xref: /external/webkit/WebCore/rendering/RenderBlock.cpp

/*
 * Copyright (C) 1999 Lars Knoll (knoll (at) kde.org)
 *           (C) 1999 Antti Koivisto (koivisto (at) kde.org)
 *           (C) 2007 David Smith (catfish.man (at) gmail.com)
 * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple 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 "RenderBlock.h"

#include "Document.h"
#include "Element.h"
#include "FloatQuad.h"
#include "Frame.h"
#include "FrameView.h"
#include "GraphicsContext.h"
#include "HTMLFormElement.h"
#include "HTMLNames.h"
#include "HitTestResult.h"
#include "InlineTextBox.h"
#include "RenderFlexibleBox.h"
#include "RenderImage.h"
#include "RenderInline.h"
#include "RenderMarquee.h"
#include "RenderReplica.h"
#include "RenderTableCell.h"
#include "RenderTextFragment.h"
#include "RenderTheme.h"
#include "RenderView.h"
#include "SelectionController.h"
#include "Settings.h"
#include "TransformState.h"
#include <wtf/StdLibExtras.h>

#ifdef ANDROID_LAYOUT
#include "Settings.h"
#endif

using namespace std;
using namespace WTF;
using namespace Unicode;

namespace WebCore {

// Number of pixels to allow as a fudge factor when clicking above or below a line.
// clicking up to verticalLineClickFudgeFactor pixels above a line will correspond to the closest point on the line.
static const int verticalLineClickFudgeFactor = 3;

using namespace HTMLNames;

struct ColumnInfo : public Noncopyable {
    ColumnInfo()
        : m_desiredColumnWidth(0)
        , m_desiredColumnCount(1)
        { }
    int m_desiredColumnWidth;
    unsigned m_desiredColumnCount;
    Vector<IntRect> m_columnRects;
};

typedef WTF::HashMap<const RenderBox*, ColumnInfo*> ColumnInfoMap;
static ColumnInfoMap* gColumnInfoMap = 0;

typedef WTF::HashMap<const RenderBlock*, HashSet<RenderBox*>*> PercentHeightDescendantsMap;
static PercentHeightDescendantsMap* gPercentHeightDescendantsMap = 0;

typedef WTF::HashMap<const RenderBox*, HashSet<RenderBlock*>*> PercentHeightContainerMap;
static PercentHeightContainerMap* gPercentHeightContainerMap = 0;

typedef WTF::HashMap<RenderBlock*, ListHashSet<RenderInline*>*> ContinuationOutlineTableMap;

typedef WTF::HashSet<RenderBlock*> DelayedUpdateScrollInfoSet;
static int gDelayUpdateScrollInfo = 0;
static DelayedUpdateScrollInfoSet* gDelayedUpdateScrollInfoSet = 0;

// Our MarginInfo state used when laying out block children.
RenderBlock::MarginInfo::MarginInfo(RenderBlock* block, int top, int bottom)
{
    // Whether or not we can collapse our own margins with our children.  We don't do this
    // if we had any border/padding (obviously), if we're the root or HTML elements, or if
    // we're positioned, floating, a table cell.
    m_canCollapseWithChildren = !block->isRenderView() && !block->isRoot() && !block->isPositioned() &&
        !block->isFloating() && !block->isTableCell() && !block->hasOverflowClip() && !block->isInlineBlockOrInlineTable();

    m_canCollapseTopWithChildren = m_canCollapseWithChildren && (top == 0) && block->style()->marginTopCollapse() != MSEPARATE;

    // If any height other than auto is specified in CSS, then we don't collapse our bottom
    // margins with our children's margins.  To do otherwise would be to risk odd visual
    // effects when the children overflow out of the parent block and yet still collapse
    // with it.  We also don't collapse if we have any bottom border/padding.
    m_canCollapseBottomWithChildren = m_canCollapseWithChildren && (bottom == 0) &&
        (block->style()->height().isAuto() && block->style()->height().value() == 0) && block->style()->marginBottomCollapse() != MSEPARATE;

    m_quirkContainer = block->isTableCell() || block->isBody() || block->style()->marginTopCollapse() == MDISCARD ||
        block->style()->marginBottomCollapse() == MDISCARD;

    m_atTopOfBlock = true;
    m_atBottomOfBlock = false;

    m_posMargin = m_canCollapseTopWithChildren ? block->maxTopMargin(true) : 0;
    m_negMargin = m_canCollapseTopWithChildren ? block->maxTopMargin(false) : 0;

    m_topQuirk = m_bottomQuirk = m_determinedTopQuirk = false;
}

// -------------------------------------------------------------------------------------------------------

RenderBlock::RenderBlock(Node* node)
      : RenderBox(node)
      , m_floatingObjects(0)
      , m_positionedObjects(0)
      , m_inlineContinuation(0)
      , m_maxMargin(0)
      , m_lineHeight(-1)
{
    setChildrenInline(true);
}

RenderBlock::~RenderBlock()
{
    delete m_floatingObjects;
    delete m_positionedObjects;
    delete m_maxMargin;

    if (hasColumns())
        delete gColumnInfoMap->take(this);

    if (gPercentHeightDescendantsMap) {
        if (HashSet<RenderBox*>* descendantSet = gPercentHeightDescendantsMap->take(this)) {
            HashSet<RenderBox*>::iterator end = descendantSet->end();
            for (HashSet<RenderBox*>::iterator descendant = descendantSet->begin(); descendant != end; ++descendant) {
                HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->get(*descendant);
                ASSERT(containerSet);
                if (!containerSet)
                    continue;
                ASSERT(containerSet->contains(this));
                containerSet->remove(this);
                if (containerSet->isEmpty()) {
                    gPercentHeightContainerMap->remove(*descendant);
                    delete containerSet;
                }
            }
            delete descendantSet;
        }
    }
}

void RenderBlock::destroy()
{
    // Make sure to destroy anonymous children first while they are still connected to the rest of the tree, so that they will
    // properly dirty line boxes that they are removed from. Effects that do :before/:after only on hover could crash otherwise.
    children()->destroyLeftoverChildren();

    // Destroy our continuation before anything other than anonymous children.
    // The reason we don't destroy it before anonymous children is that they may
    // have continuations of their own that are anonymous children of our continuation.
    if (m_inlineContinuation) {
        m_inlineContinuation->destroy();
        m_inlineContinuation = 0;
    }

    if (!documentBeingDestroyed()) {
        if (firstLineBox()) {
            // We can't wait for RenderBox::destroy to clear the selection,
            // because by then we will have nuked the line boxes.
            // FIXME: The SelectionController should be responsible for this when it
            // is notified of DOM mutations.
            if (isSelectionBorder())
                view()->clearSelection();

            // If we are an anonymous block, then our line boxes might have children
            // that will outlast this block. In the non-anonymous block case those
            // children will be destroyed by the time we return from this function.
            if (isAnonymousBlock()) {
                for (InlineFlowBox* box = firstLineBox(); box; box = box->nextFlowBox()) {
                    while (InlineBox* childBox = box->firstChild())
                        childBox->remove();
                }
            }
        } else if (isInline() && parent())
            parent()->dirtyLinesFromChangedChild(this);
    }

    m_lineBoxes.deleteLineBoxes(renderArena());

    RenderBox::destroy();
}

void RenderBlock::styleWillChange(StyleDifference diff, const RenderStyle* newStyle)
{
    setReplaced(newStyle->isDisplayReplacedType());

    if (style() && parent() && diff == StyleDifferenceLayout && style()->position() != newStyle->position()) {
        if (newStyle->position() == StaticPosition)
            // Clear our positioned objects list. Our absolutely positioned descendants will be
            // inserted into our containing block's positioned objects list during layout.
            removePositionedObjects(0);
        else if (style()->position() == StaticPosition) {
            // Remove our absolutely positioned descendants from their current containing block.
            // They will be inserted into our positioned objects list during layout.
            RenderObject* cb = parent();
            while (cb && (cb->style()->position() == StaticPosition || (cb->isInline() && !cb->isReplaced())) && !cb->isRenderView()) {
                if (cb->style()->position() == RelativePosition && cb->isInline() && !cb->isReplaced()) {
                    cb = cb->containingBlock();
                    break;
                }
                cb = cb->parent();
            }

            if (cb->isRenderBlock())
                toRenderBlock(cb)->removePositionedObjects(this);
        }
    }

    RenderBox::styleWillChange(diff, newStyle);
}

void RenderBlock::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
{
    RenderBox::styleDidChange(diff, oldStyle);

    // FIXME: We could save this call when the change only affected non-inherited properties
    for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
        if (child->isAnonymousBlock()) {
            RefPtr<RenderStyle> newStyle = RenderStyle::create();
            newStyle->inheritFrom(style());
            newStyle->setDisplay(BLOCK);
            child->setStyle(newStyle.release());
        }
    }

    m_lineHeight = -1;

    // Update pseudos for :before and :after now.
    if (!isAnonymous() && document()->usesBeforeAfterRules() && canHaveChildren()) {
        updateBeforeAfterContent(BEFORE);
        updateBeforeAfterContent(AFTER);
    }
    updateFirstLetter();
}

void RenderBlock::updateBeforeAfterContent(PseudoId pseudoId)
{
    // If this is an anonymous wrapper, then the parent applies its own pseudo-element style to it.
    if (parent() && parent()->createsAnonymousWrapper())
        return;
    return children()->updateBeforeAfterContent(this, pseudoId);
}

void RenderBlock::addChild(RenderObject* newChild, RenderObject* beforeChild)
{
    // Make sure we don't append things after :after-generated content if we have it.
    if (!beforeChild && isAfterContent(lastChild()))
        beforeChild = lastChild();

    bool madeBoxesNonInline = false;

    // If the requested beforeChild is not one of our children, then this is because
    // there is an anonymous container within this object that contains the beforeChild.
    if (beforeChild && beforeChild->parent() != this) {
        RenderObject* anonymousChild = beforeChild->parent();
        ASSERT(anonymousChild);

        while (anonymousChild->parent() != this)
            anonymousChild = anonymousChild->parent();

        ASSERT(anonymousChild->isAnonymous());

        if (anonymousChild->isAnonymousBlock()) {
            // Insert the child into the anonymous block box instead of here.
            if (newChild->isInline() || beforeChild->parent()->firstChild() != beforeChild)
                beforeChild->parent()->addChild(newChild, beforeChild);
            else
                addChild(newChild, beforeChild->parent());
            return;
        }

        ASSERT(anonymousChild->isTable());
        if ((newChild->isTableCol() && newChild->style()->display() == TABLE_COLUMN_GROUP)
                || (newChild->isRenderBlock() && newChild->style()->display() == TABLE_CAPTION)
                || newChild->isTableSection()
                || newChild->isTableRow()
                || newChild->isTableCell()) {
            // Insert into the anonymous table.
            anonymousChild->addChild(newChild, beforeChild);
            return;
        }

        // Go on to insert before the anonymous table.
        beforeChild = anonymousChild;
    }

    // A block has to either have all of its children inline, or all of its children as blocks.
    // So, if our children are currently inline and a block child has to be inserted, we move all our
    // inline children into anonymous block boxes.
    if (childrenInline() && !newChild->isInline() && !newChild->isFloatingOrPositioned()) {
        // This is a block with inline content. Wrap the inline content in anonymous blocks.
        makeChildrenNonInline(beforeChild);
        madeBoxesNonInline = true;

        if (beforeChild && beforeChild->parent() != this) {
            beforeChild = beforeChild->parent();
            ASSERT(beforeChild->isAnonymousBlock());
            ASSERT(beforeChild->parent() == this);
        }
    } else if (!childrenInline() && (newChild->isFloatingOrPositioned() || newChild->isInline())) {
        // If we're inserting an inline child but all of our children are blocks, then we have to make sure
        // it is put into an anomyous block box. We try to use an existing anonymous box if possible, otherwise
        // a new one is created and inserted into our list of children in the appropriate position.
        RenderObject* afterChild = beforeChild ? beforeChild->previousSibling() : lastChild();

        if (afterChild && afterChild->isAnonymousBlock()) {
            afterChild->addChild(newChild);
            return;
        }

        if (newChild->isInline()) {
            // No suitable existing anonymous box - create a new one.
            RenderBlock* newBox = createAnonymousBlock();
            RenderBox::addChild(newBox, beforeChild);
            newBox->addChild(newChild);
            return;
        }
    }

    RenderBox::addChild(newChild, beforeChild);

    if (madeBoxesNonInline && parent() && isAnonymousBlock() && parent()->isRenderBlock())
        toRenderBlock(parent())->removeLeftoverAnonymousBlock(this);
    // this object may be dead here
}

static void getInlineRun(RenderObject* start, RenderObject* boundary,
                         RenderObject*& inlineRunStart,
                         RenderObject*& inlineRunEnd)
{
    // Beginning at |start| we find the largest contiguous run of inlines that
    // we can.  We denote the run with start and end points, |inlineRunStart|
    // and |inlineRunEnd|.  Note that these two values may be the same if
    // we encounter only one inline.
    //
    // We skip any non-inlines we encounter as long as we haven't found any
    // inlines yet.
    //
    // |boundary| indicates a non-inclusive boundary point.  Regardless of whether |boundary|
    // is inline or not, we will not include it in a run with inlines before it.  It's as though we encountered
    // a non-inline.

    // Start by skipping as many non-inlines as we can.
    RenderObject * curr = start;
    bool sawInline;
    do {
        while (curr && !(curr->isInline() || curr->isFloatingOrPositioned()))
            curr = curr->nextSibling();

        inlineRunStart = inlineRunEnd = curr;

        if (!curr)
            return; // No more inline children to be found.

        sawInline = curr->isInline();

        curr = curr->nextSibling();
        while (curr && (curr->isInline() || curr->isFloatingOrPositioned()) && (curr != boundary)) {
            inlineRunEnd = curr;
            if (curr->isInline())
                sawInline = true;
            curr = curr->nextSibling();
        }
    } while (!sawInline);
}

void RenderBlock::deleteLineBoxTree()
{
    m_lineBoxes.deleteLineBoxTree(renderArena());
}

RootInlineBox* RenderBlock::createRootInlineBox()
{
    return new (renderArena()) RootInlineBox(this);
}

RootInlineBox* RenderBlock::createAndAppendRootInlineBox()
{
    RootInlineBox* rootBox = createRootInlineBox();
    m_lineBoxes.appendLineBox(rootBox);
    return rootBox;
}

void RenderBlock::moveChildTo(RenderObject* to, RenderObjectChildList* toChildList, RenderObject* child)
{
    ASSERT(this == child->parent());
    toChildList->appendChildNode(to, children()->removeChildNode(this, child, false), false);
}

void RenderBlock::moveChildTo(RenderObject* to, RenderObjectChildList* toChildList, RenderObject* beforeChild, RenderObject* child)
{
    ASSERT(this == child->parent());
    ASSERT(!beforeChild || to == beforeChild->parent());
    toChildList->insertChildNode(to, children()->removeChildNode(this, child, false), beforeChild, false);
}

void RenderBlock::moveAllChildrenTo(RenderObject* to, RenderObjectChildList* toChildList)
{
    RenderObject* nextChild = children()->firstChild();
    while (nextChild) {
        RenderObject* child = nextChild;
        nextChild = child->nextSibling();
        toChildList->appendChildNode(to, children()->removeChildNode(this, child, false), false);
    }
}

void RenderBlock::moveAllChildrenTo(RenderObject* to, RenderObjectChildList* toChildList, RenderObject* beforeChild)
{
    ASSERT(!beforeChild || to == beforeChild->parent());
    if (!beforeChild) {
        moveAllChildrenTo(to, toChildList);
        return;
    }
    RenderObject* nextChild = children()->firstChild();
    while (nextChild) {
        RenderObject* child = nextChild;
        nextChild = child->nextSibling();
        toChildList->insertChildNode(to, children()->removeChildNode(this, child, false), beforeChild, false);
    }
}

void RenderBlock::makeChildrenNonInline(RenderObject *insertionPoint)
{
    // makeChildrenNonInline takes a block whose children are *all* inline and it
    // makes sure that inline children are coalesced under anonymous
    // blocks.  If |insertionPoint| is defined, then it represents the insertion point for
    // the new block child that is causing us to have to wrap all the inlines.  This
    // means that we cannot coalesce inlines before |insertionPoint| with inlines following
    // |insertionPoint|, because the new child is going to be inserted in between the inlines,
    // splitting them.
    ASSERT(isInlineBlockOrInlineTable() || !isInline());
    ASSERT(!insertionPoint || insertionPoint->parent() == this);

    setChildrenInline(false);

    RenderObject *child = firstChild();
    if (!child)
        return;

    deleteLineBoxTree();

    while (child) {
        RenderObject *inlineRunStart, *inlineRunEnd;
        getInlineRun(child, insertionPoint, inlineRunStart, inlineRunEnd);

        if (!inlineRunStart)
            break;

        child = inlineRunEnd->nextSibling();

        RenderBlock* block = createAnonymousBlock();
        children()->insertChildNode(this, block, inlineRunStart);
        RenderObject* o = inlineRunStart;
        while (o != inlineRunEnd) {
            RenderObject* no = o;
            o = no->nextSibling();

            moveChildTo(block, block->children(), no);
        }
        moveChildTo(block, block->children(), inlineRunEnd);
    }

#ifndef NDEBUG
    for (RenderObject *c = firstChild(); c; c = c->nextSibling())
        ASSERT(!c->isInline());
#endif

    repaint();
}

void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
{
    ASSERT(child->isAnonymousBlock());
    ASSERT(!child->childrenInline());

    if (child->inlineContinuation())
        return;

    RenderObject* firstAnChild = child->m_children.firstChild();
    RenderObject* lastAnChild = child->m_children.lastChild();
    if (firstAnChild) {
        RenderObject* o = firstAnChild;
        while (o) {
            o->setParent(this);
            o = o->nextSibling();
        }
        firstAnChild->setPreviousSibling(child->previousSibling());
        lastAnChild->setNextSibling(child->nextSibling());
        if (child->previousSibling())
            child->previousSibling()->setNextSibling(firstAnChild);
        if (child->nextSibling())
            child->nextSibling()->setPreviousSibling(lastAnChild);
    } else {
        if (child->previousSibling())
            child->previousSibling()->setNextSibling(child->nextSibling());
        if (child->nextSibling())
            child->nextSibling()->setPreviousSibling(child->previousSibling());
    }
    if (child == m_children.firstChild())
        m_children.setFirstChild(firstAnChild);
    if (child == m_children.lastChild())
        m_children.setLastChild(lastAnChild);
    child->setParent(0);
    child->setPreviousSibling(0);
    child->setNextSibling(0);

    child->children()->setFirstChild(0);
    child->m_next = 0;

    child->destroy();
}

void RenderBlock::removeChild(RenderObject* oldChild)
{
    // If this child is a block, and if our previous and next siblings are
    // both anonymous blocks with inline content, then we can go ahead and
    // fold the inline content back together.
    RenderObject* prev = oldChild->previousSibling();
    RenderObject* next = oldChild->nextSibling();
    bool canDeleteAnonymousBlocks = !documentBeingDestroyed() && !isInline() && !oldChild->isInline() &&
                                    (!oldChild->isRenderBlock() || !toRenderBlock(oldChild)->inlineContinuation()) &&
                                    (!prev || (prev->isAnonymousBlock() && prev->childrenInline())) &&
                                    (!next || (next->isAnonymousBlock() && next->childrenInline()));
    if (canDeleteAnonymousBlocks && prev && next) {
        // Take all the children out of the |next| block and put them in
        // the |prev| block.
        prev->setNeedsLayoutAndPrefWidthsRecalc();
        RenderBlock* nextBlock = toRenderBlock(next);
        RenderBlock* prevBlock = toRenderBlock(prev);
        nextBlock->moveAllChildrenTo(prevBlock, prevBlock->children());
        // Delete the now-empty block's lines and nuke it.
        nextBlock->deleteLineBoxTree();
        nextBlock->destroy();
    }

    RenderBox::removeChild(oldChild);

    RenderObject* child = prev ? prev : next;
    if (canDeleteAnonymousBlocks && child && !child->previousSibling() && !child->nextSibling() && !isFlexibleBox()) {
        // The removal has knocked us down to containing only a single anonymous
        // box.  We can go ahead and pull the content right back up into our
        // box.
        setNeedsLayoutAndPrefWidthsRecalc();
        RenderBlock* anonBlock = toRenderBlock(children()->removeChildNode(this, child, false));
        setChildrenInline(true);
        anonBlock->moveAllChildrenTo(this, children());
        // Delete the now-empty block's lines and nuke it.
        anonBlock->deleteLineBoxTree();
        anonBlock->destroy();
    }

    // If this was our last child be sure to clear out our line boxes.
    if (childrenInline() && !firstChild())
        lineBoxes()->deleteLineBoxes(renderArena());
}

bool RenderBlock::isSelfCollapsingBlock() const
{
    // We are not self-collapsing if we
    // (a) have a non-zero height according to layout (an optimization to avoid wasting time)
    // (b) are a table,
    // (c) have border/padding,
    // (d) have a min-height
    // (e) have specified that one of our margins can't collapse using a CSS extension
    if (height() > 0 ||
        isTable() || (borderBottom() + paddingBottom() + borderTop() + paddingTop()) != 0 ||
        style()->minHeight().isPositive() ||
        style()->marginTopCollapse() == MSEPARATE || style()->marginBottomCollapse() == MSEPARATE)
        return false;

    bool hasAutoHeight = style()->height().isAuto();
    if (style()->height().isPercent() && !style()->htmlHacks()) {
        hasAutoHeight = true;
        for (RenderBlock* cb = containingBlock(); !cb->isRenderView(); cb = cb->containingBlock()) {
            if (cb->style()->height().isFixed() || cb->isTableCell())
                hasAutoHeight = false;
        }
    }

    // If the height is 0 or auto, then whether or not we are a self-collapsing block depends
    // on whether we have content that is all self-collapsing or not.
    if (hasAutoHeight || ((style()->height().isFixed() || style()->height().isPercent()) && style()->height().isZero())) {
        // If the block has inline children, see if we generated any line boxes.  If we have any
        // line boxes, then we can't be self-collapsing, since we have content.
        if (childrenInline())
            return !firstLineBox();

        // Whether or not we collapse is dependent on whether all our normal flow children
        // are also self-collapsing.
        for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
            if (child->isFloatingOrPositioned())
                continue;
            if (!child->isSelfCollapsingBlock())
                return false;
        }
        return true;
    }
    return false;
}

void RenderBlock::startDelayUpdateScrollInfo()
{
    if (gDelayUpdateScrollInfo == 0) {
        ASSERT(!gDelayedUpdateScrollInfoSet);
        gDelayedUpdateScrollInfoSet = new DelayedUpdateScrollInfoSet;
    }
    ASSERT(gDelayedUpdateScrollInfoSet);
    ++gDelayUpdateScrollInfo;
}

void RenderBlock::finishDelayUpdateScrollInfo()
{
    --gDelayUpdateScrollInfo;
    ASSERT(gDelayUpdateScrollInfo >= 0);
    if (gDelayUpdateScrollInfo == 0) {
        ASSERT(gDelayedUpdateScrollInfoSet);

        OwnPtr<DelayedUpdateScrollInfoSet> infoSet(gDelayedUpdateScrollInfoSet);
        gDelayedUpdateScrollInfoSet = 0;

        for (DelayedUpdateScrollInfoSet::iterator it = infoSet->begin(); it != infoSet->end(); ++it) {
            RenderBlock* block = *it;
            if (block->hasOverflowClip()) {
                block->layer()->updateScrollInfoAfterLayout();
            }
        }
    }
}

void RenderBlock::updateScrollInfoAfterLayout()
{
    if (hasOverflowClip()) {
        if (gDelayUpdateScrollInfo)
            gDelayedUpdateScrollInfoSet->add(this);
        else
            layer()->updateScrollInfoAfterLayout();
    }
}

void RenderBlock::layout()
{
    // Update our first letter info now.
    updateFirstLetter();

    // Table cells call layoutBlock directly, so don't add any logic here.  Put code into
    // layoutBlock().
    layoutBlock(false);

    // It's safe to check for control clip here, since controls can never be table cells.
    // If we have a lightweight clip, there can never be any overflow from children.
    if (hasControlClip() && m_overflow)
        clearLayoutOverflow();
}

void RenderBlock::layoutBlock(bool relayoutChildren)
{
    ASSERT(needsLayout());

    if (isInline() && !isInlineBlockOrInlineTable()) // Inline <form>s inside various table elements can
        return;                                      // cause us to come in here.  Just bail.

    if (!relayoutChildren && layoutOnlyPositionedObjects())
        return;

    LayoutRepainter repainter(*this, m_everHadLayout && checkForRepaintDuringLayout());
    LayoutStateMaintainer statePusher(view(), this, IntSize(x(), y()), hasColumns() || hasTransform() || hasReflection());

    int oldWidth = width();
    int oldColumnWidth = desiredColumnWidth();

#ifdef ANDROID_LAYOUT
    int oldVisibleWidth = m_visibleWidth;
#endif

    calcWidth();
    calcColumnWidth();

    m_overflow.clear();

    if (oldWidth != width() || oldColumnWidth != desiredColumnWidth())
        relayoutChildren = true;

#ifdef ANDROID_LAYOUT
    const Settings* settings = document()->settings();
    ASSERT(settings);
    if (oldVisibleWidth != m_visibleWidth
            && settings->layoutAlgorithm() == Settings::kLayoutFitColumnToScreen)
        relayoutChildren = true;
#endif

    clearFloats();

    int previousHeight = height();
    setHeight(0);

    // We use four values, maxTopPos, maxTopNeg, maxBottomPos, and maxBottomNeg, to track
    // our current maximal positive and negative margins.  These values are used when we
    // are collapsed with adjacent blocks, so for example, if you have block A and B
    // collapsing together, then you'd take the maximal positive margin from both A and B
    // and subtract it from the maximal negative margin from both A and B to get the
    // true collapsed margin.  This algorithm is recursive, so when we finish layout()
    // our block knows its current maximal positive/negative values.
    //
    // Start out by setting our margin values to our current margins.  Table cells have
    // no margins, so we don't fill in the values for table cells.
    bool isCell = isTableCell();
    if (!isCell) {
        initMaxMarginValues();

        setTopMarginQuirk(style()->marginTop().quirk());
        setBottomMarginQuirk(style()->marginBottom().quirk());

        Node* n = node();
        if (n && n->hasTagName(formTag) && static_cast<HTMLFormElement*>(n)->isMalformed()) {
            // See if this form is malformed (i.e., unclosed). If so, don't give the form
            // a bottom margin.
            setMaxBottomMargins(0, 0);
        }
    }

    // For overflow:scroll blocks, ensure we have both scrollbars in place always.
    if (scrollsOverflow()) {
        if (style()->overflowX() == OSCROLL)
            layer()->setHasHorizontalScrollbar(true);
        if (style()->overflowY() == OSCROLL)
            layer()->setHasVerticalScrollbar(true);
    }

    int repaintTop = 0;
    int repaintBottom = 0;
    int maxFloatBottom = 0;
    if (childrenInline())
        layoutInlineChildren(relayoutChildren, repaintTop, repaintBottom);
    else
        layoutBlockChildren(relayoutChildren, maxFloatBottom);

    // Expand our intrinsic height to encompass floats.
    int toAdd = borderBottom() + paddingBottom() + horizontalScrollbarHeight();
    if (floatBottom() > (height() - toAdd) && expandsToEncloseOverhangingFloats())
        setHeight(floatBottom() + toAdd);

    // Now lay out our columns within this intrinsic height, since they can slightly affect the intrinsic height as
    // we adjust for clean column breaks.
    int singleColumnBottom = layoutColumns();

    // Calculate our new height.
    int oldHeight = height();
    calcHeight();
    if (oldHeight != height()) {
        if (oldHeight > height() && maxFloatBottom > height() && !childrenInline()) {
            // One of our children's floats may have become an overhanging float for us. We need to look for it.
            for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
                if (child->isBlockFlow() && !child->isFloatingOrPositioned()) {
                    RenderBlock* block = toRenderBlock(child);
                    if (block->floatBottom() + block->y() > height())
                        addOverhangingFloats(block, -block->x(), -block->y(), false);
                }
            }
        }

        // We have to rebalance columns to the new height.
        layoutColumns(singleColumnBottom);
    }

    if (previousHeight != height())
        relayoutChildren = true;

    // It's weird that we're treating float information as normal flow overflow, but we do this because floatRect() isn't
    // able to be propagated up the render tree yet.  Overflow information is however.  This check is designed to catch anyone
    // who wasn't going to propagate float information up to the parent and yet could potentially be painted by its ancestor.
    if (isRoot() || expandsToEncloseOverhangingFloats())
        addOverflowFromFloats();

    // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
    if (!hasColumns()) {
        if (childrenInline())
            addOverflowFromInlineChildren();
        else
            addOverflowFromBlockChildren();
    }

    // Add visual overflow from box-shadow and reflections.
    addShadowOverflow();

    layoutPositionedObjects(relayoutChildren || isRoot());

    positionListMarker();

    statePusher.pop();

    // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if
    // we overflow or not.
    updateScrollInfoAfterLayout();

    // Repaint with our new bounds if they are different from our old bounds.
    bool didFullRepaint = repainter.repaintAfterLayout();
    if (!didFullRepaint && repaintTop != repaintBottom && (style()->visibility() == VISIBLE || enclosingLayer()->hasVisibleContent())) {
        int repaintLeft = min(leftVisualOverflow(), leftLayoutOverflow());
        int repaintRight = max(rightVisualOverflow(), rightLayoutOverflow());
        IntRect repaintRect(repaintLeft, repaintTop, repaintRight - repaintLeft, repaintBottom - repaintTop);

        // FIXME: Deal with multiple column repainting.  We have to split the repaint
        // rect up into multiple rects if it spans columns.

        repaintRect.inflate(maximalOutlineSize(PaintPhaseOutline));

        if (hasOverflowClip()) {
            // Adjust repaint rect for scroll offset
            int x = repaintRect.x();
            int y = repaintRect.y();
            layer()->subtractScrolledContentOffset(x, y);
            repaintRect.setX(x);
            repaintRect.setY(y);

            // Don't allow this rect to spill out of our overflow box.
            repaintRect.intersect(IntRect(0, 0, width(), height()));
        }

        // Make sure the rect is still non-empty after intersecting for overflow above
        if (!repaintRect.isEmpty()) {
            repaintRectangle(repaintRect); // We need to do a partial repaint of our content.
            if (hasReflection())
                repaintRectangle(reflectedRect(repaintRect));
        }
    }
    setNeedsLayout(false);
}

void RenderBlock::addOverflowFromBlockChildren()
{
    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
        if (!child->isFloatingOrPositioned())
            addOverflowFromChild(child);
    }
}

void RenderBlock::addOverflowFromFloats()
{
    IntRect result;
    if (!m_floatingObjects)
        return;
    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for (; (r = it.current()); ++it) {
        if (r->m_shouldPaint && !r->m_renderer->hasSelfPaintingLayer())
            addOverflowFromChild(r->m_renderer, IntSize(r->m_left + r->m_renderer->marginLeft(), r->m_top + r->m_renderer->marginTop()));
    }
    return;
}

bool RenderBlock::expandsToEncloseOverhangingFloats() const
{
    return isInlineBlockOrInlineTable() || isFloatingOrPositioned() || hasOverflowClip() || (parent() && parent()->isFlexibleBox()) || hasColumns() || isTableCell() || isFieldset();
}

void RenderBlock::adjustPositionedBlock(RenderBox* child, const MarginInfo& marginInfo)
{
    if (child->style()->hasStaticX()) {
        if (style()->direction() == LTR)
            child->layer()->setStaticX(borderLeft() + paddingLeft());
        else
            child->layer()->setStaticX(borderRight() + paddingRight());
    }

    if (child->style()->hasStaticY()) {
        int y = height();
        if (!marginInfo.canCollapseWithTop()) {
            child->calcVerticalMargins();
            int marginTop = child->marginTop();
            int collapsedTopPos = marginInfo.posMargin();
            int collapsedTopNeg = marginInfo.negMargin();
            if (marginTop > 0) {
                if (marginTop > collapsedTopPos)
                    collapsedTopPos = marginTop;
            } else {
                if (-marginTop > collapsedTopNeg)
                    collapsedTopNeg = -marginTop;
            }
            y += (collapsedTopPos - collapsedTopNeg) - marginTop;
        }
        RenderLayer* childLayer = child->layer();
        if (childLayer->staticY() != y) {
            child->layer()->setStaticY(y);
            child->setChildNeedsLayout(true, false);
        }
    }
}

void RenderBlock::adjustFloatingBlock(const MarginInfo& marginInfo)
{
    // The float should be positioned taking into account the bottom margin
    // of the previous flow.  We add that margin into the height, get the
    // float positioned properly, and then subtract the margin out of the
    // height again.  In the case of self-collapsing blocks, we always just
    // use the top margins, since the self-collapsing block collapsed its
    // own bottom margin into its top margin.
    //
    // Note also that the previous flow may collapse its margin into the top of
    // our block.  If this is the case, then we do not add the margin in to our
    // height when computing the position of the float.   This condition can be tested
    // for by simply calling canCollapseWithTop.  See
    // http://www.hixie.ch/tests/adhoc/css/box/block/margin-collapse/046.html for
    // an example of this scenario.
    int marginOffset = marginInfo.canCollapseWithTop() ? 0 : marginInfo.margin();
    setHeight(height() + marginOffset);
    positionNewFloats();
    setHeight(height() - marginOffset);
}

bool RenderBlock::handleSpecialChild(RenderBox* child, const MarginInfo& marginInfo)
{
    // Handle in the given order
    return handlePositionedChild(child, marginInfo)
        || handleFloatingChild(child, marginInfo)
        || handleRunInChild(child);
}


bool RenderBlock::handlePositionedChild(RenderBox* child, const MarginInfo& marginInfo)
{
    if (child->isPositioned()) {
        child->containingBlock()->insertPositionedObject(child);
        adjustPositionedBlock(child, marginInfo);
        return true;
    }
    return false;
}

bool RenderBlock::handleFloatingChild(RenderBox* child, const MarginInfo& marginInfo)
{
    if (child->isFloating()) {
        insertFloatingObject(child);
        adjustFloatingBlock(marginInfo);
        return true;
    }
    return false;
}

bool RenderBlock::handleRunInChild(RenderBox* child)
{
    // See if we have a run-in element with inline children.  If the
    // children aren't inline, then just treat the run-in as a normal
    // block.
    if (!child->isRunIn() || !child->childrenInline())
        return false;
    // FIXME: We don't handle non-block elements with run-in for now.
    if (!child->isRenderBlock())
        return false;

    // Get the next non-positioned/non-floating RenderBlock.
    RenderBlock* blockRunIn = toRenderBlock(child);
    RenderObject* curr = blockRunIn->nextSibling();
    while (curr && curr->isFloatingOrPositioned())
        curr = curr->nextSibling();

    if (!curr || !curr->isRenderBlock() || !curr->childrenInline() || curr->isRunIn() || curr->isAnonymous())
        return false;

    RenderBlock* currBlock = toRenderBlock(curr);

    // Remove the old child.
    children()->removeChildNode(this, blockRunIn);

    // Create an inline.
    Node* runInNode = blockRunIn->node();
    RenderInline* inlineRunIn = new (renderArena()) RenderInline(runInNode ? runInNode : document());
    inlineRunIn->setStyle(blockRunIn->style());

    bool runInIsGenerated = child->style()->styleType() == BEFORE || child->style()->styleType() == AFTER;

    // Move the nodes from the old child to the new child, but skip any :before/:after content.  It has already
    // been regenerated by the new inline.
    for (RenderObject* runInChild = blockRunIn->firstChild(); runInChild; runInChild = runInChild->nextSibling()) {
        if (runInIsGenerated || (runInChild->style()->styleType() != BEFORE && runInChild->style()->styleType() != AFTER)) {
            blockRunIn->children()->removeChildNode(blockRunIn, runInChild, false);
            inlineRunIn->addChild(runInChild); // Use addChild instead of appendChildNode since it handles correct placement of the children relative to :after-generated content.
        }
    }

    // Now insert the new child under |currBlock|.
    currBlock->children()->insertChildNode(currBlock, inlineRunIn, currBlock->firstChild());

    // If the run-in had an element, we need to set the new renderer.
    if (runInNode)
        runInNode->setRenderer(inlineRunIn);

    // Destroy the block run-in.
    blockRunIn->destroy();

    // The block acts like an inline, so just null out its
    // position.

    return true;
}

int RenderBlock::collapseMargins(RenderBox* child, MarginInfo& marginInfo)
{
    // Get our max pos and neg top margins.
    int posTop = child->maxTopMargin(true);
    int negTop = child->maxTopMargin(false);

    // For self-collapsing blocks, collapse our bottom margins into our
    // top to get new posTop and negTop values.
    if (child->isSelfCollapsingBlock()) {
        posTop = max(posTop, child->maxBottomMargin(true));
        negTop = max(negTop, child->maxBottomMargin(false));
    }

    // See if the top margin is quirky. We only care if this child has
    // margins that will collapse with us.
    bool topQuirk = child->isTopMarginQuirk() || style()->marginTopCollapse() == MDISCARD;

    if (marginInfo.canCollapseWithTop()) {
        // This child is collapsing with the top of the
        // block.  If it has larger margin values, then we need to update
        // our own maximal values.
        if (!style()->htmlHacks() || !marginInfo.quirkContainer() || !topQuirk)
            setMaxTopMargins(max(posTop, maxTopPosMargin()), max(negTop, maxTopNegMargin()));

        // The minute any of the margins involved isn't a quirk, don't
        // collapse it away, even if the margin is smaller (www.webreference.com
        // has an example of this, a <dt> with 0.8em author-specified inside
        // a <dl> inside a <td>.
        if (!marginInfo.determinedTopQuirk() && !topQuirk && (posTop-negTop)) {
            setTopMarginQuirk(false);
            marginInfo.setDeterminedTopQuirk(true);
        }

        if (!marginInfo.determinedTopQuirk() && topQuirk && marginTop() == 0)
            // We have no top margin and our top child has a quirky margin.
            // We will pick up this quirky margin and pass it through.
            // This deals with the <td><div><p> case.
            // Don't do this for a block that split two inlines though.  You do
            // still apply margins in this case.
            setTopMarginQuirk(true);
    }

    if (marginInfo.quirkContainer() && marginInfo.atTopOfBlock() && (posTop - negTop))
        marginInfo.setTopQuirk(topQuirk);

    int ypos = height();
    if (child->isSelfCollapsingBlock()) {
        // This child has no height.  We need to compute our
        // position before we collapse the child's margins together,
        // so that we can get an accurate position for the zero-height block.
        int collapsedTopPos = max(marginInfo.posMargin(), child->maxTopMargin(true));
        int collapsedTopNeg = max(marginInfo.negMargin(), child->maxTopMargin(false));
        marginInfo.setMargin(collapsedTopPos, collapsedTopNeg);

        // Now collapse the child's margins together, which means examining our
        // bottom margin values as well.
        marginInfo.setPosMarginIfLarger(child->maxBottomMargin(true));
        marginInfo.setNegMarginIfLarger(child->maxBottomMargin(false));

        if (!marginInfo.canCollapseWithTop())
            // We need to make sure that the position of the self-collapsing block
            // is correct, since it could have overflowing content
            // that needs to be positioned correctly (e.g., a block that
            // had a specified height of 0 but that actually had subcontent).
            ypos = height() + collapsedTopPos - collapsedTopNeg;
    }
    else {
        if (child->style()->marginTopCollapse() == MSEPARATE) {
            setHeight(height() + marginInfo.margin() + child->marginTop());
            ypos = height();
        }
        else if (!marginInfo.atTopOfBlock() ||
            (!marginInfo.canCollapseTopWithChildren()
             && (!style()->htmlHacks() || !marginInfo.quirkContainer() || !marginInfo.topQuirk()))) {
            // We're collapsing with a previous sibling's margins and not
            // with the top of the block.
            setHeight(height() + max(marginInfo.posMargin(), posTop) - max(marginInfo.negMargin(), negTop));
            ypos = height();
        }

        marginInfo.setPosMargin(child->maxBottomMargin(true));
        marginInfo.setNegMargin(child->maxBottomMargin(false));

        if (marginInfo.margin())
            marginInfo.setBottomQuirk(child->isBottomMarginQuirk() || style()->marginBottomCollapse() == MDISCARD);
    }

    return ypos;
}

int RenderBlock::clearFloatsIfNeeded(RenderBox* child, MarginInfo& marginInfo, int oldTopPosMargin, int oldTopNegMargin, int yPos)
{
    int heightIncrease = getClearDelta(child, yPos);
    if (!heightIncrease)
        return yPos;

    if (child->isSelfCollapsingBlock()) {
        // For self-collapsing blocks that clear, they can still collapse their
        // margins with following siblings.  Reset the current margins to represent
        // the self-collapsing block's margins only.
        // CSS2.1 states:
        // "An element that has had clearance applied to it never collapses its top margin with its parent block's bottom margin.
        // Therefore if we are at the bottom of the block, let's go ahead and reset margins to only include the
        // self-collapsing block's bottom margin.
        bool atBottomOfBlock = true;
        for (RenderBox* curr = child->nextSiblingBox(); curr && atBottomOfBlock; curr = curr->nextSiblingBox()) {
            if (!curr->isFloatingOrPositioned())
                atBottomOfBlock = false;
        }
        if (atBottomOfBlock) {
            marginInfo.setPosMargin(child->maxBottomMargin(true));
            marginInfo.setNegMargin(child->maxBottomMargin(false));
        } else {
            marginInfo.setPosMargin(max(child->maxTopMargin(true), child->maxBottomMargin(true)));
            marginInfo.setNegMargin(max(child->maxTopMargin(false), child->maxBottomMargin(false)));
        }

        // Adjust our height such that we are ready to be collapsed with subsequent siblings (or the bottom
        // of the parent block).
        setHeight(child->y() - max(0, marginInfo.margin()));
    } else
        // Increase our height by the amount we had to clear.
        setHeight(height() + heightIncrease);

    if (marginInfo.canCollapseWithTop()) {
        // We can no longer collapse with the top of the block since a clear
        // occurred.  The empty blocks collapse into the cleared block.
        // FIXME: This isn't quite correct.  Need clarification for what to do
        // if the height the cleared block is offset by is smaller than the
        // margins involved.
        setMaxTopMargins(oldTopPosMargin, oldTopNegMargin);
        marginInfo.setAtTopOfBlock(false);
    }

    return yPos + heightIncrease;
}

int RenderBlock::estimateVerticalPosition(RenderBox* child, const MarginInfo& marginInfo)
{
    // FIXME: We need to eliminate the estimation of vertical position, because when it's wrong we sometimes trigger a pathological
    // relayout if there are intruding floats.
    int yPosEstimate = height();
    if (!marginInfo.canCollapseWithTop()) {
        int childMarginTop = child->selfNeedsLayout() ? child->marginTop() : child->collapsedMarginTop();
        yPosEstimate += max(marginInfo.margin(), childMarginTop);
    }
    yPosEstimate += getClearDelta(child, yPosEstimate);
    return yPosEstimate;
}

void RenderBlock::determineHorizontalPosition(RenderBox* child)
{
    if (style()->direction() == LTR) {
        int xPos = borderLeft() + paddingLeft();

        // Add in our left margin.
        int chPos = xPos + child->marginLeft();

        // Some objects (e.g., tables, horizontal rules, overflow:auto blocks) avoid floats.  They need
        // to shift over as necessary to dodge any floats that might get in the way.
        if (child->avoidsFloats()) {
            int leftOff = leftOffset(height(), false);
            if (style()->textAlign() != WEBKIT_CENTER && child->style()->marginLeft().type() != Auto) {
                if (child->marginLeft() < 0)
                    leftOff += child->marginLeft();
                chPos = max(chPos, leftOff); // Let the float sit in the child's margin if it can fit.
            }
            else if (leftOff != xPos) {
                // The object is shifting right. The object might be centered, so we need to
                // recalculate our horizontal margins. Note that the containing block content
                // width computation will take into account the delta between |leftOff| and |xPos|
                // so that we can just pass the content width in directly to the |calcHorizontalMargins|
                // function.
                child->calcHorizontalMargins(child->style()->marginLeft(), child->style()->marginRight(), lineWidth(child->y(), false));
                chPos = leftOff + child->marginLeft();
            }
        }
        view()->addLayoutDelta(IntSize(child->x() - chPos, 0));
        child->setLocation(chPos, child->y());
    } else {
        int xPos = width() - borderRight() - paddingRight() - verticalScrollbarWidth();
        int chPos = xPos - (child->width() + child->marginRight());
        if (child->avoidsFloats()) {
            int rightOff = rightOffset(height(), false);
            if (style()->textAlign() != WEBKIT_CENTER && child->style()->marginRight().type() != Auto) {
                if (child->marginRight() < 0)
                    rightOff -= child->marginRight();
                chPos = min(chPos, rightOff - child->width()); // Let the float sit in the child's margin if it can fit.
            } else if (rightOff != xPos) {
                // The object is shifting left. The object might be centered, so we need to
                // recalculate our horizontal margins. Note that the containing block content
                // width computation will take into account the delta between |rightOff| and |xPos|
                // so that we can just pass the content width in directly to the |calcHorizontalMargins|
                // function.
                child->calcHorizontalMargins(child->style()->marginLeft(), child->style()->marginRight(), lineWidth(child->y(), false));
                chPos = rightOff - child->marginRight() - child->width();
            }
        }
        view()->addLayoutDelta(IntSize(child->x() - chPos, 0));
        child->setLocation(chPos, child->y());
    }
}

void RenderBlock::setCollapsedBottomMargin(const MarginInfo& marginInfo)
{
    if (marginInfo.canCollapseWithBottom() && !marginInfo.canCollapseWithTop()) {
        // Update our max pos/neg bottom margins, since we collapsed our bottom margins
        // with our children.
        setMaxBottomMargins(max(maxBottomPosMargin(), marginInfo.posMargin()), max(maxBottomNegMargin(), marginInfo.negMargin()));

        if (!marginInfo.bottomQuirk())
            setBottomMarginQuirk(false);

        if (marginInfo.bottomQuirk() && marginBottom() == 0)
            // We have no bottom margin and our last child has a quirky margin.
            // We will pick up this quirky margin and pass it through.
            // This deals with the <td><div><p> case.
            setBottomMarginQuirk(true);
    }
}

void RenderBlock::handleBottomOfBlock(int top, int bottom, MarginInfo& marginInfo)
{
    marginInfo.setAtBottomOfBlock(true);

    // If we can't collapse with children then go ahead and add in the bottom margin.
    if (!marginInfo.canCollapseWithBottom() && !marginInfo.canCollapseWithTop()
        && (!style()->htmlHacks() || !marginInfo.quirkContainer() || !marginInfo.bottomQuirk()))
        setHeight(height() + marginInfo.margin());

    // Now add in our bottom border/padding.
    setHeight(height() + bottom);

    // Negative margins can cause our height to shrink below our minimal height (border/padding).
    // If this happens, ensure that the computed height is increased to the minimal height.
    setHeight(max(height(), top + bottom));

    // Update our bottom collapsed margin info.
    setCollapsedBottomMargin(marginInfo);
}

void RenderBlock::layoutBlockChildren(bool relayoutChildren, int& maxFloatBottom)
{
    if (gPercentHeightDescendantsMap) {
        if (HashSet<RenderBox*>* descendants = gPercentHeightDescendantsMap->get(this)) {
            HashSet<RenderBox*>::iterator end = descendants->end();
            for (HashSet<RenderBox*>::iterator it = descendants->begin(); it != end; ++it) {
                RenderBox* box = *it;
                while (box != this) {
                    if (box->normalChildNeedsLayout())
                        break;
                    box->setChildNeedsLayout(true, false);
                    box = box->containingBlock();
                    ASSERT(box);
                    if (!box)
                        break;
                }
            }
        }
    }

    int top = borderTop() + paddingTop();
    int bottom = borderBottom() + paddingBottom() + horizontalScrollbarHeight();

    setHeight(top);

    // The margin struct caches all our current margin collapsing state.  The compact struct caches state when we encounter compacts,
    MarginInfo marginInfo(this, top, bottom);

    // Fieldsets need to find their legend and position it inside the border of the object.
    // The legend then gets skipped during normal layout.
    RenderObject* legend = layoutLegend(relayoutChildren);

    int previousFloatBottom = 0;
    maxFloatBottom = 0;

    RenderBox* next = firstChildBox();

    while (next) {
        RenderBox* child = next;
        next = child->nextSiblingBox();

        if (legend == child)
            continue; // Skip the legend, since it has already been positioned up in the fieldset's border.

        // Make sure we layout children if they need it.
        // FIXME: Technically percentage height objects only need a relayout if their percentage isn't going to be turned into
        // an auto value.  Add a method to determine this, so that we can avoid the relayout.
        if (relayoutChildren || ((child->style()->height().isPercent() || child->style()->minHeight().isPercent() || child->style()->maxHeight().isPercent()) && !isRenderView()))
            child->setChildNeedsLayout(true, false);

        // If relayoutChildren is set and we have percentage padding, we also need to invalidate the child's pref widths.
        if (relayoutChildren && (child->style()->paddingLeft().isPercent() || child->style()->paddingRight().isPercent()))
            child->setPrefWidthsDirty(true, false);

        // Handle the four types of special elements first.  These include positioned content, floating content, compacts and
        // run-ins.  When we encounter these four types of objects, we don't actually lay them out as normal flow blocks.
        if (handleSpecialChild(child, marginInfo))
            continue;

        // Lay out the child.
        layoutBlockChild(child, marginInfo, previousFloatBottom, maxFloatBottom);
    }

    // Now do the handling of the bottom of the block, adding in our bottom border/padding and
    // determining the correct collapsed bottom margin information.
    handleBottomOfBlock(top, bottom, marginInfo);
}

void RenderBlock::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, int& previousFloatBottom, int& maxFloatBottom)
{
    int oldTopPosMargin = maxTopPosMargin();
    int oldTopNegMargin = maxTopNegMargin();

    // The child is a normal flow object.  Compute its vertical margins now.
    child->calcVerticalMargins();

    // Do not allow a collapse if the margin top collapse style is set to SEPARATE.
    if (child->style()->marginTopCollapse() == MSEPARATE) {
        marginInfo.setAtTopOfBlock(false);
        marginInfo.clearMargin();
    }

    // Try to guess our correct y position.  In most cases this guess will
    // be correct.  Only if we're wrong (when we compute the real y position)
    // will we have to potentially relayout.
    int yPosEstimate = estimateVerticalPosition(child, marginInfo);

    // Cache our old rect so that we can dirty the proper repaint rects if the child moves.
    IntRect oldRect(child->x(), child->y() , child->width(), child->height());
#ifndef NDEBUG
    IntSize oldLayoutDelta = view()->layoutDelta();
#endif
    // Go ahead and position the child as though it didn't collapse with the top.
    view()->addLayoutDelta(IntSize(0, child->y() - yPosEstimate));
    child->setLocation(child->x(), yPosEstimate);

    bool markDescendantsWithFloats = false;
    if (yPosEstimate != oldRect.y() && !child->avoidsFloats() && child->isBlockFlow() && toRenderBlock(child)->containsFloats())
        markDescendantsWithFloats = true;
    else if (!child->avoidsFloats() || child->shrinkToAvoidFloats()) {
        // If an element might be affected by the presence of floats, then always mark it for
        // layout.
        int fb = max(previousFloatBottom, floatBottom());
        if (fb > yPosEstimate)
            markDescendantsWithFloats = true;
    }

    if (child->isRenderBlock()) {
        if (markDescendantsWithFloats)
            toRenderBlock(child)->markAllDescendantsWithFloatsForLayout();

        previousFloatBottom = max(previousFloatBottom, oldRect.y() + toRenderBlock(child)->floatBottom());
    }

    bool childHadLayout = child->m_everHadLayout;
    bool childNeededLayout = child->needsLayout();
    if (childNeededLayout)
        child->layout();

    // Now determine the correct ypos based off examination of collapsing margin
    // values.
    int yBeforeClear = collapseMargins(child, marginInfo);

    // Now check for clear.
    int yAfterClear = clearFloatsIfNeeded(child, marginInfo, oldTopPosMargin, oldTopNegMargin, yBeforeClear);

    view()->addLayoutDelta(IntSize(0, yPosEstimate - yAfterClear));
    child->setLocation(child->x(), yAfterClear);

    // Now we have a final y position.  See if it really does end up being different from our estimate.
    if (yAfterClear != yPosEstimate) {
        if (child->shrinkToAvoidFloats()) {
            // The child's width depends on the line width.
            // When the child shifts to clear an item, its width can
            // change (because it has more available line width).
            // So go ahead and mark the item as dirty.
            child->setChildNeedsLayout(true, false);
        }
        if (!child->avoidsFloats() && child->isBlockFlow() && toRenderBlock(child)->containsFloats())
            toRenderBlock(child)->markAllDescendantsWithFloatsForLayout();
        // Our guess was wrong. Make the child lay itself out again.
        child->layoutIfNeeded();
    }

    // We are no longer at the top of the block if we encounter a non-empty child.
    // This has to be done after checking for clear, so that margins can be reset if a clear occurred.
    if (marginInfo.atTopOfBlock() && !child->isSelfCollapsingBlock())
        marginInfo.setAtTopOfBlock(false);

    // Now place the child in the correct horizontal position
    determineHorizontalPosition(child);

    // Update our height now that the child has been placed in the correct position.
    setHeight(height() + child->height());
    if (child->style()->marginBottomCollapse() == MSEPARATE) {
        setHeight(height() + child->marginBottom());
        marginInfo.clearMargin();
    }
    // If the child has overhanging floats that intrude into following siblings (or possibly out
    // of this block), then the parent gets notified of the floats now.
    if (child->isBlockFlow() && toRenderBlock(child)->containsFloats())
        maxFloatBottom = max(maxFloatBottom, addOverhangingFloats(toRenderBlock(child), -child->x(), -child->y(), !childNeededLayout));

    IntSize childOffset(child->x() - oldRect.x(), child->y() - oldRect.y());
    if (childOffset.width() || childOffset.height()) {
        view()->addLayoutDelta(childOffset);

        // If the child moved, we have to repaint it as well as any floating/positioned
        // descendants.  An exception is if we need a layout.  In this case, we know we're going to
        // repaint ourselves (and the child) anyway.
        if (childHadLayout && !selfNeedsLayout() && child->checkForRepaintDuringLayout())
            child->repaintDuringLayoutIfMoved(oldRect);
    }

    if (!childHadLayout && child->checkForRepaintDuringLayout()) {
        child->repaint();
        child->repaintOverhangingFloats(true);
    }

    ASSERT(oldLayoutDelta == view()->layoutDelta());
}

bool RenderBlock::layoutOnlyPositionedObjects()
{
    if (!posChildNeedsLayout() || normalChildNeedsLayout() || selfNeedsLayout())
        return false;

    LayoutStateMaintainer statePusher(view(), this, IntSize(x(), y()), hasColumns() || hasTransform() || hasReflection());

    if (needsPositionedMovementLayout()) {
        tryLayoutDoingPositionedMovementOnly();
        if (needsLayout())
            return false;
    }

    // All we have to is lay out our positioned objects.
    layoutPositionedObjects(false);

    statePusher.pop();

    updateScrollInfoAfterLayout();

#ifdef ANDROID_FIX
    // iframe flatten will call FrameView::layout() which calls performPostLayoutTasks,
    // which may make us need to layout again
    if (!posChildNeedsLayout() || normalChildNeedsLayout() || selfNeedsLayout())
        return false;
#endif

    setNeedsLayout(false);
    return true;
}

void RenderBlock::layoutPositionedObjects(bool relayoutChildren)
{
    if (m_positionedObjects) {
        RenderBox* r;
        Iterator end = m_positionedObjects->end();
        for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
            r = *it;
            // When a non-positioned block element moves, it may have positioned children that are implicitly positioned relative to the
            // non-positioned block.  Rather than trying to detect all of these movement cases, we just always lay out positioned
            // objects that are positioned implicitly like this.  Such objects are rare, and so in typical DHTML menu usage (where everything is
            // positioned explicitly) this should not incur a performance penalty.
            if (relayoutChildren || (r->style()->hasStaticY() && r->parent() != this && r->parent()->isBlockFlow()))
                r->setChildNeedsLayout(true, false);

            // If relayoutChildren is set and we have percentage padding, we also need to invalidate the child's pref widths.
            //if (relayoutChildren && (r->style()->paddingLeft().isPercent() || r->style()->paddingRight().isPercent()))
                r->setPrefWidthsDirty(true, false);

            // We don't have to do a full layout.  We just have to update our position. Try that first. If we have shrink-to-fit width
            // and we hit the available width constraint, the layoutIfNeeded() will catch it and do a full layout.
            if (r->needsPositionedMovementLayoutOnly())
                r->tryLayoutDoingPositionedMovementOnly();
            r->layoutIfNeeded();
        }
    }
}

void RenderBlock::markPositionedObjectsForLayout()
{
    if (m_positionedObjects) {
        RenderBox* r;
        Iterator end = m_positionedObjects->end();
        for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
            r = *it;
            r->setChildNeedsLayout(true);
        }
    }
}

void RenderBlock::repaintOverhangingFloats(bool paintAllDescendants)
{
    // Repaint any overhanging floats (if we know we're the one to paint them).
    if (hasOverhangingFloats()) {
        // We think that we must be in a bad state if m_floatingObjects is nil at this point, so
        // we assert on Debug builds and nil-check Release builds.
        ASSERT(m_floatingObjects);
        if (!m_floatingObjects)
            return;

        FloatingObject* r;
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);

        // FIXME: Avoid disabling LayoutState. At the very least, don't disable it for floats originating
        // in this block. Better yet would be to push extra state for the containers of other floats.
        view()->disableLayoutState();
        for ( ; (r = it.current()); ++it) {
            // Only repaint the object if it is overhanging, is not in its own layer, and
            // is our responsibility to paint (m_shouldPaint is set). When paintAllDescendants is true, the latter
            // condition is replaced with being a descendant of us.
            if (r->m_bottom > height() && ((paintAllDescendants && r->m_renderer->isDescendantOf(this)) || r->m_shouldPaint) && !r->m_renderer->hasSelfPaintingLayer()) {
                r->m_renderer->repaint();
                r->m_renderer->repaintOverhangingFloats();
            }
        }
        view()->enableLayoutState();
    }
}

void RenderBlock::paint(PaintInfo& paintInfo, int tx, int ty)
{
    tx += x();
    ty += y();

    PaintPhase phase = paintInfo.phase;

    // Check if we need to do anything at all.
    // FIXME: Could eliminate the isRoot() check if we fix background painting so that the RenderView
    // paints the root's background.
    if (!isRoot()) {
        IntRect overflowBox = visibleOverflowRect();
        overflowBox.inflate(maximalOutlineSize(paintInfo.phase));
        overflowBox.move(tx, ty);
        if (!overflowBox.intersects(paintInfo.rect))
            return;
    }

    bool pushedClip = pushContentsClip(paintInfo, tx, ty);
    paintObject(paintInfo, tx, ty);
    if (pushedClip)
        popContentsClip(paintInfo, phase, tx, ty);

    // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
    // z-index.  We paint after we painted the background/border, so that the scrollbars will
    // sit above the background/border.
    if (hasOverflowClip() && style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && shouldPaintWithinRoot(paintInfo))
        layer()->paintOverflowControls(paintInfo.context, tx, ty, paintInfo.rect);
}

void RenderBlock::paintColumnRules(PaintInfo& paintInfo, int tx, int ty)
{
    const Color& ruleColor = style()->columnRuleColor();
    bool ruleTransparent = style()->columnRuleIsTransparent();
    EBorderStyle ruleStyle = style()->columnRuleStyle();
    int ruleWidth = style()->columnRuleWidth();
    int colGap = columnGap();
    bool renderRule = ruleStyle > BHIDDEN && !ruleTransparent && ruleWidth <= colGap;
    if (!renderRule)
        return;

    // We need to do multiple passes, breaking up our child painting into strips.
    int currXOffset = 0;
    int ruleAdd = borderLeft() + paddingLeft();
    int ruleX = 0;
    Vector<IntRect>* colRects = columnRects();
    unsigned colCount = colRects->size();
    for (unsigned i = 0; i < colCount; i++) {
        // For each rect, we clip to the rect, and then we adjust our coords.
        IntRect colRect = colRects->at(i);

        // Move to the next position.
        if (style()->direction() == LTR) {
            ruleX += colRect.width() + colGap / 2;
            currXOffset += colRect.width() + colGap;
        } else {
            ruleX -= (colRect.width() + colGap / 2);
            currXOffset -= (colRect.width() + colGap);
        }

        // Now paint the column rule.
        if (i < colCount - 1) {
            int ruleStart = tx + ruleX - ruleWidth / 2 + ruleAdd;
            int ruleEnd = ruleStart + ruleWidth;
            int ruleTop = ty + borderTop() + paddingTop();
            int ruleBottom = ruleTop + contentHeight();
            drawLineForBoxSide(paintInfo.context, ruleStart, ruleTop, ruleEnd, ruleBottom,
                               style()->direction() == LTR ? BSLeft : BSRight, ruleColor, style()->color(), ruleStyle, 0, 0);
        }

        ruleX = currXOffset;
    }
}

void RenderBlock::paintColumnContents(PaintInfo& paintInfo, int tx, int ty, bool paintingFloats)
{
    // We need to do multiple passes, breaking up our child painting into strips.
    GraphicsContext* context = paintInfo.context;
    int currXOffset = 0;
    int currYOffset = 0;
    int colGap = columnGap();
    Vector<IntRect>* colRects = columnRects();
    unsigned colCount = colRects->size();
    for (unsigned i = 0; i < colCount; i++) {
        // For each rect, we clip to the rect, and then we adjust our coords.
        IntRect colRect = colRects->at(i);
        colRect.move(tx, ty);
        context->save();

        // Each strip pushes a clip, since column boxes are specified as being
        // like overflow:hidden.
        context->clip(colRect);

        // Adjust tx and ty to change where we paint.
        PaintInfo info(paintInfo);
        info.rect.intersect(colRect);

        // Adjust our x and y when painting.
        int finalX = tx + currXOffset;
        int finalY = ty + currYOffset;
        if (paintingFloats)
            paintFloats(info, finalX, finalY, paintInfo.phase == PaintPhaseSelection || paintInfo.phase == PaintPhaseTextClip);
        else
            paintContents(info, finalX, finalY);

        // Move to the next position.
        if (style()->direction() == LTR)
            currXOffset += colRect.width() + colGap;
        else
            currXOffset -= (colRect.width() + colGap);

        currYOffset -= colRect.height();

        context->restore();
    }
}

void RenderBlock::paintContents(PaintInfo& paintInfo, int tx, int ty)
{
    // Avoid painting descendants of the root element when stylesheets haven't loaded.  This eliminates FOUC.
    // It's ok not to draw, because later on, when all the stylesheets do load, updateStyleSelector on the Document
    // will do a full repaint().
    if (document()->didLayoutWithPendingStylesheets() && !isRenderView())
        return;

    if (childrenInline())
        m_lineBoxes.paint(this, paintInfo, tx, ty);
    else
        paintChildren(paintInfo, tx, ty);
}

void RenderBlock::paintChildren(PaintInfo& paintInfo, int tx, int ty)
{
    PaintPhase newPhase = (paintInfo.phase == PaintPhaseChildOutlines) ? PaintPhaseOutline : paintInfo.phase;
    newPhase = (newPhase == PaintPhaseChildBlockBackgrounds) ? PaintPhaseChildBlockBackground : newPhase;

    // We don't paint our own background, but we do let the kids paint their backgrounds.
    PaintInfo info(paintInfo);
    info.phase = newPhase;
    info.paintingRoot = paintingRootForChildren(paintInfo);
    bool isPrinting = document()->printing();

    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
        // Check for page-break-before: always, and if it's set, break and bail.
        if (isPrinting && !childrenInline() && child->style()->pageBreakBefore() == PBALWAYS &&
            inRootBlockContext() && (ty + child->y()) > paintInfo.rect.y() &&
            (ty + child->y()) < paintInfo.rect.bottom()) {
            view()->setBestTruncatedAt(ty + child->y(), this, true);
            return;
        }

        if (!child->hasSelfPaintingLayer() && !child->isFloating())
            child->paint(info, tx, ty);

        // Check for page-break-after: always, and if it's set, break and bail.
        if (isPrinting && !childrenInline() && child->style()->pageBreakAfter() == PBALWAYS &&
            inRootBlockContext() && (ty + child->y() + child->height()) > paintInfo.rect.y() &&
            (ty + child->y() + child->height()) < paintInfo.rect.bottom()) {
            view()->setBestTruncatedAt(ty + child->y() + child->height() + max(0, child->collapsedMarginBottom()), this, true);
            return;
        }
    }
}

void RenderBlock::paintCaret(PaintInfo& paintInfo, int tx, int ty, CaretType type)
{
    SelectionController* selection = type == CursorCaret ? document()->frame()->selection() : document()->frame()->dragCaretController();

    // Paint the caret if the SelectionController says so or if caret browsing is enabled
    bool caretBrowsing = document()->frame()->settings() && document()->frame()->settings()->caretBrowsingEnabled();
    RenderObject* caretPainter = selection->caretRenderer();
    if (caretPainter == this && (selection->isContentEditable() || caretBrowsing)) {
        // Convert the painting offset into the local coordinate system of this renderer,
        // to match the localCaretRect computed by the SelectionController
        offsetForContents(tx, ty);

        if (type == CursorCaret)
            document()->frame()->selection()->paintCaret(paintInfo.context, tx, ty, paintInfo.rect);
        else
            document()->frame()->paintDragCaret(paintInfo.context, tx, ty, paintInfo.rect);
    }
}

void RenderBlock::paintObject(PaintInfo& paintInfo, int tx, int ty)
{
    PaintPhase paintPhase = paintInfo.phase;

    // 1. paint background, borders etc
    if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && style()->visibility() == VISIBLE) {
        if (hasBoxDecorations())
            paintBoxDecorations(paintInfo, tx, ty);
        if (hasColumns())
            paintColumnRules(paintInfo, tx, ty);
    }

    if (paintPhase == PaintPhaseMask && style()->visibility() == VISIBLE) {
        paintMask(paintInfo, tx, ty);
        return;
    }

    // We're done.  We don't bother painting any children.
    if (paintPhase == PaintPhaseBlockBackground)
        return;

    // Adjust our painting position if we're inside a scrolled layer (e.g., an overflow:auto div).s
    int scrolledX = tx;
    int scrolledY = ty;
    if (hasOverflowClip())
        layer()->subtractScrolledContentOffset(scrolledX, scrolledY);

    // 2. paint contents
    if (paintPhase != PaintPhaseSelfOutline) {
        if (hasColumns())
            paintColumnContents(paintInfo, scrolledX, scrolledY);
        else
            paintContents(paintInfo, scrolledX, scrolledY);
    }

    // 3. paint selection
    // FIXME: Make this work with multi column layouts.  For now don't fill gaps.
    bool isPrinting = document()->printing();
    if (!isPrinting && !hasColumns())
        paintSelection(paintInfo, scrolledX, scrolledY); // Fill in gaps in selection on lines and between blocks.

    // 4. paint floats.
    if (paintPhase == PaintPhaseFloat || paintPhase == PaintPhaseSelection || paintPhase == PaintPhaseTextClip) {
        if (hasColumns())
            paintColumnContents(paintInfo, scrolledX, scrolledY, true);
        else
            paintFloats(paintInfo, scrolledX, scrolledY, paintPhase == PaintPhaseSelection || paintPhase == PaintPhaseTextClip);
    }

    // 5. paint outline.
    if ((paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseSelfOutline) && hasOutline() && style()->visibility() == VISIBLE)
        paintOutline(paintInfo.context, tx, ty, width(), height(), style());

    // 6. paint continuation outlines.
    if ((paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseChildOutlines)) {
        if (inlineContinuation() && inlineContinuation()->hasOutline() && inlineContinuation()->style()->visibility() == VISIBLE) {
            RenderInline* inlineRenderer = toRenderInline(inlineContinuation()->node()->renderer());
            if (!inlineRenderer->hasSelfPaintingLayer())
                containingBlock()->addContinuationWithOutline(inlineRenderer);
            else if (!inlineRenderer->firstLineBox())
                inlineRenderer->paintOutline(paintInfo.context, tx - x() + inlineRenderer->containingBlock()->x(),
                                             ty - y() + inlineRenderer->containingBlock()->y());
        }
        paintContinuationOutlines(paintInfo, tx, ty);
    }

    // 7. paint caret.
    // If the caret's node's render object's containing block is this block, and the paint action is PaintPhaseForeground,
    // then paint the caret.
    if (paintPhase == PaintPhaseForeground) {
        paintCaret(paintInfo, scrolledX, scrolledY, CursorCaret);
        paintCaret(paintInfo, scrolledX, scrolledY, DragCaret);
    }
}

void RenderBlock::paintFloats(PaintInfo& paintInfo, int tx, int ty, bool preservePhase)
{
    if (!m_floatingObjects)
        return;

    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for (; (r = it.current()); ++it) {
        // Only paint the object if our m_shouldPaint flag is set.
        if (r->m_shouldPaint && !r->m_renderer->hasSelfPaintingLayer()) {
            PaintInfo currentPaintInfo(paintInfo);
            currentPaintInfo.phase = preservePhase ? paintInfo.phase : PaintPhaseBlockBackground;
            int currentTX = tx + r->m_left - r->m_renderer->x() + r->m_renderer->marginLeft();
            int currentTY = ty + r->m_top - r->m_renderer->y() + r->m_renderer->marginTop();
            r->m_renderer->paint(currentPaintInfo, currentTX, currentTY);
            if (!preservePhase) {
                currentPaintInfo.phase = PaintPhaseChildBlockBackgrounds;
                r->m_renderer->paint(currentPaintInfo, currentTX, currentTY);
                currentPaintInfo.phase = PaintPhaseFloat;
                r->m_renderer->paint(currentPaintInfo, currentTX, currentTY);
                currentPaintInfo.phase = PaintPhaseForeground;
                r->m_renderer->paint(currentPaintInfo, currentTX, currentTY);
                currentPaintInfo.phase = PaintPhaseOutline;
                r->m_renderer->paint(currentPaintInfo, currentTX, currentTY);
            }
        }
    }
}

void RenderBlock::paintEllipsisBoxes(PaintInfo& paintInfo, int tx, int ty)
{
    if (!shouldPaintWithinRoot(paintInfo) || !firstLineBox())
        return;

    if (style()->visibility() == VISIBLE && paintInfo.phase == PaintPhaseForeground) {
        // We can check the first box and last box and avoid painting if we don't
        // intersect.
        int yPos = ty + firstLineBox()->y();
        int h = lastLineBox()->y() + lastLineBox()->height() - firstLineBox()->y();
        if (yPos >= paintInfo.rect.bottom() || yPos + h <= paintInfo.rect.y())
            return;

        // See if our boxes intersect with the dirty rect.  If so, then we paint
        // them.  Note that boxes can easily overlap, so we can't make any assumptions
        // based off positions of our first line box or our last line box.
        for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
            yPos = ty + curr->y();
            h = curr->height();
            if (curr->ellipsisBox() && yPos < paintInfo.rect.bottom() && yPos + h > paintInfo.rect.y())
                curr->paintEllipsisBox(paintInfo, tx, ty);
        }
    }
}

static ContinuationOutlineTableMap* continuationOutlineTable()
{
    DEFINE_STATIC_LOCAL(ContinuationOutlineTableMap, table, ());
    return &table;
}

void RenderBlock::addContinuationWithOutline(RenderInline* flow)
{
    // We can't make this work if the inline is in a layer.  We'll just rely on the broken
    // way of painting.
    ASSERT(!flow->layer() && !flow->isInlineContinuation());

    ContinuationOutlineTableMap* table = continuationOutlineTable();
    ListHashSet<RenderInline*>* continuations = table->get(this);
    if (!continuations) {
        continuations = new ListHashSet<RenderInline*>;
        table->set(this, continuations);
    }

    continuations->add(flow);
}

void RenderBlock::paintContinuationOutlines(PaintInfo& info, int tx, int ty)
{
    ContinuationOutlineTableMap* table = continuationOutlineTable();
    if (table->isEmpty())
        return;

    ListHashSet<RenderInline*>* continuations = table->get(this);
    if (!continuations)
        return;

    // Paint each continuation outline.
    ListHashSet<RenderInline*>::iterator end = continuations->end();
    for (ListHashSet<RenderInline*>::iterator it = continuations->begin(); it != end; ++it) {
        // Need to add in the coordinates of the intervening blocks.
        RenderInline* flow = *it;
        RenderBlock* block = flow->containingBlock();
        for ( ; block && block != this; block = block->containingBlock()) {
            tx += block->x();
            ty += block->y();
        }
        ASSERT(block);
        flow->paintOutline(info.context, tx, ty);
    }

    // Delete
    delete continuations;
    table->remove(this);
}

void RenderBlock::setSelectionState(SelectionState s)
{
    if (selectionState() == s)
        return;

    if (s == SelectionInside && selectionState() != SelectionNone)
        return;

    if ((s == SelectionStart && selectionState() == SelectionEnd) ||
        (s == SelectionEnd && selectionState() == SelectionStart))
        RenderBox::setSelectionState(SelectionBoth);
    else
        RenderBox::setSelectionState(s);

    RenderBlock* cb = containingBlock();
    if (cb && !cb->isRenderView())
        cb->setSelectionState(s);
}

bool RenderBlock::shouldPaintSelectionGaps() const
{
    return selectionState() != SelectionNone && style()->visibility() == VISIBLE && isSelectionRoot();
}

bool RenderBlock::isSelectionRoot() const
{
    if (!node())
        return false;

    // FIXME: Eventually tables should have to learn how to fill gaps between cells, at least in simple non-spanning cases.
    if (isTable())
        return false;

    if (isBody() || isRoot() || hasOverflowClip() || isRelPositioned() ||
        isFloatingOrPositioned() || isTableCell() || isInlineBlockOrInlineTable() || hasTransform() ||
        hasReflection() || hasMask())
        return true;

    if (view() && view()->selectionStart()) {
        Node* startElement = view()->selectionStart()->node();
        if (startElement && startElement->rootEditableElement() == node())
            return true;
    }

    return false;
}

GapRects RenderBlock::selectionGapRectsForRepaint(RenderBoxModelObject* repaintContainer)
{
    ASSERT(!needsLayout());

    if (!shouldPaintSelectionGaps())
        return GapRects();

    // FIXME: this is broken with transforms
    TransformState transformState(TransformState::ApplyTransformDirection, FloatPoint());
    mapLocalToContainer(repaintContainer, false, false, transformState);
    FloatPoint offsetFromRepaintContainer = transformState.mappedPoint();
    int x = offsetFromRepaintContainer.x();
    int y = offsetFromRepaintContainer.y();

    if (hasOverflowClip())
        layer()->subtractScrolledContentOffset(x, y);

    int lastTop = 0;
    int lastLeft = leftSelectionOffset(this, lastTop);
    int lastRight = rightSelectionOffset(this, lastTop);

    return fillSelectionGaps(this, x, y, x, y, lastTop, lastLeft, lastRight);
}

void RenderBlock::paintSelection(PaintInfo& paintInfo, int tx, int ty)
{
    if (shouldPaintSelectionGaps() && paintInfo.phase == PaintPhaseForeground) {
        int lastTop = 0;
        int lastLeft = leftSelectionOffset(this, lastTop);
        int lastRight = rightSelectionOffset(this, lastTop);
        paintInfo.context->save();
        IntRect gapRectsBounds = fillSelectionGaps(this, tx, ty, tx, ty, lastTop, lastLeft, lastRight, &paintInfo);
        if (!gapRectsBounds.isEmpty()) {
            if (RenderLayer* layer = enclosingLayer()) {
                gapRectsBounds.move(IntSize(-tx, -ty));
                if (!hasLayer()) {
                    FloatRect localBounds(gapRectsBounds);
                    gapRectsBounds = localToContainerQuad(localBounds, layer->renderer()).enclosingBoundingBox();
                }
                layer->addBlockSelectionGapsBounds(gapRectsBounds);
            }
        }
        paintInfo.context->restore();
    }
}

#ifndef BUILDING_ON_TIGER
static void clipOutPositionedObjects(const RenderObject::PaintInfo* paintInfo, int tx, int ty, ListHashSet<RenderBox*>* positionedObjects)
{
    if (!positionedObjects)
        return;

    ListHashSet<RenderBox*>::const_iterator end = positionedObjects->end();
    for (ListHashSet<RenderBox*>::const_iterator it = positionedObjects->begin(); it != end; ++it) {
        RenderBox* r = *it;
        paintInfo->context->clipOut(IntRect(tx + r->x(), ty + r->y(), r->width(), r->height()));
    }
}
#endif

GapRects RenderBlock::fillSelectionGaps(RenderBlock* rootBlock, int blockX, int blockY, int tx, int ty,
                                        int& lastTop, int& lastLeft, int& lastRight, const PaintInfo* paintInfo)
{
#ifndef BUILDING_ON_TIGER
    // IMPORTANT: Callers of this method that intend for painting to happen need to do a save/restore.
    // Clip out floating and positioned objects when painting selection gaps.
    if (paintInfo) {
        // Note that we don't clip out overflow for positioned objects.  We just stick to the border box.
        clipOutPositionedObjects(paintInfo, tx, ty, m_positionedObjects);
        if (isBody() || isRoot()) // The <body> must make sure to examine its containingBlock's positioned objects.
            for (RenderBlock* cb = containingBlock(); cb && !cb->isRenderView(); cb = cb->containingBlock())
                clipOutPositionedObjects(paintInfo, cb->x(), cb->y(), cb->m_positionedObjects);
        if (m_floatingObjects) {
            for (DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects); it.current(); ++it) {
                FloatingObject* r = it.current();
                paintInfo->context->clipOut(IntRect(tx + r->m_left + r->m_renderer->marginLeft(),
                                                    ty + r->m_top + r->m_renderer->marginTop(),
                                                    r->m_renderer->width(), r->m_renderer->height()));
            }
        }
    }
#endif

    // FIXME: overflow: auto/scroll regions need more math here, since painting in the border box is different from painting in the padding box (one is scrolled, the other is
    // fixed).
    GapRects result;
    if (!isBlockFlow()) // FIXME: Make multi-column selection gap filling work someday.
        return result;

    if (hasColumns() || hasTransform()) {
        // FIXME: We should learn how to gap fill multiple columns and transforms eventually.
        lastTop = (ty - blockY) + height();
        lastLeft = leftSelectionOffset(rootBlock, height());
        lastRight = rightSelectionOffset(rootBlock, height());
        return result;
    }

    if (childrenInline())
        result = fillInlineSelectionGaps(rootBlock, blockX, blockY, tx, ty, lastTop, lastLeft, lastRight, paintInfo);
    else
        result = fillBlockSelectionGaps(rootBlock, blockX, blockY, tx, ty, lastTop, lastLeft, lastRight, paintInfo);

    // Go ahead and fill the vertical gap all the way to the bottom of our block if the selection extends past our block.
    if (rootBlock == this && (selectionState() != SelectionBoth && selectionState() != SelectionEnd))
        result.uniteCenter(fillVerticalSelectionGap(lastTop, lastLeft, lastRight, ty + height(),
                                                    rootBlock, blockX, blockY, paintInfo));
    return result;
}

GapRects RenderBlock::fillInlineSelectionGaps(RenderBlock* rootBlock, int blockX, int blockY, int tx, int ty,
                                              int& lastTop, int& lastLeft, int& lastRight, const PaintInfo* paintInfo)
{
    GapRects result;

    bool containsStart = selectionState() == SelectionStart || selectionState() == SelectionBoth;

    if (!firstLineBox()) {
        if (containsStart) {
            // Go ahead and update our lastY to be the bottom of the block.  <hr>s or empty blocks with height can trip this
            // case.
            lastTop = (ty - blockY) + height();
            lastLeft = leftSelectionOffset(rootBlock, height());
            lastRight = rightSelectionOffset(rootBlock, height());
        }
        return result;
    }

    RootInlineBox* lastSelectedLine = 0;
    RootInlineBox* curr;
    for (curr = firstRootBox(); curr && !curr->hasSelectedChildren(); curr = curr->nextRootBox()) { }

    // Now paint the gaps for the lines.
    for (; curr && curr->hasSelectedChildren(); curr = curr->nextRootBox()) {
        int selTop =  curr->selectionTop();
        int selHeight = curr->selectionHeight();

        if (!containsStart && !lastSelectedLine &&
            selectionState() != SelectionStart && selectionState() != SelectionBoth)
            result.uniteCenter(fillVerticalSelectionGap(lastTop, lastLeft, lastRight, ty + selTop,
                                                        rootBlock, blockX, blockY, paintInfo));

        if (!paintInfo || (ty + selTop < paintInfo->rect.bottom() && ty + selTop + selHeight > paintInfo->rect.y()))
            result.unite(curr->fillLineSelectionGap(selTop, selHeight, rootBlock, blockX, blockY, tx, ty, paintInfo));

        lastSelectedLine = curr;
    }

    if (containsStart && !lastSelectedLine)
        // VisibleSelection must start just after our last line.
        lastSelectedLine = lastRootBox();

    if (lastSelectedLine && selectionState() != SelectionEnd && selectionState() != SelectionBoth) {
        // Go ahead and update our lastY to be the bottom of the last selected line.
        lastTop = (ty - blockY) + lastSelectedLine->selectionBottom();
        lastLeft = leftSelectionOffset(rootBlock, lastSelectedLine->selectionBottom());
        lastRight = rightSelectionOffset(rootBlock, lastSelectedLine->selectionBottom());
    }
    return result;
}

GapRects RenderBlock::fillBlockSelectionGaps(RenderBlock* rootBlock, int blockX, int blockY, int tx, int ty,
                                             int& lastTop, int& lastLeft, int& lastRight, const PaintInfo* paintInfo)
{
    GapRects result;

    // Go ahead and jump right to the first block child that contains some selected objects.
    RenderBox* curr;
    for (curr = firstChildBox(); curr && curr->selectionState() == SelectionNone; curr = curr->nextSiblingBox()) { }

    for (bool sawSelectionEnd = false; curr && !sawSelectionEnd; curr = curr->nextSiblingBox()) {
        SelectionState childState = curr->selectionState();
        if (childState == SelectionBoth || childState == SelectionEnd)
            sawSelectionEnd = true;

        if (curr->isFloatingOrPositioned())
            continue; // We must be a normal flow object in order to even be considered.

        if (curr->isRelPositioned() && curr->hasLayer()) {
            // If the relposition offset is anything other than 0, then treat this just like an absolute positioned element.
            // Just disregard it completely.
            IntSize relOffset = curr->layer()->relativePositionOffset();
            if (relOffset.width() || relOffset.height())
                continue;
        }

        bool paintsOwnSelection = curr->shouldPaintSelectionGaps() || curr->isTable(); // FIXME: Eventually we won't special-case table like this.
        bool fillBlockGaps = paintsOwnSelection || (curr->canBeSelectionLeaf() && childState != SelectionNone);
        if (fillBlockGaps) {
            // We need to fill the vertical gap above this object.
            if (childState == SelectionEnd || childState == SelectionInside)
                // Fill the gap above the object.
                result.uniteCenter(fillVerticalSelectionGap(lastTop, lastLeft, lastRight,
                                                            ty + curr->y(), rootBlock, blockX, blockY, paintInfo));

            // Only fill side gaps for objects that paint their own selection if we know for sure the selection is going to extend all the way *past*
            // our object.  We know this if the selection did not end inside our object.
            if (paintsOwnSelection && (childState == SelectionStart || sawSelectionEnd))
                childState = SelectionNone;

            // Fill side gaps on this object based off its state.
            bool leftGap, rightGap;
            getHorizontalSelectionGapInfo(childState, leftGap, rightGap);

            if (leftGap)
                result.uniteLeft(fillLeftSelectionGap(this, curr->x(), curr->y(), curr->height(), rootBlock, blockX, blockY, tx, ty, paintInfo));
            if (rightGap)
                result.uniteRight(fillRightSelectionGap(this, curr->x() + curr->width(), curr->y(), curr->height(), rootBlock, blockX, blockY, tx, ty, paintInfo));

            // Update lastTop to be just underneath the object.  lastLeft and lastRight extend as far as
            // they can without bumping into floating or positioned objects.  Ideally they will go right up
            // to the border of the root selection block.
            lastTop = (ty - blockY) + (curr->y() + curr->height());
            lastLeft = leftSelectionOffset(rootBlock, curr->y() + curr->height());
            lastRight = rightSelectionOffset(rootBlock, curr->y() + curr->height());
        } else if (childState != SelectionNone)
            // We must be a block that has some selected object inside it.  Go ahead and recur.
            result.unite(toRenderBlock(curr)->fillSelectionGaps(rootBlock, blockX, blockY, tx + curr->x(), ty + curr->y(),
                                                                            lastTop, lastLeft, lastRight, paintInfo));
    }
    return result;
}

IntRect RenderBlock::fillHorizontalSelectionGap(RenderObject* selObj, int xPos, int yPos, int width, int height, const PaintInfo* paintInfo)
{
    if (width <= 0 || height <= 0)
        return IntRect();
    IntRect gapRect(xPos, yPos, width, height);
    if (paintInfo && selObj->style()->visibility() == VISIBLE)
        paintInfo->context->fillRect(gapRect, selObj->selectionBackgroundColor(), selObj->style()->colorSpace());
    return gapRect;
}

IntRect RenderBlock::fillVerticalSelectionGap(int lastTop, int lastLeft, int lastRight, int bottomY, RenderBlock* rootBlock,
                                              int blockX, int blockY, const PaintInfo* paintInfo)
{
    int top = blockY + lastTop;
    int height = bottomY - top;
    if (height <= 0)
        return IntRect();

    // Get the selection offsets for the bottom of the gap
    int left = blockX + max(lastLeft, leftSelectionOffset(rootBlock, bottomY));
    int right = blockX + min(lastRight, rightSelectionOffset(rootBlock, bottomY));
    int width = right - left;
    if (width <= 0)
        return IntRect();

    IntRect gapRect(left, top, width, height);
    if (paintInfo)
        paintInfo->context->fillRect(gapRect, selectionBackgroundColor(), style()->colorSpace());
    return gapRect;
}

IntRect RenderBlock::fillLeftSelectionGap(RenderObject* selObj, int xPos, int yPos, int height, RenderBlock* rootBlock,
                                          int blockX, int /*blockY*/, int tx, int ty, const PaintInfo* paintInfo)
{
    int top = yPos + ty;
    int left = blockX + max(leftSelectionOffset(rootBlock, yPos), leftSelectionOffset(rootBlock, yPos + height));
    int right = min(xPos + tx, blockX + min(rightSelectionOffset(rootBlock, yPos), rightSelectionOffset(rootBlock, yPos + height)));
    int width = right - left;
    if (width <= 0)
        return IntRect();

    IntRect gapRect(left, top, width, height);
    if (paintInfo)
        paintInfo->context->fillRect(gapRect, selObj->selectionBackgroundColor(), selObj->style()->colorSpace());
    return gapRect;
}

IntRect RenderBlock::fillRightSelectionGap(RenderObject* selObj, int xPos, int yPos, int height, RenderBlock* rootBlock,
                                           int blockX, int /*blockY*/, int tx, int ty, const PaintInfo* paintInfo)
{
    int left = max(xPos + tx, blockX + max(leftSelectionOffset(rootBlock, yPos), leftSelectionOffset(rootBlock, yPos + height)));
    int top = yPos + ty;
    int right = blockX + min(rightSelectionOffset(rootBlock, yPos), rightSelectionOffset(rootBlock, yPos + height));
    int width = right - left;
    if (width <= 0)
        return IntRect();

    IntRect gapRect(left, top, width, height);
    if (paintInfo)
        paintInfo->context->fillRect(gapRect, selObj->selectionBackgroundColor(), selObj->style()->colorSpace());
    return gapRect;
}

void RenderBlock::getHorizontalSelectionGapInfo(SelectionState state, bool& leftGap, bool& rightGap)
{
    bool ltr = style()->direction() == LTR;
    leftGap = (state == RenderObject::SelectionInside) ||
              (state == RenderObject::SelectionEnd && ltr) ||
              (state == RenderObject::SelectionStart && !ltr);
    rightGap = (state == RenderObject::SelectionInside) ||
               (state == RenderObject::SelectionStart && ltr) ||
               (state == RenderObject::SelectionEnd && !ltr);
}

int RenderBlock::leftSelectionOffset(RenderBlock* rootBlock, int yPos)
{
    int left = leftOffset(yPos, false);
    if (left == borderLeft() + paddingLeft()) {
        if (rootBlock != this)
            // The border can potentially be further extended by our containingBlock().
            return containingBlock()->leftSelectionOffset(rootBlock, yPos + y());
        return left;
    }
    else {
        RenderBlock* cb = this;
        while (cb != rootBlock) {
            left += cb->x();
            cb = cb->containingBlock();
        }
    }

    return left;
}

int RenderBlock::rightSelectionOffset(RenderBlock* rootBlock, int yPos)
{
    int right = rightOffset(yPos, false);
    if (right == (contentWidth() + (borderLeft() + paddingLeft()))) {
        if (rootBlock != this)
            // The border can potentially be further extended by our containingBlock().
            return containingBlock()->rightSelectionOffset(rootBlock, yPos + y());
        return right;
    }
    else {
        RenderBlock* cb = this;
        while (cb != rootBlock) {
            right += cb->x();
            cb = cb->containingBlock();
        }
    }
    return right;
}

void RenderBlock::insertPositionedObject(RenderBox* o)
{
    // Create the list of special objects if we don't aleady have one
    if (!m_positionedObjects)
        m_positionedObjects = new ListHashSet<RenderBox*>;

    m_positionedObjects->add(o);
}

void RenderBlock::removePositionedObject(RenderBox* o)
{
    if (m_positionedObjects)
        m_positionedObjects->remove(o);
}

void RenderBlock::removePositionedObjects(RenderBlock* o)
{
    if (!m_positionedObjects)
        return;

    RenderBox* r;

    Iterator end = m_positionedObjects->end();

    Vector<RenderBox*, 16> deadObjects;

    for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
        r = *it;
        if (!o || r->isDescendantOf(o)) {
            if (o)
                r->setChildNeedsLayout(true, false);

            // It is parent blocks job to add positioned child to positioned objects list of its containing block
            // Parent layout needs to be invalidated to ensure this happens.
            RenderObject* p = r->parent();
            while (p && !p->isRenderBlock())
                p = p->parent();
            if (p)
                p->setChildNeedsLayout(true);

            deadObjects.append(r);
        }
    }

    for (unsigned i = 0; i < deadObjects.size(); i++)
        m_positionedObjects->remove(deadObjects.at(i));
}

void RenderBlock::insertFloatingObject(RenderBox* o)
{
    ASSERT(o->isFloating());

    // Create the list of special objects if we don't aleady have one
    if (!m_floatingObjects) {
        m_floatingObjects = new DeprecatedPtrList<FloatingObject>;
        m_floatingObjects->setAutoDelete(true);
    } else {
        // Don't insert the object again if it's already in the list
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        FloatingObject* f;
        while ( (f = it.current()) ) {
            if (f->m_renderer == o) return;
            ++it;
        }
    }

    // Create the special object entry & append it to the list

    o->layoutIfNeeded();

    FloatingObject* newObj = new FloatingObject(o->style()->floating() == FLEFT ? FloatingObject::FloatLeft : FloatingObject::FloatRight);

    newObj->m_top = -1;
    newObj->m_bottom = -1;
    newObj->m_width = o->width() + o->marginLeft() + o->marginRight();
    newObj->m_shouldPaint = !o->hasSelfPaintingLayer(); // If a layer exists, the float will paint itself.  Otherwise someone else will.
    newObj->m_isDescendant = true;
    newObj->m_renderer = o;

    m_floatingObjects->append(newObj);
}

void RenderBlock::removeFloatingObject(RenderBox* o)
{
    if (m_floatingObjects) {
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        while (it.current()) {
            if (it.current()->m_renderer == o) {
                if (childrenInline())
                    markLinesDirtyInVerticalRange(0, it.current()->m_bottom);
                m_floatingObjects->removeRef(it.current());
            }
            ++it;
        }
    }
}

bool RenderBlock::positionNewFloats()
{
    if (!m_floatingObjects)
        return false;

    FloatingObject* f = m_floatingObjects->last();

    // If all floats have already been positioned, then we have no work to do.
    if (!f || f->m_top != -1)
        return false;

    // Move backwards through our floating object list until we find a float that has
    // already been positioned.  Then we'll be able to move forward, positioning all of
    // the new floats that need it.
    FloatingObject* lastFloat = m_floatingObjects->getPrev();
    while (lastFloat && lastFloat->m_top == -1) {
        f = m_floatingObjects->prev();
        lastFloat = m_floatingObjects->getPrev();
    }

    int y = height();

    // The float cannot start above the y position of the last positioned float.
    if (lastFloat)
        y = max(lastFloat->m_top, y);

    // Now walk through the set of unpositioned floats and place them.
    while (f) {
        // The containing block is responsible for positioning floats, so if we have floats in our
        // list that come from somewhere else, do not attempt to position them.
        if (f->m_renderer->containingBlock() != this) {
            f = m_floatingObjects->next();
            continue;
        }

        RenderBox* o = f->m_renderer;
        int _height = o->height() + o->marginTop() + o->marginBottom();

        int ro = rightOffset(); // Constant part of right offset.
        int lo = leftOffset(); // Constat part of left offset.
        int fwidth = f->m_width; // The width we look for.
        if (ro - lo < fwidth)
            fwidth = ro - lo; // Never look for more than what will be available.

        IntRect oldRect(o->x(), o->y() , o->width(), o->height());

        if (o->style()->clear() & CLEFT)
            y = max(leftBottom(), y);
        if (o->style()->clear() & CRIGHT)
            y = max(rightBottom(), y);

        if (o->style()->floating() == FLEFT) {
            int heightRemainingLeft = 1;
            int heightRemainingRight = 1;
            int fx = leftRelOffset(y, lo, false, &heightRemainingLeft);
            while (rightRelOffset(y, ro, false, &heightRemainingRight)-fx < fwidth) {
                y += min(heightRemainingLeft, heightRemainingRight);
                fx = leftRelOffset(y, lo, false, &heightRemainingLeft);
            }
            fx = max(0, fx);
            f->m_left = fx;
            o->setLocation(fx + o->marginLeft(), y + o->marginTop());
        } else {
            int heightRemainingLeft = 1;
            int heightRemainingRight = 1;
            int fx = rightRelOffset(y, ro, false, &heightRemainingRight);
            while (fx - leftRelOffset(y, lo, false, &heightRemainingLeft) < fwidth) {
                y += min(heightRemainingLeft, heightRemainingRight);
                fx = rightRelOffset(y, ro, false, &heightRemainingRight);
            }
            f->m_left = fx - f->m_width;
            o->setLocation(fx - o->marginRight() - o->width(), y + o->marginTop());
        }

        f->m_top = y;
        f->m_bottom = f->m_top + _height;

        // If the child moved, we have to repaint it.
        if (o->checkForRepaintDuringLayout())
            o->repaintDuringLayoutIfMoved(oldRect);

        f = m_floatingObjects->next();
    }
    return true;
}

void RenderBlock::newLine(EClear clear)
{
    positionNewFloats();
    // set y position
    int newY = 0;
    switch (clear)
    {
        case CLEFT:
            newY = leftBottom();
            break;
        case CRIGHT:
            newY = rightBottom();
            break;
        case CBOTH:
            newY = floatBottom();
        default:
            break;
    }
    if (height() < newY)
        setHeight(newY);
}

void RenderBlock::addPercentHeightDescendant(RenderBox* descendant)
{
    if (!gPercentHeightDescendantsMap) {
        gPercentHeightDescendantsMap = new PercentHeightDescendantsMap;
        gPercentHeightContainerMap = new PercentHeightContainerMap;
    }

    HashSet<RenderBox*>* descendantSet = gPercentHeightDescendantsMap->get(this);
    if (!descendantSet) {
        descendantSet = new HashSet<RenderBox*>;
        gPercentHeightDescendantsMap->set(this, descendantSet);
    }
    bool added = descendantSet->add(descendant).second;
    if (!added) {
        ASSERT(gPercentHeightContainerMap->get(descendant));
        ASSERT(gPercentHeightContainerMap->get(descendant)->contains(this));
        return;
    }

    HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->get(descendant);
    if (!containerSet) {
        containerSet = new HashSet<RenderBlock*>;
        gPercentHeightContainerMap->set(descendant, containerSet);
    }
    ASSERT(!containerSet->contains(this));
    containerSet->add(this);
}

void RenderBlock::removePercentHeightDescendant(RenderBox* descendant)
{
    if (!gPercentHeightContainerMap)
        return;

    HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->take(descendant);
    if (!containerSet)
        return;

    HashSet<RenderBlock*>::iterator end = containerSet->end();
    for (HashSet<RenderBlock*>::iterator it = containerSet->begin(); it != end; ++it) {
        RenderBlock* container = *it;
        HashSet<RenderBox*>* descendantSet = gPercentHeightDescendantsMap->get(container);
        ASSERT(descendantSet);
        if (!descendantSet)
            continue;
        ASSERT(descendantSet->contains(descendant));
        descendantSet->remove(descendant);
        if (descendantSet->isEmpty()) {
            gPercentHeightDescendantsMap->remove(container);
            delete descendantSet;
        }
    }

    delete containerSet;
}

HashSet<RenderBox*>* RenderBlock::percentHeightDescendants() const
{
    return gPercentHeightDescendantsMap ? gPercentHeightDescendantsMap->get(this) : 0;
}

int RenderBlock::leftOffset() const
{
    return borderLeft() + paddingLeft();
}

int RenderBlock::leftRelOffset(int y, int fixedOffset, bool applyTextIndent, int* heightRemaining) const
{
    int left = fixedOffset;
    if (m_floatingObjects) {
        if ( heightRemaining ) *heightRemaining = 1;
        FloatingObject* r;
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        for ( ; (r = it.current()); ++it )
        {
            if (r->m_top <= y && r->m_bottom > y &&
                r->type() == FloatingObject::FloatLeft &&
                r->m_left + r->m_width > left) {
                left = r->m_left + r->m_width;
                if ( heightRemaining ) *heightRemaining = r->m_bottom - y;
            }
        }
    }

    if (applyTextIndent && style()->direction() == LTR) {
        int cw = 0;
        if (style()->textIndent().isPercent())
            cw = containingBlock()->availableWidth();
        left += style()->textIndent().calcMinValue(cw);
    }

    return left;
}

int RenderBlock::rightOffset() const
{
    return borderLeft() + paddingLeft() + availableWidth();
}

int RenderBlock::rightRelOffset(int y, int fixedOffset, bool applyTextIndent, int* heightRemaining) const
{
    int right = fixedOffset;

    if (m_floatingObjects) {
        if (heightRemaining) *heightRemaining = 1;
        FloatingObject* r;
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        for ( ; (r = it.current()); ++it )
        {
            if (r->m_top <= y && r->m_bottom > y &&
                r->type() == FloatingObject::FloatRight &&
                r->m_left < right) {
                right = r->m_left;
                if ( heightRemaining ) *heightRemaining = r->m_bottom - y;
            }
        }
    }

    if (applyTextIndent && style()->direction() == RTL) {
        int cw = 0;
        if (style()->textIndent().isPercent())
            cw = containingBlock()->availableWidth();
        right -= style()->textIndent().calcMinValue(cw);
    }

    return right;
}

int
RenderBlock::lineWidth(int y, bool firstLine) const
{
    int result = rightOffset(y, firstLine) - leftOffset(y, firstLine);
    return (result < 0) ? 0 : result;
}

int RenderBlock::nextFloatBottomBelow(int height) const
{
    if (!m_floatingObjects)
        return 0;

    int bottom = INT_MAX;
    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for ( ; (r = it.current()); ++it) {
        if (r->m_bottom > height)
            bottom = min(r->m_bottom, bottom);
    }

    return bottom == INT_MAX ? 0 : bottom;
}

int
RenderBlock::floatBottom() const
{
    if (!m_floatingObjects) return 0;
    int bottom = 0;
    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for ( ; (r = it.current()); ++it )
        if (r->m_bottom>bottom)
            bottom = r->m_bottom;
    return bottom;
}

IntRect RenderBlock::floatRect() const
{
    IntRect result;
    if (!m_floatingObjects || hasOverflowClip() || hasColumns())
        return result;
    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for (; (r = it.current()); ++it) {
        if (r->m_shouldPaint && !r->m_renderer->hasSelfPaintingLayer()) {
            IntRect childRect = r->m_renderer->visibleOverflowRect();
            childRect.move(r->m_left + r->m_renderer->marginLeft(), r->m_top + r->m_renderer->marginTop());
            result.unite(childRect);
        }
    }

    return result;
}

int RenderBlock::lowestPosition(bool includeOverflowInterior, bool includeSelf) const
{
    int bottom = includeSelf && width() > 0 ? height() : 0;

    if (!includeOverflowInterior && (hasOverflowClip() || hasControlClip()))
        return bottom;

    if (!firstChild() && (!width() || !height()))
        return bottom;

    if (!hasColumns()) {
        // FIXME: Come up with a way to use the layer tree to avoid visiting all the kids.
        // For now, we have to descend into all the children, since we may have a huge abs div inside
        // a tiny rel div buried somewhere deep in our child tree.  In this case we have to get to
        // the abs div.
        // See the last test case in https://bugs.webkit.org/show_bug.cgi?id=9314 for why this is a problem.
        // For inline children, we miss relative positioned boxes that might be buried inside <span>s.
        for (RenderObject* c = firstChild(); c; c = c->nextSibling()) {
            if (!c->isFloatingOrPositioned() && c->isBox()) {
                RenderBox* childBox = toRenderBox(c);
                bottom = max(bottom, childBox->y() + childBox->lowestPosition(false));
            }
        }
    }

    if (includeSelf && isRelPositioned())
        bottom += relativePositionOffsetY();
    if (!includeOverflowInterior && hasOverflowClip())
        return bottom;

    int relativeOffset = includeSelf && isRelPositioned() ? relativePositionOffsetY() : 0;

    if (includeSelf)
        bottom = max(bottom, bottomLayoutOverflow() + relativeOffset);

    if (m_positionedObjects) {
        RenderBox* r;
        Iterator end = m_positionedObjects->end();
        for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
            r = *it;
            // Fixed positioned objects do not scroll and thus should not constitute
            // part of the lowest position.
            if (r->style()->position() != FixedPosition) {
                // FIXME: Should work for overflow sections too.
                // If a positioned object lies completely to the left of the root it will be unreachable via scrolling.
                // Therefore we should not allow it to contribute to the lowest position.
                if (!isRenderView() || r->x() + r->width() > 0 || r->x() + r->rightmostPosition(false) > 0) {
                    int lp = r->y() + r->lowestPosition(false);
                    bottom = max(bottom, lp + relativeOffset);
                }
            }
        }
    }

    if (hasColumns()) {
        Vector<IntRect>* colRects = columnRects();
        for (unsigned i = 0; i < colRects->size(); i++)
            bottom = max(bottom, colRects->at(i).bottom() + relativeOffset);
        return bottom;
    }

    if (m_floatingObjects) {
        FloatingObject* r;
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        for ( ; (r = it.current()); ++it ) {
            if (r->m_shouldPaint || r->m_renderer->hasSelfPaintingLayer()) {
                int lp = r->m_top + r->m_renderer->marginTop() + r->m_renderer->lowestPosition(false);
                bottom = max(bottom, lp + relativeOffset);
            }
        }
    }

    if (!includeSelf) {
        bottom = max(bottom, borderTop() + paddingTop() + paddingBottom() + relativeOffset);
        if (childrenInline()) {
            if (lastRootBox()) {
                int childBottomEdge = lastRootBox()->selectionBottom();
                bottom = max(bottom, childBottomEdge + paddingBottom() + relativeOffset);
            }
        } else {
            // Find the last normal flow child.
            RenderBox* currBox = lastChildBox();
            while (currBox && currBox->isFloatingOrPositioned())
                currBox = currBox->previousSiblingBox();
            if (currBox) {
                int childBottomEdge = currBox->y() + currBox->height() + currBox->collapsedMarginBottom();
                bottom = max(bottom, childBottomEdge + paddingBottom() + relativeOffset);
            }
        }
    }

    return bottom;
}

int RenderBlock::rightmostPosition(bool includeOverflowInterior, bool includeSelf) const
{
    int right = includeSelf && height() > 0 ? width() : 0;

    if (!includeOverflowInterior && (hasOverflowClip() || hasControlClip()))
        return right;

    if (!firstChild() && (!width() || !height()))
        return right;

    if (!hasColumns()) {
        // FIXME: Come up with a way to use the layer tree to avoid visiting all the kids.
        // For now, we have to descend into all the children, since we may have a huge abs div inside
        // a tiny rel div buried somewhere deep in our child tree.  In this case we have to get to
        // the abs div.
        for (RenderObject* c = firstChild(); c; c = c->nextSibling()) {
            if (!c->isFloatingOrPositioned() && c->isBox()) {
                RenderBox* childBox = toRenderBox(c);
                right = max(right, childBox->x() + childBox->rightmostPosition(false));
            }
        }
    }

    if (includeSelf && isRelPositioned())
        right += relativePositionOffsetX();

    if (!includeOverflowInterior && hasOverflowClip())
        return right;

    int relativeOffset = includeSelf && isRelPositioned() ? relativePositionOffsetX() : 0;

    if (includeSelf)
        right = max(right, rightLayoutOverflow() + relativeOffset);

    if (m_positionedObjects) {
        RenderBox* r;
        Iterator end = m_positionedObjects->end();
        for (Iterator it = m_positionedObjects->begin() ; it != end; ++it) {
            r = *it;
            // Fixed positioned objects do not scroll and thus should not constitute
            // part of the rightmost position.
            if (r->style()->position() != FixedPosition) {
                // FIXME: Should work for overflow sections too.
                // If a positioned object lies completely above the root it will be unreachable via scrolling.
                // Therefore we should not allow it to contribute to the rightmost position.
                if (!isRenderView() || r->y() + r->height() > 0 || r->y() + r->lowestPosition(false) > 0) {
                    int rp = r->x() + r->rightmostPosition(false);
                    right = max(right, rp + relativeOffset);
                }
            }
        }
    }

    if (hasColumns()) {
        // This only matters for LTR
        if (style()->direction() == LTR)
            right = max(columnRects()->last().right() + relativeOffset, right);
        return right;
    }

    if (m_floatingObjects) {
        FloatingObject* r;
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        for ( ; (r = it.current()); ++it ) {
            if (r->m_shouldPaint || r->m_renderer->hasSelfPaintingLayer()) {
                int rp = r->m_left + r->m_renderer->marginLeft() + r->m_renderer->rightmostPosition(false);
                right = max(right, rp + relativeOffset);
            }
        }
    }

    if (!includeSelf) {
        right = max(right, borderLeft() + paddingLeft() + paddingRight() + relativeOffset);
        if (childrenInline()) {
            for (InlineRunBox* currBox = firstLineBox(); currBox; currBox = currBox->nextLineBox()) {
                int childRightEdge = currBox->x() + currBox->width();

                // If this node is a root editable element, then the rightmostPosition should account for a caret at the end.
                // FIXME: Need to find another way to do this, since scrollbars could show when we don't want them to.
                if (node() && node()->isContentEditable() && node() == node()->rootEditableElement() && style()->direction() == LTR && !paddingRight())
                    childRightEdge += 1;
                right = max(right, childRightEdge + paddingRight() + relativeOffset);
            }
        } else {
            // Walk all normal flow children.
            for (RenderBox* currBox = firstChildBox(); currBox; currBox = currBox->nextSiblingBox()) {
                if (currBox->isFloatingOrPositioned())
                    continue;
                int childRightEdge = currBox->x() + currBox->width() + currBox->marginRight();
                right = max(right, childRightEdge + paddingRight() + relativeOffset);
            }
        }
    }

    return right;
}

int RenderBlock::leftmostPosition(bool includeOverflowInterior, bool includeSelf) const
{
    int left = includeSelf && height() > 0 ? 0 : width();

    if (!includeOverflowInterior && (hasOverflowClip() || hasControlClip()))
        return left;

    if (!firstChild() && (!width() || !height()))
        return left;

    if (!hasColumns()) {
        // FIXME: Come up with a way to use the layer tree to avoid visiting all the kids.
        // For now, we have to descend into all the children, since we may have a huge abs div inside
        // a tiny rel div buried somewhere deep in our child tree.  In this case we have to get to
        // the abs div.
        for (RenderObject* c = firstChild(); c; c = c->nextSibling()) {
            if (!c->isFloatingOrPositioned() && c->isBox()) {
                RenderBox* childBox = toRenderBox(c);
                left = min(left, childBox->x() + childBox->leftmostPosition(false));
            }
        }
    }

    if (includeSelf && isRelPositioned())
        left += relativePositionOffsetX();

    if (!includeOverflowInterior && hasOverflowClip())
        return left;

    int relativeOffset = includeSelf && isRelPositioned() ? relativePositionOffsetX() : 0;

    if (includeSelf)
        left = min(left, leftLayoutOverflow() + relativeOffset);

    if (m_positionedObjects) {
        RenderBox* r;
        Iterator end = m_positionedObjects->end();
        for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
            r = *it;
            // Fixed positioned objects do not scroll and thus should not constitute
            // part of the leftmost position.
            if (r->style()->position() != FixedPosition) {
                // FIXME: Should work for overflow sections too.
                // If a positioned object lies completely above the root it will be unreachable via scrolling.
                // Therefore we should not allow it to contribute to the leftmost position.
                if (!isRenderView() || r->y() + r->height() > 0 || r->y() + r->lowestPosition(false) > 0) {
                    int lp = r->x() + r->leftmostPosition(false);
                    left = min(left, lp + relativeOffset);
                }
            }
        }
    }

    if (hasColumns()) {
        // This only matters for RTL
        if (style()->direction() == RTL)
            left = min(columnRects()->last().x() + relativeOffset, left);
        return left;
    }

    if (m_floatingObjects) {
        FloatingObject* r;
        DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
        for ( ; (r = it.current()); ++it ) {
            if (r->m_shouldPaint || r->m_renderer->hasSelfPaintingLayer()) {
                int lp = r->m_left + r->m_renderer->marginLeft() + r->m_renderer->leftmostPosition(false);
                left = min(left, lp + relativeOffset);
            }
        }
    }

    if (!includeSelf && firstLineBox()) {
        for (InlineRunBox* currBox = firstLineBox(); currBox; currBox = currBox->nextLineBox())
            left = min(left, (int)currBox->x() + relativeOffset);
    }

    return left;
}

int
RenderBlock::leftBottom()
{
    if (!m_floatingObjects) return 0;
    int bottom = 0;
    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for ( ; (r = it.current()); ++it )
        if (r->m_bottom > bottom && r->type() == FloatingObject::FloatLeft)
            bottom = r->m_bottom;

    return bottom;
}

int
RenderBlock::rightBottom()
{
    if (!m_floatingObjects) return 0;
    int bottom = 0;
    FloatingObject* r;
    DeprecatedPtrListIterator<FloatingObject> it(*m_floatingObjects);
    for ( ; (r = it.current()); ++it )
        if (r->m_bottom>bottom && r->type() == FloatingObject::FloatRight)
            bottom = r->m_bottom;

    return bottom;
}

void RenderBlock::markLinesDirtyInVerticalRange(int top, int bottom, RootInlineBox* highest)
{
    if (top >= bottom)
        return;

    RootInlineBox* lowestDirtyLine = lastRootBox();
    RootInlineBox* afterLowest = lowestDirtyLine;
    while (lowestDirtyLine && lowestDirtyLine->blockHeight() >= bottom) {
        afterLowest = lowestDirtyLine;
        lowestDirtyLine = lowestDirtyLine->prevRootBox();
    }

    while (afterLowest && afterLowest != highest && afterLowest->blockHeight() >= top) {
        afterLowest->markDirty();
        afterLowest = afterLowest->prevRootBox();
    }
}

void RenderBlock::clearFloats()
{
    // Inline blocks are covered by the isReplaced() check in the avoidFloats method.
    if (avoidsFloats() || isRoot() || isRenderView() || isFloatingOrPositioned() || isTableCell()) {
        if (m_floatingObjects)