[New Multicolumn] Add support for column-span:all

Source/core/rendering/RenderMultiColumnFlowThread.h

Index: Source/core/rendering/RenderMultiColumnFlowThread.h
diff --git a/Source/core/rendering/RenderMultiColumnFlowThread.h b/Source/core/rendering/RenderMultiColumnFlowThread.h
index 3f10b58eb40d4c4f193bd3462365bd1d853828ce..301dce5a4dea5bc7738069d31c1e575bb3c0e322 100644
--- a/Source/core/rendering/RenderMultiColumnFlowThread.h
+++ b/Source/core/rendering/RenderMultiColumnFlowThread.h
@@ -28,10 +28,12 @@
 #define RenderMultiColumnFlowThread_h
 
 #include "core/rendering/RenderFlowThread.h"
+#include "wtf/HashMap.h"
 
 namespace blink {
 
 class RenderMultiColumnSet;
+class RenderMultiColumnSpannerPlaceholder;
 
 // Flow thread implementation for CSS multicol. This will be inserted as an anonymous child block of
 // the actual multicol container (i.e. the RenderBlockFlow whose style computes to non-auto
@@ -51,17 +53,26 @@ class RenderMultiColumnSet;
 // container. It's the RenderMultiColumnSet objects that take up the necessary amount of space, and
 // make sure that the columns are painted and hit-tested correctly.
 //
+// Column spanner (column-span:all) renderers also become siblings of the column sets, even if they
+// occur elsewhere in the DOM tree. A RenderMultiColumnSpannerPlaceholder is created and inserted at
+// the position in the render tree where the spanner naturally occurs. The spanner itself is
+// reparented as a sibling of the column sets. The containing block of a spanner is the multicol
+// container, not its parent block. None of the DOM ancestors between the spanner and the multicol
+// container should affect rendering of the spanner in any way.
+//
 // The width of the flow thread is the same as the column width. The width of a column set is the
 // same as the content box width of the multicol container; in other words exactly enough to hold
 // the number of columns to be used, stacked horizontally, plus column gaps between them.
 //
 // Since it's the first child of the multicol container, the flow thread is laid out first, albeit
 // in a slightly special way, since it's not to take up any space in its ancestors. Afterwards, the
-// column sets are laid out. They get their height from the columns that they hold. In single
-// column-row constrained height non-balancing cases this will simply be the same as the content
-// height of the multicol container itself. In most other cases we'll have to calculate optimal
-// column heights ourselves, though. This process is referred to as column balancing, and then we
-// infer the column set height from the flow thread's height.
+// column sets and spanners are laid out. Column sets get their height from the columns that they
+// hold. In single column-row constrained height non-balancing cases without spanners this will
+// simply be the same as the content height of the multicol container itself. In most other cases
+// we'll have to calculate optimal column heights ourselves, though. This process is referred to as
+// column balancing, and then we infer the column set height from the height of the flow thread
+// portion occupied by each set. Column spanners are just laid out as normal blocks within the
+// multicol container, and get their size and position via the regular layout machinery.
 //
 // More on column balancing: the columns' height is unknown in the first layout pass when
 // balancing. This means that we cannot insert any implicit (soft / unforced) breaks (and pagination
@@ -96,8 +107,14 @@ public:
 
     RenderMultiColumnSet* firstMultiColumnSet() const;
     RenderMultiColumnSet* lastMultiColumnSet() const;
+    RenderBox* firstColumnSetOrSpanner() const;
+    static RenderBox* nextColumnSetOrSpannerSiblingOf(const RenderBox*);
+    static RenderBox* previousColumnSetOrSpannerSiblingOf(const RenderBox*);
+
+    RenderMultiColumnSpannerPlaceholder* findColumnSpannerPlaceholder(RenderBox* spanner) const { return m_spannerMap.get(spanner); }
 
-    virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0) OVERRIDE;
+    // Find the set inside which the specified renderer would be rendered.
+    RenderMultiColumnSet* findSetRendering(RenderObject*) const;
 
     // Populate the flow thread with what's currently its siblings. Called when a regular block
     // becomes a multicol container.
@@ -111,7 +128,6 @@ public:
     unsigned columnCount() const { return m_columnCount; }
     LayoutUnit columnHeightAvailable() const { return m_columnHeightAvailable; }
     void setColumnHeightAvailable(LayoutUnit available) { m_columnHeightAvailable = available; }
-    virtual bool heightIsAuto() const { return !columnHeightAvailable() || multiColumnBlockFlow()->style()->columnFill() == ColumnFillBalance; }
     bool progressionIsInline() const { return m_progressionIsInline; }
 
     virtual LayoutSize columnOffset(const LayoutPoint&) const OVERRIDE FINAL;
@@ -123,6 +139,8 @@ public:
 
     bool recalculateColumnHeights();
 
+    void advanceToNextColumnSet(RenderMultiColumnSpannerPlaceholder*);
+
 protected:
     RenderMultiColumnFlowThread();
     void setProgressionIsInline(bool isInline) { m_progressionIsInline = isInline; }
@@ -131,10 +149,14 @@ protected:
 
 private:
     void calculateColumnCountAndWidth(LayoutUnit& width, unsigned& count) const;
+    virtual bool isDescendantValidColumnSpanner(RenderObject* descendant) const;
 
     virtual const char* renderName() const OVERRIDE;
     virtual void addRegionToThread(RenderMultiColumnSet*) OVERRIDE;
     virtual void willBeRemovedFromTree() OVERRIDE;
+    virtual RenderObject* resolveMovedChild(RenderObject* child) const OVERRIDE;
+    virtual void flowThreadDescendantInserted(RenderObject*) OVERRIDE;
+    virtual void flowThreadRelativeWillBeRemoved(RenderObject*) OVERRIDE;

[Julien - ping for review, 2014/09/03 23:22:23]

Relative seems too ambiguous to me (there is a relationships between every node
in the tree as they share the same ancestor).

[mstensho (USE GERRIT), 2014/09/04 12:14:02]

Done.

     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const OVERRIDE;
     virtual void updateLogicalWidth() OVERRIDE;
     virtual void setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage) OVERRIDE;
@@ -143,11 +165,21 @@ private:
     virtual bool addForcedRegionBreak(LayoutUnit, RenderObject* breakChild, bool isBefore, LayoutUnit* offsetBreakAdjustment = 0) OVERRIDE;
     virtual bool isPageLogicalHeightKnown() const OVERRIDE;
 
+    typedef HashMap<RenderBox*, RenderMultiColumnSpannerPlaceholder*> SpannerMap;
+    SpannerMap m_spannerMap;
+
+    // The last set we worked on. It's not to be used as the "current set". The concept of a
+    // "current set" is difficult, since layout may jump back and forth in the tree, due to wrong
+    // top location estimates (due to e.g. margin collapsing), and possibly for other reasons.
+    RenderMultiColumnSet* m_lastSetWorkedOn;

[Julien - ping for review, 2014/09/03 23:22:23]

Wouldn't this be better passed in as a parameter?

[mstensho (USE GERRIT), 2014/09/04 12:14:02]

It's used in RenderMultiColumnFlowThread::columnSetAtBlockOffset() which may be
called from pretty much anywhere, so RenderMultiColumnFlowThread seems like the
best place to store it.

+
     unsigned m_columnCount; // The used value of column-count
     LayoutUnit m_columnHeightAvailable; // Total height available to columns, or 0 if auto.
+    bool m_inLayout; // Set while we're laying out the flow thread, during which colum set heights are unknown.

[Julien - ping for review, 2014/09/03 23:22:23]

Maybe it would be better to call this m_ColumnSetHeightIsUnknown? While
m_isInLayout is OK (notice the 'is'), it seems very generic IMO.

[mstensho (USE GERRIT), 2014/09/04 12:14:02]

Done.

     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.
+    bool m_beingEvacuated;
 };
 
 } // namespace blink