Use variable length key (rather than accumulated matrix) as save layer hoisting key

src/gpu/GrRecordReplaceDraw.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrRecordReplaceDraw_DEFINED
 #define GrRecordReplaceDraw_DEFINED
 
@@ skipping 14 matching lines @@
 
 // GrReplacements collects op ranges that can be replaced with
 // a single drawBitmap call (using a precomputed bitmap).
 class GrReplacements {
 public:
     // All the operations between fStart and fStop (inclusive) will be replaced with
     // a single drawBitmap call using fPos, fImage and fPaint.
     class ReplacementInfo {
     public:
         struct Key {
-            Key(uint32_t pictureID, unsigned int start, const SkMatrix& ctm)
+            Key(uint32_t pictureID, unsigned int start, const int* key, int keySize)
             : fPictureID(pictureID)
             , fStart(start)
-            , fCTM(ctm) {
-                fCTM.getType(); // force initialization of type so hashes match
-
-                // Key needs to be tightly packed.
-                GR_STATIC_ASSERT(sizeof(Key) == sizeof(uint32_t) +      // picture ID
-                                                sizeof(int) +           // start
-                                                9 * sizeof(SkScalar)    // 3x3 from CTM
-                                                +sizeof(uint32_t));     // matrix's type
+            , fKey(key)
+            , fKeySize(keySize) {
             }
 
-            bool operator==(const Key& other) const { 
-                return fPictureID == other.fPictureID &&
-                       fStart == other.fStart &&
-                       fCTM.cheapEqualTo(other.fCTM); // TODO: should be fuzzy
+            bool operator==(const Key& other) const {
+                if (fKeySize != other.fKeySize) {
+                    return false;
+                }
+                return !memcmp(fKey, other.fKey, fKeySize * sizeof(int));
             }
 
             uint32_t     pictureID() const { return fPictureID; }
             unsigned int start() const { return fStart; }
 
+            const int* key() const { return fKey; }
+            int keySize() const { return fKeySize; }
+
         private:
             const uint32_t     fPictureID;
             const unsigned int fStart;
-            const SkMatrix     fCTM;
+            const int*         fKey;
+            const int          fKeySize;
         };
 
         static const Key& GetKey(const ReplacementInfo& layer) { return layer.fKey; }
         static uint32_t Hash(const Key& key) {
-            return SkChecksum::Murmur3(reinterpret_cast<const uint32_t*>(&key), sizeof(Key));
+            return SkChecksum::Murmur3(reinterpret_cast<const uint32_t*>(key.key()), 
+                                       key.keySize()*sizeof(int));
         }
 
-        ReplacementInfo(uint32_t pictureID, unsigned int start, const SkMatrix& ctm)
-            : fKey(pictureID, start, ctm)
+        ReplacementInfo(uint32_t pictureID, unsigned int start, const int* key, int keySize)
+            : fKey(pictureID, start, key, keySize)
             , fImage(NULL)
             , fPaint(NULL) {
         }
         ~ReplacementInfo() { fImage->unref(); SkDELETE(fPaint); }
 
         unsigned int start() const { return fKey.start(); }
 
         const Key       fKey;
         unsigned        fStop;
         SkIPoint        fPos;
         SkImage*        fImage;  // Owns a ref
         const SkPaint*  fPaint;  // Owned by this object
 
         SkIRect         fSrcRect;
     };
 
     ~GrReplacements() { this->freeAll(); }
 
     // Add a new replacement range.
-    ReplacementInfo* newReplacement(uint32_t pictureID, unsigned int start, const SkMatrix& ctm);
+    ReplacementInfo* newReplacement(uint32_t pictureID, unsigned int start, const int* key, int keySize);
 
     // look up a replacement range by its pictureID, start offset and the CTM
     // TODO: also need to add clip to lookup
-    const ReplacementInfo* lookupByStart(uint32_t pictureID, size_t start, 
-                                         const SkMatrix& ctm) const;
+    const ReplacementInfo* lookupByStart(uint32_t pictureID, int start,
+                                         const int* key, int keyBytes) const;
 
 private:
     SkTDynamicHash<ReplacementInfo, ReplacementInfo::Key> fReplacementHash;
 
     void freeAll();
 };
 
 // Draw an SkPicture into an SkCanvas replacing saveLayer/restore blocks with
 // drawBitmap calls.  A convenience wrapper around SkRecords::Draw.
 // It returns the number of saveLayer/restore blocks replaced with drawBitmap calls.
 int GrRecordReplaceDraw(const SkPicture*,
                         SkCanvas*,
                         const GrReplacements*,
                         const SkMatrix& initialMatrix,
                         SkDrawPictureCallback*);
 
 #endif // GrRecordReplaceDraw_DEFINED