[New Multicolumn] Support for paged overflow. (By mstensho).

Source/core/rendering/RenderMultiColumnFlowThread.h

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 66 matching lines @@
 // RenderMultiColumnSet::recordSpaceShortage()). We'll relayout (to find new break points and the
 // new lowest amount of space increase that could affect where they occur, in case we need another
 // round) until we've reached an acceptable height (where everything fits perfectly in the number of
 // columns that we have specified). The rule of thumb is that we shouldn't have to perform more of
 // such iterations than the number of columns that we have.
 //
 // For each layout iteration done for column balancing, the flow thread will need a deep layout if
 // column heights changed in the previous pass, since column height changes may affect break points
 // and pagination struts anywhere in the tree, and currently no way exists to do this in a more
 // optimized manner.
-class RenderMultiColumnFlowThread FINAL : public RenderFlowThread {
+class RenderMultiColumnFlowThread : public RenderFlowThread {
 public:
     virtual ~RenderMultiColumnFlowThread();
 
     static RenderMultiColumnFlowThread* createAnonymous(Document&, RenderStyle* parentStyle);
 
     virtual bool isRenderMultiColumnFlowThread() const OVERRIDE FINAL { return true; }
 
     RenderBlockFlow* multiColumnBlockFlow() const { return toRenderBlockFlow(parent()); }
 
     RenderMultiColumnSet* firstMultiColumnSet() const;
     RenderMultiColumnSet* lastMultiColumnSet() const;
 
     virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0) OVERRIDE;
 
     // Populate the flow thread with what's currently its siblings. Called when a regular block
     // becomes a multicol container.
     void populate();
 
     // Empty the flow thread by moving everything to the parent. Remove all multicol specific
     // renderers. Then destroy the flow thread. Called when a multicol container becomes a regular
     // block.
     void evacuateAndDestroy();
 
     unsigned columnCount() const { return m_columnCount; }
     LayoutUnit columnHeightAvailable() const { return m_columnHeightAvailable; }
     void setColumnHeightAvailable(LayoutUnit available) { m_columnHeightAvailable = available; }
-    bool requiresBalancing() const { return !columnHeightAvailable() || multiColumnBlockFlow()->style()->columnFill() == ColumnFillBalance; }
+    virtual bool heightIsAuto() const { return !columnHeightAvailable() || multiColumnBlockFlow()->style()->columnFill() == ColumnFillBalance; }
+    bool progressionIsInline() const { return m_progressionIsInline; }
 
     virtual LayoutSize columnOffset(const LayoutPoint&) const OVERRIDE FINAL;
 
     // Do we need to set a new width and lay out?
-    bool needsNewWidth() const;
+    virtual bool needsNewWidth() const;
 
     void layoutColumns(bool relayoutChildren, SubtreeLayoutScope&);
 
     bool recalculateColumnHeights();
 
+protected:
+    RenderMultiColumnFlowThread();
+    void setProgressionIsInline(bool isInline) { m_progressionIsInline = isInline; }
+
+    virtual void layout() OVERRIDE;
+
 private:
-    RenderMultiColumnFlowThread();
-
     void calculateColumnCountAndWidth(LayoutUnit& width, unsigned& count) const;
 
     virtual const char* renderName() const OVERRIDE;
     virtual void addRegionToThread(RenderMultiColumnSet*) OVERRIDE;
     virtual void willBeRemovedFromTree() OVERRIDE;
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const OVERRIDE;
-    virtual void updateLogicalWidth() OVERRIDE FINAL;
-    virtual void layout() OVERRIDE FINAL;
+    virtual void updateLogicalWidth() OVERRIDE;
     virtual void setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage) OVERRIDE;
     virtual void updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight) OVERRIDE;
     virtual RenderMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const OVERRIDE;
     virtual bool addForcedRegionBreak(LayoutUnit, RenderObject* breakChild, bool isBefore, LayoutUnit* offsetBreakAdjustment = 0) OVERRIDE;
     virtual bool isPageLogicalHeightKnown() const OVERRIDE;
 
     unsigned m_columnCount; // The used value of column-count
     LayoutUnit m_columnHeightAvailable; // Total height available to columns, or 0 if auto.
     bool m_inBalancingPass; // Set when relayouting for column balancing.
     bool m_needsColumnHeightsRecalculation; // Set when we need to recalculate the column set heights after layout.
+    bool m_progressionIsInline; // Always true for regular multicol. False for paged-y overflow.
 };
 
 } // namespace WebCore
 
 #endif // RenderMultiColumnFlowThread_h