Column balancing support in the region based multicol implementation.

Source/core/rendering/RenderBlock.h

 /*
  * 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.
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     LayoutUnit applyAfterBreak(RenderBox* child, LayoutUnit logicalOffset, MarginInfo&); // If the child has an after break, then return a new offset that shifts to the top of the next page/column.
 
 public:
     LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const;
     LayoutUnit pageLogicalHeightForOffset(LayoutUnit offset) const;
     LayoutUnit pageRemainingLogicalHeightForOffset(LayoutUnit offset, PageBoundaryRule = IncludePageBoundary) const;
     
 protected:
     bool pushToNextPageWithMinimumLogicalHeight(LayoutUnit& adjustment, LayoutUnit logicalOffset, LayoutUnit minimumLogicalHeight) const;
 
+    // A page break is required at some offset due to space shortage in the current fragmentainer.
+    void setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage);
+
+    // Update minimum page height required to avoid fragmentation where it shouldn't occur (inside
+    // unbreakable content, between orphans and widows, etc.). This will be used as a hint to the
+    // column balancer to help set a good minimum column height.
+    void updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight);
+
     LayoutUnit adjustForUnsplittableChild(RenderBox* child, LayoutUnit logicalOffset, bool includeMargins = false); // If the child is unsplittable and can't fit on the current page, return the top of the next page/column.
     void adjustLinePositionForPagination(RootInlineBox*, LayoutUnit& deltaOffset, RenderFlowThread*); // Computes a deltaOffset value that put a line at the top of the next page if it doesn't fit on the current page.
     LayoutUnit adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox* child, bool atBeforeSideOfBlock);
 
     // Adjust from painting offsets to the local coords of this renderer
     void offsetForContents(LayoutPoint&) const;
 
     // This function is called to test a line box that has moved in the block direction to see if it has ended up in a new
     // region/page/column that has a different available line width than the old one. Used to know when you have to dirty a
     // line, i.e., that it can't be re-used.
@@ skipping 205 matching lines @@
     static String string(const int value);
 };
 template<> struct ValueToString<RenderBlock::FloatingObject*> {
     static String string(const RenderBlock::FloatingObject*);
 };
 #endif
 
 } // namespace WebCore
 
 #endif // RenderBlock_h