WebCore/rendering/RenderBlock.h
changeset 0 4f2f89ce4247
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/WebCore/rendering/RenderBlock.h	Fri Sep 17 09:02:29 2010 +0300
@@ -0,0 +1,601 @@
+/*
+ * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
+ *           (C) 1999 Antti Koivisto (koivisto@kde.org)
+ *           (C) 2007 David Smith (catfish.man@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.
+ */
+
+#ifndef RenderBlock_h
+#define RenderBlock_h
+
+#include "DeprecatedPtrList.h"
+#include "GapRects.h"
+#include "RenderBox.h"
+#include "RenderLineBoxList.h"
+#include "RootInlineBox.h"
+#include <wtf/ListHashSet.h>
+
+namespace WebCore {
+
+class InlineIterator;
+class RenderInline;
+
+struct BidiRun;
+
+template <class Iterator, class Run> class BidiResolver;
+template <class Iterator> struct MidpointState;
+typedef BidiResolver<InlineIterator, BidiRun> InlineBidiResolver;
+typedef MidpointState<InlineIterator> LineMidpointState;
+
+enum CaretType { CursorCaret, DragCaret };
+
+class RenderBlock : public RenderBox {
+public:
+    RenderBlock(Node*);
+    virtual ~RenderBlock();
+
+    const RenderObjectChildList* children() const { return &m_children; }
+    RenderObjectChildList* children() { return &m_children; }
+
+    virtual void destroy();
+
+    // These two functions are overridden for inline-block.
+    virtual int lineHeight(bool firstLine, bool isRootLineBox = false) const;
+    virtual int baselinePosition(bool firstLine, bool isRootLineBox = false) const;
+
+    RenderLineBoxList* lineBoxes() { return &m_lineBoxes; }
+    const RenderLineBoxList* lineBoxes() const { return &m_lineBoxes; }
+
+    InlineFlowBox* firstLineBox() const { return m_lineBoxes.firstLineBox(); }
+    InlineFlowBox* lastLineBox() const { return m_lineBoxes.lastLineBox(); }
+
+    void deleteLineBoxTree();
+
+    virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0);
+    virtual void removeChild(RenderObject*);
+
+    virtual void layoutBlock(bool relayoutChildren);
+
+    void insertPositionedObject(RenderBox*);
+    void removePositionedObject(RenderBox*);
+    void removePositionedObjects(RenderBlock*);
+
+    typedef ListHashSet<RenderBox*, 4> PositionedObjectsListHashSet;
+    PositionedObjectsListHashSet* positionedObjects() const { return m_positionedObjects; }
+
+    void addPercentHeightDescendant(RenderBox*);
+    static void removePercentHeightDescendant(RenderBox*);
+    HashSet<RenderBox*>* percentHeightDescendants() const;
+
+    RootInlineBox* createAndAppendRootInlineBox();
+
+    bool generatesLineBoxesForInlineChild(RenderObject*, bool isLineEmpty = true, bool previousLineBrokeCleanly = true);
+
+    void markAllDescendantsWithFloatsForLayout(RenderBox* floatToRemove = 0, bool inLayout = true);
+    void markPositionedObjectsForLayout();
+
+    bool containsFloats() { return m_floatingObjects && !m_floatingObjects->isEmpty(); }
+    bool containsFloat(RenderObject*);
+
+    int lineWidth(int y, bool firstLine) const;
+    
+    virtual int lowestPosition(bool includeOverflowInterior = true, bool includeSelf = true) const;
+    virtual int rightmostPosition(bool includeOverflowInterior = true, bool includeSelf = true) const;
+    virtual int leftmostPosition(bool includeOverflowInterior = true, bool includeSelf = true) const;
+
+    int rightOffset(int y, bool firstLine) const { return rightRelOffset(y, rightOffset(), firstLine); }
+    int leftOffset(int y, bool firstLine) const { return leftRelOffset(y, leftOffset(), firstLine); }
+
+    virtual VisiblePosition positionForPoint(const IntPoint&);
+    
+    // Block flows subclass availableWidth to handle multi column layout (shrinking the width available to children when laying out.)
+    virtual int availableWidth() const;
+    
+    RootInlineBox* firstRootBox() const { return static_cast<RootInlineBox*>(firstLineBox()); }
+    RootInlineBox* lastRootBox() const { return static_cast<RootInlineBox*>(lastLineBox()); }
+
+    bool containsNonZeroBidiLevel() const;
+
+    GapRects selectionGapRectsForRepaint(RenderBoxModelObject* repaintContainer);
+    IntRect fillLeftSelectionGap(RenderObject* selObj, int xPos, int yPos, int height, RenderBlock* rootBlock, 
+                                 int blockX, int blockY, int tx, int ty, const PaintInfo*);
+    IntRect fillRightSelectionGap(RenderObject* selObj, int xPos, int yPos, int height, RenderBlock* rootBlock,
+                                  int blockX, int blockY, int tx, int ty, const PaintInfo*);
+    IntRect fillHorizontalSelectionGap(RenderObject* selObj, int xPos, int yPos, int width, int height, const PaintInfo*);
+
+    void getHorizontalSelectionGapInfo(SelectionState, bool& leftGap, bool& rightGap);
+
+    // Helper methods for computing line counts and heights for line counts.
+    RootInlineBox* lineAtIndex(int);
+    int lineCount();
+    int heightForLineCount(int);
+    void clearTruncation();
+
+    void adjustRectForColumns(IntRect&) const;
+    virtual void adjustForColumns(IntSize&, const IntPoint&) const;
+
+    void addContinuationWithOutline(RenderInline*);
+
+    RenderBoxModelObject* continuation() const { return m_continuation; }
+    void setContinuation(RenderBoxModelObject* c) { m_continuation = c; }
+    virtual RenderBoxModelObject* virtualContinuation() const { return continuation(); }
+    bool isAnonymousBlockContinuation() const { return continuation() && isAnonymousBlock(); }
+    RenderInline* inlineElementContinuation() const;
+    RenderBlock* blockElementContinuation() const;
+
+    // This function is a convenience helper for creating an anonymous block that inherits its
+    // style from this RenderBlock.
+    RenderBlock* createAnonymousBlock(bool isFlexibleBox = false) const;
+    RenderBlock* createAnonymousColumnsBlock() const;
+    RenderBlock* createAnonymousColumnSpanBlock() const;
+    RenderBlock* createAnonymousBlockWithSameTypeAs(RenderBlock* otherAnonymousBlock) const;
+    
+    static void appendRunsForObject(int start, int end, RenderObject*, InlineBidiResolver&);    
+    static bool requiresLineBox(const InlineIterator&, bool isLineEmpty = true, bool previousLineBrokeCleanly = true);
+
+    Vector<IntRect>* columnRects() const;
+    int columnGap() const;
+
+protected:
+    // These functions are only used internally to manipulate the render tree structure via remove/insert/appendChildNode.
+    // Since they are typically called only to move objects around within anonymous blocks (which only have layers in
+    // the case of column spans), the default for fullRemoveInsert is false rather than true.
+    void moveChildTo(RenderBlock* to, RenderObject* child, bool fullRemoveInsert = false)
+    {
+        return moveChildTo(to, child, 0, fullRemoveInsert);
+    }
+    void moveChildTo(RenderBlock* to, RenderObject* child, RenderObject* beforeChild, bool fullRemoveInsert = false);
+    void moveAllChildrenTo(RenderBlock* to, bool fullRemoveInsert = false)
+    {
+        return moveAllChildrenTo(to, 0, fullRemoveInsert);
+    }
+    void moveAllChildrenTo(RenderBlock* to, RenderObject* beforeChild, bool fullRemoveInsert = false)
+    {
+        return moveChildrenTo(to, firstChild(), 0, beforeChild, fullRemoveInsert);
+    }
+    // Move all of the kids from |startChild| up to but excluding |endChild|.  0 can be passed as the endChild to denote
+    // that all the kids from |startChild| onwards should be added.
+    void moveChildrenTo(RenderBlock* to, RenderObject* startChild, RenderObject* endChild, bool fullRemoveInsert = false)
+    {
+        return moveChildrenTo(to, startChild, endChild, 0, fullRemoveInsert);
+    }
+    void moveChildrenTo(RenderBlock* to, RenderObject* startChild, RenderObject* endChild, RenderObject* beforeChild, bool fullRemoveInsert = false);
+    
+    int maxTopPosMargin() const { return m_maxMargin ? m_maxMargin->m_topPos : MaxMargin::topPosDefault(this); }
+    int maxTopNegMargin() const { return m_maxMargin ? m_maxMargin->m_topNeg : MaxMargin::topNegDefault(this); }
+    int maxBottomPosMargin() const { return m_maxMargin ? m_maxMargin->m_bottomPos : MaxMargin::bottomPosDefault(this); }
+    int maxBottomNegMargin() const { return m_maxMargin ? m_maxMargin->m_bottomNeg : MaxMargin::bottomNegDefault(this); }
+    void setMaxTopMargins(int pos, int neg);
+    void setMaxBottomMargins(int pos, int neg);
+    
+    void initMaxMarginValues()
+    {
+        if (m_maxMargin) {
+            m_maxMargin->m_topPos = MaxMargin::topPosDefault(this);
+            m_maxMargin->m_topNeg = MaxMargin::topNegDefault(this);
+            m_maxMargin->m_bottomPos = MaxMargin::bottomPosDefault(this);
+            m_maxMargin->m_bottomNeg = MaxMargin::bottomNegDefault(this);
+        }
+    }
+
+    virtual void layout();
+
+    void layoutPositionedObjects(bool relayoutChildren);
+
+    virtual void paint(PaintInfo&, int tx, int ty);
+    virtual void paintObject(PaintInfo&, int tx, int ty);
+
+    int rightRelOffset(int y, int fixedOffset, bool applyTextIndent = true, int* heightRemaining = 0) const;
+    int leftRelOffset(int y, int fixedOffset, bool applyTextIndent = true, int* heightRemaining = 0) const;
+
+    virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, int x, int y, int tx, int ty, HitTestAction);
+
+    virtual void calcPrefWidths();
+
+    virtual int firstLineBoxBaseline() const;
+    virtual int lastLineBoxBaseline() const;
+
+    virtual void updateFirstLetter();
+
+    virtual void updateHitTestResult(HitTestResult&, const IntPoint&);
+
+    // Delay update scrollbar until finishDelayRepaint() will be
+    // called. This function is used when a flexbox is laying out its
+    // descendant. If multiple calls are made to startDelayRepaint(),
+    // finishDelayRepaint() will do nothing until finishDelayRepaint()
+    // is called the same number of times.
+    static void startDelayUpdateScrollInfo();
+    static void finishDelayUpdateScrollInfo();
+
+    virtual void styleWillChange(StyleDifference, const RenderStyle* newStyle);
+    virtual void styleDidChange(StyleDifference, const RenderStyle* oldStyle);
+
+    virtual bool hasLineIfEmpty() const;
+    bool layoutOnlyPositionedObjects();
+
+#if ENABLE(SVG)
+protected:
+
+    // Only used by RenderSVGText, which explicitely overrides RenderBlock::layoutBlock(), do NOT use for anything else.
+    void forceLayoutInlineChildren()
+    {
+        int repaintTop = 0;
+        int repaintBottom = 0;
+        layoutInlineChildren(true, repaintTop, repaintBottom);
+    }
+#endif
+
+private:
+    virtual RenderObjectChildList* virtualChildren() { return children(); }
+    virtual const RenderObjectChildList* virtualChildren() const { return children(); }
+
+    virtual const char* renderName() const;
+
+    virtual bool isRenderBlock() const { return true; }
+    virtual bool isBlockFlow() const { return (!isInline() || isReplaced()) && !isTable(); }
+    virtual bool isInlineBlockOrInlineTable() const { return isInline() && isReplaced(); }
+
+    void makeChildrenNonInline(RenderObject* insertionPoint = 0);
+    virtual void removeLeftoverAnonymousBlock(RenderBlock* child);
+
+    virtual void dirtyLinesFromChangedChild(RenderObject* child) { m_lineBoxes.dirtyLinesFromChangedChild(this, child); }
+
+    void addChildToContinuation(RenderObject* newChild, RenderObject* beforeChild);
+    void addChildIgnoringContinuation(RenderObject* newChild, RenderObject* beforeChild);
+    void addChildToAnonymousColumnBlocks(RenderObject* newChild, RenderObject* beforeChild);
+    virtual void addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild, RenderObject* beforeChild = 0);
+    
+    virtual bool isSelfCollapsingBlock() const;
+
+    virtual int maxTopMargin(bool positive) const { return positive ? maxTopPosMargin() : maxTopNegMargin(); }
+    virtual int maxBottomMargin(bool positive) const { return positive ? maxBottomPosMargin() : maxBottomNegMargin(); }
+
+    virtual void repaintOverhangingFloats(bool paintAllDescendants);
+
+    void layoutBlockChildren(bool relayoutChildren, int& maxFloatBottom);
+    void layoutInlineChildren(bool relayoutChildren, int& repaintTop, int& repaintBottom);
+
+    virtual void positionListMarker() { }
+
+    virtual void borderFitAdjust(int& x, int& w) const; // Shrink the box in which the border paints if border-fit is set.
+
+    virtual void updateBeforeAfterContent(PseudoId);
+
+    virtual RootInlineBox* createRootInlineBox(); // Subclassed by SVG and Ruby.
+
+    // Called to lay out the legend for a fieldset.
+    virtual RenderObject* layoutLegend(bool /*relayoutChildren*/) { return 0; }
+
+    struct FloatWithRect {
+        FloatWithRect(RenderBox* f)
+            : object(f)
+            , rect(IntRect(f->x() - f->marginLeft(), f->y() - f->marginTop(), f->width() + f->marginLeft() + f->marginRight(), f->height() + f->marginTop() + f->marginBottom()))
+            , everHadLayout(f->m_everHadLayout)
+        {
+        }
+
+        RenderBox* object;
+        IntRect rect;
+        bool everHadLayout;
+    };
+
+    // The following functions' implementations are in RenderBlockLineLayout.cpp.
+    RootInlineBox* determineStartPosition(bool& firstLine, bool& fullLayout, bool& previousLineBrokeCleanly,
+                                          InlineBidiResolver&, Vector<FloatWithRect>& floats, unsigned& numCleanFloats);
+    RootInlineBox* determineEndPosition(RootInlineBox* startBox, InlineIterator& cleanLineStart,
+                                        BidiStatus& cleanLineBidiStatus,
+                                        int& yPos);
+    bool matchedEndLine(const InlineBidiResolver&, const InlineIterator& endLineStart, const BidiStatus& endLineStatus,
+                        RootInlineBox*& endLine, int& endYPos, int& repaintBottom, int& repaintTop);
+
+    void skipTrailingWhitespace(InlineIterator&, bool isLineEmpty, bool previousLineBrokeCleanly);
+    int skipLeadingWhitespace(InlineBidiResolver&, bool firstLine, bool isLineEmpty, bool previousLineBrokeCleanly);
+    void fitBelowFloats(int widthToFit, bool firstLine, int& availableWidth);
+    InlineIterator findNextLineBreak(InlineBidiResolver&, bool firstLine, bool& isLineEmpty, bool& previousLineBrokeCleanly, bool& hyphenated, EClear* = 0);
+    RootInlineBox* constructLine(unsigned runCount, BidiRun* firstRun, BidiRun* lastRun, bool firstLine, bool lastLine, RenderObject* endObject);
+    InlineFlowBox* createLineBoxes(RenderObject*, bool firstLine);
+    void computeHorizontalPositionsForLine(RootInlineBox*, bool firstLine, BidiRun* firstRun, BidiRun* trailingSpaceRun, bool reachedEnd, GlyphOverflowAndFallbackFontsMap&);
+    void computeVerticalPositionsForLine(RootInlineBox*, BidiRun*, GlyphOverflowAndFallbackFontsMap&);
+    void deleteEllipsisLineBoxes();
+    void checkLinesForTextOverflow();
+    void addOverflowFromInlineChildren();
+    // End of functions defined in RenderBlockLineLayout.cpp.
+
+    void addOverflowFromBlockChildren();
+    void addOverflowFromFloats();
+
+    void paintFloats(PaintInfo&, int tx, int ty, bool preservePhase = false);
+    void paintContents(PaintInfo&, int tx, int ty);
+    void paintColumnContents(PaintInfo&, int tx, int ty, bool paintFloats = false);
+    void paintColumnRules(PaintInfo&, int tx, int ty);
+    void paintChildren(PaintInfo&, int tx, int ty);
+    void paintEllipsisBoxes(PaintInfo&, int tx, int ty);
+    void paintSelection(PaintInfo&, int tx, int ty);
+    void paintCaret(PaintInfo&, int tx, int ty, CaretType);
+
+    void insertFloatingObject(RenderBox*);
+    void removeFloatingObject(RenderBox*);
+
+    // Called from lineWidth, to position the floats added in the last line.
+    // Returns ture if and only if it has positioned any floats.
+    bool positionNewFloats();
+    void clearFloats();
+    int getClearDelta(RenderBox* child, int yPos);
+
+    virtual bool avoidsFloats() const;
+
+    bool hasOverhangingFloats() { return parent() && !hasColumns() && floatBottom() > height(); }
+    void addIntrudingFloats(RenderBlock* prev, int xoffset, int yoffset);
+    int addOverhangingFloats(RenderBlock* child, int xoffset, int yoffset, bool makeChildPaintOtherFloats);
+
+    int nextFloatBottomBelow(int) const;
+    int floatBottom() const;
+    inline int leftBottom();
+    inline int rightBottom();
+
+    int rightOffset() const;
+    int leftOffset() const;
+    virtual bool hitTestColumns(const HitTestRequest&, HitTestResult&, int x, int y, int tx, int ty, HitTestAction);
+    virtual bool hitTestContents(const HitTestRequest&, HitTestResult&, int x, int y, int tx, int ty, HitTestAction);
+
+    virtual bool isPointInOverflowControl(HitTestResult&, int x, int y, int tx, int ty);
+
+    void calcInlinePrefWidths();
+    void calcBlockPrefWidths();
+
+    // Obtains the nearest enclosing block (including this block) that contributes a first-line style to our inline
+    // children.
+    virtual RenderBlock* firstLineBlock() const;
+
+    virtual IntRect rectWithOutlineForRepaint(RenderBoxModelObject* repaintContainer, int outlineWidth);
+    virtual RenderStyle* outlineStyleForRepaint() const;
+    
+    virtual RenderObject* hoverAncestor() const;
+    virtual void updateDragState(bool dragOn);
+    virtual void childBecameNonInline(RenderObject* child);
+
+    virtual IntRect selectionRectForRepaint(RenderBoxModelObject* repaintContainer, bool /*clipToVisibleContent*/)
+    {
+        return selectionGapRectsForRepaint(repaintContainer);
+    }
+    virtual bool shouldPaintSelectionGaps() const;
+    bool isSelectionRoot() const;
+    GapRects fillSelectionGaps(RenderBlock* rootBlock, int blockX, int blockY, int tx, int ty,
+                               int& lastTop, int& lastLeft, int& lastRight, const PaintInfo* = 0);
+    GapRects fillInlineSelectionGaps(RenderBlock* rootBlock, int blockX, int blockY, int tx, int ty,
+                                     int& lastTop, int& lastLeft, int& lastRight, const PaintInfo*);
+    GapRects fillBlockSelectionGaps(RenderBlock* rootBlock, int blockX, int blockY, int tx, int ty,
+                                    int& lastTop, int& lastLeft, int& lastRight, const PaintInfo*);
+    IntRect fillVerticalSelectionGap(int lastTop, int lastLeft, int lastRight, int bottomY, RenderBlock* rootBlock,
+                                     int blockX, int blockY, const PaintInfo*);
+    int leftSelectionOffset(RenderBlock* rootBlock, int y);
+    int rightSelectionOffset(RenderBlock* rootBlock, int y);
+
+    virtual void absoluteRects(Vector<IntRect>&, int tx, int ty);
+    virtual void absoluteQuads(Vector<FloatQuad>&);
+
+    int desiredColumnWidth() const;
+    unsigned desiredColumnCount() const;
+    void setDesiredColumnCountAndWidth(int count, int width);
+
+    void paintContinuationOutlines(PaintInfo&, int tx, int ty);
+
+    virtual IntRect localCaretRect(InlineBox*, int caretOffset, int* extraWidthToEndOfLine = 0);
+
+    virtual void addFocusRingRects(Vector<IntRect>&, int tx, int ty);
+
+    void adjustPointToColumnContents(IntPoint&) const;
+    void adjustForBorderFit(int x, int& left, int& right) const; // Helper function for borderFitAdjust
+
+    void markLinesDirtyInVerticalRange(int top, int bottom, RootInlineBox* highest = 0);
+
+    void newLine(EClear);
+
+    Position positionForBox(InlineBox*, bool start = true) const;
+    Position positionForRenderer(RenderObject*, bool start = true) const;
+    VisiblePosition positionForPointWithInlineChildren(const IntPoint&);
+
+    // Adjust tx and ty from painting offsets to the local coords of this renderer
+    void offsetForContents(int& tx, int& ty) const;
+
+    void calcColumnWidth();
+    int layoutColumns(int endOfContent = -1, int requestedColumnHeight = -1);
+    int visibleTopOfHighestFloatExtendingBelow(int bottom, int maxHeight) const;
+    void makeChildrenAnonymousColumnBlocks(RenderObject* beforeChild, RenderBlock* newBlockBox, RenderObject* newChild);
+
+    bool expandsToEncloseOverhangingFloats() const;
+
+    void updateScrollInfoAfterLayout();
+
+    RenderObject* splitAnonymousBlocksAroundChild(RenderObject* beforeChild);
+    void splitBlocks(RenderBlock* fromBlock, RenderBlock* toBlock, RenderBlock* middleBlock,
+                     RenderObject* beforeChild, RenderBoxModelObject* oldCont);
+    void splitFlow(RenderObject* beforeChild, RenderBlock* newBlockBox,
+                   RenderObject* newChild, RenderBoxModelObject* oldCont);
+    RenderBlock* clone() const;
+    RenderBlock* continuationBefore(RenderObject* beforeChild);
+    RenderBlock* containingColumnsBlock(bool allowAnonymousColumnBlock = true);
+    RenderBlock* columnsBlockForSpanningElement(RenderObject* newChild);
+    
+    struct FloatingObject : Noncopyable {
+        enum Type {
+            FloatLeft,
+            FloatRight
+        };
+
+        FloatingObject(Type type)
+            : m_renderer(0)
+            , m_top(0)
+            , m_bottom(0)
+            , m_left(0)
+            , m_width(0)
+            , m_type(type)
+            , m_shouldPaint(true)
+            , m_isDescendant(false)
+        {
+        }
+
+        Type type() { return static_cast<Type>(m_type); }
+
+        RenderBox* m_renderer;
+        int m_top;
+        int m_bottom;
+        int m_left;
+        int m_width;
+        unsigned m_type : 1; // Type (left or right aligned)
+        bool m_shouldPaint : 1;
+        bool m_isDescendant : 1;
+    };
+
+    class MarginInfo {
+        // Collapsing flags for whether we can collapse our margins with our children's margins.
+        bool m_canCollapseWithChildren : 1;
+        bool m_canCollapseTopWithChildren : 1;
+        bool m_canCollapseBottomWithChildren : 1;
+
+        // Whether or not we are a quirky container, i.e., do we collapse away top and bottom
+        // margins in our container.  Table cells and the body are the common examples. We
+        // also have a custom style property for Safari RSS to deal with TypePad blog articles.
+        bool m_quirkContainer : 1;
+
+        // This flag tracks whether we are still looking at child margins that can all collapse together at the beginning of a block.  
+        // They may or may not collapse with the top margin of the block (|m_canCollapseTopWithChildren| tells us that), but they will
+        // always be collapsing with one another.  This variable can remain set to true through multiple iterations 
+        // as long as we keep encountering self-collapsing blocks.
+        bool m_atTopOfBlock : 1;
+
+        // This flag is set when we know we're examining bottom margins and we know we're at the bottom of the block.
+        bool m_atBottomOfBlock : 1;
+
+        // These variables are used to detect quirky margins that we need to collapse away (in table cells
+        // and in the body element).
+        bool m_topQuirk : 1;
+        bool m_bottomQuirk : 1;
+        bool m_determinedTopQuirk : 1;
+
+        // These flags track the previous maximal positive and negative margins.
+        int m_posMargin;
+        int m_negMargin;
+
+    public:
+        MarginInfo(RenderBlock* b, int top, int bottom);
+
+        void setAtTopOfBlock(bool b) { m_atTopOfBlock = b; }
+        void setAtBottomOfBlock(bool b) { m_atBottomOfBlock = b; }
+        void clearMargin() { m_posMargin = m_negMargin = 0; }
+        void setTopQuirk(bool b) { m_topQuirk = b; }
+        void setBottomQuirk(bool b) { m_bottomQuirk = b; }
+        void setDeterminedTopQuirk(bool b) { m_determinedTopQuirk = b; }
+        void setPosMargin(int p) { m_posMargin = p; }
+        void setNegMargin(int n) { m_negMargin = n; }
+        void setPosMarginIfLarger(int p) { if (p > m_posMargin) m_posMargin = p; }
+        void setNegMarginIfLarger(int n) { if (n > m_negMargin) m_negMargin = n; }
+
+        void setMargin(int p, int n) { m_posMargin = p; m_negMargin = n; }
+
+        bool atTopOfBlock() const { return m_atTopOfBlock; }
+        bool canCollapseWithTop() const { return m_atTopOfBlock && m_canCollapseTopWithChildren; }
+        bool canCollapseWithBottom() const { return m_atBottomOfBlock && m_canCollapseBottomWithChildren; }
+        bool canCollapseTopWithChildren() const { return m_canCollapseTopWithChildren; }
+        bool canCollapseBottomWithChildren() const { return m_canCollapseBottomWithChildren; }
+        bool quirkContainer() const { return m_quirkContainer; }
+        bool determinedTopQuirk() const { return m_determinedTopQuirk; }
+        bool topQuirk() const { return m_topQuirk; }
+        bool bottomQuirk() const { return m_bottomQuirk; }
+        int posMargin() const { return m_posMargin; }
+        int negMargin() const { return m_negMargin; }
+        int margin() const { return m_posMargin - m_negMargin; }
+    };
+
+    void layoutBlockChild(RenderBox* child, MarginInfo&, int& previousFloatBottom, int& maxFloatBottom);
+    void adjustPositionedBlock(RenderBox* child, const MarginInfo&);
+    void adjustFloatingBlock(const MarginInfo&);
+    bool handleSpecialChild(RenderBox* child, const MarginInfo&);
+    bool handleFloatingChild(RenderBox* child, const MarginInfo&);
+    bool handlePositionedChild(RenderBox* child, const MarginInfo&);
+    bool handleRunInChild(RenderBox* child);
+    int collapseMargins(RenderBox* child, MarginInfo&);
+    int clearFloatsIfNeeded(RenderBox* child, MarginInfo&, int oldTopPosMargin, int oldTopNegMargin, int yPos);
+    int estimateVerticalPosition(RenderBox* child, const MarginInfo&);
+    void determineHorizontalPosition(RenderBox* child);
+    void handleBottomOfBlock(int top, int bottom, MarginInfo&);
+    void setCollapsedBottomMargin(const MarginInfo&);
+    // End helper functions and structs used by layoutBlockChildren.
+
+    typedef PositionedObjectsListHashSet::const_iterator Iterator;
+    DeprecatedPtrList<FloatingObject>* m_floatingObjects;
+    
+    PositionedObjectsListHashSet* m_positionedObjects;
+
+    // An inline can be split with blocks occurring in between the inline content.
+    // When this occurs we need a pointer to our next object.  We can basically be
+    // split into a sequence of inlines and blocks.  The continuation will either be
+    // an anonymous block (that houses other blocks) or it will be an inline flow.
+    RenderBoxModelObject* m_continuation;
+
+    // Allocated only when some of these fields have non-default values
+    struct MaxMargin : Noncopyable {
+        MaxMargin(const RenderBlock* o) 
+            : m_topPos(topPosDefault(o))
+            , m_topNeg(topNegDefault(o))
+            , m_bottomPos(bottomPosDefault(o))
+            , m_bottomNeg(bottomNegDefault(o))
+        { 
+        }
+
+        static int topPosDefault(const RenderBlock* o) { return o->marginTop() > 0 ? o->marginTop() : 0; }
+        static int topNegDefault(const RenderBlock* o) { return o->marginTop() < 0 ? -o->marginTop() : 0; }
+        static int bottomPosDefault(const RenderBlock* o) { return o->marginBottom() > 0 ? o->marginBottom() : 0; }
+        static int bottomNegDefault(const RenderBlock* o) { return o->marginBottom() < 0 ? -o->marginBottom() : 0; }
+
+        int m_topPos;
+        int m_topNeg;
+        int m_bottomPos;
+        int m_bottomNeg;
+     };
+
+    MaxMargin* m_maxMargin;
+
+    RenderObjectChildList m_children;
+    RenderLineBoxList m_lineBoxes;   // All of the root line boxes created for this block flow.  For example, <div>Hello<br>world.</div> will have two total lines for the <div>.
+
+    mutable int m_lineHeight;
+
+    // RenderRubyBase objects need to be able to split and merge, moving their children around
+    // (calling moveChildTo, moveAllChildrenTo, and makeChildrenNonInline).
+    friend class RenderRubyBase;
+};
+
+inline RenderBlock* toRenderBlock(RenderObject* object)
+{ 
+    ASSERT(!object || object->isRenderBlock());
+    return static_cast<RenderBlock*>(object);
+}
+
+inline const RenderBlock* toRenderBlock(const RenderObject* object)
+{ 
+    ASSERT(!object || object->isRenderBlock());
+    return static_cast<const RenderBlock*>(object);
+}
+
+// This will catch anyone doing an unnecessary cast.
+void toRenderBlock(const RenderBlock*);
+
+} // namespace WebCore
+
+#endif // RenderBlock_h