Jump to the next outer column when an inner column is too short.

third_party/WebKit/Source/core/layout/LayoutBlock.cpp

 /*
  * 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, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. 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
@@ skipping 2635 matching lines @@
             // question (i.e. no remaining space), rather than being part of the latter (i.e. one
             // whole page length of remaining space).
             remainingHeight = intMod(remainingHeight, pageLogicalHeight);
         }
         return remainingHeight;
     }
 
     return flowThread->pageRemainingLogicalHeightForOffset(offset, pageBoundaryRule);
 }
 
+LayoutUnit LayoutBlock::calculatePaginationStrutToFitContent(LayoutUnit offset, LayoutUnit strutToNextPage, LayoutUnit contentLogicalHeight) const
+{
+    ASSERT(strutToNextPage == pageRemainingLogicalHeightForOffset(offset, AssociateWithLatterPage));
+    LayoutUnit nextPageLogicalTop = offset + strutToNextPage;
+    if (pageLogicalHeightForOffset(nextPageLogicalTop) >= contentLogicalHeight)
+        return strutToNextPage; // Content fits just fine in the next page or column.
+
+    // Moving to the top of the next page or column doesn't result in enough space for the content
+    // that we're trying to fit. If we're in a nested fragmentation context, we may find enough
+    // space if we move to a column further ahead, by effectively breaking to the next outer
+    // fragmentainer.
+    LayoutFlowThread* flowThread = flowThreadContainingBlock();
+    if (!flowThread) {
+        // If there's no flow thread, we're not nested. All pages have the same height. Give up.
+        return strutToNextPage;
+    }
+    // Start searching for a suitable offset at the top of the next page or column.
+    LayoutUnit flowThreadOffset = offsetFromLogicalTopOfFirstPage() + nextPageLogicalTop;
+    return strutToNextPage + flowThread->nextLogicalTopForUnbreakableContent(flowThreadOffset, contentLogicalHeight) - flowThreadOffset;
+}
+
 void LayoutBlock::paginatedContentWasLaidOut(LayoutUnit logicalTopOffsetAfterPagination)
 {
     if (LayoutFlowThread* flowThread = flowThreadContainingBlock())
         flowThread->contentWasLaidOut(offsetFromLogicalTopOfFirstPage() + logicalTopOffsetAfterPagination);
 }
 
 LayoutUnit LayoutBlock::collapsedMarginBeforeForChild(const LayoutBox& child) const
 {
     // If the child has the same directionality as we do, then we can just return its
     // collapsed margin.
@@ skipping 225 matching lines @@
 void LayoutBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const LayoutObject* obj) const
 {
     showLayoutObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace blink