Add support for printing multicol containers, and enable it.

third_party/WebKit/Source/core/layout/LayoutMultiColumnFlowThread.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 10 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 
 #ifndef LayoutMultiColumnFlowThread_h
 #define LayoutMultiColumnFlowThread_h
 
 #include "core/CoreExport.h"
+#include "core/layout/FragmentationContext.h"
 #include "core/layout/LayoutFlowThread.h"
 
 namespace blink {
 
 class LayoutMultiColumnSet;
 class LayoutMultiColumnSpannerPlaceholder;
 
 // Flow thread implementation for CSS multicol. This will be inserted as an anonymous child block of
 // the actual multicol container (i.e. the LayoutBlockFlow whose style computes to non-auto
 // column-count and/or column-width). LayoutMultiColumnFlowThread is the heart of the multicol
@@ skipping 64 matching lines @@
 // 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.
 //
 // There's also some documentation online:
 // https://sites.google.com/a/chromium.org/dev/developers/design-documents/multi-column-layout
-class CORE_EXPORT LayoutMultiColumnFlowThread : public LayoutFlowThread {
+class CORE_EXPORT LayoutMultiColumnFlowThread : public LayoutFlowThread, public FragmentationContext {
 public:
     ~LayoutMultiColumnFlowThread() override;
 
     static LayoutMultiColumnFlowThread* createAnonymous(Document&, const ComputedStyle& parentStyle);
 
     bool isLayoutMultiColumnFlowThread() const final { return true; }
 
     LayoutBlockFlow* multiColumnBlockFlow() const { return toLayoutBlockFlow(parent()); }
 
     LayoutMultiColumnSet* firstMultiColumnSet() const;
@@ skipping 57 matching lines @@
     void skipColumnSpanner(LayoutBox*, LayoutUnit logicalTopInFlowThread);
 
     bool recalculateColumnHeights();
 
     void columnRuleStyleDidChange();
 
     // Remove the spanner placeholder and return true if the specified object is no longer a valid spanner.
     bool removeSpannerPlaceholderIfNoLongerValid(LayoutBox* spannerObjectInFlowThread);
 
     LayoutMultiColumnFlowThread* enclosingFlowThread() const;
-    LayoutUnit blockOffsetInEnclosingFlowThread() const { ASSERT(enclosingFlowThread()); return m_blockOffsetInEnclosingFlowThread; }
+    FragmentationContext* enclosingFragmentationContext() const;
+    LayoutUnit blockOffsetInEnclosingFragmentationContext() const { ASSERT(enclosingFragmentationContext()); return m_blockOffsetInEnclosingFragmentationContext; }
 
     // If we've run out of columns in the last fragmentainer group (column row), we have to insert
     // another fragmentainer group in order to hold more columns. This means that we're moving to
     // the next outer column (in the enclosing fragmentation context).
     void appendNewFragmentainerGroupIfNeeded(LayoutUnit offsetInFlowThread);
 
+    // Implementing FragmentationContext:
+    bool isFragmentainerLogicalHeightKnown() final;
+    LayoutUnit fragmentainerLogicalHeightAt(LayoutUnit blockOffset) final;
+    LayoutUnit remainingLogicalHeightAt(LayoutUnit blockOffset) final;
+    LayoutMultiColumnFlowThread* associatedFlowThread() final { return this; }
+
     const char* name() const override { return "LayoutMultiColumnFlowThread"; }
 
 protected:
     LayoutMultiColumnFlowThread();
     void setProgressionIsInline(bool isInline) { m_progressionIsInline = isInline; }
 
     void layout() override;
 
 private:
     void calculateColumnCountAndWidth(LayoutUnit& width, unsigned& count) const;
@@ skipping 14 matching lines @@
     void contentWasLaidOut(LayoutUnit logicalTopInFlowThreadAfterPagination) override;
 
     // 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.
     LayoutMultiColumnSet* m_lastSetWorkedOn;
 
     unsigned m_columnCount; // The used value of column-count
     LayoutUnit m_columnHeightAvailable; // Total height available to columns, or 0 if auto.
 
-    // Cached block offset from this flow thread to the enclosing flow thread, if any. In the
-    // coordinate space of the enclosing flow thread.
-    LayoutUnit m_blockOffsetInEnclosingFlowThread;
+    // Cached block offset from this flow thread to the enclosing fragmentation context, if any. In
+    // the coordinate space of the enclosing fragmentation context.
+    LayoutUnit m_blockOffsetInEnclosingFragmentationContext;
 
     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_isBeingEvacuated;
 };
 
 // Cannot use DEFINE_LAYOUT_OBJECT_TYPE_CASTS here, because isMultiColumnFlowThread() is defined in
 // LayoutFlowThread, not in LayoutObject.
 DEFINE_TYPE_CASTS(LayoutMultiColumnFlowThread, LayoutFlowThread, object, object->isLayoutMultiColumnFlowThread(), object.isLayoutMultiColumnFlowThread());
 
 } // namespace blink
 
 #endif // LayoutMultiColumnFlowThread_h