Avoid regenerating cached textblobs on integer scrolls

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 105 matching lines @@
             bool fInitialized;
             bool fDrawAsPaths;
         };
 
         struct BigGlyph {
             BigGlyph(const SkPath& path, int vx, int vy) : fPath(path), fVx(vx), fVy(vy) {}
             SkPath fPath;
             int fVx;
             int fVy;
         };
-
+#ifdef SK_DEBUG
+        mutable SkScalar fTotalXError;
+        mutable SkScalar fTotalYError;
+#endif
         SkTArray<BigGlyph> fBigGlyphs;
+        GrColor fColor; // the original color on the paint
         SkMatrix fViewMatrix;
         SkScalar fX;
         SkScalar fY;
         SkPaint::Style fStyle;
         int fRunCount;
         uint32_t fUniqueID;
         GrMemoryPool* fPool;
 
         // all glyph / vertex offsets are into these pools.
         unsigned char* fVertices;
@@ skipping 26 matching lines @@
     typedef BitmapTextBlob::Run Run;
     typedef Run::SubRunInfo PerSubRunInfo;
 
     void appendGlyph(BitmapTextBlob*, int runIndex, GrGlyph::PackedID, int left, int top,
                      GrColor color, GrFontScaler*, const SkIRect& clipRect);
 
     inline void flushRunAsPaths(const SkTextBlob::RunIterator&, const SkPaint&, SkDrawFilter*,
                                 const SkMatrix& viewMatrix, const SkIRect& clipBounds, SkScalar x,
                                 SkScalar y);
     inline void flushRun(GrDrawTarget*, GrPipelineBuilder*, BitmapTextBlob*, int run, GrColor,
-                         uint8_t paintAlpha);
+                         uint8_t paintAlpha, SkScalar transX, SkScalar transY);
     inline void flushBigGlyphs(BitmapTextBlob* cacheBlob, GrRenderTarget* rt,
-                               const GrPaint& grPaint, const GrClip& clip);
+                               const GrPaint& grPaint, const GrClip& clip,
+                               SkScalar transX, SkScalar transY);
 
     // We have to flush SkTextBlobs differently from drawText / drawPosText
     void flush(GrDrawTarget*, const SkTextBlob*, BitmapTextBlob*, GrRenderTarget*, const SkPaint&,
                const GrPaint&, SkDrawFilter*, const GrClip&, const SkMatrix& viewMatrix,
-               const SkIRect& clipBounds, SkScalar x, SkScalar y);
+               const SkIRect& clipBounds, SkScalar x, SkScalar y, SkScalar transX, SkScalar transY);
     void flush(GrDrawTarget*, BitmapTextBlob*, GrRenderTarget*, const SkPaint&,
                const GrPaint&, const GrClip&, const SkMatrix& viewMatrix);
 
     void internalDrawText(BitmapTextBlob*, int runIndex, SkGlyphCache*, const SkPaint&,
                           const SkMatrix& viewMatrix, const char text[], size_t byteLength,
                           SkScalar x, SkScalar y, const SkIRect& clipRect);
     void internalDrawPosText(BitmapTextBlob*, int runIndex, SkGlyphCache*, const SkPaint&,
                              const SkMatrix& viewMatrix,
                              const char text[], size_t byteLength,
                              const SkScalar pos[], int scalarsPerPosition,
                              const SkPoint& offset, const SkIRect& clipRect);
 
     // sets up the descriptor on the blob and returns a detached cache.  Client must attach
     inline SkGlyphCache* setupCache(Run*, const SkPaint&, const SkMatrix& viewMatrix);
-    static inline bool MustRegenerateBlob(const BitmapTextBlob&, const SkPaint&,
+    static inline bool MustRegenerateBlob(SkScalar* outTransX, SkScalar* outTransY,
+                                          const BitmapTextBlob&, const SkPaint&,
                                           const SkMatrix& viewMatrix, SkScalar x, SkScalar y);
     void regenerateTextBlob(BitmapTextBlob* bmp, const SkPaint& skPaint, const SkMatrix& viewMatrix,
                             const SkTextBlob* blob, SkScalar x, SkScalar y,
                             SkDrawFilter* drawFilter, const SkIRect& clipRect);
 
     GrBatchTextStrike* fCurrStrike;
     GrTextBlobCache* fCache;
 
     friend class GrTextBlobCache;
     friend class BitmapTextBatch;
 
     typedef GrTextContext INHERITED;
 };
 
 #endif