Srcover for sprite blitters.

src/core/SkLinearBitmapPipeline.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLinearBitmapPipeline_DEFINED
 #define SkLinearBitmapPipeline_DEFINED
 
 #include "SkColor.h"
 #include "SkImageInfo.h"
 #include "SkMatrix.h"
 #include "SkShader.h"
 
 class SkEmbeddableLinearPipeline;
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // SkLinearBitmapPipeline - encapsulates all the machinery for doing floating point pixel
 // processing in a linear color space.
 // Note: this class has unusual alignment requirements due to its use of SIMD instructions. The
 // class SkEmbeddableLinearPipeline below manages these requirements.
 class SkLinearBitmapPipeline {
 public:
+    // Constructor to support producing an SkBlitter.
     SkLinearBitmapPipeline(
         const SkMatrix& inverse,
         SkFilterQuality filterQuality,
         SkShader::TileMode xTile, SkShader::TileMode yTile,
         SkColor paintColor,
         const SkPixmap& srcPixmap);
 
+    // Constructor to support producing an SkSpriteBlitter.
+    SkLinearBitmapPipeline(
+        SkPixmap& dstPixmap,
+        const SkPixmap& srcPixmap,
+        SkIPoint leftTop,
+        SkXfermode::Mode xferMode);
+
+    // Constructor to support producing an SkBlitter.
     SkLinearBitmapPipeline(
         const SkLinearBitmapPipeline& pipeline,
         const SkPixmap& srcPixmap,
         SkXfermode::Mode xferMode,
         const SkImageInfo& dstInfo);
 
     static bool ClonePipelineForBlitting(
         SkEmbeddableLinearPipeline* pipelineStorage,
         const SkLinearBitmapPipeline& pipeline,
         SkMatrix::TypeMask matrixMask,
@@ skipping 89 matching lines @@
 private:
     enum {
         kActualSize = sizeof(SkLinearBitmapPipeline),
         kPaddedSize = SkAlignPtr(kActualSize + 12),
     };
     void* fPipelineStorage[kPaddedSize / sizeof(void*)];
     SkLinearBitmapPipeline* fPipeline{nullptr};
 };
 
 #endif  // SkLinearBitmapPipeline_DEFINED