RenderElement.cpp   [plain text]

/*
 * 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, 2013, 2015 Apple Inc. All rights reserved.
 * Copyright (C) 2010, 2012 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 "RenderElement.h"

#include "AXObjectCache.h"
#include "ContentData.h"
#include "ControlStates.h"
#include "CursorList.h"
#include "ElementChildIterator.h"
#include "EventHandler.h"
#include "Frame.h"
#include "FrameSelection.h"
#include "HTMLBodyElement.h"
#include "HTMLHtmlElement.h"
#include "HTMLNames.h"
#include "FlowThreadController.h"
#include "RenderBlock.h"
#include "RenderCounter.h"
#include "RenderDeprecatedFlexibleBox.h"
#include "RenderFlexibleBox.h"
#include "RenderImage.h"
#include "RenderImageResourceStyleImage.h"
#include "RenderInline.h"
#include "RenderIterator.h"
#include "RenderLayer.h"
#include "RenderLayerCompositor.h"
#include "RenderLineBreak.h"
#include "RenderListItem.h"
#include "RenderNamedFlowThread.h"
#include "RenderRegion.h"
#include "RenderTableCaption.h"
#include "RenderTableCell.h"
#include "RenderTableCol.h"
#include "RenderTableRow.h"
#include "RenderText.h"
#include "RenderTheme.h"
#include "RenderView.h"
#include "SVGRenderSupport.h"
#include "Settings.h"
#include "ShadowRoot.h"
#include "StyleResolver.h"
#include <wtf/MathExtras.h>
#include <wtf/StackStats.h>

#if ENABLE(CSS_GRID_LAYOUT)
#include "RenderGrid.h"
#endif

namespace WebCore {

bool RenderElement::s_affectsParentBlock = false;
bool RenderElement::s_noLongerAffectsParentBlock = false;
    
static HashMap<const RenderObject*, ControlStates*>& controlStatesRendererMap()
{
    static NeverDestroyed<HashMap<const RenderObject*, ControlStates*>> map;
    return map;
}

inline RenderElement::RenderElement(ContainerNode& elementOrDocument, Ref<RenderStyle>&& style, unsigned baseTypeFlags)
    : RenderObject(elementOrDocument)
    , m_baseTypeFlags(baseTypeFlags)
    , m_ancestorLineBoxDirty(false)
    , m_hasInitializedStyle(false)
    , m_renderInlineAlwaysCreatesLineBoxes(false)
    , m_renderBoxNeedsLazyRepaint(false)
    , m_hasPausedImageAnimations(false)
    , m_hasCounterNodeMap(false)
    , m_isCSSAnimating(false)
    , m_hasContinuation(false)
    , m_renderBlockHasMarginBeforeQuirk(false)
    , m_renderBlockHasMarginAfterQuirk(false)
    , m_renderBlockHasBorderOrPaddingLogicalWidthChanged(false)
    , m_renderBlockFlowHasMarkupTruncation(false)
    , m_renderBlockFlowLineLayoutPath(RenderBlockFlow::UndeterminedPath)
    , m_firstChild(nullptr)
    , m_lastChild(nullptr)
    , m_style(WTF::move(style))
{
}

RenderElement::RenderElement(Element& element, Ref<RenderStyle>&& style, unsigned baseTypeFlags)
    : RenderElement(static_cast<ContainerNode&>(element), WTF::move(style), baseTypeFlags)
{
}

RenderElement::RenderElement(Document& document, Ref<RenderStyle>&& style, unsigned baseTypeFlags)
    : RenderElement(static_cast<ContainerNode&>(document), WTF::move(style), baseTypeFlags)
{
}

RenderElement::~RenderElement()
{
    if (hasInitializedStyle()) {
        for (const FillLayer* bgLayer = m_style->backgroundLayers(); bgLayer; bgLayer = bgLayer->next()) {
            if (StyleImage* backgroundImage = bgLayer->image())
                backgroundImage->removeClient(this);
        }

        for (const FillLayer* maskLayer = m_style->maskLayers(); maskLayer; maskLayer = maskLayer->next()) {
            if (StyleImage* maskImage = maskLayer->image())
                maskImage->removeClient(this);
        }

        if (StyleImage* borderImage = m_style->borderImage().image())
            borderImage->removeClient(this);

        if (StyleImage* maskBoxImage = m_style->maskBoxImage().image())
            maskBoxImage->removeClient(this);

#if ENABLE(CSS_SHAPES)
        if (auto shapeValue = m_style->shapeOutside()) {
            if (auto shapeImage = shapeValue->image())
                shapeImage->removeClient(this);
        }
#endif
    }
    if (m_hasPausedImageAnimations)
        view().removeRendererWithPausedImageAnimations(*this);
}

RenderPtr<RenderElement> RenderElement::createFor(Element& element, Ref<RenderStyle>&& style)
{
    // Minimal support for content properties replacing an entire element.
    // Works only if we have exactly one piece of content and it's a URL.
    // Otherwise acts as if we didn't support this feature.
    const ContentData* contentData = style.get().contentData();
    if (contentData && !contentData->next() && is<ImageContentData>(*contentData) && !element.isPseudoElement()) {
        auto& styleImage = downcast<ImageContentData>(*contentData).image();
        auto image = createRenderer<RenderImage>(element, WTF::move(style), const_cast<StyleImage*>(&styleImage));
        image->setIsGeneratedContent();
        return WTF::move(image);
    }

    switch (style.get().display()) {
    case NONE:
        return nullptr;
    case INLINE:
        return createRenderer<RenderInline>(element, WTF::move(style));
    case BLOCK:
    case INLINE_BLOCK:
    case COMPACT:
        return createRenderer<RenderBlockFlow>(element, WTF::move(style));
    case LIST_ITEM:
        return createRenderer<RenderListItem>(element, WTF::move(style));
    case TABLE:
    case INLINE_TABLE:
        return createRenderer<RenderTable>(element, WTF::move(style));
    case TABLE_ROW_GROUP:
    case TABLE_HEADER_GROUP:
    case TABLE_FOOTER_GROUP:
        return createRenderer<RenderTableSection>(element, WTF::move(style));
    case TABLE_ROW:
        return createRenderer<RenderTableRow>(element, WTF::move(style));
    case TABLE_COLUMN_GROUP:
    case TABLE_COLUMN:
        return createRenderer<RenderTableCol>(element, WTF::move(style));
    case TABLE_CELL:
        return createRenderer<RenderTableCell>(element, WTF::move(style));
    case TABLE_CAPTION:
        return createRenderer<RenderTableCaption>(element, WTF::move(style));
    case BOX:
    case INLINE_BOX:
        return createRenderer<RenderDeprecatedFlexibleBox>(element, WTF::move(style));
    case FLEX:
    case INLINE_FLEX:
    case WEBKIT_FLEX:
    case WEBKIT_INLINE_FLEX:
        return createRenderer<RenderFlexibleBox>(element, WTF::move(style));
#if ENABLE(CSS_GRID_LAYOUT)
    case GRID:
    case INLINE_GRID:
        return createRenderer<RenderGrid>(element, WTF::move(style));
#endif
    }
    ASSERT_NOT_REACHED();
    return nullptr;
}

enum StyleCacheState {
    Cached,
    Uncached
};

static PassRefPtr<RenderStyle> firstLineStyleForCachedUncachedType(StyleCacheState type, const RenderElement& renderer, RenderStyle* style)
{
    RenderElement& rendererForFirstLineStyle = renderer.isBeforeOrAfterContent() ? *renderer.parent() : const_cast<RenderElement&>(renderer);

    if (rendererForFirstLineStyle.isRenderBlockFlow() || rendererForFirstLineStyle.isRenderButton()) {
        if (RenderBlock* firstLineBlock = rendererForFirstLineStyle.firstLineBlock()) {
            if (type == Cached)
                return firstLineBlock->getCachedPseudoStyle(FIRST_LINE, style);
            return firstLineBlock->getUncachedPseudoStyle(PseudoStyleRequest(FIRST_LINE), style, firstLineBlock == &renderer ? style : nullptr);
        }
    } else if (!rendererForFirstLineStyle.isAnonymous() && rendererForFirstLineStyle.isRenderInline()) {
        RenderStyle& parentStyle = rendererForFirstLineStyle.parent()->firstLineStyle();
        if (&parentStyle != &rendererForFirstLineStyle.parent()->style()) {
            if (type == Cached) {
                // A first-line style is in effect. Cache a first-line style for ourselves.
                rendererForFirstLineStyle.style().setHasPseudoStyle(FIRST_LINE_INHERITED);
                return rendererForFirstLineStyle.getCachedPseudoStyle(FIRST_LINE_INHERITED, &parentStyle);
            }
            return rendererForFirstLineStyle.getUncachedPseudoStyle(PseudoStyleRequest(FIRST_LINE_INHERITED), &parentStyle, style);
        }
    }
    return nullptr;
}

PassRefPtr<RenderStyle> RenderElement::uncachedFirstLineStyle(RenderStyle* style) const
{
    if (!document().styleSheetCollection().usesFirstLineRules())
        return nullptr;

    return firstLineStyleForCachedUncachedType(Uncached, *this, style);
}

RenderStyle* RenderElement::cachedFirstLineStyle() const
{
    ASSERT(document().styleSheetCollection().usesFirstLineRules());

    RenderStyle& style = this->style();
    if (RefPtr<RenderStyle> firstLineStyle = firstLineStyleForCachedUncachedType(Cached, *this, &style))
        return firstLineStyle.get();

    return &style;
}

StyleDifference RenderElement::adjustStyleDifference(StyleDifference diff, unsigned contextSensitiveProperties) const
{
    // If transform changed, and we are not composited, need to do a layout.
    if (contextSensitiveProperties & ContextSensitivePropertyTransform) {
        // FIXME: when transforms are taken into account for overflow, we will need to do a layout.
        if (!hasLayer() || !downcast<RenderLayerModelObject>(*this).layer()->isComposited()) {
            if (!hasLayer())
                diff = std::max(diff, StyleDifferenceLayout);
            else {
                // We need to set at least SimplifiedLayout, but if PositionedMovementOnly is already set
                // then we actually need SimplifiedLayoutAndPositionedMovement.
                diff = std::max(diff, (diff == StyleDifferenceLayoutPositionedMovementOnly) ? StyleDifferenceSimplifiedLayoutAndPositionedMovement : StyleDifferenceSimplifiedLayout);
            }
        
        } else
            diff = std::max(diff, StyleDifferenceRecompositeLayer);
    }

    if (contextSensitiveProperties & ContextSensitivePropertyOpacity) {
        if (!hasLayer() || !downcast<RenderLayerModelObject>(*this).layer()->isComposited())
            diff = std::max(diff, StyleDifferenceRepaintLayer);
        else
            diff = std::max(diff, StyleDifferenceRecompositeLayer);
    }

    if (contextSensitiveProperties & ContextSensitivePropertyClipPath) {
        if (hasLayer()
            && downcast<RenderLayerModelObject>(*this).layer()->isComposited()
            && hasClipPath()
            && RenderLayerCompositor::canCompositeClipPath(*downcast<RenderLayerModelObject>(*this).layer()))
            diff = std::max(diff, StyleDifferenceRecompositeLayer);
        else
            diff = std::max(diff, StyleDifferenceRepaint);
    }
    
    if ((contextSensitiveProperties & ContextSensitivePropertyFilter) && hasLayer()) {
        RenderLayer* layer = downcast<RenderLayerModelObject>(*this).layer();
        if (!layer->isComposited() || layer->paintsWithFilters())
            diff = std::max(diff, StyleDifferenceRepaintLayer);
        else
            diff = std::max(diff, StyleDifferenceRecompositeLayer);
    }
    
    // The answer to requiresLayer() for plugins, iframes, and canvas can change without the actual
    // style changing, since it depends on whether we decide to composite these elements. When the
    // layer status of one of these elements changes, we need to force a layout.
    if (diff < StyleDifferenceLayout && isRenderLayerModelObject()) {
        if (hasLayer() != downcast<RenderLayerModelObject>(*this).requiresLayer())
            diff = StyleDifferenceLayout;
    }

    // If we have no layer(), just treat a RepaintLayer hint as a normal Repaint.
    if (diff == StyleDifferenceRepaintLayer && !hasLayer())
        diff = StyleDifferenceRepaint;

    return diff;
}

inline bool RenderElement::hasImmediateNonWhitespaceTextChildOrBorderOrOutline() const
{
    for (auto& child : childrenOfType<RenderObject>(*this)) {
        if (is<RenderText>(child) && !downcast<RenderText>(child).isAllCollapsibleWhitespace())
            return true;
        if (child.style().hasOutline() || child.style().hasBorder())
            return true;
    }
    return false;
}

inline bool RenderElement::shouldRepaintForStyleDifference(StyleDifference diff) const
{
    return diff == StyleDifferenceRepaint || (diff == StyleDifferenceRepaintIfTextOrBorderOrOutline && hasImmediateNonWhitespaceTextChildOrBorderOrOutline());
}

void RenderElement::updateFillImages(const FillLayer* oldLayers, const FillLayer* newLayers)
{
    // Optimize the common case
    if (FillLayer::imagesIdentical(oldLayers, newLayers))
        return;
    
    // Go through the new layers and addClients first, to avoid removing all clients of an image.
    for (const FillLayer* currNew = newLayers; currNew; currNew = currNew->next()) {
        if (currNew->image())
            currNew->image()->addClient(this);
    }

    for (const FillLayer* currOld = oldLayers; currOld; currOld = currOld->next()) {
        if (currOld->image())
            currOld->image()->removeClient(this);
    }
}

void RenderElement::updateImage(StyleImage* oldImage, StyleImage* newImage)
{
    if (oldImage == newImage)
        return;
    if (oldImage)
        oldImage->removeClient(this);
    if (newImage)
        newImage->addClient(this);
}

#if ENABLE(CSS_SHAPES)
void RenderElement::updateShapeImage(const ShapeValue* oldShapeValue, const ShapeValue* newShapeValue)
{
    if (oldShapeValue || newShapeValue)
        updateImage(oldShapeValue ? oldShapeValue->image() : nullptr, newShapeValue ? newShapeValue->image() : nullptr);
}
#endif

void RenderElement::initializeStyle()
{
    styleWillChange(StyleDifferenceNewStyle, style());

    m_hasInitializedStyle = true;

    updateFillImages(nullptr, m_style->backgroundLayers());
    updateFillImages(nullptr, m_style->maskLayers());

    updateImage(nullptr, m_style->borderImage().image());
    updateImage(nullptr, m_style->maskBoxImage().image());

#if ENABLE(CSS_SHAPES)
    updateShapeImage(nullptr, m_style->shapeOutside());
#endif

    // We need to ensure that view->maximalOutlineSize() is valid for any repaints that happen
    // during styleDidChange (it's used by clippedOverflowRectForRepaint()).
    if (m_style->outlineWidth() > 0 && m_style->outlineSize() > maximalOutlineSize(PaintPhaseOutline))
        view().setMaximalOutlineSize(std::max(theme().platformFocusRingMaxWidth(), static_cast<int>(m_style->outlineSize())));

    styleDidChange(StyleDifferenceNewStyle, nullptr);

    // We shouldn't have any text children that would need styleDidChange at this point.
    ASSERT(!childrenOfType<RenderText>(*this).first());

    // It would be nice to assert that !parent() here, but some RenderLayer subrenderers
    // have their parent set before getting a call to initializeStyle() :|
}

void RenderElement::setStyle(Ref<RenderStyle>&& style, StyleDifference minimalStyleDifference)
{
    // FIXME: Should change RenderView so it can use initializeStyle too.
    // If we do that, we can assert m_hasInitializedStyle unconditionally,
    // and remove the check of m_hasInitializedStyle below too.
    ASSERT(m_hasInitializedStyle || isRenderView());

    if (m_style.ptr() == style.ptr() && minimalStyleDifference != StyleDifferenceEqual) {
        // FIXME: Can we change things so we never hit this code path?
        // We need to run through adjustStyleDifference() for iframes, plugins, and canvas so
        // style sharing is disabled for them. That should ensure that we never hit this code path.
        ASSERT(!isRenderIFrame());
        ASSERT(!isEmbeddedObject());
        ASSERT(!isCanvas());
        return;
    }

    StyleDifference diff = StyleDifferenceEqual;
    unsigned contextSensitiveProperties = ContextSensitivePropertyNone;
    if (m_hasInitializedStyle)
        diff = m_style->diff(style.get(), contextSensitiveProperties);

    diff = std::max(diff, minimalStyleDifference);

    diff = adjustStyleDifference(diff, contextSensitiveProperties);

    styleWillChange(diff, style.get());

    Ref<RenderStyle> oldStyle(m_style.replace(WTF::move(style)));

    updateFillImages(oldStyle.get().backgroundLayers(), m_style->backgroundLayers());
    updateFillImages(oldStyle.get().maskLayers(), m_style->maskLayers());

    updateImage(oldStyle.get().borderImage().image(), m_style->borderImage().image());
    updateImage(oldStyle.get().maskBoxImage().image(), m_style->maskBoxImage().image());

#if ENABLE(CSS_SHAPES)
    updateShapeImage(oldStyle.get().shapeOutside(), m_style->shapeOutside());
#endif

    // We need to ensure that view->maximalOutlineSize() is valid for any repaints that happen
    // during styleDidChange (it's used by clippedOverflowRectForRepaint()).
    if (m_style->outlineWidth() > 0 && m_style->outlineSize() > maximalOutlineSize(PaintPhaseOutline))
        view().setMaximalOutlineSize(std::max(theme().platformFocusRingMaxWidth(), static_cast<int>(m_style->outlineSize())));

    bool doesNotNeedLayout = !parent();

    styleDidChange(diff, oldStyle.ptr());

    // Text renderers use their parent style. Notify them about the change.
    for (auto& child : childrenOfType<RenderText>(*this))
        child.styleDidChange(diff, oldStyle.ptr());

    // FIXME: |this| might be destroyed here. This can currently happen for a RenderTextFragment when
    // its first-letter block gets an update in RenderTextFragment::styleDidChange. For RenderTextFragment(s),
    // we will safely bail out with the doesNotNeedLayout flag. We might want to broaden this condition
    // in the future as we move renderer changes out of layout and into style changes.
    if (doesNotNeedLayout)
        return;

    // Now that the layer (if any) has been updated, we need to adjust the diff again,
    // check whether we should layout now, and decide if we need to repaint.
    StyleDifference updatedDiff = adjustStyleDifference(diff, contextSensitiveProperties);
    
    if (diff <= StyleDifferenceLayoutPositionedMovementOnly) {
        if (updatedDiff == StyleDifferenceLayout)
            setNeedsLayoutAndPrefWidthsRecalc();
        else if (updatedDiff == StyleDifferenceLayoutPositionedMovementOnly)
            setNeedsPositionedMovementLayout(oldStyle.ptr());
        else if (updatedDiff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
            setNeedsPositionedMovementLayout(oldStyle.ptr());
            setNeedsSimplifiedNormalFlowLayout();
        } else if (updatedDiff == StyleDifferenceSimplifiedLayout)
            setNeedsSimplifiedNormalFlowLayout();
    }

    if (updatedDiff == StyleDifferenceRepaintLayer || shouldRepaintForStyleDifference(updatedDiff)) {
        // Do a repaint with the new style now, e.g., for example if we go from
        // not having an outline to having an outline.
        repaint();
    }
}

void RenderElement::addChild(RenderObject* newChild, RenderObject* beforeChild)
{
    bool needsTable = false;

    if (is<RenderTableCol>(*newChild)) {
        RenderTableCol& newTableColumn = downcast<RenderTableCol>(*newChild);
        bool isColumnInColumnGroup = newTableColumn.isTableColumn() && is<RenderTableCol>(*this);
        needsTable = !is<RenderTable>(*this) && !isColumnInColumnGroup;
    } else if (is<RenderTableCaption>(*newChild))
        needsTable = !is<RenderTable>(*this);
    else if (is<RenderTableSection>(*newChild))
        needsTable = !is<RenderTable>(*this);
    else if (is<RenderTableRow>(*newChild))
        needsTable = !is<RenderTableSection>(*this);
    else if (is<RenderTableCell>(*newChild))
        needsTable = !is<RenderTableRow>(*this);

    if (needsTable) {
        RenderTable* table;
        RenderObject* afterChild = beforeChild ? beforeChild->previousSibling() : m_lastChild;
        if (afterChild && afterChild->isAnonymous() && is<RenderTable>(*afterChild) && !afterChild->isBeforeContent())
            table = downcast<RenderTable>(afterChild);
        else {
            table = RenderTable::createAnonymousWithParentRenderer(this);
            addChild(table, beforeChild);
        }
        table->addChild(newChild);
    } else
        insertChildInternal(newChild, beforeChild, NotifyChildren);

    if (is<RenderText>(*newChild))
        downcast<RenderText>(*newChild).styleDidChange(StyleDifferenceEqual, nullptr);

    // SVG creates renderers for <g display="none">, as SVG requires children of hidden
    // <g>s to have renderers - at least that's how our implementation works. Consider:
    // <g display="none"><foreignObject><body style="position: relative">FOO...
    // - requiresLayer() would return true for the <body>, creating a new RenderLayer
    // - when the document is painted, both layers are painted. The <body> layer doesn't
    //   know that it's inside a "hidden SVG subtree", and thus paints, even if it shouldn't.
    // To avoid the problem alltogether, detect early if we're inside a hidden SVG subtree
    // and stop creating layers at all for these cases - they're not used anyways.
    if (newChild->hasLayer() && !layerCreationAllowedForSubtree())
        downcast<RenderLayerModelObject>(*newChild).layer()->removeOnlyThisLayer();

    SVGRenderSupport::childAdded(*this, *newChild);
}

void RenderElement::removeChild(RenderObject& oldChild)
{
    removeChildInternal(oldChild, NotifyChildren);
}

void RenderElement::destroyLeftoverChildren()
{
    while (m_firstChild) {
        if (m_firstChild->style().styleType() == FIRST_LETTER && !m_firstChild->isText()) {
            m_firstChild->removeFromParent(); // :first-letter fragment renderers are destroyed by their remaining text fragment.
        } else {
            // Destroy any anonymous children remaining in the render tree, as well as implicit (shadow) DOM elements like those used in the engine-based text fields.
            if (m_firstChild->node())
                m_firstChild->node()->setRenderer(nullptr);
            m_firstChild->destroy();
        }
    }
}

void RenderElement::insertChildInternal(RenderObject* newChild, RenderObject* beforeChild, NotifyChildrenType notifyChildren)
{
    ASSERT(canHaveChildren() || canHaveGeneratedChildren());
    ASSERT(!newChild->parent());
    ASSERT(!isRenderBlockFlow() || (!newChild->isTableSection() && !newChild->isTableRow() && !newChild->isTableCell()));

    while (beforeChild && beforeChild->parent() && beforeChild->parent() != this)
        beforeChild = beforeChild->parent();

    // This should never happen, but if it does prevent render tree corruption
    // where child->parent() ends up being owner but child->nextSibling()->parent()
    // is not owner.
    if (beforeChild && beforeChild->parent() != this) {
        ASSERT_NOT_REACHED();
        return;
    }

    newChild->setParent(this);

    if (m_firstChild == beforeChild)
        m_firstChild = newChild;

    if (beforeChild) {
        RenderObject* previousSibling = beforeChild->previousSibling();
        if (previousSibling)
            previousSibling->setNextSibling(newChild);
        newChild->setPreviousSibling(previousSibling);
        newChild->setNextSibling(beforeChild);
        beforeChild->setPreviousSibling(newChild);
    } else {
        if (lastChild())
            lastChild()->setNextSibling(newChild);
        newChild->setPreviousSibling(lastChild());
        m_lastChild = newChild;
    }

    if (!documentBeingDestroyed()) {
        if (notifyChildren == NotifyChildren)
            newChild->insertedIntoTree();
        if (is<RenderElement>(*newChild))
            RenderCounter::rendererSubtreeAttached(downcast<RenderElement>(*newChild));
    }

    newChild->setNeedsLayoutAndPrefWidthsRecalc();
    setPreferredLogicalWidthsDirty(true);
    if (!normalChildNeedsLayout())
        setChildNeedsLayout(); // We may supply the static position for an absolute positioned child.

    if (AXObjectCache* cache = document().axObjectCache())
        cache->childrenChanged(this, newChild);
    if (is<RenderBlockFlow>(*this))
        downcast<RenderBlockFlow>(*this).invalidateLineLayoutPath();
}

void RenderElement::removeChildInternal(RenderObject& oldChild, NotifyChildrenType notifyChildren)
{
    ASSERT(canHaveChildren() || canHaveGeneratedChildren());
    ASSERT(oldChild.parent() == this);

    if (oldChild.isFloatingOrOutOfFlowPositioned())
        downcast<RenderBox>(oldChild).removeFloatingOrPositionedChildFromBlockLists();

    // So that we'll get the appropriate dirty bit set (either that a normal flow child got yanked or
    // that a positioned child got yanked). We also repaint, so that the area exposed when the child
    // disappears gets repainted properly.
    if (!documentBeingDestroyed() && notifyChildren == NotifyChildren && oldChild.everHadLayout()) {
        oldChild.setNeedsLayoutAndPrefWidthsRecalc();
        // We only repaint |oldChild| if we have a RenderLayer as its visual overflow may not be tracked by its parent.
        if (oldChild.isBody())
            view().repaintRootContents();
        else
            oldChild.repaint();
    }

    // If we have a line box wrapper, delete it.
    if (is<RenderBox>(oldChild))
        downcast<RenderBox>(oldChild).deleteLineBoxWrapper();
    else if (is<RenderLineBreak>(oldChild))
        downcast<RenderLineBreak>(oldChild).deleteInlineBoxWrapper();

    // If oldChild is the start or end of the selection, then clear the selection to
    // avoid problems of invalid pointers.
    if (!documentBeingDestroyed() && oldChild.isSelectionBorder())
        frame().selection().setNeedsSelectionUpdate();

    if (!documentBeingDestroyed() && notifyChildren == NotifyChildren)
        oldChild.willBeRemovedFromTree();

    // WARNING: There should be no code running between willBeRemovedFromTree and the actual removal below.
    // This is needed to avoid race conditions where willBeRemovedFromTree would dirty the tree's structure
    // and the code running here would force an untimely rebuilding, leaving |oldChild| dangling.
    
    RenderObject* nextSibling = oldChild.nextSibling();

    if (oldChild.previousSibling())
        oldChild.previousSibling()->setNextSibling(nextSibling);
    if (nextSibling)
        nextSibling->setPreviousSibling(oldChild.previousSibling());

    if (m_firstChild == &oldChild)
        m_firstChild = nextSibling;
    if (m_lastChild == &oldChild)
        m_lastChild = oldChild.previousSibling();

    oldChild.setPreviousSibling(nullptr);
    oldChild.setNextSibling(nullptr);
    oldChild.setParent(nullptr);

    // rendererRemovedFromTree walks the whole subtree. We can improve performance
    // by skipping this step when destroying the entire tree.
    if (!documentBeingDestroyed() && is<RenderElement>(oldChild))
        RenderCounter::rendererRemovedFromTree(downcast<RenderElement>(oldChild));

    if (AXObjectCache* cache = document().existingAXObjectCache())
        cache->childrenChanged(this);
}

static void addLayers(RenderElement& renderer, RenderLayer* parentLayer, RenderElement*& newObject, RenderLayer*& beforeChild)
{
    if (renderer.hasLayer()) {
        if (!beforeChild && newObject) {
            // We need to figure out the layer that follows newObject. We only do
            // this the first time we find a child layer, and then we update the
            // pointer values for newObject and beforeChild used by everyone else.
            beforeChild = newObject->parent()->findNextLayer(parentLayer, newObject);
            newObject = nullptr;
        }
        parentLayer->addChild(downcast<RenderLayerModelObject>(renderer).layer(), beforeChild);
        return;
    }

    for (auto& child : childrenOfType<RenderElement>(renderer))
        addLayers(child, parentLayer, newObject, beforeChild);
}

void RenderElement::addLayers(RenderLayer* parentLayer)
{
    if (!parentLayer)
        return;

    RenderElement* renderer = this;
    RenderLayer* beforeChild = nullptr;
    WebCore::addLayers(*this, parentLayer, renderer, beforeChild);
}

void RenderElement::removeLayers(RenderLayer* parentLayer)
{
    if (!parentLayer)
        return;

    if (hasLayer()) {
        parentLayer->removeChild(downcast<RenderLayerModelObject>(*this).layer());
        return;
    }

    for (auto& child : childrenOfType<RenderElement>(*this))
        child.removeLayers(parentLayer);
}

void RenderElement::moveLayers(RenderLayer* oldParent, RenderLayer* newParent)
{
    if (!newParent)
        return;

    if (hasLayer()) {
        RenderLayer* layer = downcast<RenderLayerModelObject>(*this).layer();
        ASSERT(oldParent == layer->parent());
        if (oldParent)
            oldParent->removeChild(layer);
        newParent->addChild(layer);
        return;
    }

    for (auto& child : childrenOfType<RenderElement>(*this))
        child.moveLayers(oldParent, newParent);
}

RenderLayer* RenderElement::findNextLayer(RenderLayer* parentLayer, RenderObject* startPoint, bool checkParent)
{
    // Error check the parent layer passed in. If it's null, we can't find anything.
    if (!parentLayer)
        return nullptr;

    // Step 1: If our layer is a child of the desired parent, then return our layer.
    RenderLayer* ourLayer = hasLayer() ? downcast<RenderLayerModelObject>(*this).layer() : nullptr;
    if (ourLayer && ourLayer->parent() == parentLayer)
        return ourLayer;

    // Step 2: If we don't have a layer, or our layer is the desired parent, then descend
    // into our siblings trying to find the next layer whose parent is the desired parent.
    if (!ourLayer || ourLayer == parentLayer) {
        for (RenderObject* child = startPoint ? startPoint->nextSibling() : firstChild(); child; child = child->nextSibling()) {
            if (!is<RenderElement>(*child))
                continue;
            RenderLayer* nextLayer = downcast<RenderElement>(*child).findNextLayer(parentLayer, nullptr, false);
            if (nextLayer)
                return nextLayer;
        }
    }

    // Step 3: If our layer is the desired parent layer, then we're finished. We didn't
    // find anything.
    if (parentLayer == ourLayer)
        return nullptr;

    // Step 4: If |checkParent| is set, climb up to our parent and check its siblings that
    // follow us to see if we can locate a layer.
    if (checkParent && parent())
        return parent()->findNextLayer(parentLayer, this, true);

    return nullptr;
}

bool RenderElement::layerCreationAllowedForSubtree() const
{
    RenderElement* parentRenderer = parent();
    while (parentRenderer) {
        if (parentRenderer->isSVGHiddenContainer())
            return false;
        parentRenderer = parentRenderer->parent();
    }
    
    return true;
}

void RenderElement::propagateStyleToAnonymousChildren(StylePropagationType propagationType)
{
    // FIXME: We could save this call when the change only affected non-inherited properties.
    for (auto& elementChild : childrenOfType<RenderElement>(*this)) {
        if (!elementChild.isAnonymous() || elementChild.style().styleType() != NOPSEUDO)
            continue;

        if (propagationType == PropagateToBlockChildrenOnly && !is<RenderBlock>(elementChild))
            continue;

#if ENABLE(FULLSCREEN_API)
        if (elementChild.isRenderFullScreen() || elementChild.isRenderFullScreenPlaceholder())
            continue;
#endif

        // RenderFlowThreads are updated through the RenderView::styleDidChange function.
        if (is<RenderFlowThread>(elementChild))
            continue;

        auto newStyle = RenderStyle::createAnonymousStyleWithDisplay(&style(), elementChild.style().display());
        if (style().specifiesColumns()) {
            if (elementChild.style().specifiesColumns())
                newStyle.get().inheritColumnPropertiesFrom(&style());
            if (elementChild.style().columnSpan())
                newStyle.get().setColumnSpan(ColumnSpanAll);
        }

        // Preserve the position style of anonymous block continuations as they can have relative or sticky position when
        // they contain block descendants of relative or sticky positioned inlines.
        if (elementChild.isInFlowPositioned() && downcast<RenderBlock>(elementChild).isAnonymousBlockContinuation())
            newStyle.get().setPosition(elementChild.style().position());

        elementChild.setStyle(WTF::move(newStyle));
    }
}

static inline bool rendererHasBackground(const RenderElement* renderer)
{
    return renderer && renderer->hasBackground();
}

void RenderElement::styleWillChange(StyleDifference diff, const RenderStyle& newStyle)
{
    RenderStyle* oldStyle = hasInitializedStyle() ? &style() : nullptr;
    if (oldStyle) {
        // If our z-index changes value or our visibility changes,
        // we need to dirty our stacking context's z-order list.
        bool visibilityChanged = m_style->visibility() != newStyle.visibility()
            || m_style->zIndex() != newStyle.zIndex()
            || m_style->hasAutoZIndex() != newStyle.hasAutoZIndex();
#if ENABLE(DASHBOARD_SUPPORT)
        if (visibilityChanged)
            document().setAnnotatedRegionsDirty(true);
#endif
#if PLATFORM(IOS) && ENABLE(TOUCH_EVENTS)
        if (visibilityChanged)
            document().dirtyTouchEventRects();
#endif
        if (visibilityChanged) {
            if (AXObjectCache* cache = document().existingAXObjectCache())
                cache->childrenChanged(parent(), this);
        }

        // Keep layer hierarchy visibility bits up to date if visibility changes.
        if (m_style->visibility() != newStyle.visibility()) {
            if (RenderLayer* layer = enclosingLayer()) {
                if (newStyle.visibility() == VISIBLE)
                    layer->setHasVisibleContent();
                else if (layer->hasVisibleContent() && (this == &layer->renderer() || layer->renderer().style().visibility() != VISIBLE)) {
                    layer->dirtyVisibleContentStatus();
                    if (diff > StyleDifferenceRepaintLayer)
                        repaint();
                }
            }
        }

        if (m_parent && (newStyle.outlineSize() < m_style->outlineSize() || shouldRepaintForStyleDifference(diff)))
            repaint();
        if (isFloating() && (m_style->floating() != newStyle.floating()))
            // For changes in float styles, we need to conceivably remove ourselves
            // from the floating objects list.
            downcast<RenderBox>(*this).removeFloatingOrPositionedChildFromBlockLists();
        else if (isOutOfFlowPositioned() && (m_style->position() != newStyle.position()))
            // For changes in positioning styles, we need to conceivably remove ourselves
            // from the positioned objects list.
            downcast<RenderBox>(*this).removeFloatingOrPositionedChildFromBlockLists();

        s_affectsParentBlock = isFloatingOrOutOfFlowPositioned()
            && (!newStyle.isFloating() && !newStyle.hasOutOfFlowPosition())
            && parent() && (parent()->isRenderBlockFlow() || parent()->isRenderInline());

        s_noLongerAffectsParentBlock = ((!isFloating() && newStyle.isFloating()) || (!isOutOfFlowPositioned() && newStyle.hasOutOfFlowPosition()))
            && parent() && parent()->isRenderBlock();

        // reset style flags
        if (diff == StyleDifferenceLayout || diff == StyleDifferenceLayoutPositionedMovementOnly) {
            setFloating(false);
            clearPositionedState();
        }
        setHorizontalWritingMode(true);
        setHasBoxDecorations(false);
        setHasOverflowClip(false);
        setHasTransformRelatedProperty(false);
        setHasReflection(false);
    } else {
        s_affectsParentBlock = false;
        s_noLongerAffectsParentBlock = false;
    }

    bool newStyleUsesFixedBackgrounds = newStyle.hasFixedBackgroundImage();
    bool oldStyleUsesFixedBackgrounds = m_style->hasFixedBackgroundImage();
    if (newStyleUsesFixedBackgrounds || oldStyleUsesFixedBackgrounds) {
        bool repaintFixedBackgroundsOnScroll = !frame().settings().fixedBackgroundsPaintRelativeToDocument();

        bool newStyleSlowScroll = repaintFixedBackgroundsOnScroll && newStyleUsesFixedBackgrounds;
        bool oldStyleSlowScroll = oldStyle && repaintFixedBackgroundsOnScroll && oldStyleUsesFixedBackgrounds;
        bool drawsRootBackground = isRoot() || (isBody() && !rendererHasBackground(document().documentElement()->renderer()));
        if (drawsRootBackground && repaintFixedBackgroundsOnScroll) {
            if (view().compositor().supportsFixedRootBackgroundCompositing()) {
                if (newStyleSlowScroll && newStyle.hasEntirelyFixedBackground())
                    newStyleSlowScroll = false;

                if (oldStyleSlowScroll && m_style->hasEntirelyFixedBackground())
                    oldStyleSlowScroll = false;
            }
        }

        if (oldStyleSlowScroll != newStyleSlowScroll) {
            if (oldStyleSlowScroll)
                view().frameView().removeSlowRepaintObject(this);

            if (newStyleSlowScroll)
                view().frameView().addSlowRepaintObject(this);
        }
    }

    if (isRoot() || isBody())
        view().frameView().updateExtendBackgroundIfNecessary();
}

void RenderElement::handleDynamicFloatPositionChange()
{
    // We have gone from not affecting the inline status of the parent flow to suddenly
    // having an impact.  See if there is a mismatch between the parent flow's
    // childrenInline() state and our state.
    setInline(style().isDisplayInlineType());
    if (isInline() != parent()->childrenInline()) {
        if (!isInline())
            downcast<RenderBoxModelObject>(*parent()).childBecameNonInline(*this);
        else {
            // An anonymous block must be made to wrap this inline.
            RenderBlock* block = downcast<RenderBlock>(*parent()).createAnonymousBlock();
            parent()->insertChildInternal(block, this, RenderElement::NotifyChildren);
            parent()->removeChildInternal(*this, RenderElement::NotifyChildren);
            block->insertChildInternal(this, nullptr, RenderElement::NotifyChildren);
        }
    }
}

void RenderElement::removeAnonymousWrappersForInlinesIfNecessary()
{
    RenderBlock& parentBlock = downcast<RenderBlock>(*parent());
    if (!parentBlock.canCollapseAnonymousBlockChild())
        return;

    // We have changed to floated or out-of-flow positioning so maybe all our parent's
    // children can be inline now. Bail if there are any block children left on the line,
    // otherwise we can proceed to stripping solitary anonymous wrappers from the inlines.
    // FIXME: We should also handle split inlines here - we exclude them at the moment by returning
    // if we find a continuation.
    RenderObject* current = parent()->firstChild();
    while (current && ((current->isAnonymousBlock() && !downcast<RenderBlock>(*current).isAnonymousBlockContinuation()) || current->style().isFloating() || current->style().hasOutOfFlowPosition()))
        current = current->nextSibling();

    if (current)
        return;

    RenderObject* next;
    for (current = parent()->firstChild(); current; current = next) {
        next = current->nextSibling();
        if (current->isAnonymousBlock())
            parentBlock.collapseAnonymousBoxChild(parentBlock, downcast<RenderBlock>(current));
    }
}

#if !PLATFORM(IOS)
static bool areNonIdenticalCursorListsEqual(const RenderStyle* a, const RenderStyle* b)
{
    ASSERT(a->cursors() != b->cursors());
    return a->cursors() && b->cursors() && *a->cursors() == *b->cursors();
}

static inline bool areCursorsEqual(const RenderStyle* a, const RenderStyle* b)
{
    return a->cursor() == b->cursor() && (a->cursors() == b->cursors() || areNonIdenticalCursorListsEqual(a, b));
}
#endif

void RenderElement::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
{
    if (s_affectsParentBlock)
        handleDynamicFloatPositionChange();

    if (s_noLongerAffectsParentBlock)
        removeAnonymousWrappersForInlinesIfNecessary();

    SVGRenderSupport::styleChanged(*this, oldStyle);

    if (!m_parent)
        return;
    
    if (diff == StyleDifferenceLayout || diff == StyleDifferenceSimplifiedLayout) {
        RenderCounter::rendererStyleChanged(*this, oldStyle, m_style.ptr());

        // If the object already needs layout, then setNeedsLayout won't do
        // any work. But if the containing block has changed, then we may need
        // to mark the new containing blocks for layout. The change that can
        // directly affect the containing block of this object is a change to
        // the position style.
        if (needsLayout() && oldStyle->position() != m_style->position())
            markContainingBlocksForLayout();

        if (diff == StyleDifferenceLayout)
            setNeedsLayoutAndPrefWidthsRecalc();
        else
            setNeedsSimplifiedNormalFlowLayout();
    } else if (diff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
        setNeedsPositionedMovementLayout(oldStyle);
        setNeedsSimplifiedNormalFlowLayout();
    } else if (diff == StyleDifferenceLayoutPositionedMovementOnly)
        setNeedsPositionedMovementLayout(oldStyle);

    // Don't check for repaint here; we need to wait until the layer has been
    // updated by subclasses before we know if we have to repaint (in setStyle()).

#if !PLATFORM(IOS)
    if (oldStyle && !areCursorsEqual(oldStyle, &style()))
        frame().eventHandler().scheduleCursorUpdate();
#endif
}

void RenderElement::insertedIntoTree()
{
    if (auto* containerFlowThread = parent()->renderNamedFlowThreadWrapper())
        containerFlowThread->addFlowChild(*this);

    // Keep our layer hierarchy updated. Optimize for the common case where we don't have any children
    // and don't have a layer attached to ourselves.
    RenderLayer* layer = nullptr;
    if (firstChild() || hasLayer()) {
        layer = parent()->enclosingLayer();
        addLayers(layer);
    }

    // If |this| is visible but this object was not, tell the layer it has some visible content
    // that needs to be drawn and layer visibility optimization can't be used
    if (parent()->style().visibility() != VISIBLE && style().visibility() == VISIBLE && !hasLayer()) {
        if (!layer)
            layer = parent()->enclosingLayer();
        if (layer)
            layer->setHasVisibleContent();
    }

    RenderObject::insertedIntoTree();
}

void RenderElement::willBeRemovedFromTree()
{
    // If we remove a visible child from an invisible parent, we don't know the layer visibility any more.
    RenderLayer* layer = nullptr;
    if (parent()->style().visibility() != VISIBLE && style().visibility() == VISIBLE && !hasLayer()) {
        if ((layer = parent()->enclosingLayer()))
            layer->dirtyVisibleContentStatus();
    }
    // Keep our layer hierarchy updated.
    if (firstChild() || hasLayer()) {
        if (!layer)
            layer = parent()->enclosingLayer();
        removeLayers(layer);
    }

    if (m_style->hasFixedBackgroundImage() && !frame().settings().fixedBackgroundsPaintRelativeToDocument())
        view().frameView().removeSlowRepaintObject(this);

    if (isOutOfFlowPositioned() && parent()->childrenInline())
        parent()->dirtyLinesFromChangedChild(*this);

    if (auto* containerFlowThread = parent()->renderNamedFlowThreadWrapper())
        containerFlowThread->removeFlowChild(*this);

    RenderObject::willBeRemovedFromTree();
}

void RenderElement::willBeDestroyed()
{
    animation().cancelAnimations(*this);

    destroyLeftoverChildren();

    if (hasCounterNodeMap())
        RenderCounter::destroyCounterNodes(*this);

    RenderObject::willBeDestroyed();

#if !ASSERT_DISABLED
    if (!documentBeingDestroyed() && view().hasRenderNamedFlowThreads()) {
        // After remove, the object and the associated information should not be in any flow thread.
        for (auto& flowThread : *view().flowThreadController().renderNamedFlowThreadList()) {
            ASSERT(!flowThread->hasChild(*this));
            ASSERT(!flowThread->hasChildInfo(this));
        }
    }
#endif
}

void RenderElement::setNeedsPositionedMovementLayout(const RenderStyle* oldStyle)
{
    ASSERT(!isSetNeedsLayoutForbidden());
    if (needsPositionedMovementLayout())
        return;
    setNeedsPositionedMovementLayoutBit(true);
    markContainingBlocksForLayout();
    if (hasLayer()) {
        if (oldStyle && style().diffRequiresLayerRepaint(*oldStyle, downcast<RenderLayerModelObject>(*this).layer()->isComposited()))
            setLayerNeedsFullRepaint();
        else
            setLayerNeedsFullRepaintForPositionedMovementLayout();
    }
}

void RenderElement::clearChildNeedsLayout()
{
    setNormalChildNeedsLayoutBit(false);
    setPosChildNeedsLayoutBit(false);
    setNeedsSimplifiedNormalFlowLayoutBit(false);
    setNormalChildNeedsLayoutBit(false);
    setNeedsPositionedMovementLayoutBit(false);
}

void RenderElement::setNeedsSimplifiedNormalFlowLayout()
{
    ASSERT(!isSetNeedsLayoutForbidden());
    if (needsSimplifiedNormalFlowLayout())
        return;
    setNeedsSimplifiedNormalFlowLayoutBit(true);
    markContainingBlocksForLayout();
    if (hasLayer())
        setLayerNeedsFullRepaint();
}

RenderElement& RenderElement::rendererForRootBackground()
{
    ASSERT(isRoot());
    if (!hasBackground() && is<HTMLHtmlElement>(element())) {
        // 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.
        if (auto* body = document().body()) {
            if (auto* renderer = body->renderer())
                return *renderer;
        }
    }
    return *this;
}

RenderElement* RenderElement::hoverAncestor() const
{
    // When searching for the hover ancestor and encountering a named flow thread,
    // the search will continue with the DOM ancestor of the top-most element
    // in the named flow thread.
    // See https://bugs.webkit.org/show_bug.cgi?id=111749
    RenderElement* hoverAncestor = parent();

    // Skip anonymous blocks directly flowed into flow threads as it would
    // prevent us from continuing the search on the DOM tree when reaching the named flow thread.
    if (hoverAncestor && hoverAncestor->isAnonymousBlock() && hoverAncestor->parent() && hoverAncestor->parent()->isRenderNamedFlowThread())
        hoverAncestor = hoverAncestor->parent();

    if (hoverAncestor && hoverAncestor->isRenderNamedFlowThread()) {
        hoverAncestor = nullptr;
        if (Element* element = this->element()) {
            if (auto parent = element->parentNode())
                hoverAncestor = parent->renderer();
        }
    }

    return hoverAncestor;
}

static inline void paintPhase(RenderElement& element, PaintPhase phase, PaintInfo& paintInfo, const LayoutPoint& childPoint)
{
    paintInfo.phase = phase;
    element.paint(paintInfo, childPoint);
}

void RenderElement::paintAsInlineBlock(PaintInfo& paintInfo, const LayoutPoint& childPoint)
{
    // Paint all phases atomically, as though the element established its own stacking context.
    // (See Appendix E.2, section 6.4 on inline block/table/replaced elements in the CSS2.1 specification.)
    // This is also used by other elements (e.g. flex items and grid items).
    if (paintInfo.phase == PaintPhaseSelection) {
        paint(paintInfo, childPoint);
    } else if (paintInfo.phase == PaintPhaseForeground) {
        paintPhase(*this, PaintPhaseBlockBackground, paintInfo, childPoint);
        paintPhase(*this, PaintPhaseChildBlockBackgrounds, paintInfo, childPoint);
        paintPhase(*this, PaintPhaseFloat, paintInfo, childPoint);
        paintPhase(*this, PaintPhaseForeground, paintInfo, childPoint);
        paintPhase(*this, PaintPhaseOutline, paintInfo, childPoint);

        // Reset |paintInfo| to the original phase.
        paintInfo.phase = PaintPhaseForeground;
    }
}

void RenderElement::layout()
{
    StackStats::LayoutCheckPoint layoutCheckPoint;
    ASSERT(needsLayout());
    RenderObject* child = firstChild();
    while (child) {
        if (child->needsLayout())
            downcast<RenderElement>(*child).layout();
        ASSERT(!child->needsLayout());
        child = child->nextSibling();
    }
    clearNeedsLayout();
}

static bool mustRepaintFillLayers(const RenderElement& renderer, const FillLayer* layer)
{
    // Nobody will use multiple layers without wanting fancy positioning.
    if (layer->next())
        return true;

    // Make sure we have a valid image.
    StyleImage* image = layer->image();
    if (!image || !image->canRender(&renderer, renderer.style().effectiveZoom()))
        return false;

    if (!layer->xPosition().isZero() || !layer->yPosition().isZero())
        return true;

    EFillSizeType sizeType = layer->sizeType();

    if (sizeType == Contain || sizeType == Cover)
        return true;

    if (sizeType == SizeLength) {
        LengthSize size = layer->sizeLength();
        if (size.width().isPercentOrCalculated() || size.height().isPercentOrCalculated())
            return true;
        // If the image has neither an intrinsic width nor an intrinsic height, its size is determined as for 'contain'.
        if ((size.width().isAuto() || size.height().isAuto()) && image->isGeneratedImage())
            return true;
    } else if (image->usesImageContainerSize())
        return true;

    return false;
}

static bool mustRepaintBackgroundOrBorder(const RenderElement& renderer)
{
    if (renderer.hasMask() && mustRepaintFillLayers(renderer, renderer.style().maskLayers()))
        return true;

    // If we don't have a background/border/mask, then nothing to do.
    if (!renderer.hasBoxDecorations())
        return false;

    if (mustRepaintFillLayers(renderer, renderer.style().backgroundLayers()))
        return true;

    // Our fill layers are ok. Let's check border.
    if (renderer.style().hasBorder() && renderer.borderImageIsLoadedAndCanBeRendered())
        return true;

    return false;
}

bool RenderElement::repaintAfterLayoutIfNeeded(const RenderLayerModelObject* repaintContainer, const LayoutRect& oldBounds, const LayoutRect& oldOutlineBox, const LayoutRect* newBoundsPtr, const LayoutRect* newOutlineBoxRectPtr)
{
    if (view().printing())
        return false; // Don't repaint if we're printing.

    // This ASSERT fails due to animations. See https://bugs.webkit.org/show_bug.cgi?id=37048
    // ASSERT(!newBoundsPtr || *newBoundsPtr == clippedOverflowRectForRepaint(repaintContainer));
    LayoutRect newBounds = newBoundsPtr ? *newBoundsPtr : clippedOverflowRectForRepaint(repaintContainer);
    LayoutRect newOutlineBox;

    bool fullRepaint = selfNeedsLayout();
    // Presumably a background or a border exists if border-fit:lines was specified.
    if (!fullRepaint && style().borderFit() == BorderFitLines)
        fullRepaint = true;
    if (!fullRepaint) {
        // This ASSERT fails due to animations. See https://bugs.webkit.org/show_bug.cgi?id=37048
        // ASSERT(!newOutlineBoxRectPtr || *newOutlineBoxRectPtr == outlineBoundsForRepaint(repaintContainer));
        newOutlineBox = newOutlineBoxRectPtr ? *newOutlineBoxRectPtr : outlineBoundsForRepaint(repaintContainer);
        if (newOutlineBox.location() != oldOutlineBox.location() || (mustRepaintBackgroundOrBorder(*this) && (newBounds != oldBounds || newOutlineBox != oldOutlineBox)))
            fullRepaint = true;
    }

    if (!repaintContainer)
        repaintContainer = &view();

    if (fullRepaint) {
        repaintUsingContainer(repaintContainer, oldBounds);
        if (newBounds != oldBounds)
            repaintUsingContainer(repaintContainer, newBounds);
        return true;
    }

    if (newBounds == oldBounds && newOutlineBox == oldOutlineBox)
        return false;

    LayoutUnit deltaLeft = newBounds.x() - oldBounds.x();
    if (deltaLeft > 0)
        repaintUsingContainer(repaintContainer, LayoutRect(oldBounds.x(), oldBounds.y(), deltaLeft, oldBounds.height()));
    else if (deltaLeft < 0)
        repaintUsingContainer(repaintContainer, LayoutRect(newBounds.x(), newBounds.y(), -deltaLeft, newBounds.height()));

    LayoutUnit deltaRight = newBounds.maxX() - oldBounds.maxX();
    if (deltaRight > 0)
        repaintUsingContainer(repaintContainer, LayoutRect(oldBounds.maxX(), newBounds.y(), deltaRight, newBounds.height()));
    else if (deltaRight < 0)
        repaintUsingContainer(repaintContainer, LayoutRect(newBounds.maxX(), oldBounds.y(), -deltaRight, oldBounds.height()));

    LayoutUnit deltaTop = newBounds.y() - oldBounds.y();
    if (deltaTop > 0)
        repaintUsingContainer(repaintContainer, LayoutRect(oldBounds.x(), oldBounds.y(), oldBounds.width(), deltaTop));
    else if (deltaTop < 0)
        repaintUsingContainer(repaintContainer, LayoutRect(newBounds.x(), newBounds.y(), newBounds.width(), -deltaTop));

    LayoutUnit deltaBottom = newBounds.maxY() - oldBounds.maxY();
    if (deltaBottom > 0)
        repaintUsingContainer(repaintContainer, LayoutRect(newBounds.x(), oldBounds.maxY(), newBounds.width(), deltaBottom));
    else if (deltaBottom < 0)
        repaintUsingContainer(repaintContainer, LayoutRect(oldBounds.x(), newBounds.maxY(), oldBounds.width(), -deltaBottom));

    if (newOutlineBox == oldOutlineBox)
        return false;

    // We didn't move, but we did change size. Invalidate the delta, which will consist of possibly
    // two rectangles (but typically only one).
    const RenderStyle& outlineStyle = outlineStyleForRepaint();
    LayoutUnit outlineWidth = outlineStyle.outlineSize();
    LayoutBoxExtent insetShadowExtent = style().getBoxShadowInsetExtent();
    LayoutUnit width = absoluteValue(newOutlineBox.width() - oldOutlineBox.width());
    if (width) {
        LayoutUnit shadowLeft;
        LayoutUnit shadowRight;
        style().getBoxShadowHorizontalExtent(shadowLeft, shadowRight);
        LayoutUnit borderRight = is<RenderBox>(*this) ? downcast<RenderBox>(*this).borderRight() : LayoutUnit::fromPixel(0);
        LayoutUnit boxWidth = is<RenderBox>(*this) ? downcast<RenderBox>(*this).width() : LayoutUnit();
        LayoutUnit minInsetRightShadowExtent = std::min<LayoutUnit>(-insetShadowExtent.right(), std::min<LayoutUnit>(newBounds.width(), oldBounds.width()));
        LayoutUnit borderWidth = std::max<LayoutUnit>(borderRight, std::max<LayoutUnit>(valueForLength(style().borderTopRightRadius().width(), boxWidth), valueForLength(style().borderBottomRightRadius().width(), boxWidth)));
        LayoutUnit decorationsWidth = std::max<LayoutUnit>(-outlineStyle.outlineOffset(), borderWidth + minInsetRightShadowExtent) + std::max<LayoutUnit>(outlineWidth, shadowRight);
        LayoutRect rightRect(newOutlineBox.x() + std::min(newOutlineBox.width(), oldOutlineBox.width()) - decorationsWidth,
            newOutlineBox.y(),
            width + decorationsWidth,
            std::max(newOutlineBox.height(), oldOutlineBox.height()));
        LayoutUnit right = std::min<LayoutUnit>(newBounds.maxX(), oldBounds.maxX());
        if (rightRect.x() < right) {
            rightRect.setWidth(std::min(rightRect.width(), right - rightRect.x()));
            repaintUsingContainer(repaintContainer, rightRect);
        }
    }
    LayoutUnit height = absoluteValue(newOutlineBox.height() - oldOutlineBox.height());
    if (height) {
        LayoutUnit shadowTop;
        LayoutUnit shadowBottom;
        style().getBoxShadowVerticalExtent(shadowTop, shadowBottom);
        LayoutUnit borderBottom = is<RenderBox>(*this) ? downcast<RenderBox>(*this).borderBottom() : LayoutUnit::fromPixel(0);
        LayoutUnit boxHeight = is<RenderBox>(*this) ? downcast<RenderBox>(*this).height() : LayoutUnit();
        LayoutUnit minInsetBottomShadowExtent = std::min<LayoutUnit>(-insetShadowExtent.bottom(), std::min<LayoutUnit>(newBounds.height(), oldBounds.height()));
        LayoutUnit borderHeight = std::max<LayoutUnit>(borderBottom, std::max<LayoutUnit>(valueForLength(style().borderBottomLeftRadius().height(), boxHeight),
            valueForLength(style().borderBottomRightRadius().height(), boxHeight)));
        LayoutUnit decorationsHeight = std::max<LayoutUnit>(-outlineStyle.outlineOffset(), borderHeight + minInsetBottomShadowExtent) + std::max<LayoutUnit>(outlineWidth, shadowBottom);
        LayoutRect bottomRect(newOutlineBox.x(),
            std::min(newOutlineBox.maxY(), oldOutlineBox.maxY()) - decorationsHeight,
            std::max(newOutlineBox.width(), oldOutlineBox.width()),
            height + decorationsHeight);
        LayoutUnit bottom = std::min(newBounds.maxY(), oldBounds.maxY());
        if (bottomRect.y() < bottom) {
            bottomRect.setHeight(std::min(bottomRect.height(), bottom - bottomRect.y()));
            repaintUsingContainer(repaintContainer, bottomRect);
        }
    }
    return false;
}

bool RenderElement::borderImageIsLoadedAndCanBeRendered() const
{
    ASSERT(style().hasBorder());

    StyleImage* borderImage = style().borderImage().image();
    return borderImage && borderImage->canRender(this, style().effectiveZoom()) && borderImage->isLoaded();
}

bool RenderElement::mayCauseRepaintInsideViewport(const IntRect* optionalViewportRect) const
{
    auto& frameView = view().frameView();
    if (frameView.isOffscreen())
        return false;

    if (!hasOverflowClip()) {
        // FIXME: Computing the overflow rect is expensive if any descendant has
        // its own self-painting layer. As a result, we prefer to abort early in
        // this case and assume it may cause us to repaint inside the viewport.
        if (!hasLayer() || downcast<RenderLayerModelObject>(*this).layer()->firstChild())
            return true;
    }

    // Compute viewport rect if it was not provided.
    const IntRect& visibleRect = optionalViewportRect ? *optionalViewportRect : frameView.windowToContents(frameView.windowClipRect());
    return visibleRect.intersects(enclosingIntRect(absoluteClippedOverflowRect()));
}

static bool shouldRepaintForImageAnimation(const RenderElement& renderer, const IntRect& visibleRect)
{
    const Document& document = renderer.document();
    if (document.inPageCache())
        return false;
#if PLATFORM(IOS)
    if (document.frame()->timersPaused())
        return false;
#endif
    if (document.activeDOMObjectsAreSuspended())
        return false;
    if (renderer.style().visibility() != VISIBLE)
        return false;
    if (renderer.view().frameView().isOffscreen())
        return false;

    // Use background rect if we are the root or if we are the body and the background is propagated to the root.
    // FIXME: This is overly conservative as the image may not be a background-image, in which case it will not
    // be propagated to the root. At this point, we unfortunately don't have access to the image anymore so we
    // can no longer check if it is a background image.
    bool backgroundIsPaintedByRoot = renderer.isRoot();
    if (renderer.isBody()) {
        auto& rootRenderer = *renderer.parent(); // If <body> has a renderer then <html> does too.
        ASSERT(rootRenderer.isRoot());
        ASSERT(is<HTMLHtmlElement>(rootRenderer.element()));
        // FIXME: Should share body background propagation code.
        backgroundIsPaintedByRoot = !rootRenderer.hasBackground();

    }
    LayoutRect backgroundPaintingRect = backgroundIsPaintedByRoot ? renderer.view().backgroundRect(&renderer.view()) : renderer.absoluteClippedOverflowRect();
    if (!visibleRect.intersects(enclosingIntRect(backgroundPaintingRect)))
        return false;

    return true;
}

void RenderElement::newImageAnimationFrameAvailable(CachedImage& image)
{
    if (document().inPageCache())
        return;
    auto& frameView = view().frameView();
    auto visibleRect = frameView.windowToContents(frameView.windowClipRect());
    if (!shouldRepaintForImageAnimation(*this, visibleRect)) {
        // FIXME: It would be better to pass the image along with the renderer
        // so that we can be smarter about detecting if the image is inside the
        // viewport in repaintForPausedImageAnimationsIfNeeded().
        view().addRendererWithPausedImageAnimations(*this);
        return;
    }
    imageChanged(&image);
}

bool RenderElement::repaintForPausedImageAnimationsIfNeeded(const IntRect& visibleRect)
{
    ASSERT(m_hasPausedImageAnimations);
    if (!shouldRepaintForImageAnimation(*this, visibleRect))
        return false;
    repaint();
    return true;
}

RenderNamedFlowThread* RenderElement::renderNamedFlowThreadWrapper()
{
    auto* renderer = this;
    while (renderer && renderer->isAnonymousBlock() && !is<RenderNamedFlowThread>(*renderer))
        renderer = renderer->parent();
    return is<RenderNamedFlowThread>(renderer) ? downcast<RenderNamedFlowThread>(renderer) : nullptr;
}

bool RenderElement::hasControlStatesForRenderer(const RenderObject* o)
{
    return controlStatesRendererMap().contains(o);
}

ControlStates* RenderElement::controlStatesForRenderer(const RenderObject* o)
{
    return controlStatesRendererMap().get(o);
}

void RenderElement::removeControlStatesForRenderer(const RenderObject* o)
{
    ControlStates* states = controlStatesRendererMap().get(o);
    if (states) {
        controlStatesRendererMap().remove(o);
        delete states;
    }
}

void RenderElement::addControlStatesForRenderer(const RenderObject* o, ControlStates* states)
{
    controlStatesRendererMap().add(o, states);
}

RenderStyle* RenderElement::getCachedPseudoStyle(PseudoId pseudo, RenderStyle* parentStyle) const
{
    if (pseudo < FIRST_INTERNAL_PSEUDOID && !style().hasPseudoStyle(pseudo))
        return nullptr;

    RenderStyle* cachedStyle = style().getCachedPseudoStyle(pseudo);
    if (cachedStyle)
        return cachedStyle;

    RefPtr<RenderStyle> result = getUncachedPseudoStyle(PseudoStyleRequest(pseudo), parentStyle);
    if (result)
        return style().addCachedPseudoStyle(result.release());
    return nullptr;
}

PassRefPtr<RenderStyle> RenderElement::getUncachedPseudoStyle(const PseudoStyleRequest& pseudoStyleRequest, RenderStyle* parentStyle, RenderStyle* ownStyle) const
{
    if (pseudoStyleRequest.pseudoId < FIRST_INTERNAL_PSEUDOID && !ownStyle && !style().hasPseudoStyle(pseudoStyleRequest.pseudoId))
        return nullptr;

    if (!parentStyle) {
        ASSERT(!ownStyle);
        parentStyle = &style();
    }

    if (isAnonymous())
        return nullptr;

    if (pseudoStyleRequest.pseudoId == FIRST_LINE_INHERITED) {
        RefPtr<RenderStyle> result = document().ensureStyleResolver().styleForElement(element(), parentStyle, DisallowStyleSharing);
        result->setStyleType(FIRST_LINE_INHERITED);
        return result.release();
    }

    return document().ensureStyleResolver().pseudoStyleForElement(element(), pseudoStyleRequest, parentStyle);
}

RenderBlock* RenderElement::containingBlockForFixedPosition() const
{
    const RenderElement* object = this;
    while (object && !object->canContainFixedPositionObjects())
        object = object->parent();

    ASSERT(!object || !object->isAnonymousBlock());
    return const_cast<RenderBlock*>(downcast<RenderBlock>(object));
}

RenderBlock* RenderElement::containingBlockForAbsolutePosition() const
{
    const RenderElement* object = this;
    while (object && !object->canContainAbsolutelyPositionedObjects())
        object = object->parent();

    // For a relatively positioned inline, return its nearest non-anonymous containing block,
    // not the inline itself, to avoid having a positioned objects list in all RenderInlines
    // and use RenderBlock* as RenderElement::containingBlock's return type.
    // Use RenderBlock::container() to obtain the inline.
    if (object && !is<RenderBlock>(*object))
        object = object->containingBlock();

    while (object && object->isAnonymousBlock())
        object = object->containingBlock();

    return const_cast<RenderBlock*>(downcast<RenderBlock>(object));
}

static inline bool isNonRenderBlockInline(const RenderElement& object)
{
    return (object.isInline() && !object.isReplaced()) || !object.isRenderBlock();
}

RenderBlock* RenderElement::containingBlockForObjectInFlow() const
{
    const RenderElement* object = this;
    while (object && isNonRenderBlockInline(*object))
        object = object->parent();
    return const_cast<RenderBlock*>(downcast<RenderBlock>(object));
}

Color RenderElement::selectionColor(int colorProperty) const
{
    // If the element is unselectable, or we are only painting the selection,
    // don't override the foreground color with the selection foreground color.
    if (style().userSelect() == SELECT_NONE
        || (view().frameView().paintBehavior() & (PaintBehaviorSelectionOnly | PaintBehaviorSelectionAndBackgroundsOnly)))
        return Color();

    if (RefPtr<RenderStyle> pseudoStyle = selectionPseudoStyle()) {
        Color color = pseudoStyle->visitedDependentColor(colorProperty);
        if (!color.isValid())
            color = pseudoStyle->visitedDependentColor(CSSPropertyColor);
        return color;
    }

    if (frame().selection().isFocusedAndActive())
        return theme().activeSelectionForegroundColor();
    return theme().inactiveSelectionForegroundColor();
}

PassRefPtr<RenderStyle> RenderElement::selectionPseudoStyle() const
{
    if (isAnonymous())
        return nullptr;

    if (ShadowRoot* root = element()->containingShadowRoot()) {
        if (root->type() == ShadowRoot::UserAgentShadowRoot) {
            if (Element* shadowHost = element()->shadowHost())
                return shadowHost->renderer()->getUncachedPseudoStyle(PseudoStyleRequest(SELECTION));
        }
    }

    return getUncachedPseudoStyle(PseudoStyleRequest(SELECTION));
}

Color RenderElement::selectionForegroundColor() const
{
    return selectionColor(CSSPropertyWebkitTextFillColor);
}

Color RenderElement::selectionEmphasisMarkColor() const
{
    return selectionColor(CSSPropertyWebkitTextEmphasisColor);
}

Color RenderElement::selectionBackgroundColor() const
{
    if (style().userSelect() == SELECT_NONE)
        return Color();

    if (frame().selection().shouldShowBlockCursor() && frame().selection().isCaret())
        return style().visitedDependentColor(CSSPropertyColor).blendWithWhite();

    RefPtr<RenderStyle> pseudoStyle = selectionPseudoStyle();
    if (pseudoStyle && pseudoStyle->visitedDependentColor(CSSPropertyBackgroundColor).isValid())
        return pseudoStyle->visitedDependentColor(CSSPropertyBackgroundColor).blendWithWhite();

    if (frame().selection().isFocusedAndActive())
        return theme().activeSelectionBackgroundColor();
    return theme().inactiveSelectionBackgroundColor();
}

bool RenderElement::getLeadingCorner(FloatPoint& point) const
{
    if (!isInline() || isReplaced()) {
        point = localToAbsolute(FloatPoint(), UseTransforms);
        return true;
    }

    // find the next text/image child, to get a position
    const RenderObject* o = this;
    while (o) {
        const RenderObject* p = o;
        if (RenderObject* child = o->firstChildSlow())
            o = child;
        else if (o->nextSibling())
            o = o->nextSibling();
        else {
            RenderObject* next = 0;
            while (!next && o->parent()) {
                o = o->parent();
                next = o->nextSibling();
            }
            o = next;

            if (!o)
                break;
        }
        ASSERT(o);

        if (!o->isInline() || o->isReplaced()) {
            point = o->localToAbsolute(FloatPoint(), UseTransforms);
            return true;
        }

        if (p->node() && p->node() == element() && is<RenderText>(*o) && !downcast<RenderText>(*o).firstTextBox()) {
            // do nothing - skip unrendered whitespace that is a child or next sibling of the anchor
        } else if (is<RenderText>(*o) || o->isReplaced()) {
            point = FloatPoint();
            if (is<RenderText>(*o) && downcast<RenderText>(*o).firstTextBox())
                point.move(downcast<RenderText>(*o).linesBoundingBox().x(), downcast<RenderText>(*o).topOfFirstText());
            else if (is<RenderBox>(*o))
                point.moveBy(downcast<RenderBox>(*o).location());
            point = o->container()->localToAbsolute(point, UseTransforms);
            return true;
        }
    }
    
    // If the target doesn't have any children or siblings that could be used to calculate the scroll position, we must be
    // at the end of the document. Scroll to the bottom. FIXME: who said anything about scrolling?
    if (!o && document().view()) {
        point = FloatPoint(0, document().view()->contentsHeight());
        return true;
    }
    return false;
}

bool RenderElement::getTrailingCorner(FloatPoint& point) const
{
    if (!isInline() || isReplaced()) {
        point = localToAbsolute(LayoutPoint(downcast<RenderBox>(*this).size()), UseTransforms);
        return true;
    }

    // find the last text/image child, to get a position
    const RenderObject* o = this;
    while (o) {
        if (RenderObject* child = o->lastChildSlow())
            o = child;
        else if (o->previousSibling())
            o = o->previousSibling();
        else {
            RenderObject* prev = 0;
            while (!prev) {
                o = o->parent();
                if (!o)
                    return false;
                prev = o->previousSibling();
            }
            o = prev;
        }
        ASSERT(o);
        if (is<RenderText>(*o) || o->isReplaced()) {
            point = FloatPoint();
            if (is<RenderText>(*o)) {
                IntRect linesBox = downcast<RenderText>(*o).linesBoundingBox();
                if (!linesBox.maxX() && !linesBox.maxY())
                    continue;
                point.moveBy(linesBox.maxXMaxYCorner());
            } else
                point.moveBy(downcast<RenderBox>(*o).frameRect().maxXMaxYCorner());
            point = o->container()->localToAbsolute(point, UseTransforms);
            return true;
        }
    }
    return true;
}

LayoutRect RenderElement::anchorRect() const
{
    FloatPoint leading, trailing;
    getLeadingCorner(leading);
    getTrailingCorner(trailing);

    FloatPoint upperLeft = leading;
    FloatPoint lowerRight = trailing;

    // Vertical writing modes might mean the leading point is not in the top left
    if (!isInline() || isReplaced()) {
        upperLeft = FloatPoint(std::min(leading.x(), trailing.x()), std::min(leading.y(), trailing.y()));
        lowerRight = FloatPoint(std::max(leading.x(), trailing.x()), std::max(leading.y(), trailing.y()));
    } // Otherwise, it's not obvious what to do.

    return enclosingLayoutRect(FloatRect(upperLeft, lowerRight.expandedTo(upperLeft) - upperLeft));
}

const RenderElement* RenderElement::enclosingRendererWithTextDecoration(TextDecoration textDecoration, bool firstLine) const
{
    const RenderElement* current = this;
    do {
        if (current->isRenderBlock())
            return current;
        if (!current->isRenderInline() || current->isRubyText())
            return nullptr;
        
        const RenderStyle& styleToUse = firstLine ? current->firstLineStyle() : current->style();
        if (styleToUse.textDecoration() & textDecoration)
            return current;
        current = current->parent();
    } while (current && (!current->element() || (!is<HTMLAnchorElement>(*current->element()) && !current->element()->hasTagName(HTMLNames::fontTag))));

    return current;
}

}