[New Multicolumn] Layout support for column-span:all.

Source/core/rendering/RenderFlowThread.h

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. 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.
@@ skipping 46 matching lines @@
     virtual bool isRenderPagedFlowThread() const { return false; }
 
     virtual bool supportsPaintInvalidationStateCachedOffsets() const override { return false; }
 
     virtual void layout() override;
 
     // Always create a RenderLayer for the RenderFlowThread so that we
     // can easily avoid drawing the children directly.
     virtual LayerType layerTypeRequired() const override final { return NormalLayer; }
 
+    // Skip past a column spanner during flow thread layout. Spanners are not laid out inside the
+    // flow thread, since the flow thread is not in a spanner's containing block chain (since the
+    // containing block is the multicol container). If the spanner follows right after a column set
+    // (as opposed to following another spanner), we may have to stretch the flow thread to ensure
+    // completely filled columns in the preceding column set. Return this adjustment, if any.
+    virtual LayoutUnit skipColumnSpanner(RenderBox*, LayoutUnit logicalTopInFlowThread) { return LayoutUnit(); }
+
     virtual void flowThreadDescendantWasInserted(RenderObject*) { }
     virtual void flowThreadDescendantWillBeRemoved(RenderObject*) { }
 
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) override final;
 
     virtual void addRegionToThread(RenderMultiColumnSet*) = 0;
     virtual void removeRegionFromThread(RenderMultiColumnSet*);
 
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
 
@@ skipping 30 matching lines @@
         return flowThreadPoint + columnOffset(flowThreadPoint);
     }
 
     void pushFlowThreadLayoutState(const RenderObject&);
     void popFlowThreadLayoutState();
     LayoutUnit offsetFromLogicalTopOfFirstRegion(const RenderBlock*) const;
 
     // Used to estimate the maximum height of the flow thread.
     static LayoutUnit maxLogicalHeight() { return LayoutUnit::max() / 2; }
 
+    virtual RenderMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const = 0;
+
 protected:
     virtual const char* renderName() const = 0;
 
     void updateRegionsFlowThreadPortionRect();
 
-    virtual RenderMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const = 0;
-
     bool cachedOffsetFromLogicalTopOfFirstRegion(const RenderBox*, LayoutUnit&) const;
     void setOffsetFromLogicalTopOfFirstRegion(const RenderBox*, LayoutUnit);
     void clearOffsetFromLogicalTopOfFirstRegion(const RenderBox*);
 
     const RenderBox* currentStatePusherRenderBox() const;
 
     RenderMultiColumnSetList m_multiColumnSetList;
 
     typedef PODInterval<LayoutUnit, RenderMultiColumnSet*> MultiColumnSetInterval;
     typedef PODIntervalTree<LayoutUnit, RenderMultiColumnSet*> MultiColumnSetIntervalTree;
 
-    class RegionSearchAdapter {
+    class MultiColumnSetSearchAdapter {
     public:
-        RegionSearchAdapter(LayoutUnit offset)
+        MultiColumnSetSearchAdapter(LayoutUnit offset)
             : m_offset(offset)
             , m_result(0)
         {
         }
 
         const LayoutUnit& lowValue() const { return m_offset; }
         const LayoutUnit& highValue() const { return m_offset; }
         void collectIfNeeded(const MultiColumnSetInterval&);
 
-        RenderRegion* result() const { return m_result; }
+        RenderMultiColumnSet* result() const { return m_result; }
 
     private:
         LayoutUnit m_offset;
-        RenderRegion* m_result;
+        RenderMultiColumnSet* m_result;
     };

[Julien - ping for review, 2015/01/19 10:05:11]

FYI I keep reading this patch which looks like a great refactoring on its own
(it's really a 2 minutes review)

 
     // Stack of objects that pushed a LayoutState object on the RenderView. The
     // objects on the stack are the ones that are curently in the process of being
     // laid out.
     ListHashSet<const RenderObject*> m_statePusherObjectsStack;
     typedef HashMap<const RenderBox*, LayoutUnit> RenderBoxToOffsetMap;
     RenderBoxToOffsetMap m_boxesToOffsetMap;
 
     MultiColumnSetIntervalTree m_multiColumnSetIntervalTree;
 
@@ skipping 11 matching lines @@
 };
 
 template <> struct ValueToString<RenderMultiColumnSet*> {
     static String string(const RenderMultiColumnSet* value) { return String::format("%p", value); }
 };
 #endif
 
 } // namespace blink
 
 #endif // RenderFlowThread_h