Fix supercluster logic.

Source/core/rendering/FastTextAutosizer.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 52 matching lines @@
 
     void record(const RenderBlock*);
     void destroy(const RenderBlock*);
 
     void beginLayout(RenderBlock*);
     void endLayout(RenderBlock*);
 
     void inflateListItem(RenderListItem*, RenderListMarker*);
 
 private:
+    typedef HashSet<const RenderBlock*> BlockSet;
+
+    struct Supercluster {

[pdr., 2014/02/06 22:03:27]

Can you add a comment here describing what superclusters are used for?

[skobes, 2014/02/06 23:55:50]

Done.

+        explicit Supercluster(const BlockSet* roots)
+            : m_roots(roots)
+            , m_multiplier(0)
+            , m_anyClusterHasEnoughText(false)
+        {
+        }
+
+        const BlockSet* const m_roots;
+        float m_multiplier;
+        bool m_anyClusterHasEnoughText;
+    };
+
     struct Cluster {
-        explicit Cluster(const RenderBlock* root, bool autosize, Cluster* parent)
+        explicit Cluster(const RenderBlock* root, bool autosize, Cluster* parent, Supercluster* supercluster = 0)
             : m_root(root)
             , m_deepestBlockContainingAllText(0)
             , m_parent(parent)
             , m_autosize(autosize)
             , m_multiplier(0)
             , m_textLength(-1)
+            , m_supercluster(supercluster)
         {
         }
 
-        const RenderBlock* m_root;
+        const RenderBlock* const m_root;
         // The deepest block containing all text is computed lazily (see:
         // deepestBlockContainingAllText). A value of 0 indicates the value has not been computed yet.
         const RenderBlock* m_deepestBlockContainingAllText;
         Cluster* m_parent;
         bool m_autosize;
         // The multiplier is computed lazily (see: clusterMultiplier) because it must be calculated
         // after the lowest block containing all text has entered layout (the
         // m_blocksThatHaveBegunLayout assertions cover this). Note: the multiplier is still
         // calculated when m_autosize is false because child clusters may depend on this multiplier.
         float m_multiplier;
         // Text length is computed lazily (see: textLength). This is an approximation and characters
         // are assumed to be 1em wide. Negative values indicate the length has not been computed.
         int m_textLength;
+        // A set of blocks that are similar to this block.
+        Supercluster* m_supercluster;
     };
 
     enum TextLeafSearch {
         First,
         Last
     };
 
-    typedef HashSet<const RenderBlock*> BlockSet;
-    typedef HashMap<const RenderBlock*, OwnPtr<Cluster> > ClusterMap;
-    typedef Vector<Cluster*> ClusterStack;
+    typedef HashMap<AtomicString, OwnPtr<Supercluster> > SuperclusterMap;
+    typedef Vector<OwnPtr<Cluster> > ClusterStack;
 
     // Fingerprints are computed during style recalc, for (some subset of)
     // blocks that will become cluster roots.
     class FingerprintMapper {
     public:
         void add(const RenderBlock*, AtomicString);
         void remove(const RenderBlock*);
         AtomicString get(const RenderBlock*);
         BlockSet& getBlocks(AtomicString);
     private:
         typedef HashMap<const RenderBlock*, AtomicString> FingerprintMap;
         typedef HashMap<AtomicString, OwnPtr<BlockSet> > ReverseFingerprintMap;
 
         FingerprintMap m_fingerprints;
         ReverseFingerprintMap m_blocksForFingerprint;
     };
 
     explicit FastTextAutosizer(const Document*);
 
     void inflate(RenderBlock*);
     bool enabled();
     void prepareRenderViewInfo(RenderView*);
     bool isFingerprintingCandidate(const RenderBlock*);
     bool clusterHasEnoughTextToAutosize(Cluster*);
     float textLength(Cluster*);
     AtomicString computeFingerprint(const RenderBlock*);
-    Cluster* maybeGetOrCreateCluster(const RenderBlock*);
-    Cluster* addSupercluster(AtomicString, const RenderBlock*);
+    Cluster* maybeCreateCluster(const RenderBlock*);
+    Supercluster* getSupercluster(const RenderBlock*);
     const RenderBlock* deepestCommonAncestor(BlockSet&);
     float clusterMultiplier(Cluster*);
+    float superclusterMultiplier(Supercluster*);
+    float multiplierFromBlock(const RenderBlock*);
     void applyMultiplier(RenderObject*, float);
     bool mightBeWiderOrNarrowerDescendant(const RenderBlock*);
     bool isWiderDescendant(Cluster*);
     bool isNarrowerDescendant(Cluster*);
 
     Cluster* currentCluster() const;
 
     RenderObject* nextChildSkippingChildrenOfBlocks(const RenderObject*, const RenderObject*);
 
     const RenderBlock* deepestBlockContainingAllText(Cluster*);
     // Returns the first text leaf that is in the current cluster. We attempt to not include text
     // from descendant clusters but because descendant clusters may not exist, this is only an approximation.
     // The TraversalDirection controls whether we return the first or the last text leaf.
     const RenderObject* findTextLeaf(const RenderObject*, size_t&, TextLeafSearch);
 
     const Document* m_document;
     int m_frameWidth; // Frame width in density-independent pixels (DIPs).
     int m_layoutWidth; // Layout width in CSS pixels.
     float m_baseMultiplier; // Includes accessibility font scale factor and device scale adjustment.
 #ifndef NDEBUG
     bool m_renderViewInfoPrepared;
     BlockSet m_blocksThatHaveBegunLayout; // Used to ensure we don't compute properties of a block before beginLayout() is called on it.
 #endif
 
     // Clusters are created and destroyed during layout. The map key is the
     // cluster root. Clusters whose roots share the same fingerprint use the
     // same multiplier.
-    ClusterMap m_clusters;
+    SuperclusterMap m_superclusters;
     ClusterStack m_clusterStack;
     FingerprintMapper m_fingerprintMapper;
 };
 
 } // namespace WebCore
 
 #endif // FastTextAutosizer_h