Source/core/rendering/RenderBoxModelObject.cpp

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
 *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
 * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 * Copyright (C) 2010 Google Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"
#include "core/rendering/RenderBoxModelObject.h"

#include "core/HTMLNames.h"
#include "core/frame/Settings.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/page/scrolling/ScrollingConstraints.h"
#include "core/rendering/ImageQualityController.h"
#include "core/rendering/RenderBlock.h"
#include "core/rendering/RenderFlowThread.h"
#include "core/rendering/RenderGeometryMap.h"
#include "core/rendering/RenderInline.h"
#include "core/rendering/RenderLayer.h"
#include "core/rendering/RenderObjectInlines.h"
#include "core/rendering/RenderRegion.h"
#include "core/rendering/RenderTextFragment.h"
#include "core/rendering/RenderView.h"
#include "core/rendering/compositing/CompositedLayerMapping.h"
#include "core/rendering/compositing/RenderLayerCompositor.h"
#include "core/rendering/style/ShadowList.h"
#include "platform/LengthFunctions.h"
#include "platform/geometry/TransformState.h"
#include "platform/graphics/DrawLooperBuilder.h"
#include "platform/graphics/GraphicsContextStateSaver.h"
#include "platform/graphics/Path.h"
#include "wtf/CurrentTime.h"

namespace blink {

using namespace HTMLNames;

// The HashMap for storing continuation pointers.
// An inline can be split with blocks occuring in between the inline content.
// When this occurs we need a pointer to the next object. We can basically be
// split into a sequence of inlines and blocks. The continuation will either be
// an anonymous block (that houses other blocks) or it will be an inline flow.
// <b><i><p>Hello</p></i></b>. In this example the <i> will have a block as
// its continuation but the <b> will just have an inline as its continuation.
typedef WillBeHeapHashMap<RawPtrWillBeMember<const RenderBoxModelObject>, RawPtrWillBeMember<RenderBoxModelObject> > ContinuationMap;
static OwnPtrWillBePersistent<ContinuationMap>* continuationMap = 0;

// This HashMap is similar to the continuation map, but connects first-letter
// renderers to their remaining text fragments.
typedef WillBeHeapHashMap<RawPtrWillBeMember<const RenderBoxModelObject>, RawPtrWillBeMember<RenderTextFragment> > FirstLetterRemainingTextMap;
static OwnPtrWillBePersistent<FirstLetterRemainingTextMap>* firstLetterRemainingTextMap = 0;

void RenderBoxModelObject::setSelectionState(SelectionState state)
{
    if (state == SelectionInside && selectionState() != SelectionNone)
        return;

    if ((state == SelectionStart && selectionState() == SelectionEnd)
        || (state == SelectionEnd && selectionState() == SelectionStart))
        RenderObject::setSelectionState(SelectionBoth);
    else
        RenderObject::setSelectionState(state);

    // FIXME: We should consider whether it is OK propagating to ancestor RenderInlines.
    // This is a workaround for http://webkit.org/b/32123
    // The containing block can be null in case of an orphaned tree.
    RenderBlock* containingBlock = this->containingBlock();
    if (containingBlock && !containingBlock->isRenderView())
        containingBlock->setSelectionState(state);
}

void RenderBoxModelObject::contentChanged(ContentChangeType changeType)
{
    if (!hasLayer())
        return;

    layer()->contentChanged(changeType);
}

bool RenderBoxModelObject::hasAcceleratedCompositing() const
{
    return view()->compositor()->hasAcceleratedCompositing();
}

InterpolationQuality RenderBoxModelObject::chooseInterpolationQuality(GraphicsContext* context, Image* image, const void* layer, const LayoutSize& size)
{
    return ImageQualityController::imageQualityController()->chooseInterpolationQuality(context, this, image, layer, size);
}

RenderBoxModelObject::RenderBoxModelObject(ContainerNode* node)
    : RenderLayerModelObject(node)
{
}

RenderBoxModelObject::~RenderBoxModelObject()
{
    ImageQualityController::remove(this);
}

void RenderBoxModelObject::willBeDestroyed()
{
    // A continuation of this RenderObject should be destroyed at subclasses.
    ASSERT(!continuation());

    // If this is a first-letter object with a remaining text fragment then the
    // entry needs to be cleared from the map.
    if (firstLetterRemainingText())
        setFirstLetterRemainingText(0);

    RenderLayerModelObject::willBeDestroyed();
}

bool RenderBoxModelObject::calculateHasBoxDecorations() const
{
    RenderStyle* styleToUse = style();
    ASSERT(styleToUse);
    return hasBackground() || styleToUse->hasBorder() || styleToUse->hasAppearance() || styleToUse->boxShadow();
}

void RenderBoxModelObject::updateFromStyle()
{
    RenderLayerModelObject::updateFromStyle();

    RenderStyle* styleToUse = style();
    setHasBoxDecorationBackground(calculateHasBoxDecorations());
    setInline(styleToUse->isDisplayInlineType());
    setPositionState(styleToUse->position());
    setHorizontalWritingMode(styleToUse->isHorizontalWritingMode());
}

static LayoutSize accumulateInFlowPositionOffsets(const RenderObject* child)
{
    if (!child->isAnonymousBlock() || !child->isRelPositioned())
        return LayoutSize();
    LayoutSize offset;
    RenderObject* p = toRenderBlock(child)->inlineElementContinuation();
    while (p && p->isRenderInline()) {
        if (p->isRelPositioned()) {
            RenderInline* renderInline = toRenderInline(p);
            offset += renderInline->offsetForInFlowPosition();
        }
        p = p->parent();
    }
    return offset;
}

bool RenderBoxModelObject::hasAutoHeightOrContainingBlockWithAutoHeight() const
{
    Length logicalHeightLength = style()->logicalHeight();
    if (logicalHeightLength.isAuto())
        return true;

    // For percentage heights: The percentage is calculated with respect to the height of the generated box's
    // containing block. If the height of the containing block is not specified explicitly (i.e., it depends
    // on content height), and this element is not absolutely positioned, the value computes to 'auto'.
    if (!logicalHeightLength.isPercent() || isOutOfFlowPositioned() || document().inQuirksMode())
        return false;

    // Anonymous block boxes are ignored when resolving percentage values that would refer to it:
    // the closest non-anonymous ancestor box is used instead.
    RenderBlock* cb = containingBlock();
    while (cb->isAnonymous())
        cb = cb->containingBlock();

    // Matching RenderBox::percentageLogicalHeightIsResolvableFromBlock() by
    // ignoring table cell's attribute value, where it says that table cells violate
    // what the CSS spec says to do with heights. Basically we
    // don't care if the cell specified a height or not.
    if (cb->isTableCell())
        return false;

    // Match RenderBox::availableLogicalHeightUsing by special casing
    // the render view. The available height is taken from the frame.
    if (cb->isRenderView())
        return false;

    if (!cb->style()->logicalHeight().isAuto() || (!cb->style()->logicalTop().isAuto() && !cb->style()->logicalBottom().isAuto()))
        return false;

    return true;
}

LayoutSize RenderBoxModelObject::relativePositionOffset() const
{
    LayoutSize offset = accumulateInFlowPositionOffsets(this);

    RenderBlock* containingBlock = this->containingBlock();

    // Objects that shrink to avoid floats normally use available line width when computing containing block width.  However
    // in the case of relative positioning using percentages, we can't do this.  The offset should always be resolved using the
    // available width of the containing block.  Therefore we don't use containingBlockLogicalWidthForContent() here, but instead explicitly
    // call availableWidth on our containing block.
    if (!style()->left().isAuto()) {
        if (!style()->right().isAuto() && !containingBlock->style()->isLeftToRightDirection())
            offset.setWidth(-valueForLength(style()->right(), containingBlock->availableWidth()));
        else
            offset.expand(valueForLength(style()->left(), containingBlock->availableWidth()), 0);
    } else if (!style()->right().isAuto()) {
        offset.expand(-valueForLength(style()->right(), containingBlock->availableWidth()), 0);
    }

    // If the containing block of a relatively positioned element does not
    // specify a height, a percentage top or bottom offset should be resolved as
    // auto. An exception to this is if the containing block has the WinIE quirk
    // where <html> and <body> assume the size of the viewport. In this case,
    // calculate the percent offset based on this height.
    // See <https://bugs.webkit.org/show_bug.cgi?id=26396>.
    if (!style()->top().isAuto()
        && (!containingBlock->hasAutoHeightOrContainingBlockWithAutoHeight()
            || !style()->top().isPercent()
            || containingBlock->stretchesToViewport()))
        offset.expand(0, valueForLength(style()->top(), containingBlock->availableHeight()));

    else if (!style()->bottom().isAuto()
        && (!containingBlock->hasAutoHeightOrContainingBlockWithAutoHeight()
            || !style()->bottom().isPercent()
            || containingBlock->stretchesToViewport()))
        offset.expand(0, -valueForLength(style()->bottom(), containingBlock->availableHeight()));

    return offset;
}

LayoutPoint RenderBoxModelObject::adjustedPositionRelativeToOffsetParent(const LayoutPoint& startPoint) const
{
    // If the element is the HTML body element or doesn't have a parent
    // return 0 and stop this algorithm.
    if (isBody() || !parent())
        return LayoutPoint();

    LayoutPoint referencePoint = startPoint;
    referencePoint.move(parent()->columnOffset(referencePoint));

    // If the offsetParent of the element is null, or is the HTML body element,
    // return the distance between the canvas origin and the left border edge
    // of the element and stop this algorithm.
    Element* element = offsetParent();
    if (!element)
        return referencePoint;

    if (const RenderBoxModelObject* offsetParent = element->renderBoxModelObject()) {
        if (offsetParent->isBox() && !offsetParent->isBody())
            referencePoint.move(-toRenderBox(offsetParent)->borderLeft(), -toRenderBox(offsetParent)->borderTop());
        if (!isOutOfFlowPositioned() || flowThreadContainingBlock()) {
            if (isRelPositioned())
                referencePoint.move(relativePositionOffset());

            RenderObject* current;
            for (current = parent(); current != offsetParent && current->parent(); current = current->parent()) {
                // FIXME: What are we supposed to do inside SVG content?
                if (!isOutOfFlowPositioned()) {
                    if (current->isBox() && !current->isTableRow())
                        referencePoint.moveBy(toRenderBox(current)->topLeftLocation());
                    referencePoint.move(current->parent()->columnOffset(referencePoint));
                }
            }

            if (offsetParent->isBox() && offsetParent->isBody() && !offsetParent->isPositioned())
                referencePoint.moveBy(toRenderBox(offsetParent)->topLeftLocation());
        }
    }

    return referencePoint;
}

LayoutSize RenderBoxModelObject::offsetForInFlowPosition() const
{
    return isRelPositioned() ? relativePositionOffset() : LayoutSize();
}

LayoutUnit RenderBoxModelObject::offsetLeft() const
{
    // Note that RenderInline and RenderBox override this to pass a different
    // startPoint to adjustedPositionRelativeToOffsetParent.
    return adjustedPositionRelativeToOffsetParent(LayoutPoint()).x();
}

LayoutUnit RenderBoxModelObject::offsetTop() const
{
    // Note that RenderInline and RenderBox override this to pass a different
    // startPoint to adjustedPositionRelativeToOffsetParent.
    return adjustedPositionRelativeToOffsetParent(LayoutPoint()).y();
}

int RenderBoxModelObject::pixelSnappedOffsetWidth() const
{
    return snapSizeToPixel(offsetWidth(), offsetLeft());
}

int RenderBoxModelObject::pixelSnappedOffsetHeight() const
{
    return snapSizeToPixel(offsetHeight(), offsetTop());
}

LayoutUnit RenderBoxModelObject::computedCSSPadding(const Length& padding) const
{
    LayoutUnit w = 0;
    if (padding.isPercent())
        w = containingBlockLogicalWidthForContent();
    return minimumValueForLength(padding, w);
}

RoundedRect RenderBoxModelObject::getBackgroundRoundedRect(const LayoutRect& borderRect, InlineFlowBox* box, LayoutUnit inlineBoxWidth, LayoutUnit inlineBoxHeight,
    bool includeLogicalLeftEdge, bool includeLogicalRightEdge) const
{
    RoundedRect border = style()->getRoundedBorderFor(borderRect, includeLogicalLeftEdge, includeLogicalRightEdge);
    if (box && (box->nextLineBox() || box->prevLineBox())) {
        RoundedRect segmentBorder = style()->getRoundedBorderFor(LayoutRect(0, 0, inlineBoxWidth, inlineBoxHeight), includeLogicalLeftEdge, includeLogicalRightEdge);
        border.setRadii(segmentBorder.radii());
    }

    return border;
}

void RenderBoxModelObject::clipRoundedInnerRect(GraphicsContext * context, const LayoutRect& rect, const RoundedRect& clipRect)
{
    if (clipRect.isRenderable())
        context->clipRoundedRect(clipRect);
    else {
        // We create a rounded rect for each of the corners and clip it, while making sure we clip opposing corners together.
        if (!clipRect.radii().topLeft().isEmpty() || !clipRect.radii().bottomRight().isEmpty()) {
            IntRect topCorner(clipRect.rect().x(), clipRect.rect().y(), rect.maxX() - clipRect.rect().x(), rect.maxY() - clipRect.rect().y());
            RoundedRect::Radii topCornerRadii;
            topCornerRadii.setTopLeft(clipRect.radii().topLeft());
            context->clipRoundedRect(RoundedRect(topCorner, topCornerRadii));

            IntRect bottomCorner(rect.x(), rect.y(), clipRect.rect().maxX() - rect.x(), clipRect.rect().maxY() - rect.y());
            RoundedRect::Radii bottomCornerRadii;
            bottomCornerRadii.setBottomRight(clipRect.radii().bottomRight());
            context->clipRoundedRect(RoundedRect(bottomCorner, bottomCornerRadii));
        }

        if (!clipRect.radii().topRight().isEmpty() || !clipRect.radii().bottomLeft().isEmpty()) {
            IntRect topCorner(rect.x(), clipRect.rect().y(), clipRect.rect().maxX() - rect.x(), rect.maxY() - clipRect.rect().y());
            RoundedRect::Radii topCornerRadii;
            topCornerRadii.setTopRight(clipRect.radii().topRight());
            context->clipRoundedRect(RoundedRect(topCorner, topCornerRadii));

            IntRect bottomCorner(clipRect.rect().x(), rect.y(), rect.maxX() - clipRect.rect().x(), clipRect.rect().maxY() - rect.y());
            RoundedRect::Radii bottomCornerRadii;
            bottomCornerRadii.setBottomLeft(clipRect.radii().bottomLeft());
            context->clipRoundedRect(RoundedRect(bottomCorner, bottomCornerRadii));
        }
    }
}

// FIXME: See crbug.com/382491. The use of getCTM in this context is incorrect because the matrix returned does not
// include scales applied at raster time, such as the device zoom.
static LayoutRect shrinkRectByOnePixel(GraphicsContext* context, const LayoutRect& rect)
{
    LayoutRect shrunkRect = rect;
    AffineTransform transform = context->getCTM();
    shrunkRect.inflateX(-static_cast<LayoutUnit>(ceil(1 / transform.xScale())));
    shrunkRect.inflateY(-static_cast<LayoutUnit>(ceil(1 / transform.yScale())));
    return shrunkRect;
}

LayoutRect RenderBoxModelObject::borderInnerRectAdjustedForBleedAvoidance(GraphicsContext* context, const LayoutRect& rect, BackgroundBleedAvoidance bleedAvoidance) const
{
    // We shrink the rectangle by one pixel on each side to make it fully overlap the anti-aliased background border
    return (bleedAvoidance == BackgroundBleedBackgroundOverBorder) ? shrinkRectByOnePixel(context, rect) : rect;
}

RoundedRect RenderBoxModelObject::backgroundRoundedRectAdjustedForBleedAvoidance(GraphicsContext* context, const LayoutRect& borderRect, BackgroundBleedAvoidance bleedAvoidance, InlineFlowBox* box, const LayoutSize& boxSize, bool includeLogicalLeftEdge, bool includeLogicalRightEdge) const
{
    if (bleedAvoidance == BackgroundBleedShrinkBackground) {
        // We shrink the rectangle by one pixel on each side because the bleed is one pixel maximum.
        return getBackgroundRoundedRect(shrinkRectByOnePixel(context, borderRect), box, boxSize.width(), boxSize.height(), includeLogicalLeftEdge, includeLogicalRightEdge);
    }
    if (bleedAvoidance == BackgroundBleedBackgroundOverBorder)
        return style()->getRoundedInnerBorderFor(borderRect, includeLogicalLeftEdge, includeLogicalRightEdge);

    return getBackgroundRoundedRect(borderRect, box, boxSize.width(), boxSize.height(), includeLogicalLeftEdge, includeLogicalRightEdge);
}

static void applyBoxShadowForBackground(GraphicsContext* context, const RenderObject* renderer)
{
    const ShadowList* shadowList = renderer->style()->boxShadow();
    ASSERT(shadowList);
    for (size_t i = shadowList->shadows().size(); i--; ) {
        const ShadowData& boxShadow = shadowList->shadows()[i];
        if (boxShadow.style() != Normal)
            continue;
        FloatSize shadowOffset(boxShadow.x(), boxShadow.y());
        context->setShadow(shadowOffset, boxShadow.blur(), boxShadow.color(),
            DrawLooperBuilder::ShadowRespectsTransforms, DrawLooperBuilder::ShadowIgnoresAlpha);
        return;
    }
}

void RenderBoxModelObject::paintFillLayerExtended(const PaintInfo& paintInfo, const Color& color, const FillLayer& bgLayer, const LayoutRect& rect,
    BackgroundBleedAvoidance bleedAvoidance, InlineFlowBox* box, const LayoutSize& boxSize, CompositeOperator op, RenderObject* backgroundObject)
{
    GraphicsContext* context = paintInfo.context;
    if (rect.isEmpty())
        return;

    bool includeLeftEdge = box ? box->includeLogicalLeftEdge() : true;
    bool includeRightEdge = box ? box->includeLogicalRightEdge() : true;

    bool hasRoundedBorder = style()->hasBorderRadius() && (includeLeftEdge || includeRightEdge);
    bool clippedWithLocalScrolling = hasOverflowClip() && bgLayer.attachment() == LocalBackgroundAttachment;
    bool isBorderFill = bgLayer.clip() == BorderFillBox;
    bool isRoot = this->isDocumentElement();

    Color bgColor = color;
    StyleImage* bgImage = bgLayer.image();
    bool shouldPaintBackgroundImage = bgImage && bgImage->canRender(*this, style()->effectiveZoom());

    bool forceBackgroundToWhite = false;
    if (document().printing()) {
        if (style()->printColorAdjust() == PrintColorAdjustEconomy)
            forceBackgroundToWhite = true;
        if (document().settings() && document().settings()->shouldPrintBackgrounds())
            forceBackgroundToWhite = false;
    }

    // When printing backgrounds is disabled or using economy mode,
    // change existing background colors and images to a solid white background.
    // If there's no bg color or image, leave it untouched to avoid affecting transparency.
    // We don't try to avoid loading the background images, because this style flag is only set
    // when printing, and at that point we've already loaded the background images anyway. (To avoid
    // loading the background images we'd have to do this check when applying styles rather than
    // while rendering.)
    if (forceBackgroundToWhite) {
        // Note that we can't reuse this variable below because the bgColor might be changed
        bool shouldPaintBackgroundColor = !bgLayer.next() && bgColor.alpha();
        if (shouldPaintBackgroundImage || shouldPaintBackgroundColor) {
            bgColor = Color::white;
            shouldPaintBackgroundImage = false;
        }
    }

    bool colorVisible = bgColor.alpha();

    // Fast path for drawing simple color backgrounds.
    if (!isRoot && !clippedWithLocalScrolling && !shouldPaintBackgroundImage && isBorderFill && !bgLayer.next()) {
        if (!colorVisible)
            return;

        bool boxShadowShouldBeAppliedToBackground = this->boxShadowShouldBeAppliedToBackground(bleedAvoidance, box);
        GraphicsContextStateSaver shadowStateSaver(*context, boxShadowShouldBeAppliedToBackground);
        if (boxShadowShouldBeAppliedToBackground)
            applyBoxShadowForBackground(context, this);

        if (hasRoundedBorder && bleedAvoidance != BackgroundBleedClipBackground) {
            RoundedRect border = backgroundRoundedRectAdjustedForBleedAvoidance(context, rect, bleedAvoidance, box, boxSize, includeLeftEdge, includeRightEdge);
            if (border.isRenderable())
                context->fillRoundedRect(border, bgColor);
            else {
                context->save();
                clipRoundedInnerRect(context, rect, border);
                context->fillRect(border.rect(), bgColor);
                context->restore();
            }
        } else {
            context->fillRect(pixelSnappedIntRect(rect), bgColor);
        }

        return;
    }

    // BorderFillBox radius clipping is taken care of by BackgroundBleedClipBackground
    bool clipToBorderRadius = hasRoundedBorder && !(isBorderFill && bleedAvoidance == BackgroundBleedClipBackground);
    GraphicsContextStateSaver clipToBorderStateSaver(*context, clipToBorderRadius);
    if (clipToBorderRadius) {
        RoundedRect border = isBorderFill ? backgroundRoundedRectAdjustedForBleedAvoidance(context, rect, bleedAvoidance, box, boxSize, includeLeftEdge, includeRightEdge) : getBackgroundRoundedRect(rect, box, boxSize.width(), boxSize.height(), includeLeftEdge, includeRightEdge);

        // Clip to the padding or content boxes as necessary.
        if (bgLayer.clip() == ContentFillBox) {
            border = style()->getRoundedInnerBorderFor(border.rect(),
                paddingTop() + borderTop(), paddingBottom() + borderBottom(), paddingLeft() + borderLeft(), paddingRight() + borderRight(), includeLeftEdge, includeRightEdge);
        } else if (bgLayer.clip() == PaddingFillBox)
            border = style()->getRoundedInnerBorderFor(border.rect(), includeLeftEdge, includeRightEdge);

        clipRoundedInnerRect(context, rect, border);
    }

    int bLeft = includeLeftEdge ? borderLeft() : 0;
    int bRight = includeRightEdge ? borderRight() : 0;
    LayoutUnit pLeft = includeLeftEdge ? paddingLeft() : LayoutUnit();
    LayoutUnit pRight = includeRightEdge ? paddingRight() : LayoutUnit();

    GraphicsContextStateSaver clipWithScrollingStateSaver(*context, clippedWithLocalScrolling);
    LayoutRect scrolledPaintRect = rect;
    if (clippedWithLocalScrolling) {
        // Clip to the overflow area.
        RenderBox* thisBox = toRenderBox(this);
        context->clip(thisBox->overflowClipRect(rect.location()));

        // Adjust the paint rect to reflect a scrolled content box with borders at the ends.
        IntSize offset = thisBox->scrolledContentOffset();
        scrolledPaintRect.move(-offset);
        scrolledPaintRect.setWidth(bLeft + thisBox->scrollWidth() + bRight);
        scrolledPaintRect.setHeight(borderTop() + thisBox->scrollHeight() + borderBottom());
    }

    GraphicsContextStateSaver backgroundClipStateSaver(*context, false);
    IntRect maskRect;

    switch (bgLayer.clip()) {
    case PaddingFillBox:
    case ContentFillBox: {
        if (clipToBorderRadius)
            break;

        // Clip to the padding or content boxes as necessary.
        bool includePadding = bgLayer.clip() == ContentFillBox;
        LayoutRect clipRect = LayoutRect(scrolledPaintRect.x() + bLeft + (includePadding ? pLeft : LayoutUnit()),
            scrolledPaintRect.y() + borderTop() + (includePadding ? paddingTop() : LayoutUnit()),
            scrolledPaintRect.width() - bLeft - bRight - (includePadding ? pLeft + pRight : LayoutUnit()),
            scrolledPaintRect.height() - borderTop() - borderBottom() - (includePadding ? paddingTop() + paddingBottom() : LayoutUnit()));
        backgroundClipStateSaver.save();
        context->clip(clipRect);

        break;
    }
    case TextFillBox: {
        // First figure out how big the mask has to be.  It should be no bigger than what we need
        // to actually render, so we should intersect the dirty rect with the border box of the background.
        maskRect = pixelSnappedIntRect(rect);
        maskRect.intersect(paintInfo.rect);

        // We draw the background into a separate layer, to be later masked with yet another layer
        // holding the text content.
        backgroundClipStateSaver.save();
        context->clip(maskRect);
        context->beginTransparencyLayer(1);

        break;
    }
    case BorderFillBox:
        break;
    default:
        ASSERT_NOT_REACHED();
        break;
    }

    // Only fill with a base color (e.g., white) if we're the root document, since iframes/frames with
    // no background in the child document should show the parent's background.
    bool isOpaqueRoot = false;
    if (isRoot) {
        isOpaqueRoot = true;
        if (!bgLayer.next() && bgColor.hasAlpha() && view()->frameView()) {
            Element* ownerElement = document().ownerElement();
            if (ownerElement) {
                if (!isHTMLFrameElement(*ownerElement)) {
                    // Locate the <body> element using the DOM.  This is easier than trying
                    // to crawl around a render tree with potential :before/:after content and
                    // anonymous blocks created by inline <body> tags etc.  We can locate the <body>
                    // render object very easily via the DOM.
                    HTMLElement* body = document().body();
                    if (body) {
                        // Can't scroll a frameset document anyway.
                        isOpaqueRoot = body->hasTagName(framesetTag);
                    } else {
                        // SVG documents and XML documents with SVG root nodes are transparent.
                        isOpaqueRoot = !document().hasSVGRootNode();
                    }
                }
            } else {
                isOpaqueRoot = !view()->frameView()->isTransparent();
            }
        }
    }

    // Paint the color first underneath all images, culled if background image occludes it.
    // FIXME: In the bgLayer->hasFiniteBounds() case, we could improve the culling test
    // by verifying whether the background image covers the entire layout rect.
    if (!bgLayer.next()) {
        IntRect backgroundRect(pixelSnappedIntRect(scrolledPaintRect));
        bool boxShadowShouldBeAppliedToBackground = this->boxShadowShouldBeAppliedToBackground(bleedAvoidance, box);
        if (boxShadowShouldBeAppliedToBackground || !shouldPaintBackgroundImage || !bgLayer.hasOpaqueImage(this) || !bgLayer.hasRepeatXY() || (isOpaqueRoot && !toRenderBox(this)->height()))  {
            if (!boxShadowShouldBeAppliedToBackground)
                backgroundRect.intersect(paintInfo.rect);

            GraphicsContextStateSaver shadowStateSaver(*context, boxShadowShouldBeAppliedToBackground);
            if (boxShadowShouldBeAppliedToBackground)
                applyBoxShadowForBackground(context, this);

            if (isOpaqueRoot) {
                // If we have an alpha and we are painting the root element, go ahead and blend with the base background color.
                Color baseColor = view()->frameView()->baseBackgroundColor();
                bool shouldClearDocumentBackground = document().settings() && document().settings()->shouldClearDocumentBackground();
                CompositeOperator operation = shouldClearDocumentBackground ? CompositeCopy : context->compositeOperation();

                if (baseColor.alpha()) {
                    if (bgColor.alpha())
                        baseColor = baseColor.blend(bgColor);
                    context->fillRect(backgroundRect, baseColor, operation);
                } else if (bgColor.alpha()) {
                    context->fillRect(backgroundRect, bgColor, operation);
                } else if (shouldClearDocumentBackground) {
                    context->clearRect(backgroundRect);
                }
            } else if (bgColor.alpha()) {
                context->fillRect(backgroundRect, bgColor, context->compositeOperation());
            }
        }
    }

    // no progressive loading of the background image
    if (shouldPaintBackgroundImage) {
        BackgroundImageGeometry geometry;
        calculateBackgroundImageGeometry(paintInfo.paintContainer(), bgLayer, scrolledPaintRect, geometry, backgroundObject);
        geometry.clip(paintInfo.rect);
        if (!geometry.destRect().isEmpty()) {
            CompositeOperator compositeOp = op == CompositeSourceOver ? bgLayer.composite() : op;
            RenderObject* clientForBackgroundImage = backgroundObject ? backgroundObject : this;
            RefPtr<Image> image = bgImage->image(clientForBackgroundImage, geometry.tileSize());
            InterpolationQuality interpolationQuality = chooseInterpolationQuality(context, image.get(), &bgLayer, geometry.tileSize());
            if (bgLayer.maskSourceType() == MaskLuminance)
                context->setColorFilter(ColorFilterLuminanceToAlpha);
            InterpolationQuality previousInterpolationQuality = context->imageInterpolationQuality();
            context->setImageInterpolationQuality(interpolationQuality);
            context->drawTiledImage(image.get(), geometry.destRect(), geometry.relativePhase(), geometry.tileSize(),
                compositeOp, bgLayer.blendMode(), geometry.spaceSize());
            context->setImageInterpolationQuality(previousInterpolationQuality);
        }
    }

    if (bgLayer.clip() == TextFillBox) {
        // Create the text mask layer.
        context->setCompositeOperation(CompositeDestinationIn);
        context->beginTransparencyLayer(1);

        // FIXME: Workaround for https://code.google.com/p/skia/issues/detail?id=1291.
        context->clearRect(maskRect);

        // Now draw the text into the mask. We do this by painting using a special paint phase that signals to
        // InlineTextBoxes that they should just add their contents to the clip.
        PaintInfo info(context, maskRect, PaintPhaseTextClip, PaintBehaviorForceBlackText, 0);
        context->setCompositeOperation(CompositeSourceOver);
        if (box) {
            RootInlineBox& root = box->root();
            box->paint(info, LayoutPoint(scrolledPaintRect.x() - box->x(), scrolledPaintRect.y() - box->y()), root.lineTop(), root.lineBottom());
        } else {
            LayoutSize localOffset = isBox() ? toRenderBox(this)->locationOffset() : LayoutSize();
            paint(info, scrolledPaintRect.location() - localOffset);
        }

        context->endLayer();
        context->endLayer();
    }
}

static inline int resolveWidthForRatio(int height, const FloatSize& intrinsicRatio)
{
    return ceilf(height * intrinsicRatio.width() / intrinsicRatio.height());
}

static inline int resolveHeightForRatio(int width, const FloatSize& intrinsicRatio)
{
    return ceilf(width * intrinsicRatio.height() / intrinsicRatio.width());
}

static inline IntSize resolveAgainstIntrinsicWidthOrHeightAndRatio(const IntSize& size, const FloatSize& intrinsicRatio, int useWidth, int useHeight)
{
    if (intrinsicRatio.isEmpty()) {
        if (useWidth)
            return IntSize(useWidth, size.height());
        return IntSize(size.width(), useHeight);
    }

    if (useWidth)
        return IntSize(useWidth, resolveHeightForRatio(useWidth, intrinsicRatio));
    return IntSize(resolveWidthForRatio(useHeight, intrinsicRatio), useHeight);
}

static inline IntSize resolveAgainstIntrinsicRatio(const IntSize& size, const FloatSize& intrinsicRatio)
{
    // Two possible solutions: (size.width(), solutionHeight) or (solutionWidth, size.height())
    // "... must be assumed to be the largest dimensions..." = easiest answer: the rect with the largest surface area.

    int solutionWidth = resolveWidthForRatio(size.height(), intrinsicRatio);
    int solutionHeight = resolveHeightForRatio(size.width(), intrinsicRatio);
    if (solutionWidth <= size.width()) {
        if (solutionHeight <= size.height()) {
            // If both solutions fit, choose the one covering the larger area.
            int areaOne = solutionWidth * size.height();
            int areaTwo = size.width() * solutionHeight;
            if (areaOne < areaTwo)
                return IntSize(size.width(), solutionHeight);
            return IntSize(solutionWidth, size.height());
        }

        // Only the first solution fits.
        return IntSize(solutionWidth, size.height());
    }

    // Only the second solution fits, assert that.
    ASSERT(solutionHeight <= size.height());
    return IntSize(size.width(), solutionHeight);
}

IntSize RenderBoxModelObject::calculateImageIntrinsicDimensions(StyleImage* image, const IntSize& positioningAreaSize, ScaleByEffectiveZoomOrNot shouldScaleOrNot) const
{
    // A generated image without a fixed size, will always return the container size as intrinsic size.
    if (image->isGeneratedImage() && image->usesImageContainerSize())
        return IntSize(positioningAreaSize.width(), positioningAreaSize.height());

    Length intrinsicWidth;
    Length intrinsicHeight;
    FloatSize intrinsicRatio;
    image->computeIntrinsicDimensions(this, intrinsicWidth, intrinsicHeight, intrinsicRatio);

    ASSERT(!intrinsicWidth.isPercent());
    ASSERT(!intrinsicHeight.isPercent());

    IntSize resolvedSize(intrinsicWidth.value(), intrinsicHeight.value());
    IntSize minimumSize(resolvedSize.width() > 0 ? 1 : 0, resolvedSize.height() > 0 ? 1 : 0);
    if (shouldScaleOrNot == ScaleByEffectiveZoom)
        resolvedSize.scale(style()->effectiveZoom());
    resolvedSize.clampToMinimumSize(minimumSize);

    if (!resolvedSize.isEmpty())
        return resolvedSize;

    // If the image has one of either an intrinsic width or an intrinsic height:
    // * and an intrinsic aspect ratio, then the missing dimension is calculated from the given dimension and the ratio.
    // * and no intrinsic aspect ratio, then the missing dimension is assumed to be the size of the rectangle that
    //   establishes the coordinate system for the 'background-position' property.
    if (resolvedSize.width() > 0 || resolvedSize.height() > 0)
        return resolveAgainstIntrinsicWidthOrHeightAndRatio(positioningAreaSize, intrinsicRatio, resolvedSize.width(), resolvedSize.height());

    // If the image has no intrinsic dimensions and has an intrinsic ratio the dimensions must be assumed to be the
    // largest dimensions at that ratio such that neither dimension exceeds the dimensions of the rectangle that
    // establishes the coordinate system for the 'background-position' property.
    if (!intrinsicRatio.isEmpty())
        return resolveAgainstIntrinsicRatio(positioningAreaSize, intrinsicRatio);

    // If the image has no intrinsic ratio either, then the dimensions must be assumed to be the rectangle that
    // establishes the coordinate system for the 'background-position' property.
    return positioningAreaSize;
}

static inline void applySubPixelHeuristicForTileSize(LayoutSize& tileSize, const IntSize& positioningAreaSize)
{
    tileSize.setWidth(positioningAreaSize.width() - tileSize.width() <= 1 ? tileSize.width().ceil() : tileSize.width().floor());
    tileSize.setHeight(positioningAreaSize.height() - tileSize.height() <= 1 ? tileSize.height().ceil() : tileSize.height().floor());
}

IntSize RenderBoxModelObject::calculateFillTileSize(const FillLayer& fillLayer, const IntSize& positioningAreaSize) const
{
    StyleImage* image = fillLayer.image();
    EFillSizeType type = fillLayer.size().type;

    IntSize imageIntrinsicSize = calculateImageIntrinsicDimensions(image, positioningAreaSize, ScaleByEffectiveZoom);
    imageIntrinsicSize.scale(1 / image->imageScaleFactor(), 1 / image->imageScaleFactor());
    switch (type) {
        case SizeLength: {
            LayoutSize tileSize = positioningAreaSize;

            Length layerWidth = fillLayer.size().size.width();
            Length layerHeight = fillLayer.size().size.height();

            if (layerWidth.isFixed())
                tileSize.setWidth(layerWidth.value());
            else if (layerWidth.isPercent())
                tileSize.setWidth(valueForLength(layerWidth, positioningAreaSize.width()));

            if (layerHeight.isFixed())
                tileSize.setHeight(layerHeight.value());
            else if (layerHeight.isPercent())
                tileSize.setHeight(valueForLength(layerHeight, positioningAreaSize.height()));

            applySubPixelHeuristicForTileSize(tileSize, positioningAreaSize);

            // If one of the values is auto we have to use the appropriate
            // scale to maintain our aspect ratio.
            if (layerWidth.isAuto() && !layerHeight.isAuto()) {
                if (imageIntrinsicSize.height())
                    tileSize.setWidth(imageIntrinsicSize.width() * tileSize.height() / imageIntrinsicSize.height());
            } else if (!layerWidth.isAuto() && layerHeight.isAuto()) {
                if (imageIntrinsicSize.width())
                    tileSize.setHeight(imageIntrinsicSize.height() * tileSize.width() / imageIntrinsicSize.width());
            } else if (layerWidth.isAuto() && layerHeight.isAuto()) {
                // If both width and height are auto, use the image's intrinsic size.
                tileSize = imageIntrinsicSize;
            }

            tileSize.clampNegativeToZero();
            return flooredIntSize(tileSize);
        }
        case SizeNone: {
            // If both values are ‘auto’ then the intrinsic width and/or height of the image should be used, if any.
            if (!imageIntrinsicSize.isEmpty())
                return imageIntrinsicSize;

            // If the image has neither an intrinsic width nor an intrinsic height, its size is determined as for ‘contain’.
            type = Contain;
        }
        case Contain:
        case Cover: {
            float horizontalScaleFactor = imageIntrinsicSize.width()
                ? static_cast<float>(positioningAreaSize.width()) / imageIntrinsicSize.width() : 1;
            float verticalScaleFactor = imageIntrinsicSize.height()
                ? static_cast<float>(positioningAreaSize.height()) / imageIntrinsicSize.height() : 1;
            float scaleFactor = type == Contain ? std::min(horizontalScaleFactor, verticalScaleFactor) : std::max(horizontalScaleFactor, verticalScaleFactor);
            return IntSize(std::max(1l, lround(imageIntrinsicSize.width() * scaleFactor)), std::max(1l, lround(imageIntrinsicSize.height() * scaleFactor)));
       }
    }

    ASSERT_NOT_REACHED();
    return IntSize();
}

void RenderBoxModelObject::BackgroundImageGeometry::setNoRepeatX(int xOffset)
{
    m_destRect.move(std::max(xOffset, 0), 0);
    m_phase.setX(-std::min(xOffset, 0));
    m_destRect.setWidth(m_tileSize.width() + std::min(xOffset, 0));
}
void RenderBoxModelObject::BackgroundImageGeometry::setNoRepeatY(int yOffset)
{
    m_destRect.move(0, std::max(yOffset, 0));
    m_phase.setY(-std::min(yOffset, 0));
    m_destRect.setHeight(m_tileSize.height() + std::min(yOffset, 0));
}

void RenderBoxModelObject::BackgroundImageGeometry::useFixedAttachment(const IntPoint& attachmentPoint)
{
    IntPoint alignedPoint = attachmentPoint;
    m_phase.move(std::max(alignedPoint.x() - m_destRect.x(), 0), std::max(alignedPoint.y() - m_destRect.y(), 0));
}

void RenderBoxModelObject::BackgroundImageGeometry::clip(const IntRect& clipRect)
{
    m_destRect.intersect(clipRect);
}

IntPoint RenderBoxModelObject::BackgroundImageGeometry::relativePhase() const
{
    IntPoint phase = m_phase;
    phase += m_destRect.location() - m_destOrigin;
    return phase;
}

bool RenderBoxModelObject::fixedBackgroundPaintsInLocalCoordinates() const
{
    if (!isDocumentElement())
        return false;

    if (view()->frameView() && view()->frameView()->paintBehavior() & PaintBehaviorFlattenCompositingLayers)
        return false;

    RenderLayer* rootLayer = view()->layer();
    if (!rootLayer || rootLayer->compositingState() == NotComposited)
        return false;

    return rootLayer->compositedLayerMapping()->backgroundLayerPaintsFixedRootBackground();
}

static inline int getSpace(int areaSize, int tileSize)
{
    int numberOfTiles = areaSize / tileSize;
    int space = -1;

    if (numberOfTiles > 1)
        space = lroundf((float)(areaSize - numberOfTiles * tileSize) / (numberOfTiles - 1));

    return space;
}

void RenderBoxModelObject::calculateBackgroundImageGeometry(const RenderLayerModelObject* paintContainer, const FillLayer& fillLayer, const LayoutRect& paintRect,
    BackgroundImageGeometry& geometry, RenderObject* backgroundObject) const
{
    LayoutUnit left = 0;
    LayoutUnit top = 0;
    IntSize positioningAreaSize;
    IntRect snappedPaintRect = pixelSnappedIntRect(paintRect);

    // Determine the background positioning area and set destRect to the background painting area.
    // destRect will be adjusted later if the background is non-repeating.
    // FIXME: transforms spec says that fixed backgrounds behave like scroll inside transforms.
    bool fixedAttachment = fillLayer.attachment() == FixedBackgroundAttachment;

    if (RuntimeEnabledFeatures::fastMobileScrollingEnabled()) {
        // As a side effect of an optimization to blit on scroll, we do not honor the CSS
        // property "background-attachment: fixed" because it may result in rendering
        // artifacts. Note, these artifacts only appear if we are blitting on scroll of
        // a page that has fixed background images.
        fixedAttachment = false;
    }

    if (!fixedAttachment) {
        geometry.setDestRect(snappedPaintRect);

        LayoutUnit right = 0;
        LayoutUnit bottom = 0;
        // Scroll and Local.
        if (fillLayer.origin() != BorderFillBox) {
            left = borderLeft();
            right = borderRight();
            top = borderTop();
            bottom = borderBottom();
            if (fillLayer.origin() == ContentFillBox) {
                left += paddingLeft();
                right += paddingRight();
                top += paddingTop();
                bottom += paddingBottom();
            }
        }

        // The background of the box generated by the root element covers the entire canvas including
        // its margins. Since those were added in already, we have to factor them out when computing
        // the background positioning area.
        if (isDocumentElement()) {
            positioningAreaSize = pixelSnappedIntSize(toRenderBox(this)->size() - LayoutSize(left + right, top + bottom), toRenderBox(this)->location());
            left += marginLeft();
            top += marginTop();
        } else
            positioningAreaSize = pixelSnappedIntSize(paintRect.size() - LayoutSize(left + right, top + bottom), paintRect.location());
    } else {
        geometry.setHasNonLocalGeometry();

        IntRect viewportRect = pixelSnappedIntRect(viewRect());
        if (fixedBackgroundPaintsInLocalCoordinates())
            viewportRect.setLocation(IntPoint());
        else if (FrameView* frameView = view()->frameView())
            viewportRect.setLocation(IntPoint(frameView->scrollOffsetForFixedPosition()));

        if (paintContainer) {
            IntPoint absoluteContainerOffset = roundedIntPoint(paintContainer->localToAbsolute(FloatPoint()));
            viewportRect.moveBy(-absoluteContainerOffset);
        }

        geometry.setDestRect(pixelSnappedIntRect(viewportRect));
        positioningAreaSize = geometry.destRect().size();
    }

    const RenderObject* clientForBackgroundImage = backgroundObject ? backgroundObject : this;
    IntSize fillTileSize = calculateFillTileSize(fillLayer, positioningAreaSize);
    fillLayer.image()->setContainerSizeForRenderer(clientForBackgroundImage, fillTileSize, style()->effectiveZoom());
    geometry.setTileSize(fillTileSize);

    EFillRepeat backgroundRepeatX = fillLayer.repeatX();
    EFillRepeat backgroundRepeatY = fillLayer.repeatY();
    int availableWidth = positioningAreaSize.width() - geometry.tileSize().width();
    int availableHeight = positioningAreaSize.height() - geometry.tileSize().height();

    LayoutUnit computedXPosition = roundedMinimumValueForLength(fillLayer.xPosition(), availableWidth);
    if (backgroundRepeatX == RoundFill && positioningAreaSize.width() > 0 && fillTileSize.width() > 0) {
        long nrTiles = std::max(1l, lroundf((float)positioningAreaSize.width() / fillTileSize.width()));

        if (fillLayer.size().size.height().isAuto() && backgroundRepeatY != RoundFill) {
            fillTileSize.setHeight(fillTileSize.height() * positioningAreaSize.width() / (nrTiles * fillTileSize.width()));
        }

        fillTileSize.setWidth(positioningAreaSize.width() / nrTiles);
        geometry.setTileSize(fillTileSize);
        geometry.setPhaseX(geometry.tileSize().width() ? geometry.tileSize().width() - roundToInt(computedXPosition + left) % geometry.tileSize().width() : 0);
        geometry.setSpaceSize(IntSize());
    }

    LayoutUnit computedYPosition = roundedMinimumValueForLength(fillLayer.yPosition(), availableHeight);
    if (backgroundRepeatY == RoundFill && positioningAreaSize.height() > 0 && fillTileSize.height() > 0) {
        long nrTiles = std::max(1l, lroundf((float)positioningAreaSize.height() / fillTileSize.height()));

        if (fillLayer.size().size.width().isAuto() && backgroundRepeatX != RoundFill) {
            fillTileSize.setWidth(fillTileSize.width() * positioningAreaSize.height() / (nrTiles * fillTileSize.height()));
        }

        fillTileSize.setHeight(positioningAreaSize.height() / nrTiles);
        geometry.setTileSize(fillTileSize);
        geometry.setPhaseY(geometry.tileSize().height() ? geometry.tileSize().height() - roundToInt(computedYPosition + top) % geometry.tileSize().height() : 0);
        geometry.setSpaceSize(IntSize());
    }

    if (backgroundRepeatX == RepeatFill) {
        geometry.setPhaseX(geometry.tileSize().width() ? geometry.tileSize().width() - roundToInt(computedXPosition + left) % geometry.tileSize().width() : 0);
        geometry.setSpaceSize(IntSize());
    } else if (backgroundRepeatX == SpaceFill && fillTileSize.width() > 0) {
        int space = getSpace(positioningAreaSize.width(), geometry.tileSize().width());
        int actualWidth = geometry.tileSize().width() + space;

        if (space >= 0) {
            computedXPosition = roundedMinimumValueForLength(Length(), availableWidth);
            geometry.setSpaceSize(IntSize(space, 0));
            geometry.setPhaseX(actualWidth ? actualWidth - roundToInt(computedXPosition + left) % actualWidth : 0);
        } else {
            backgroundRepeatX = NoRepeatFill;
        }
    }
    if (backgroundRepeatX == NoRepeatFill) {
        int xOffset = fillLayer.backgroundXOrigin() == RightEdge ? availableWidth - computedXPosition : computedXPosition;
        geometry.setNoRepeatX(left + xOffset);
        geometry.setSpaceSize(IntSize(0, geometry.spaceSize().height()));
    }

    if (backgroundRepeatY == RepeatFill) {
        geometry.setPhaseY(geometry.tileSize().height() ? geometry.tileSize().height() - roundToInt(computedYPosition + top) % geometry.tileSize().height() : 0);
        geometry.setSpaceSize(IntSize(geometry.spaceSize().width(), 0));
    } else if (backgroundRepeatY == SpaceFill && fillTileSize.height() > 0) {
        int space = getSpace(positioningAreaSize.height(), geometry.tileSize().height());
        int actualHeight = geometry.tileSize().height() + space;

        if (space >= 0) {
            computedYPosition = roundedMinimumValueForLength(Length(), availableHeight);
            geometry.setSpaceSize(IntSize(geometry.spaceSize().width(), space));
            geometry.setPhaseY(actualHeight ? actualHeight - roundToInt(computedYPosition + top) % actualHeight : 0);
        } else {
            backgroundRepeatY = NoRepeatFill;
        }
    }
    if (backgroundRepeatY == NoRepeatFill) {
        int yOffset = fillLayer.backgroundYOrigin() == BottomEdge ? availableHeight - computedYPosition : computedYPosition;
        geometry.setNoRepeatY(top + yOffset);
        geometry.setSpaceSize(IntSize(geometry.spaceSize().width(), 0));
    }

    if (fixedAttachment)
        geometry.useFixedAttachment(snappedPaintRect.location());

    geometry.clip(snappedPaintRect);
    geometry.setDestOrigin(geometry.destRect().location());
}

static LayoutUnit computeBorderImageSide(const BorderImageLength& borderSlice, LayoutUnit borderSide, LayoutUnit imageSide, LayoutUnit boxExtent)
{
    if (borderSlice.isNumber())
        return borderSlice.number() * borderSide;
    if (borderSlice.length().isAuto())
        return imageSide;
    return valueForLength(borderSlice.length(), boxExtent);
}

bool RenderBoxModelObject::paintNinePieceImage(GraphicsContext* graphicsContext, const LayoutRect& rect, const RenderStyle* style,
                                               const NinePieceImage& ninePieceImage, CompositeOperator op)
{
    StyleImage* styleImage = ninePieceImage.image();
    if (!styleImage)
        return false;

    if (!styleImage->isLoaded())
        return true; // Never paint a nine-piece image incrementally, but don't paint the fallback borders either.

    if (!styleImage->canRender(*this, style->effectiveZoom()))
        return false;

    // FIXME: border-image is broken with full page zooming when tiling has to happen, since the tiling function
    // doesn't have any understanding of the zoom that is in effect on the tile.
    LayoutRect rectWithOutsets = rect;
    rectWithOutsets.expand(style->imageOutsets(ninePieceImage));
    IntRect borderImageRect = pixelSnappedIntRect(rectWithOutsets);

    IntSize imageSize = calculateImageIntrinsicDimensions(styleImage, borderImageRect.size(), DoNotScaleByEffectiveZoom);

    // If both values are ‘auto’ then the intrinsic width and/or height of the image should be used, if any.
    styleImage->setContainerSizeForRenderer(this, imageSize, style->effectiveZoom());

    int imageWidth = imageSize.width();
    int imageHeight = imageSize.height();

    float imageScaleFactor = styleImage->imageScaleFactor();
    int topSlice = std::min<int>(imageHeight, valueForLength(ninePieceImage.imageSlices().top(), imageHeight)) * imageScaleFactor;
    int rightSlice = std::min<int>(imageWidth, valueForLength(ninePieceImage.imageSlices().right(), imageWidth)) * imageScaleFactor;
    int bottomSlice = std::min<int>(imageHeight, valueForLength(ninePieceImage.imageSlices().bottom(), imageHeight)) * imageScaleFactor;
    int leftSlice = std::min<int>(imageWidth, valueForLength(ninePieceImage.imageSlices().left(), imageWidth)) * imageScaleFactor;

    ENinePieceImageRule hRule = ninePieceImage.horizontalRule();
    ENinePieceImageRule vRule = ninePieceImage.verticalRule();

    int topWidth = computeBorderImageSide(ninePieceImage.borderSlices().top(), style->borderTopWidth(), topSlice, borderImageRect.height());
    int rightWidth = computeBorderImageSide(ninePieceImage.borderSlices().right(), style->borderRightWidth(), rightSlice, borderImageRect.width());
    int bottomWidth = computeBorderImageSide(ninePieceImage.borderSlices().bottom(), style->borderBottomWidth(), bottomSlice, borderImageRect.height());
    int leftWidth = computeBorderImageSide(ninePieceImage.borderSlices().left(), style->borderLeftWidth(), leftSlice, borderImageRect.width());

    // Reduce the widths if they're too large.
    // The spec says: Given Lwidth as the width of the border image area, Lheight as its height, and Wside as the border image width
    // offset for the side, let f = min(Lwidth/(Wleft+Wright), Lheight/(Wtop+Wbottom)). If f < 1, then all W are reduced by
    // multiplying them by f.
    int borderSideWidth = std::max(1, leftWidth + rightWidth);
    int borderSideHeight = std::max(1, topWidth + bottomWidth);
    float borderSideScaleFactor = std::min((float)borderImageRect.width() / borderSideWidth, (float)borderImageRect.height() / borderSideHeight);
    if (borderSideScaleFactor < 1) {
        topWidth *= borderSideScaleFactor;
        rightWidth *= borderSideScaleFactor;
        bottomWidth *= borderSideScaleFactor;
        leftWidth *= borderSideScaleFactor;
    }

    bool drawLeft = leftSlice > 0 && leftWidth > 0;
    bool drawTop = topSlice > 0 && topWidth > 0;
    bool drawRight = rightSlice > 0 && rightWidth > 0;
    bool drawBottom = bottomSlice > 0 && bottomWidth > 0;
    bool drawMiddle = ninePieceImage.fill() && (imageWidth - leftSlice - rightSlice) > 0 && (borderImageRect.width() - leftWidth - rightWidth) > 0
                      && (imageHeight - topSlice - bottomSlice) > 0 && (borderImageRect.height() - topWidth - bottomWidth) > 0;

    RefPtr<Image> image = styleImage->image(this, imageSize);

    float destinationWidth = borderImageRect.width() - leftWidth - rightWidth;
    float destinationHeight = borderImageRect.height() - topWidth - bottomWidth;

    float sourceWidth = imageWidth - leftSlice - rightSlice;
    float sourceHeight = imageHeight - topSlice - bottomSlice;

    float leftSideScale = drawLeft ? (float)leftWidth / leftSlice : 1;
    float rightSideScale = drawRight ? (float)rightWidth / rightSlice : 1;
    float topSideScale = drawTop ? (float)topWidth / topSlice : 1;
    float bottomSideScale = drawBottom ? (float)bottomWidth / bottomSlice : 1;

    if (drawLeft) {
        // Paint the top and bottom left corners.

        // The top left corner rect is (tx, ty, leftWidth, topWidth)
        // The rect to use from within the image is obtained from our slice, and is (0, 0, leftSlice, topSlice)
        if (drawTop)
            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.location(), IntSize(leftWidth, topWidth)),
                                       LayoutRect(0, 0, leftSlice, topSlice), op);

        // The bottom left corner rect is (tx, ty + h - bottomWidth, leftWidth, bottomWidth)
        // The rect to use from within the image is (0, imageHeight - bottomSlice, leftSlice, botomSlice)
        if (drawBottom)
            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.x(), borderImageRect.maxY() - bottomWidth, leftWidth, bottomWidth),
                                       LayoutRect(0, imageHeight - bottomSlice, leftSlice, bottomSlice), op);

        // Paint the left edge.
        // Have to scale and tile into the border rect.
        if (sourceHeight > 0)
            graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.x(), borderImageRect.y() + topWidth, leftWidth, destinationHeight),
                                            IntRect(0, topSlice, leftSlice, sourceHeight),
                                            FloatSize(leftSideScale, leftSideScale), Image::StretchTile, (Image::TileRule)vRule, op);
    }

    if (drawRight) {
        // Paint the top and bottom right corners
        // The top right corner rect is (tx + w - rightWidth, ty, rightWidth, topWidth)
        // The rect to use from within the image is obtained from our slice, and is (imageWidth - rightSlice, 0, rightSlice, topSlice)
        if (drawTop)
            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.maxX() - rightWidth, borderImageRect.y(), rightWidth, topWidth),
                                       LayoutRect(imageWidth - rightSlice, 0, rightSlice, topSlice), op);

        // The bottom right corner rect is (tx + w - rightWidth, ty + h - bottomWidth, rightWidth, bottomWidth)
        // The rect to use from within the image is (imageWidth - rightSlice, imageHeight - bottomSlice, rightSlice, bottomSlice)
        if (drawBottom)
            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.maxX() - rightWidth, borderImageRect.maxY() - bottomWidth, rightWidth, bottomWidth),
                                       LayoutRect(imageWidth - rightSlice, imageHeight - bottomSlice, rightSlice, bottomSlice), op);

        // Paint the right edge.
        if (sourceHeight > 0)
            graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.maxX() - rightWidth, borderImageRect.y() + topWidth, rightWidth,
                                            destinationHeight),
                                            IntRect(imageWidth - rightSlice, topSlice, rightSlice, sourceHeight),
                                            FloatSize(rightSideScale, rightSideScale),
                                            Image::StretchTile, (Image::TileRule)vRule, op);
    }

    // Paint the top edge.
    if (drawTop && sourceWidth > 0)
        graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.x() + leftWidth, borderImageRect.y(), destinationWidth, topWidth),
                                        IntRect(leftSlice, 0, sourceWidth, topSlice),
                                        FloatSize(topSideScale, topSideScale), (Image::TileRule)hRule, Image::StretchTile, op);

    // Paint the bottom edge.
    if (drawBottom && sourceWidth > 0)
        graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.x() + leftWidth, borderImageRect.maxY() - bottomWidth,
                                        destinationWidth, bottomWidth),
                                        IntRect(leftSlice, imageHeight - bottomSlice, sourceWidth, bottomSlice),
                                        FloatSize(bottomSideScale, bottomSideScale),
                                        (Image::TileRule)hRule, Image::StretchTile, op);

    // Paint the middle.
    if (drawMiddle) {
        FloatSize middleScaleFactor(1, 1);
        if (drawTop)
            middleScaleFactor.setWidth(topSideScale);
        else if (drawBottom)
            middleScaleFactor.setWidth(bottomSideScale);
        if (drawLeft)
            middleScaleFactor.setHeight(leftSideScale);
        else if (drawRight)
            middleScaleFactor.setHeight(rightSideScale);

        // For "stretch" rules, just override the scale factor and replace. We only had to do this for the
        // center tile, since sides don't even use the scale factor unless they have a rule other than "stretch".
        // The middle however can have "stretch" specified in one axis but not the other, so we have to
        // correct the scale here.
        if (hRule == StretchImageRule)
            middleScaleFactor.setWidth(destinationWidth / sourceWidth);

        if (vRule == StretchImageRule)
            middleScaleFactor.setHeight(destinationHeight / sourceHeight);

        graphicsContext->drawTiledImage(image.get(),
            IntRect(borderImageRect.x() + leftWidth, borderImageRect.y() + topWidth, destinationWidth, destinationHeight),
            IntRect(leftSlice, topSlice, sourceWidth, sourceHeight),
            middleScaleFactor, (Image::TileRule)hRule, (Image::TileRule)vRule, op);
    }

    return true;
}

class BorderEdge {
public:
    BorderEdge(int edgeWidth, const Color& edgeColor, EBorderStyle edgeStyle, bool edgeIsTransparent, bool edgeIsPresent = true)
        : width(edgeWidth)
        , color(edgeColor)
        , style(edgeStyle)
        , isTransparent(edgeIsTransparent)
        , isPresent(edgeIsPresent)
    {
        if (style == DOUBLE && edgeWidth < 3)
            style = SOLID;
    }

    BorderEdge()
        : width(0)
        , style(BHIDDEN)
        , isTransparent(false)
        , isPresent(false)
    {
    }

    bool hasVisibleColorAndStyle() const { return style > BHIDDEN && !isTransparent; }
    bool shouldRender() const { return isPresent && width && hasVisibleColorAndStyle(); }
    bool presentButInvisible() const { return usedWidth() && !hasVisibleColorAndStyle(); }
    bool obscuresBackgroundEdge(float scale) const
    {
        if (!isPresent || isTransparent || (width * scale) < 2 || color.hasAlpha() || style == BHIDDEN)
            return false;

        if (style == DOTTED || style == DASHED)
            return false;

        if (style == DOUBLE)
            return width >= 5 * scale; // The outer band needs to be >= 2px wide at unit scale.

        return true;
    }
    bool obscuresBackground() const
    {
        if (!isPresent || isTransparent || color.hasAlpha() || style == BHIDDEN)
            return false;

        if (style == DOTTED || style == DASHED || style == DOUBLE)
            return false;

        return true;
    }

    int usedWidth() const { return isPresent ? width : 0; }

    void getDoubleBorderStripeWidths(int& outerWidth, int& innerWidth) const
    {
        int fullWidth = usedWidth();
        outerWidth = fullWidth / 3;
        innerWidth = fullWidth * 2 / 3;

        // We need certain integer rounding results
        if (fullWidth % 3 == 2)
            outerWidth += 1;

        if (fullWidth % 3 == 1)
            innerWidth += 1;
    }

    int width;
    Color color;
    EBorderStyle style;
    bool isTransparent;
    bool isPresent;
};

static bool allCornersClippedOut(const RoundedRect& border, const LayoutRect& clipRect)
{
    LayoutRect boundingRect = border.rect();
    if (clipRect.contains(boundingRect))
        return false;

    RoundedRect::Radii radii = border.radii();

    LayoutRect topLeftRect(boundingRect.location(), radii.topLeft());
    if (clipRect.intersects(topLeftRect))
        return false;

    LayoutRect topRightRect(boundingRect.location(), radii.topRight());
    topRightRect.setX(boundingRect.maxX() - topRightRect.width());
    if (clipRect.intersects(topRightRect))
        return false;

    LayoutRect bottomLeftRect(boundingRect.location(), radii.bottomLeft());
    bottomLeftRect.setY(boundingRect.maxY() - bottomLeftRect.height());
    if (clipRect.intersects(bottomLeftRect))
        return false;

    LayoutRect bottomRightRect(boundingRect.location(), radii.bottomRight());
    bottomRightRect.setX(boundingRect.maxX() - bottomRightRect.width());
    bottomRightRect.setY(boundingRect.maxY() - bottomRightRect.height());
    if (clipRect.intersects(bottomRightRect))
        return false;

    return true;
}

static bool borderWillArcInnerEdge(const LayoutSize& firstRadius, const FloatSize& secondRadius)
{
    return !firstRadius.isZero() || !secondRadius.isZero();
}

enum BorderEdgeFlag {
    TopBorderEdge = 1 << BSTop,
    RightBorderEdge = 1 << BSRight,
    BottomBorderEdge = 1 << BSBottom,
    LeftBorderEdge = 1 << BSLeft,
    AllBorderEdges = TopBorderEdge | BottomBorderEdge | LeftBorderEdge | RightBorderEdge
};

static inline BorderEdgeFlag edgeFlagForSide(BoxSide side)
{
    return static_cast<BorderEdgeFlag>(1 << side);
}

static inline bool includesEdge(BorderEdgeFlags flags, BoxSide side)
{
    return flags & edgeFlagForSide(side);
}

static inline bool includesAdjacentEdges(BorderEdgeFlags flags)
{
    return (flags & (TopBorderEdge | RightBorderEdge)) == (TopBorderEdge | RightBorderEdge)
        || (flags & (RightBorderEdge | BottomBorderEdge)) == (RightBorderEdge | BottomBorderEdge)
        || (flags & (BottomBorderEdge | LeftBorderEdge)) == (BottomBorderEdge | LeftBorderEdge)
        || (flags & (LeftBorderEdge | TopBorderEdge)) == (LeftBorderEdge | TopBorderEdge);
}

inline bool edgesShareColor(const BorderEdge& firstEdge, const BorderEdge& secondEdge)
{
    return firstEdge.color == secondEdge.color;
}

inline bool styleRequiresClipPolygon(EBorderStyle style)
{
    return style == DOTTED || style == DASHED; // These are drawn with a stroke, so we have to clip to get corner miters.
}

static bool borderStyleFillsBorderArea(EBorderStyle style)
{
    return !(style == DOTTED || style == DASHED || style == DOUBLE);
}

static bool borderStyleHasInnerDetail(EBorderStyle style)
{
    return style == GROOVE || style == RIDGE || style == DOUBLE;
}

static bool borderStyleIsDottedOrDashed(EBorderStyle style)
{
    return style == DOTTED || style == DASHED;
}

// OUTSET darkens the bottom and right (and maybe lightens the top and left)
// INSET darkens the top and left (and maybe lightens the bottom and right)
static inline bool borderStyleHasUnmatchedColorsAtCorner(EBorderStyle style, BoxSide side, BoxSide adjacentSide)
{
    // These styles match at the top/left and bottom/right.
    if (style == INSET || style == GROOVE || style == RIDGE || style == OUTSET) {
        const BorderEdgeFlags topRightFlags = edgeFlagForSide(BSTop) | edgeFlagForSide(BSRight);
        const BorderEdgeFlags bottomLeftFlags = edgeFlagForSide(BSBottom) | edgeFlagForSide(BSLeft);

        BorderEdgeFlags flags = edgeFlagForSide(side) | edgeFlagForSide(adjacentSide);
        return flags == topRightFlags || flags == bottomLeftFlags;
    }
    return false;
}

static inline bool colorsMatchAtCorner(BoxSide side, BoxSide adjacentSide, const BorderEdge edges[])
{
    if (edges[side].shouldRender() != edges[adjacentSide].shouldRender())
        return false;

    if (!edgesShareColor(edges[side], edges[adjacentSide]))
        return false;

    return !borderStyleHasUnmatchedColorsAtCorner(edges[side].style, side, adjacentSide);
}


static inline bool colorNeedsAntiAliasAtCorner(BoxSide side, BoxSide adjacentSide, const BorderEdge edges[])
{
    if (!edges[side].color.hasAlpha())
        return false;

    if (edges[side].shouldRender() != edges[adjacentSide].shouldRender())
        return false;

    if (!edgesShareColor(edges[side], edges[adjacentSide]))
        return true;

    return borderStyleHasUnmatchedColorsAtCorner(edges[side].style, side, adjacentSide);
}

// This assumes that we draw in order: top, bottom, left, right.
static inline bool willBeOverdrawn(BoxSide side, BoxSide adjacentSide, const BorderEdge edges[])
{
    switch (side) {
    case BSTop:
    case BSBottom:
        if (edges[adjacentSide].presentButInvisible())
            return false;

        if (!edgesShareColor(edges[side], edges[adjacentSide]) && edges[adjacentSide].color.hasAlpha())
            return false;

        if (!borderStyleFillsBorderArea(edges[adjacentSide].style))
            return false;

        return true;

    case BSLeft:
    case BSRight:
        // These draw last, so are never overdrawn.
        return false;
    }
    return false;
}

static inline bool borderStylesRequireMitre(BoxSide side, BoxSide adjacentSide, EBorderStyle style, EBorderStyle adjacentStyle)
{
    if (style == DOUBLE || adjacentStyle == DOUBLE || adjacentStyle == GROOVE || adjacentStyle == RIDGE)
        return true;

    if (borderStyleIsDottedOrDashed(style) != borderStyleIsDottedOrDashed(adjacentStyle))
        return true;

    if (style != adjacentStyle)
        return true;

    return borderStyleHasUnmatchedColorsAtCorner(style, side, adjacentSide);
}

static bool joinRequiresMitre(BoxSide side, BoxSide adjacentSide, const BorderEdge edges[], bool allowOverdraw)
{
    if ((edges[side].isTransparent && edges[adjacentSide].isTransparent) || !edges[adjacentSide].isPresent)
        return false;

    if (allowOverdraw && willBeOverdrawn(side, adjacentSide, edges))
        return false;

    if (!edgesShareColor(edges[side], edges[adjacentSide]))
        return true;

    if (borderStylesRequireMitre(side, adjacentSide, edges[side].style, edges[adjacentSide].style))
        return true;

    return false;
}

void RenderBoxModelObject::paintOneBorderSide(GraphicsContext* graphicsContext, const RenderStyle* style, const RoundedRect& outerBorder, const RoundedRect& innerBorder,
    const IntRect& sideRect, BoxSide side, BoxSide adjacentSide1, BoxSide adjacentSide2, const BorderEdge edges[], const Path* path,
    BackgroundBleedAvoidance bleedAvoidance, bool includeLogicalLeftEdge, bool includeLogicalRightEdge, bool antialias, const Color* overrideColor)
{
    const BorderEdge& edgeToRender = edges[side];
    ASSERT(edgeToRender.width);
    const BorderEdge& adjacentEdge1 = edges[adjacentSide1];
    const BorderEdge& adjacentEdge2 = edges[adjacentSide2];

    bool mitreAdjacentSide1 = joinRequiresMitre(side, adjacentSide1, edges, !antialias);
    bool mitreAdjacentSide2 = joinRequiresMitre(side, adjacentSide2, edges, !antialias);

    bool adjacentSide1StylesMatch = colorsMatchAtCorner(side, adjacentSide1, edges);
    bool adjacentSide2StylesMatch = colorsMatchAtCorner(side, adjacentSide2, edges);

    const Color& colorToPaint = overrideColor ? *overrideColor : edgeToRender.color;

    if (path) {
        GraphicsContextStateSaver stateSaver(*graphicsContext);
        if (innerBorder.isRenderable())
            clipBorderSidePolygon(graphicsContext, outerBorder, innerBorder, side, adjacentSide1StylesMatch, adjacentSide2StylesMatch);
        else
            clipBorderSideForComplexInnerPath(graphicsContext, outerBorder, innerBorder, side, edges);
        float thickness = std::max(std::max(edgeToRender.width, adjacentEdge1.width), adjacentEdge2.width);
        drawBoxSideFromPath(graphicsContext, outerBorder.rect(), *path, edges, edgeToRender.width, thickness, side, style,
            colorToPaint, edgeToRender.style, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge);
    } else {
        bool clipForStyle = styleRequiresClipPolygon(edgeToRender.style) && (mitreAdjacentSide1 || mitreAdjacentSide2);
        bool clipAdjacentSide1 = colorNeedsAntiAliasAtCorner(side, adjacentSide1, edges) && mitreAdjacentSide1;
        bool clipAdjacentSide2 = colorNeedsAntiAliasAtCorner(side, adjacentSide2, edges) && mitreAdjacentSide2;
        bool shouldClip = clipForStyle || clipAdjacentSide1 || clipAdjacentSide2;

        GraphicsContextStateSaver clipStateSaver(*graphicsContext, shouldClip);
        if (shouldClip) {
            bool aliasAdjacentSide1 = clipAdjacentSide1 || (clipForStyle && mitreAdjacentSide1);
            bool aliasAdjacentSide2 = clipAdjacentSide2 || (clipForStyle && mitreAdjacentSide2);
            clipBorderSidePolygon(graphicsContext, outerBorder, innerBorder, side, !aliasAdjacentSide1, !aliasAdjacentSide2);
            // Since we clipped, no need to draw with a mitre.
            mitreAdjacentSide1 = false;
            mitreAdjacentSide2 = false;
        }

        drawLineForBoxSide(graphicsContext, sideRect.x(), sideRect.y(), sideRect.maxX(), sideRect.maxY(), side, colorToPaint, edgeToRender.style,
                mitreAdjacentSide1 ? adjacentEdge1.width : 0, mitreAdjacentSide2 ? adjacentEdge2.width : 0, antialias);
    }
}

static IntRect calculateSideRect(const RoundedRect& outerBorder, const BorderEdge edges[], int side)
{
    IntRect sideRect = outerBorder.rect();
    int width = edges[side].width;

    if (side == BSTop)
        sideRect.setHeight(width);
    else if (side == BSBottom)
        sideRect.shiftYEdgeTo(sideRect.maxY() - width);
    else if (side == BSLeft)
        sideRect.setWidth(width);
    else
        sideRect.shiftXEdgeTo(sideRect.maxX() - width);

    return sideRect;
}

void RenderBoxModelObject::paintBorderSides(GraphicsContext* graphicsContext, const RenderStyle* style, const RoundedRect& outerBorder, const RoundedRect& innerBorder,
    const IntPoint& innerBorderAdjustment, const BorderEdge edges[], BorderEdgeFlags edgeSet, BackgroundBleedAvoidance bleedAvoidance,
    bool includeLogicalLeftEdge, bool includeLogicalRightEdge, bool antialias, const Color* overrideColor)
{
    bool renderRadii = outerBorder.isRounded();

    Path roundedPath;
    if (renderRadii)
        roundedPath.addRoundedRect(outerBorder);

    // The inner border adjustment for bleed avoidance mode BackgroundBleedBackgroundOverBorder
    // is only applied to sideRect, which is okay since BackgroundBleedBackgroundOverBorder
    // is only to be used for solid borders and the shape of the border painted by drawBoxSideFromPath
    // only depends on sideRect when painting solid borders.

    if (edges[BSTop].shouldRender() && includesEdge(edgeSet, BSTop)) {
        IntRect sideRect = outerBorder.rect();
        sideRect.setHeight(edges[BSTop].width + innerBorderAdjustment.y());

        bool usePath = renderRadii && (borderStyleHasInnerDetail(edges[BSTop].style) || borderWillArcInnerEdge(innerBorder.radii().topLeft(), innerBorder.radii().topRight()));
        paintOneBorderSide(graphicsContext, style, outerBorder, innerBorder, sideRect, BSTop, BSLeft, BSRight, edges, usePath ? &roundedPath : 0, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias, overrideColor);
    }

    if (edges[BSBottom].shouldRender() && includesEdge(edgeSet, BSBottom)) {
        IntRect sideRect = outerBorder.rect();
        sideRect.shiftYEdgeTo(sideRect.maxY() - edges[BSBottom].width - innerBorderAdjustment.y());

        bool usePath = renderRadii && (borderStyleHasInnerDetail(edges[BSBottom].style) || borderWillArcInnerEdge(innerBorder.radii().bottomLeft(), innerBorder.radii().bottomRight()));
        paintOneBorderSide(graphicsContext, style, outerBorder, innerBorder, sideRect, BSBottom, BSLeft, BSRight, edges, usePath ? &roundedPath : 0, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias, overrideColor);
    }

    if (edges[BSLeft].shouldRender() && includesEdge(edgeSet, BSLeft)) {
        IntRect sideRect = outerBorder.rect();
        sideRect.setWidth(edges[BSLeft].width + innerBorderAdjustment.x());

        bool usePath = renderRadii && (borderStyleHasInnerDetail(edges[BSLeft].style) || borderWillArcInnerEdge(innerBorder.radii().bottomLeft(), innerBorder.radii().topLeft()));
        paintOneBorderSide(graphicsContext, style, outerBorder, innerBorder, sideRect, BSLeft, BSTop, BSBottom, edges, usePath ? &roundedPath : 0, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias, overrideColor);
    }

    if (edges[BSRight].shouldRender() && includesEdge(edgeSet, BSRight)) {
        IntRect sideRect = outerBorder.rect();
        sideRect.shiftXEdgeTo(sideRect.maxX() - edges[BSRight].width - innerBorderAdjustment.x());

        bool usePath = renderRadii && (borderStyleHasInnerDetail(edges[BSRight].style) || borderWillArcInnerEdge(innerBorder.radii().bottomRight(), innerBorder.radii().topRight()));
        paintOneBorderSide(graphicsContext, style, outerBorder, innerBorder, sideRect, BSRight, BSTop, BSBottom, edges, usePath ? &roundedPath : 0, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias, overrideColor);
    }
}

void RenderBoxModelObject::paintTranslucentBorderSides(GraphicsContext* graphicsContext, const RenderStyle* style, const RoundedRect& outerBorder, const RoundedRect& innerBorder, const IntPoint& innerBorderAdjustment,
    const BorderEdge edges[], BorderEdgeFlags edgesToDraw, BackgroundBleedAvoidance bleedAvoidance, bool includeLogicalLeftEdge, bool includeLogicalRightEdge, bool antialias)
{
    // willBeOverdrawn assumes that we draw in order: top, bottom, left, right.
    // This is different from BoxSide enum order.
    static const BoxSide paintOrder[] = { BSTop, BSBottom, BSLeft, BSRight };

    while (edgesToDraw) {
        // Find undrawn edges sharing a color.
        Color commonColor;

        BorderEdgeFlags commonColorEdgeSet = 0;
        for (size_t i = 0; i < sizeof(paintOrder) / sizeof(paintOrder[0]); ++i) {
            BoxSide currSide = paintOrder[i];
            if (!includesEdge(edgesToDraw, currSide))
                continue;

            bool includeEdge;
            if (!commonColorEdgeSet) {
                commonColor = edges[currSide].color;
                includeEdge = true;
            } else
                includeEdge = edges[currSide].color == commonColor;

            if (includeEdge)
                commonColorEdgeSet |= edgeFlagForSide(currSide);
        }

        bool useTransparencyLayer = includesAdjacentEdges(commonColorEdgeSet) && commonColor.hasAlpha();
        if (useTransparencyLayer) {
            graphicsContext->beginTransparencyLayer(static_cast<float>(commonColor.alpha()) / 255);
            commonColor = Color(commonColor.red(), commonColor.green(), commonColor.blue());
        }

        paintBorderSides(graphicsContext, style, outerBorder, innerBorder, innerBorderAdjustment, edges, commonColorEdgeSet, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias, &commonColor);

        if (useTransparencyLayer)
            graphicsContext->endLayer();

        edgesToDraw &= ~commonColorEdgeSet;
    }
}

void RenderBoxModelObject::paintBorder(const PaintInfo& info, const LayoutRect& rect, const RenderStyle* style,
                                       BackgroundBleedAvoidance bleedAvoidance, bool includeLogicalLeftEdge, bool includeLogicalRightEdge)
{
    GraphicsContext* graphicsContext = info.context;
    // border-image is not affected by border-radius.
    if (paintNinePieceImage(graphicsContext, rect, style, style->borderImage()))
        return;

    BorderEdge edges[4];
    getBorderEdgeInfo(edges, style, includeLogicalLeftEdge, includeLogicalRightEdge);
    RoundedRect outerBorder = style->getRoundedBorderFor(rect, includeLogicalLeftEdge, includeLogicalRightEdge);
    RoundedRect innerBorder = style->getRoundedInnerBorderFor(borderInnerRectAdjustedForBleedAvoidance(graphicsContext, rect, bleedAvoidance), includeLogicalLeftEdge, includeLogicalRightEdge);

    if (outerBorder.rect().isEmpty())
        return;

    bool haveAlphaColor = false;
    bool haveAllSolidEdges = true;
    bool haveAllDoubleEdges = true;
    int numEdgesVisible = 4;
    bool allEdgesShareColor = true;
    bool allEdgesShareWidth = true;
    int firstVisibleEdge = -1;
    BorderEdgeFlags edgesToDraw = 0;

    for (int i = BSTop; i <= BSLeft; ++i) {
        const BorderEdge& currEdge = edges[i];

        if (edges[i].shouldRender())
            edgesToDraw |= edgeFlagForSide(static_cast<BoxSide>(i));

        if (currEdge.presentButInvisible()) {
            --numEdgesVisible;
            allEdgesShareColor = false;
            allEdgesShareWidth = false;
            continue;
        }

        if (!currEdge.shouldRender()) {
            --numEdgesVisible;
            continue;
        }

        if (firstVisibleEdge == -1) {
            firstVisibleEdge = i;
        } else {
            if (currEdge.color != edges[firstVisibleEdge].color)
                allEdgesShareColor = false;
            if (currEdge.width != edges[firstVisibleEdge].width)
                allEdgesShareWidth = false;
        }

        if (currEdge.color.hasAlpha())
            haveAlphaColor = true;

        if (currEdge.style != SOLID)
            haveAllSolidEdges = false;

        if (currEdge.style != DOUBLE)
            haveAllDoubleEdges = false;
    }

    // If no corner intersects the clip region, we can pretend outerBorder is
    // rectangular to improve performance.
    if (haveAllSolidEdges && outerBorder.isRounded() && allCornersClippedOut(outerBorder, info.rect))
        outerBorder.setRadii(RoundedRect::Radii());

    // isRenderable() check avoids issue described in https://bugs.webkit.org/show_bug.cgi?id=38787
    if ((haveAllSolidEdges || haveAllDoubleEdges) && allEdgesShareColor && innerBorder.isRenderable()) {
        // Fast path for drawing all solid edges and all unrounded double edges

        if (numEdgesVisible == 4 && (outerBorder.isRounded() || haveAlphaColor)
            && (haveAllSolidEdges || (!outerBorder.isRounded() && !innerBorder.isRounded()))) {
            Path path;

            if (outerBorder.isRounded() && allEdgesShareWidth) {

                // Very fast path for single stroked round rect with circular corners

                graphicsContext->fillBetweenRoundedRects(outerBorder, innerBorder, edges[firstVisibleEdge].color);
                return;
            }
            if (outerBorder.isRounded() && bleedAvoidance != BackgroundBleedClipBackground)
                path.addRoundedRect(outerBorder);
            else
                path.addRect(outerBorder.rect());

            if (haveAllDoubleEdges) {
                IntRect innerThirdRect = outerBorder.rect();
                IntRect outerThirdRect = outerBorder.rect();
                for (int side = BSTop; side <= BSLeft; ++side) {
                    int outerWidth;
                    int innerWidth;
                    edges[side].getDoubleBorderStripeWidths(outerWidth, innerWidth);

                    if (side == BSTop) {
                        innerThirdRect.shiftYEdgeTo(innerThirdRect.y() + innerWidth);
                        outerThirdRect.shiftYEdgeTo(outerThirdRect.y() + outerWidth);
                    } else if (side == BSBottom) {
                        innerThirdRect.setHeight(innerThirdRect.height() - innerWidth);
                        outerThirdRect.setHeight(outerThirdRect.height() - outerWidth);
                    } else if (side == BSLeft) {
                        innerThirdRect.shiftXEdgeTo(innerThirdRect.x() + innerWidth);
                        outerThirdRect.shiftXEdgeTo(outerThirdRect.x() + outerWidth);
                    } else {
                        innerThirdRect.setWidth(innerThirdRect.width() - innerWidth);
                        outerThirdRect.setWidth(outerThirdRect.width() - outerWidth);
                    }
                }

                RoundedRect outerThird = outerBorder;
                RoundedRect innerThird = innerBorder;
                innerThird.setRect(innerThirdRect);
                outerThird.setRect(outerThirdRect);

                if (outerThird.isRounded() && bleedAvoidance != BackgroundBleedClipBackground)
                    path.addRoundedRect(outerThird);
                else
                    path.addRect(outerThird.rect());

                if (innerThird.isRounded() && bleedAvoidance != BackgroundBleedClipBackground)
                    path.addRoundedRect(innerThird);
                else
                    path.addRect(innerThird.rect());
            }

            if (innerBorder.isRounded())
                path.addRoundedRect(innerBorder);
            else
                path.addRect(innerBorder.rect());

            graphicsContext->setFillRule(RULE_EVENODD);
            graphicsContext->setFillColor(edges[firstVisibleEdge].color);
            graphicsContext->fillPath(path);
            return;
        }
        // Avoid creating transparent layers
        if (haveAllSolidEdges && numEdgesVisible != 4 && !outerBorder.isRounded() && haveAlphaColor) {
            Path path;

            for (int i = BSTop; i <= BSLeft; ++i) {
                const BorderEdge& currEdge = edges[i];
                if (currEdge.shouldRender()) {
                    IntRect sideRect = calculateSideRect(outerBorder, edges, i);
                    path.addRect(sideRect);
                }
            }

            graphicsContext->setFillRule(RULE_NONZERO);
            graphicsContext->setFillColor(edges[firstVisibleEdge].color);
            graphicsContext->fillPath(path);
            return;
        }
    }

    bool clipToOuterBorder = outerBorder.isRounded();
    GraphicsContextStateSaver stateSaver(*graphicsContext, clipToOuterBorder);
    if (clipToOuterBorder) {
        // Clip to the inner and outer radii rects.
        if (bleedAvoidance != BackgroundBleedClipBackground)
            graphicsContext->clipRoundedRect(outerBorder);
        // isRenderable() check avoids issue described in https://bugs.webkit.org/show_bug.cgi?id=38787
        // The inside will be clipped out later (in clipBorderSideForComplexInnerPath)
        if (innerBorder.isRenderable() && !innerBorder.isEmpty())
            graphicsContext->clipOutRoundedRect(innerBorder);
    }

    // If only one edge visible antialiasing doesn't create seams
    bool antialias = shouldAntialiasLines(graphicsContext) || numEdgesVisible == 1;
    RoundedRect unadjustedInnerBorder = (bleedAvoidance == BackgroundBleedBackgroundOverBorder) ? style->getRoundedInnerBorderFor(rect, includeLogicalLeftEdge, includeLogicalRightEdge) : innerBorder;
    IntPoint innerBorderAdjustment(innerBorder.rect().x() - unadjustedInnerBorder.rect().x(), innerBorder.rect().y() - unadjustedInnerBorder.rect().y());
    if (haveAlphaColor)
        paintTranslucentBorderSides(graphicsContext, style, outerBorder, unadjustedInnerBorder, innerBorderAdjustment, edges, edgesToDraw, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias);
    else
        paintBorderSides(graphicsContext, style, outerBorder, unadjustedInnerBorder, innerBorderAdjustment, edges, edgesToDraw, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge, antialias);
}

void RenderBoxModelObject::drawBoxSideFromPath(GraphicsContext* graphicsContext, const LayoutRect& borderRect, const Path& borderPath, const BorderEdge edges[],
    float thickness, float drawThickness, BoxSide side, const RenderStyle* style, Color color, EBorderStyle borderStyle, BackgroundBleedAvoidance bleedAvoidance,
    bool includeLogicalLeftEdge, bool includeLogicalRightEdge)
{
    if (thickness <= 0)
        return;

    if (borderStyle == DOUBLE && thickness < 3)
        borderStyle = SOLID;

    switch (borderStyle) {
    case BNONE:
    case BHIDDEN:
        return;
    case DOTTED:
    case DASHED: {
        graphicsContext->setStrokeColor(color);

        // The stroke is doubled here because the provided path is the
        // outside edge of the border so half the stroke is clipped off.
        // The extra multiplier is so that the clipping mask can antialias
        // the edges to prevent jaggies.
        graphicsContext->setStrokeThickness(drawThickness * 2 * 1.1f);
        graphicsContext->setStrokeStyle(borderStyle == DASHED ? DashedStroke : DottedStroke);

        // If the number of dashes that fit in the path is odd and non-integral then we
        // will have an awkwardly-sized dash at the end of the path. To try to avoid that
        // here, we simply make the whitespace dashes ever so slightly bigger.
        // FIXME: This could be even better if we tried to manipulate the dash offset
        // and possibly the gapLength to get the corners dash-symmetrical.
        float dashLength = thickness * ((borderStyle == DASHED) ? 3.0f : 1.0f);
        float gapLength = dashLength;
        float numberOfDashes = borderPath.length() / dashLength;
        // Don't try to show dashes if we have less than 2 dashes + 2 gaps.
        // FIXME: should do this test per side.
        if (numberOfDashes >= 4) {
            bool evenNumberOfFullDashes = !((int)numberOfDashes % 2);
            bool integralNumberOfDashes = !(numberOfDashes - (int)numberOfDashes);
            if (!evenNumberOfFullDashes && !integralNumberOfDashes) {
                float numberOfGaps = numberOfDashes / 2;
                gapLength += (dashLength  / numberOfGaps);
            }

            DashArray lineDash;
            lineDash.append(dashLength);
            lineDash.append(gapLength);
            graphicsContext->setLineDash(lineDash, dashLength);
        }

        // FIXME: stroking the border path causes issues with tight corners:
        // https://bugs.webkit.org/show_bug.cgi?id=58711
        // Also, to get the best appearance we should stroke a path between the two borders.
        graphicsContext->strokePath(borderPath);
        return;
    }
    case DOUBLE: {
        // Get the inner border rects for both the outer border line and the inner border line
        int outerBorderTopWidth;
        int innerBorderTopWidth;
        edges[BSTop].getDoubleBorderStripeWidths(outerBorderTopWidth, innerBorderTopWidth);

        int outerBorderRightWidth;
        int innerBorderRightWidth;
        edges[BSRight].getDoubleBorderStripeWidths(outerBorderRightWidth, innerBorderRightWidth);

        int outerBorderBottomWidth;
        int innerBorderBottomWidth;
        edges[BSBottom].getDoubleBorderStripeWidths(outerBorderBottomWidth, innerBorderBottomWidth);

        int outerBorderLeftWidth;
        int innerBorderLeftWidth;
        edges[BSLeft].getDoubleBorderStripeWidths(outerBorderLeftWidth, innerBorderLeftWidth);

        // Draw inner border line
        {
            GraphicsContextStateSaver stateSaver(*graphicsContext);
            RoundedRect innerClip = style->getRoundedInnerBorderFor(borderRect,
                innerBorderTopWidth, innerBorderBottomWidth, innerBorderLeftWidth, innerBorderRightWidth,
                includeLogicalLeftEdge, includeLogicalRightEdge);

            graphicsContext->clipRoundedRect(innerClip);
            drawBoxSideFromPath(graphicsContext, borderRect, borderPath, edges, thickness, drawThickness, side, style, color, SOLID, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge);
        }

        // Draw outer border line
        {
            GraphicsContextStateSaver stateSaver(*graphicsContext);
            LayoutRect outerRect = borderRect;
            if (bleedAvoidance == BackgroundBleedClipBackground) {
                outerRect.inflate(1);
                ++outerBorderTopWidth;
                ++outerBorderBottomWidth;
                ++outerBorderLeftWidth;
                ++outerBorderRightWidth;
            }

            RoundedRect outerClip = style->getRoundedInnerBorderFor(outerRect,
                outerBorderTopWidth, outerBorderBottomWidth, outerBorderLeftWidth, outerBorderRightWidth,
                includeLogicalLeftEdge, includeLogicalRightEdge);
            graphicsContext->clipOutRoundedRect(outerClip);
            drawBoxSideFromPath(graphicsContext, borderRect, borderPath, edges, thickness, drawThickness, side, style, color, SOLID, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge);
        }
        return;
    }
    case RIDGE:
    case GROOVE:
    {
        EBorderStyle s1;
        EBorderStyle s2;
        if (borderStyle == GROOVE) {
            s1 = INSET;
            s2 = OUTSET;
        } else {
            s1 = OUTSET;
            s2 = INSET;
        }

        // Paint full border
        drawBoxSideFromPath(graphicsContext, borderRect, borderPath, edges, thickness, drawThickness, side, style, color, s1, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge);

        // Paint inner only
        GraphicsContextStateSaver stateSaver(*graphicsContext);
        LayoutUnit topWidth = edges[BSTop].usedWidth() / 2;
        LayoutUnit bottomWidth = edges[BSBottom].usedWidth() / 2;
        LayoutUnit leftWidth = edges[BSLeft].usedWidth() / 2;
        LayoutUnit rightWidth = edges[BSRight].usedWidth() / 2;

        RoundedRect clipRect = style->getRoundedInnerBorderFor(borderRect,
            topWidth, bottomWidth, leftWidth, rightWidth,
            includeLogicalLeftEdge, includeLogicalRightEdge);

        graphicsContext->clipRoundedRect(clipRect);
        drawBoxSideFromPath(graphicsContext, borderRect, borderPath, edges, thickness, drawThickness, side, style, color, s2, bleedAvoidance, includeLogicalLeftEdge, includeLogicalRightEdge);
        return;
    }
    case INSET:
        if (side == BSTop || side == BSLeft)
            color = color.dark();
        break;
    case OUTSET:
        if (side == BSBottom || side == BSRight)
            color = color.dark();
        break;
    default:
        break;
    }

    graphicsContext->setStrokeStyle(NoStroke);
    graphicsContext->setFillColor(color);
    graphicsContext->drawRect(pixelSnappedIntRect(borderRect));
}

void RenderBoxModelObject::clipBorderSidePolygon(GraphicsContext* graphicsContext, const RoundedRect& outerBorder, const RoundedRect& innerBorder,
                                                 BoxSide side, bool firstEdgeMatches, bool secondEdgeMatches)
{
    FloatPoint quad[4];

    const LayoutRect& outerRect = outerBorder.rect();
    const LayoutRect& innerRect = innerBorder.rect();

    FloatPoint centerPoint(innerRect.location().x().toFloat() + innerRect.width().toFloat() / 2, innerRect.location().y().toFloat() + innerRect.height().toFloat() / 2);

    // For each side, create a quad that encompasses all parts of that side that may draw,
    // including areas inside the innerBorder.
    //
    //         0----------------3
    //       0  \              /  0
    //       |\  1----------- 2  /|
    //       | 1                1 |
    //       | |                | |
    //       | |                | |
    //       | 2                2 |
    //       |/  1------------2  \|
    //       3  /              \  3
    //         0----------------3
    //
    switch (side) {
    case BSTop:
        quad[0] = outerRect.minXMinYCorner();
        quad[1] = innerRect.minXMinYCorner();
        quad[2] = innerRect.maxXMinYCorner();
        quad[3] = outerRect.maxXMinYCorner();

        if (!innerBorder.radii().topLeft().isZero()) {
            findIntersection(quad[0], quad[1],
                FloatPoint(
                    quad[1].x() + innerBorder.radii().topLeft().width(),
                    quad[1].y()),
                FloatPoint(
                    quad[1].x(),
                    quad[1].y() + innerBorder.radii().topLeft().height()),
                quad[1]);
        }

        if (!innerBorder.radii().topRight().isZero()) {
            findIntersection(quad[3], quad[2],
                FloatPoint(
                    quad[2].x() - innerBorder.radii().topRight().width(),
                    quad[2].y()),
                FloatPoint(
                    quad[2].x(),
                    quad[2].y() + innerBorder.radii().topRight().height()),
                quad[2]);
        }
        break;

    case BSLeft:
        quad[0] = outerRect.minXMinYCorner();
        quad[1] = innerRect.minXMinYCorner();
        quad[2] = innerRect.minXMaxYCorner();
        quad[3] = outerRect.minXMaxYCorner();

        if (!innerBorder.radii().topLeft().isZero()) {
            findIntersection(quad[0], quad[1],
                FloatPoint(
                    quad[1].x() + innerBorder.radii().topLeft().width(),
                    quad[1].y()),
                FloatPoint(
                    quad[1].x(),
                    quad[1].y() + innerBorder.radii().topLeft().height()),
                quad[1]);
        }

        if (!innerBorder.radii().bottomLeft().isZero()) {
            findIntersection(quad[3], quad[2],
                FloatPoint(
                    quad[2].x() + innerBorder.radii().bottomLeft().width(),
                    quad[2].y()),
                FloatPoint(
                    quad[2].x(),
                    quad[2].y() - innerBorder.radii().bottomLeft().height()),
                quad[2]);
        }
        break;

    case BSBottom:
        quad[0] = outerRect.minXMaxYCorner();
        quad[1] = innerRect.minXMaxYCorner();
        quad[2] = innerRect.maxXMaxYCorner();
        quad[3] = outerRect.maxXMaxYCorner();

        if (!innerBorder.radii().bottomLeft().isZero()) {
            findIntersection(quad[0], quad[1],
                FloatPoint(
                    quad[1].x() + innerBorder.radii().bottomLeft().width(),
                    quad[1].y()),
                FloatPoint(
                    quad[1].x(),
                    quad[1].y() - innerBorder.radii().bottomLeft().height()),
                quad[1]);
        }

        if (!innerBorder.radii().bottomRight().isZero()) {
            findIntersection(quad[3], quad[2],
                FloatPoint(
                    quad[2].x() - innerBorder.radii().bottomRight().width(),
                    quad[2].y()),
                FloatPoint(
                    quad[2].x(),
                    quad[2].y() - innerBorder.radii().bottomRight().height()),
                quad[2]);
        }
        break;

    case BSRight:
        quad[0] = outerRect.maxXMinYCorner();
        quad[1] = innerRect.maxXMinYCorner();
        quad[2] = innerRect.maxXMaxYCorner();
        quad[3] = outerRect.maxXMaxYCorner();

        if (!innerBorder.radii().topRight().isZero()) {
            findIntersection(quad[0], quad[1],
                FloatPoint(
                    quad[1].x() - innerBorder.radii().topRight().width(),
                    quad[1].y()),
                FloatPoint(
                    quad[1].x(),
                    quad[1].y() + innerBorder.radii().topRight().height()),
                quad[1]);
        }

        if (!innerBorder.radii().bottomRight().isZero()) {
            findIntersection(quad[3], quad[2],
                FloatPoint(
                    quad[2].x() - innerBorder.radii().bottomRight().width(),
                    quad[2].y()),
                FloatPoint(
                    quad[2].x(),
                    quad[2].y() - innerBorder.radii().bottomRight().height()),
                quad[2]);
        }
        break;
    }

    // If the border matches both of its adjacent sides, don't anti-alias the clip, and
    // if neither side matches, anti-alias the clip.
    if (firstEdgeMatches == secondEdgeMatches) {
        graphicsContext->clipConvexPolygon(4, quad, !firstEdgeMatches);
        return;
    }

    // If antialiasing settings for the first edge and second edge is different,
    // they have to be addressed separately. We do this by breaking the quad into
    // two parallelograms, made by moving quad[1] and quad[2].
    float ax = quad[1].x() - quad[0].x();
    float ay = quad[1].y() - quad[0].y();
    float bx = quad[2].x() - quad[1].x();
    float by = quad[2].y() - quad[1].y();
    float cx = quad[3].x() - quad[2].x();
    float cy = quad[3].y() - quad[2].y();

    const static float kEpsilon = 1e-2f;
    float r1, r2;
    if (fabsf(bx) < kEpsilon && fabsf(by) < kEpsilon) {
        // The quad was actually a triangle.
        r1 = r2 = 1.0f;
    } else {
        // Extend parallelogram a bit to hide calculation error
        const static float kExtendFill = 1e-2f;

        r1 = (-ax * by + ay * bx) / (cx * by - cy * bx) + kExtendFill;
        r2 = (-cx * by + cy * bx) / (ax * by - ay * bx) + kExtendFill;
    }

    FloatPoint firstQuad[4];
    firstQuad[0] = quad[0];
    firstQuad[1] = quad[1];
    firstQuad[2] = FloatPoint(quad[3].x() + r2 * ax, quad[3].y() + r2 * ay);
    firstQuad[3] = quad[3];
    graphicsContext->clipConvexPolygon(4, firstQuad, !firstEdgeMatches);

    FloatPoint secondQuad[4];
    secondQuad[0] = quad[0];
    secondQuad[1] = FloatPoint(quad[0].x() - r1 * cx, quad[0].y() - r1 * cy);
    secondQuad[2] = quad[2];
    secondQuad[3] = quad[3];
    graphicsContext->clipConvexPolygon(4, secondQuad, !secondEdgeMatches);
}

static IntRect calculateSideRectIncludingInner(const RoundedRect& outerBorder, const BorderEdge edges[], BoxSide side)
{
    IntRect sideRect = outerBorder.rect();
    int width;

    switch (side) {
    case BSTop:
        width = sideRect.height() - edges[BSBottom].width;
        sideRect.setHeight(width);
        break;
    case BSBottom:
        width = sideRect.height() - edges[BSTop].width;
        sideRect.shiftYEdgeTo(sideRect.maxY() - width);
        break;
    case BSLeft:
        width = sideRect.width() - edges[BSRight].width;
        sideRect.setWidth(width);
        break;
    case BSRight:
        width = sideRect.width() - edges[BSLeft].width;
        sideRect.shiftXEdgeTo(sideRect.maxX() - width);
        break;
    }

    return sideRect;
}

static RoundedRect calculateAdjustedInnerBorder(const RoundedRect&innerBorder, BoxSide side)
{
    // Expand the inner border as necessary to make it a rounded rect (i.e. radii contained within each edge).
    // This function relies on the fact we only get radii not contained within each edge if one of the radii
    // for an edge is zero, so we can shift the arc towards the zero radius corner.
    RoundedRect::Radii newRadii = innerBorder.radii();
    IntRect newRect = innerBorder.rect();

    float overshoot;
    float maxRadii;

    switch (side) {
    case BSTop:
        overshoot = newRadii.topLeft().width() + newRadii.topRight().width() - newRect.width();
        if (overshoot > 0) {
            ASSERT(!(newRadii.topLeft().width() && newRadii.topRight().width()));
            newRect.setWidth(newRect.width() + overshoot);
            if (!newRadii.topLeft().width())
                newRect.move(-overshoot, 0);
        }
        newRadii.setBottomLeft(IntSize(0, 0));
        newRadii.setBottomRight(IntSize(0, 0));
        maxRadii = std::max(newRadii.topLeft().height(), newRadii.topRight().height());
        if (maxRadii > newRect.height())
            newRect.setHeight(maxRadii);
        break;

    case BSBottom:
        overshoot = newRadii.bottomLeft().width() + newRadii.bottomRight().width() - newRect.width();
        if (overshoot > 0) {
            ASSERT(!(newRadii.bottomLeft().width() && newRadii.bottomRight().width()));
            newRect.setWidth(newRect.width() + overshoot);
            if (!newRadii.bottomLeft().width())
                newRect.move(-overshoot, 0);
        }
        newRadii.setTopLeft(IntSize(0, 0));
        newRadii.setTopRight(IntSize(0, 0));
        maxRadii = std::max(newRadii.bottomLeft().height(), newRadii.bottomRight().height());
        if (maxRadii > newRect.height()) {
            newRect.move(0, newRect.height() - maxRadii);
            newRect.setHeight(maxRadii);
        }
        break;

    case BSLeft:
        overshoot = newRadii.topLeft().height() + newRadii.bottomLeft().height() - newRect.height();
        if (overshoot > 0) {
            ASSERT(!(newRadii.topLeft().height() && newRadii.bottomLeft().height()));
            newRect.setHeight(newRect.height() + overshoot);
            if (!newRadii.topLeft().height())
                newRect.move(0, -overshoot);
        }
        newRadii.setTopRight(IntSize(0, 0));
        newRadii.setBottomRight(IntSize(0, 0));
        maxRadii = std::max(newRadii.topLeft().width(), newRadii.bottomLeft().width());
        if (maxRadii > newRect.width())
            newRect.setWidth(maxRadii);
        break;

    case BSRight:
        overshoot = newRadii.topRight().height() + newRadii.bottomRight().height() - newRect.height();
        if (overshoot > 0) {
            ASSERT(!(newRadii.topRight().height() && newRadii.bottomRight().height()));
            newRect.setHeight(newRect.height() + overshoot);
            if (!newRadii.topRight().height())
                newRect.move(0, -overshoot);
        }
        newRadii.setTopLeft(IntSize(0, 0));
        newRadii.setBottomLeft(IntSize(0, 0));
        maxRadii = std::max(newRadii.topRight().width(), newRadii.bottomRight().width());
        if (maxRadii > newRect.width()) {
            newRect.move(newRect.width() - maxRadii, 0);
            newRect.setWidth(maxRadii);
        }
        break;
    }

    return RoundedRect(newRect, newRadii);
}

void RenderBoxModelObject::clipBorderSideForComplexInnerPath(GraphicsContext* graphicsContext, const RoundedRect& outerBorder, const RoundedRect& innerBorder,
    BoxSide side, const class BorderEdge edges[])
{
    graphicsContext->clip(calculateSideRectIncludingInner(outerBorder, edges, side));
    RoundedRect adjustedInnerRect = calculateAdjustedInnerBorder(innerBorder, side);
    if (!adjustedInnerRect.isEmpty())
        graphicsContext->clipOutRoundedRect(adjustedInnerRect);
}

void RenderBoxModelObject::getBorderEdgeInfo(BorderEdge edges[], const RenderStyle* style, bool includeLogicalLeftEdge, bool includeLogicalRightEdge) const
{
    bool horizontal = style->isHorizontalWritingMode();

    edges[BSTop] = BorderEdge(style->borderTopWidth(),
        resolveColor(style, CSSPropertyBorderTopColor),
        style->borderTopStyle(),
        style->borderTopIsTransparent(),
        horizontal || includeLogicalLeftEdge);

    edges[BSRight] = BorderEdge(style->borderRightWidth(),
        resolveColor(style, CSSPropertyBorderRightColor),
        style->borderRightStyle(),
        style->borderRightIsTransparent(),
        !horizontal || includeLogicalRightEdge);

    edges[BSBottom] = BorderEdge(style->borderBottomWidth(),
        resolveColor(style, CSSPropertyBorderBottomColor),
        style->borderBottomStyle(),
        style->borderBottomIsTransparent(),
        horizontal || includeLogicalRightEdge);

    edges[BSLeft] = BorderEdge(style->borderLeftWidth(),
        resolveColor(style, CSSPropertyBorderLeftColor),
        style->borderLeftStyle(),
        style->borderLeftIsTransparent(),
        !horizontal || includeLogicalLeftEdge);
}

bool RenderBoxModelObject::borderObscuresBackgroundEdge(const FloatSize& contextScale) const
{
    BorderEdge edges[4];
    getBorderEdgeInfo(edges, style());

    for (int i = BSTop; i <= BSLeft; ++i) {
        const BorderEdge& currEdge = edges[i];
        // FIXME: for vertical text
        float axisScale = (i == BSTop || i == BSBottom) ? contextScale.height() : contextScale.width();
        if (!currEdge.obscuresBackgroundEdge(axisScale))
            return false;
    }

    return true;
}

bool RenderBoxModelObject::borderObscuresBackground() const
{
    if (!style()->hasBorder())
        return false;

    // Bail if we have any border-image for now. We could look at the image alpha to improve this.
    if (style()->borderImage().image())
        return false;

    BorderEdge edges[4];
    getBorderEdgeInfo(edges, style());

    for (int i = BSTop; i <= BSLeft; ++i) {
        const BorderEdge& currEdge = edges[i];
        if (!currEdge.obscuresBackground())
            return false;
    }

    return true;
}

bool RenderBoxModelObject::boxShadowShouldBeAppliedToBackground(BackgroundBleedAvoidance bleedAvoidance, InlineFlowBox* inlineFlowBox) const
{
    if (bleedAvoidance != BackgroundBleedNone)
        return false;

    if (style()->hasAppearance())
        return false;

    const ShadowList* shadowList = style()->boxShadow();
    if (!shadowList)
        return false;

    bool hasOneNormalBoxShadow = false;
    size_t shadowCount = shadowList->shadows().size();
    for (size_t i = 0; i < shadowCount; ++i) {
        const ShadowData& currentShadow = shadowList->shadows()[i];
        if (currentShadow.style() != Normal)
            continue;

        if (hasOneNormalBoxShadow)
            return false;
        hasOneNormalBoxShadow = true;

        if (currentShadow.spread())
            return false;
    }

    if (!hasOneNormalBoxShadow)
        return false;

    Color backgroundColor = resolveColor(CSSPropertyBackgroundColor);
    if (backgroundColor.hasAlpha())
        return false;

    const FillLayer* lastBackgroundLayer = &style()->backgroundLayers();
    for (const FillLayer* next = lastBackgroundLayer->next(); next; next = lastBackgroundLayer->next())
        lastBackgroundLayer = next;

    if (lastBackgroundLayer->clip() != BorderFillBox)
        return false;

    if (lastBackgroundLayer->image() && style()->hasBorderRadius())
        return false;

    if (inlineFlowBox && !inlineFlowBox->boxShadowCanBeAppliedToBackground(*lastBackgroundLayer))
        return false;

    if (hasOverflowClip() && lastBackgroundLayer->attachment() == LocalBackgroundAttachment)
        return false;

    return true;
}

void RenderBoxModelObject::paintBoxShadow(const PaintInfo& info, const LayoutRect& paintRect, const RenderStyle* s, ShadowStyle shadowStyle, bool includeLogicalLeftEdge, bool includeLogicalRightEdge)
{
    // FIXME: Deal with border-image.  Would be great to use border-image as a mask.
    GraphicsContext* context = info.context;
    if (!s->boxShadow())
        return;

    RoundedRect border = (shadowStyle == Inset) ? s->getRoundedInnerBorderFor(paintRect, includeLogicalLeftEdge, includeLogicalRightEdge)
        : s->getRoundedBorderFor(paintRect, includeLogicalLeftEdge, includeLogicalRightEdge);

    bool hasBorderRadius = s->hasBorderRadius();
    bool isHorizontal = s->isHorizontalWritingMode();
    bool hasOpaqueBackground = s->visitedDependentColor(CSSPropertyBackgroundColor).alpha() == 255;

    GraphicsContextStateSaver stateSaver(*context, false);

    const ShadowList* shadowList = s->boxShadow();
    for (size_t i = shadowList->shadows().size(); i--; ) {
        const ShadowData& shadow = shadowList->shadows()[i];
        if (shadow.style() != shadowStyle)
            continue;

        FloatSize shadowOffset(shadow.x(), shadow.y());
        float shadowBlur = shadow.blur();
        float shadowSpread = shadow.spread();

        if (shadowOffset.isZero() && !shadowBlur && !shadowSpread)
            continue;

        const Color& shadowColor = shadow.color();

        if (shadow.style() == Normal) {
            FloatRect fillRect = border.rect();
            fillRect.inflate(shadowSpread);
            if (fillRect.isEmpty())
                continue;

            FloatRect shadowRect(border.rect());
            shadowRect.inflate(shadowBlur + shadowSpread);
            shadowRect.move(shadowOffset);

            // Save the state and clip, if not already done.
            // The clip does not depend on any shadow-specific properties.
            if (!stateSaver.saved()) {
                stateSaver.save();
                if (hasBorderRadius) {
                    RoundedRect rectToClipOut = border;

                    // If the box is opaque, it is unnecessary to clip it out. However, doing so saves time
                    // when painting the shadow. On the other hand, it introduces subpixel gaps along the
                    // corners. Those are avoided by insetting the clipping path by one pixel.
                    if (hasOpaqueBackground)
                        rectToClipOut.inflateWithRadii(-1);

                    if (!rectToClipOut.isEmpty()) {
                        context->clipOutRoundedRect(rectToClipOut);
                    }
                } else {
                    // This IntRect is correct even with fractional shadows, because it is used for the rectangle
                    // of the box itself, which is always pixel-aligned.
                    IntRect rectToClipOut = border.rect();

                    // If the box is opaque, it is unnecessary to clip it out. However, doing so saves time
                    // when painting the shadow. On the other hand, it introduces subpixel gaps along the
                    // edges if they are not pixel-aligned. Those are avoided by insetting the clipping path
                    // by one pixel.
                    if (hasOpaqueBackground) {
                        // FIXME: The function to decide on the policy based on the transform should be a named function.
                        // FIXME: It's not clear if this check is right. What about integral scale factors?
                        // FIXME: See crbug.com/382491. The use of getCTM may also be wrong because it does not include
                        // device zoom applied at raster time.
                        AffineTransform transform = context->getCTM();
                        if (transform.a() != 1 || (transform.d() != 1 && transform.d() != -1) || transform.b() || transform.c())
                            rectToClipOut.inflate(-1);
                    }

                    if (!rectToClipOut.isEmpty()) {
                        context->clipOut(rectToClipOut);
                    }
                }
            }

            // Draw only the shadow.
            OwnPtr<DrawLooperBuilder> drawLooperBuilder = DrawLooperBuilder::create();
            drawLooperBuilder->addShadow(shadowOffset, shadowBlur, shadowColor,
                DrawLooperBuilder::ShadowRespectsTransforms, DrawLooperBuilder::ShadowIgnoresAlpha);
            context->setDrawLooper(drawLooperBuilder.release());

            if (hasBorderRadius) {
                RoundedRect influenceRect(pixelSnappedIntRect(LayoutRect(shadowRect)), border.radii());
                influenceRect.expandRadii(2 * shadowBlur + shadowSpread);
                if (allCornersClippedOut(influenceRect, info.rect))
                    context->fillRect(fillRect, Color::black);
                else {
                    // TODO: support non-integer shadows - crbug.com/334829
                    RoundedRect roundedFillRect = border;
                    roundedFillRect.inflate(shadowSpread);

                    roundedFillRect.expandRadii(shadowSpread);
                    if (!roundedFillRect.isRenderable())
                        roundedFillRect.adjustRadii();
                    context->fillRoundedRect(roundedFillRect, Color::black);
                }
            } else {
                context->fillRect(fillRect, Color::black);
            }
        } else {
            // The inset shadow case.
            GraphicsContext::Edges clippedEdges = GraphicsContext::NoEdge;
            if (!includeLogicalLeftEdge) {
                if (isHorizontal)
                    clippedEdges |= GraphicsContext::LeftEdge;
                else
                    clippedEdges |= GraphicsContext::TopEdge;
            }
            if (!includeLogicalRightEdge) {
                if (isHorizontal)
                    clippedEdges |= GraphicsContext::RightEdge;
                else
                    clippedEdges |= GraphicsContext::BottomEdge;
            }
            // TODO: support non-integer shadows - crbug.com/334828
            context->drawInnerShadow(border, shadowColor, flooredIntSize(shadowOffset), shadowBlur, shadowSpread, clippedEdges);
        }
    }
}

LayoutUnit RenderBoxModelObject::containingBlockLogicalWidthForContent() const
{
    return containingBlock()->availableLogicalWidth();
}

RenderBoxModelObject* RenderBoxModelObject::continuation() const
{
    if (!continuationMap)
        return 0;
    return (*continuationMap)->get(this);
}

void RenderBoxModelObject::setContinuation(RenderBoxModelObject* continuation)
{
    if (continuation) {
        if (!continuationMap)
            continuationMap = new OwnPtrWillBePersistent<ContinuationMap>(adoptPtrWillBeNoop(new ContinuationMap));
        (*continuationMap)->set(this, continuation);
    } else {
        if (continuationMap)
            (*continuationMap)->remove(this);
    }
}

void RenderBoxModelObject::computeLayerHitTestRects(LayerHitTestRects& rects) const
{
    RenderLayerModelObject::computeLayerHitTestRects(rects);

    // If there is a continuation then we need to consult it here, since this is
    // the root of the tree walk and it wouldn't otherwise get picked up.
    // Continuations should always be siblings in the tree, so any others should
    // get picked up already by the tree walk.
    if (continuation())
        continuation()->computeLayerHitTestRects(rects);
}

RenderTextFragment* RenderBoxModelObject::firstLetterRemainingText() const
{
    if (!firstLetterRemainingTextMap)
        return 0;
    return (*firstLetterRemainingTextMap)->get(this);
}

void RenderBoxModelObject::setFirstLetterRemainingText(RenderTextFragment* remainingText)
{
    if (remainingText) {
        if (!firstLetterRemainingTextMap)
            firstLetterRemainingTextMap = new OwnPtrWillBePersistent<FirstLetterRemainingTextMap>(adoptPtrWillBeNoop(new FirstLetterRemainingTextMap));
        (*firstLetterRemainingTextMap)->set(this, remainingText);
    } else if (firstLetterRemainingTextMap) {
        (*firstLetterRemainingTextMap)->remove(this);
    }
}

LayoutRect RenderBoxModelObject::localCaretRectForEmptyElement(LayoutUnit width, LayoutUnit textIndentOffset)
{
    ASSERT(!slowFirstChild());

    // FIXME: This does not take into account either :first-line or :first-letter
    // However, as soon as some content is entered, the line boxes will be
    // constructed and this kludge is not called any more. So only the caret size
    // of an empty :first-line'd block is wrong. I think we can live with that.
    RenderStyle* currentStyle = firstLineStyle();
    LayoutUnit height = style()->fontMetrics().height();

    enum CaretAlignment { alignLeft, alignRight, alignCenter };

    CaretAlignment alignment = alignLeft;

    switch (currentStyle->textAlign()) {
    case LEFT:
    case WEBKIT_LEFT:
        break;
    case CENTER:
    case WEBKIT_CENTER:
        alignment = alignCenter;
        break;
    case RIGHT:
    case WEBKIT_RIGHT:
        alignment = alignRight;
        break;
    case JUSTIFY:
    case TASTART:
        if (!currentStyle->isLeftToRightDirection())
            alignment = alignRight;
        break;
    case TAEND:
        if (currentStyle->isLeftToRightDirection())
            alignment = alignRight;
        break;
    }

    LayoutUnit x = borderLeft() + paddingLeft();
    LayoutUnit maxX = width - borderRight() - paddingRight();

    switch (alignment) {
    case alignLeft:
        if (currentStyle->isLeftToRightDirection())
            x += textIndentOffset;
        break;
    case alignCenter:
        x = (x + maxX) / 2;
        if (currentStyle->isLeftToRightDirection())
            x += textIndentOffset / 2;
        else
            x -= textIndentOffset / 2;
        break;
    case alignRight:
        x = maxX - caretWidth;
        if (!currentStyle->isLeftToRightDirection())
            x -= textIndentOffset;
        break;
    }
    x = std::min(x, std::max<LayoutUnit>(maxX - caretWidth, 0));

    LayoutUnit y = paddingTop() + borderTop();

    return currentStyle->isHorizontalWritingMode() ? LayoutRect(x, y, caretWidth, height) : LayoutRect(y, x, height, caretWidth);
}

bool RenderBoxModelObject::shouldAntialiasLines(GraphicsContext* context)
{
    // FIXME: We may want to not antialias when scaled by an integral value,
    // and we may want to antialias when translated by a non-integral value.
    // FIXME: See crbug.com/382491. getCTM does not include scale factors applied at raster time, such
    // as device zoom.
    return !context->getCTM().isIdentityOrTranslationOrFlipped();
}

void RenderBoxModelObject::mapAbsoluteToLocalPoint(MapCoordinatesFlags mode, TransformState& transformState) const
{
    RenderObject* o = container();
    if (!o)
        return;

    if (o->isRenderFlowThread())
        transformState.move(o->columnOffset(LayoutPoint(transformState.mappedPoint())));

    o->mapAbsoluteToLocalPoint(mode, transformState);

    LayoutSize containerOffset = offsetFromContainer(o, LayoutPoint());

    if (!style()->hasOutOfFlowPosition() && o->hasColumns()) {
        RenderBlock* block = toRenderBlock(o);
        LayoutPoint point(roundedLayoutPoint(transformState.mappedPoint()));
        point -= containerOffset;
        block->adjustForColumnRect(containerOffset, point);
    }

    bool preserve3D = mode & UseTransforms && (o->style()->preserves3D() || style()->preserves3D());
    if (mode & UseTransforms && shouldUseTransformFromContainer(o)) {
        TransformationMatrix t;
        getTransformFromContainer(o, containerOffset, t);
        transformState.applyTransform(t, preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
    } else
        transformState.move(containerOffset.width(), containerOffset.height(), preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
}

const RenderObject* RenderBoxModelObject::pushMappingToContainer(const RenderLayerModelObject* ancestorToStopAt, RenderGeometryMap& geometryMap) const
{
    ASSERT(ancestorToStopAt != this);

    bool ancestorSkipped;
    RenderObject* container = this->container(ancestorToStopAt, &ancestorSkipped);
    if (!container)
        return 0;

    bool isInline = isRenderInline();
    bool isFixedPos = !isInline && style()->position() == FixedPosition;
    bool hasTransform = !isInline && hasLayer() && layer()->transform();

    LayoutSize adjustmentForSkippedAncestor;
    if (ancestorSkipped) {
        // There can't be a transform between repaintContainer and o, because transforms create containers, so it should be safe
        // to just subtract the delta between the ancestor and o.
        adjustmentForSkippedAncestor = -ancestorToStopAt->offsetFromAncestorContainer(container);
    }

    bool offsetDependsOnPoint = false;
    LayoutSize containerOffset = offsetFromContainer(container, LayoutPoint(), &offsetDependsOnPoint);

    bool preserve3D = container->style()->preserves3D() || style()->preserves3D();
    if (shouldUseTransformFromContainer(container)) {
        TransformationMatrix t;
        getTransformFromContainer(container, containerOffset, t);
        t.translateRight(adjustmentForSkippedAncestor.width().toFloat(), adjustmentForSkippedAncestor.height().toFloat());
        geometryMap.push(this, t, preserve3D, offsetDependsOnPoint, isFixedPos, hasTransform);
    } else {
        containerOffset += adjustmentForSkippedAncestor;
        geometryMap.push(this, containerOffset, preserve3D, offsetDependsOnPoint, isFixedPos, hasTransform);
    }

    return ancestorSkipped ? ancestorToStopAt : container;
}

void RenderBoxModelObject::moveChildTo(RenderBoxModelObject* toBoxModelObject, RenderObject* child, RenderObject* beforeChild, bool fullRemoveInsert)
{
    // We assume that callers have cleared their positioned objects list for child moves (!fullRemoveInsert) so the
    // positioned renderer maps don't become stale. It would be too slow to do the map lookup on each call.
    ASSERT(!fullRemoveInsert || !isRenderBlock() || !toRenderBlock(this)->hasPositionedObjects());

    ASSERT(this == child->parent());
    ASSERT(!beforeChild || toBoxModelObject == beforeChild->parent());
    if (fullRemoveInsert && (toBoxModelObject->isRenderBlock() || toBoxModelObject->isRenderInline())) {
        // Takes care of adding the new child correctly if toBlock and fromBlock
        // have different kind of children (block vs inline).
        toBoxModelObject->addChild(virtualChildren()->removeChildNode(this, child), beforeChild);
    } else
        toBoxModelObject->virtualChildren()->insertChildNode(toBoxModelObject, virtualChildren()->removeChildNode(this, child, fullRemoveInsert), beforeChild, fullRemoveInsert);
}

void RenderBoxModelObject::moveChildrenTo(RenderBoxModelObject* toBoxModelObject, RenderObject* startChild, RenderObject* endChild, RenderObject* beforeChild, bool fullRemoveInsert)
{
    // This condition is rarely hit since this function is usually called on
    // anonymous blocks which can no longer carry positioned objects (see r120761)
    // or when fullRemoveInsert is false.
    if (fullRemoveInsert && isRenderBlock()) {
        RenderBlock* block = toRenderBlock(this);
        block->removePositionedObjects(0);
        if (block->isRenderBlockFlow())
            toRenderBlockFlow(block)->removeFloatingObjects();
    }

    ASSERT(!beforeChild || toBoxModelObject == beforeChild->parent());
    for (RenderObject* child = startChild; child && child != endChild; ) {
        // Save our next sibling as moveChildTo will clear it.
        RenderObject* nextSibling = child->nextSibling();
        moveChildTo(toBoxModelObject, child, beforeChild, fullRemoveInsert);
        child = nextSibling;
    }
}

} // namespace blink