Buffer four scanlines prior to blitting. We will eventually use this

src/core/SkBlitter.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkBlitter_DEFINED
@@ skipping 15 matching lines @@
 class SkBlitter {
 public:
     virtual ~SkBlitter();
 
     /// Blit a horizontal run of one or more pixels.
     virtual void blitH(int x, int y, int width);
     /// Blit a horizontal run of antialiased pixels; runs[] is a *sparse*
     /// zero-terminated run-length encoding of spans of constant alpha values.
     virtual void blitAntiH(int x, int y, const SkAlpha antialias[],
                            const int16_t runs[]);
+
     /// Blit a vertical run of pixels with a constant alpha value.
     virtual void blitV(int x, int y, int height, SkAlpha alpha);
     /// Blit a solid rectangle one or more pixels wide.
     virtual void blitRect(int x, int y, int width, int height);
     /** Blit a rectangle with one alpha-blended column on the left,
         width (zero or more) opaque pixels, and one alpha-blended column
         on the right.
         The result will always be at least two pixels wide.
     */
     virtual void blitAntiRect(int x, int y, int width, int height,
@@ skipping 14 matching lines @@
      *  returns false.
      */
     virtual bool isNullBlitter() const;
 
     /**
      *  Special methods for SkShaderBlitter. On all other classes this is a no-op.
      */
     virtual bool resetShaderContext(const SkShader::ContextRec&);
     virtual SkShader::Context* getShaderContext() const;
 
+    /**
+     * Special methods for blitters that can blit more than one row at a time.
+     * This function returns the number of rows that this blitter could optimally
+     * process at a time. It is still required to support blitting one scanline
+     * at a time.
+     */
+    virtual int requestRowsPreserved() const { return 1; }
+
     ///@name non-virtual helpers
     void blitMaskRegion(const SkMask& mask, const SkRegion& clip);
     void blitRectRegion(const SkIRect& rect, const SkRegion& clip);
     void blitRegion(const SkRegion& clip);
     ///@}
 
     /** @name Factories
         Return the correct blitter to use given the specified context.
      */
     static SkBlitter* Choose(const SkBitmap& device,
@@ skipping 89 matching lines @@
     SkBlitter*  apply(SkBlitter* blitter, const SkRegion* clip,
                       const SkIRect* bounds = NULL);
 
 private:
     SkNullBlitter       fNullBlitter;
     SkRectClipBlitter   fRectBlitter;
     SkRgnClipBlitter    fRgnBlitter;
 };
 
 #endif