraphicsLayerPaintForeground)
        paintFlags |= PaintLayerPaintingCompositingForegroundPhase;
    if (paintInfo.paintingPhase & GraphicsLayerPaintMask)
        paintFlags |= PaintLayerPaintingCompositingMaskPhase;
    if (paintInfo.paintingPhase & GraphicsLayerPaintChildClippingMask)
        paintFlags |= PaintLayerPaintingChildClippingMaskPhase;
    if (paintInfo.paintingPhase & GraphicsLayerPaintOverflowContents)
        paintFlags |= PaintLayerPaintingOverflowContents;
    if (paintInfo.paintingPhase & GraphicsLayerPaintCompositedScroll)
        paintFlags |= PaintLayerPaintingCompositingScrollingPhase;

    if (paintInfo.isBackgroundLayer)
        paintFlags |= (PaintLayerPaintingRootBackgroundOnly | PaintLayerPaintingCompositingForegroundPhase); // Need PaintLayerPaintingCompositingForegroundPhase to walk child layers.
    else if (compositor()->fixedRootBackgroundLayer())
        paintFlags |= PaintLayerPaintingSkipRootBackground;

    // Note carefully: in theory it is appropriate to invoke context->save() here
    // and restore the context after painting. For efficiency, we are assuming that
    // it is equivalent to manually undo this offset translation, which means we are
    // assuming that the context's space was not affected by the RenderLayer
    // painting code.

    IntSize offset = paintInfo.offsetFromRenderer;
    context->translate(-offset);

    // The dirtyRect is in the coords of the painting root.
    IntRect dirtyRect(clip);
    dirtyRect.move(offset);

    if (!(paintInfo.paintingPhase & GraphicsLayerPaintOverflowContents)) {
        LayoutRect bounds = paintInfo.compositedBounds;
        bounds.move(paintInfo.renderLayer->subpixelAccumulation());
        dirtyRect.intersect(pixelSnappedIntRect(bounds));
    } else {
        dirtyRect.move(roundedIntSize(paintInfo.renderLayer->subpixelAccumulation()));
    }

#ifndef NDEBUG
    paintInfo.renderLayer->renderer()->assertSubtreeIsLaidOut();
#endif

    if (paintInfo.renderLayer->compositingState() != PaintsIntoGroupedBacking) {
        // FIXME: GraphicsLayers need a way to split for RenderRegions.
        LayerPaintingInfo paintingInfo(paintInfo.renderLayer, dirtyRect, PaintBehaviorNormal, paintInfo.renderLayer->subpixelAccumulation());
        paintInfo.renderLayer->paintLayerContents(context, paintingInfo, paintFlags);

        ASSERT(!paintInfo.isBackgroundLayer || paintFlags & PaintLayerPaintingRootBackgroundOnly);

        if (paintInfo.renderLayer->containsDirtyOverlayScrollbars())
            paintInfo.renderLayer->paintLayerContents(context, paintingInfo, paintFlags | PaintLayerPaintingOverlayScrollbars);
    } else {
        ASSERT(compositor()->layerSquashingEnabled());
        LayerPaintingInfo paintingInfo(paintInfo.renderLayer, dirtyRect, PaintBehaviorNormal, paintInfo.renderLayer->subpixelAccumulation());
        paintInfo.renderLayer->paintLayer(context, paintingInfo, paintFlags);
    }

    ASSERT(!paintInfo.renderLayer->usedTransparency());

    // Manually restore the context to its original state by applying the opposite translation.
    context->translate(offset);
}

static void paintScrollbar(Scrollbar* scrollbar, GraphicsContext& context, const IntRect& clip)
{
    if (!scrollbar)
        return;

    context.save();
    const IntRect& scrollbarRect = scrollbar->frameRect();
    context.translate(-scrollbarRect.x(), -scrollbarRect.y());
    IntRect transformedClip = clip;
    transformedClip.moveBy(scrollbarRect.location());
    scrollbar->paint(&context, transformedClip);
    context.restore();
}

// Up-call from compositing layer drawing callback.
void CompositedLayerMapping::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase paintingPhase, const IntRect& clip)
{
    // https://code.google.com/p/chromium/issues/detail?id=343772
    DisableCompositingQueryAsserts disabler;
#ifndef NDEBUG
    // FIXME: once the state machine is ready, this can be removed and we can refer to that instead.
    if (Page* page = renderer()->frame()->page())
        page->setIsPainting(true);
#endif
    InspectorInstrumentation::willPaint(m_owningLayer.renderer(), graphicsLayer);

    if (graphicsLayer == m_graphicsLayer.get()
        || graphicsLayer == m_foregroundLayer.get()
        || graphicsLayer == m_backgroundLayer.get()
        || graphicsLayer == m_maskLayer.get()
        || graphicsLayer == m_childClippingMaskLayer.get()
        || graphicsLayer == m_scrollingContentsLayer.get()) {

        GraphicsLayerPaintInfo paintInfo;
        paintInfo.renderLayer = &m_owningLayer;
        paintInfo.compositedBounds = compositedBounds();
        paintInfo.offsetFromRenderer = graphicsLayer->offsetFromRenderer();
        paintInfo.paintingPhase = paintingPhase;
        paintInfo.isBackgroundLayer = (graphicsLayer == m_backgroundLayer);

        // We have to use the same root as for hit testing, because both methods can compute and cache clipRects.
        doPaintTask(paintInfo, &context, clip);
    } else if (graphicsLayer == m_squashingLayer.get()) {
        ASSERT(compositor()->layerSquashingEnabled());
        for (size_t i = 0; i < m_squashedLayers.size(); ++i)
            doPaintTask(m_squashedLayers[i], &context, clip);
    } else if (graphicsLayer == layerForHorizontalScrollbar()) {
        paintScrollbar(m_owningLayer.scrollableArea()->horizontalScrollbar(), context, clip);
    } else if (graphicsLayer == layerForVerticalScrollbar()) {
        paintScrollbar(m_owningLayer.scrollableArea()->verticalScrollbar(), context, clip);
    } else if (graphicsLayer == layerForScrollCorner()) {
        const IntRect& scrollCornerAndResizer = m_owningLayer.scrollableArea()->scrollCornerAndResizerRect();
        context.save();
        context.translate(-scrollCornerAndResizer.x(), -scrollCornerAndResizer.y());
        IntRect transformedClip = clip;
        transformedClip.moveBy(scrollCornerAndResizer.location());
        m_owningLayer.scrollableArea()->paintScrollCorner(&context, IntPoint(), transformedClip);
        m_owningLayer.scrollableArea()->paintResizer(&context, IntPoint(), transformedClip);
        context.restore();
    }
    InspectorInstrumentation::didPaint(m_owningLayer.renderer(), graphicsLayer, &context, clip);
#ifndef NDEBUG
    if (Page* page = renderer()->frame()->page())
        page->setIsPainting(false);
#endif
}

bool CompositedLayerMapping::isTrackingRepaints() const
{
    GraphicsLayerClient* client = compositor();
    return client ? client->isTrackingRepaints() : false;
}

struct CollectTrackedRepaintRectsFunctor {
    void operator() (GraphicsLayer* layer) const { layer->collectTrackedRepaintRects(*rects); }
    Vector<FloatRect>* rects;
};

PassOwnPtr<Vector<FloatRect> > CompositedLayerMapping::collectTrackedRepaintRects() const
{
    OwnPtr<Vector<FloatRect> > rects = adoptPtr(new Vector<FloatRect>);
    CollectTrackedRepaintRectsFunctor functor = { rects.get() };
    ApplyToGraphicsLayers(this, functor, ApplyToAllGraphicsLayers);
    return rects.release();
}

#ifndef NDEBUG
void CompositedLayerMapping::verifyNotPainting()
{
    ASSERT(!renderer()->frame()->page() || !renderer()->frame()->page()->isPainting());
}
#endif

void CompositedLayerMapping::notifyAnimationStarted(const GraphicsLayer*, double monotonicTime)
{
    renderer()->node()->document().cssPendingAnimations().notifyCompositorAnimationStarted(monotonicTime);
}

IntRect CompositedLayerMapping::pixelSnappedCompositedBounds() const
{
    LayoutRect bounds = m_compositedBounds;
    bounds.move(m_owningLayer.subpixelAccumulation());
    return pixelSnappedIntRect(bounds);
}

bool CompositedLayerMapping::updateSquashingLayerAssignment(RenderLayer* layer, LayoutSize offsetFromSquashingCLM, size_t nextSquashedLayerIndex)
{
    ASSERT(compositor()->layerSquashingEnabled());

    GraphicsLayerPaintInfo paintInfo;
    paintInfo.renderLayer = layer;
    // NOTE: composited bounds are updated elsewhere
    // NOTE: offsetFromRenderer is updated elsewhere
    paintInfo.offsetFromSquashingCLM = offsetFromSquashingCLM;
    paintInfo.paintingPhase = GraphicsLayerPaintAllWithOverflowClip;
    paintInfo.isBackgroundLayer = false;

    // Change tracking on squashing layers: at the first sign of something changed, just invalidate the layer.
    // FIXME: Perhaps we can find a tighter more clever mechanism later.
    bool updatedAssignment = false;
    if (nextSquashedLayerIndex < m_squashedLayers.size()) {
        if (!paintInfo.isEquivalentForSquashing(m_squashedLayers[nextSquashedLayerIndex])) {
            updatedAssignment = true;
        }
        m_squashedLayers[nextSquashedLayerIndex] = paintInfo;
    } else {
        m_squashedLayers.append(paintInfo);
        updatedAssignment = true;
    }
    layer->setGroupedMapping(this);
    return updatedAssignment;
}

void CompositedLayerMapping::removeRenderLayerFromSquashingGraphicsLayer(const RenderLayer* layer)
{
    size_t layerIndex = kNotFound;

    for (size_t i = 0; i < m_squashedLayers.size(); ++i) {
        if (m_squashedLayers[i].renderLayer == layer) {
            layerIndex = i;
            break;
        }
    }

    if (layerIndex == kNotFound)
        return;

    m_squashedLayers.remove(layerIndex);
}

void CompositedLayerMapping::finishAccumulatingSquashingLayers(size_t nextSquashedLayerIndex)
{
    ASSERT(compositor()->layerSquashingEnabled());

    // Any additional squashed RenderLayers in the array no longer exist, and removing invalidates the squashingLayer contents.
    if (nextSquashedLayerIndex < m_squashedLayers.size())
        m_squashedLayers.remove(nextSquashedLayerIndex, m_squashedLayers.size() - nextSquashedLayerIndex);
}

String CompositedLayerMapping::debugName(const GraphicsLayer* graphicsLayer)
{
    String name;
    if (graphicsLayer == m_graphicsLayer.get()) {
        name = m_owningLayer.debugName();
    } else if (graphicsLayer == m_squashingContainmentLayer.get()) {
        name = "Squashing Containment Layer";
    } else if (graphicsLayer == m_squashingLayer.get()) {
        name = "Squashing Layer";
    } else if (graphicsLayer == m_ancestorClippingLayer.get()) {
        name = "Ancestor Clipping Layer";
    } else if (graphicsLayer == m_foregroundLayer.get()) {
        name = m_owningLayer.debugName() + " (foreground) Layer";
    } else if (graphicsLayer == m_backgroundLayer.get()) {
        name = m_owningLayer.debugName() + " (background) Layer";
    } else if (graphicsLayer == m_childContainmentLayer.get()) {
        name = "Child Containment Layer";
    } else if (graphicsLayer == m_childTransformLayer.get()) {
        name = "Child Transform Layer";
    } else if (graphicsLayer == m_maskLayer.get()) {
        name = "Mask Layer";
    } else if (graphicsLayer == m_childClippingMaskLayer.get()) {
        name = "Child Clipping Mask Layer";
    } else if (graphicsLayer == m_layerForHorizontalScrollbar.get()) {
        name = "Horizontal Scrollbar Layer";
    } else if (graphicsLayer == m_layerForVerticalScrollbar.get()) {
        name = "Vertical Scrollbar Layer";
    } else if (graphicsLayer == m_layerForScrollCorner.get()) {
        name = "Scroll Corner Layer";
    } else if (graphicsLayer == m_scrollingLayer.get()) {
        name = "Scrolling Layer";
    } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
        name = "Scrolling Contents Layer";
    } else {
        ASSERT_NOT_REACHED();
    }

    return name;
}

} // namespace WebCore