Add support for rotating / scaling / translating gpu cached distance field textblobs

src/gpu/GrAtlasTextContext.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrAtlasTextContext_DEFINED
 #define GrAtlasTextContext_DEFINED
 
@@ skipping 217 matching lines @@
         GrMemoryPool* fPool;
         SkMaskFilter::BlurRec fBlurRec;
         StrokeInfo fStrokeInfo;
         SkTArray<BigGlyph> fBigGlyphs;
         Key fKey;
         SkMatrix fViewMatrix;
 #ifdef SK_DEBUG
         mutable SkScalar fTotalXError;
         mutable SkScalar fTotalYError;
 #endif
+        SkColor fPaintColor;
         SkScalar fX;
         SkScalar fY;
-        SkColor fPaintColor;
+
+        // We can reuse distance field text, but only if the new viewmatrix would not result in
+        // a mip change.  Because there can be multiple runs in a blob, we track the overall
+        // maximum minimum scale, and minimum maximum scale, we can support before we need to regen
+        SkScalar fMaxMinScale;
+        SkScalar fMinMaxScale;
         int fRunCount;
         uint8_t fTextType;
 
-        BitmapTextBlob() : fTextType(0) {}
+        BitmapTextBlob()
+            : fMaxMinScale(SK_ScalarMax)
+            , fMinMaxScale(SK_ScalarMax)
+            , fTextType(0) {}
 
         static const Key& GetKey(const BitmapTextBlob& blob) {
             return blob.fKey;
         }
 
         static uint32_t Hash(const Key& key) {
             return SkChecksum::Murmur3(&key, sizeof(Key));
         }
 
         void operator delete(void* p) {
@@ skipping 95 matching lines @@
     static inline bool MustRegenerateBlob(SkScalar* outTransX, SkScalar* outTransY,
                                           const BitmapTextBlob&, const SkPaint&,
                                           const SkMaskFilter::BlurRec&,
                                           const SkMatrix& viewMatrix, SkScalar x, SkScalar y);
     void regenerateTextBlob(BitmapTextBlob* bmp, const SkPaint& skPaint, GrColor,
                             const SkMatrix& viewMatrix,
                             const SkTextBlob* blob, SkScalar x, SkScalar y,
                             SkDrawFilter* drawFilter, const SkIRect& clipRect, GrRenderTarget*,
                             const GrClip&, const GrPaint&);
     inline static bool HasLCD(const SkTextBlob*);
-    inline void initDistanceFieldPaint(SkPaint*, SkScalar* textRatio, const SkMatrix&);
+    inline void initDistanceFieldPaint(BitmapTextBlob*, SkPaint*, SkScalar* textRatio,
+                                       const SkMatrix&);
 
     // Distance field text needs this table to compute a value for use in the fragment shader.
     // Because the GrAtlasTextContext can go out of scope before the final flush, this needs to be
     // refcnted and malloced
     struct DistanceAdjustTable : public SkNVRefCnt<DistanceAdjustTable> {
         DistanceAdjustTable(float gamma) { this->buildDistanceAdjustTable(gamma); }
         ~DistanceAdjustTable() { SkDELETE_ARRAY(fTable); }
 
         void buildDistanceAdjustTable(float gamma);
 
@@ skipping 13 matching lines @@
     bool fEnableDFRendering;
     SkAutoTUnref<DistanceAdjustTable> fDistanceAdjustTable;
 
     friend class GrTextBlobCache;
     friend class BitmapTextBatch;
 
     typedef GrTextContext INHERITED;
 };
 
 #endif