Extract most of the mutable state of SkShader into a separate Context object.

src/effects/gradients/SkSweepGradient.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSweepGradient_DEFINED
 #define SkSweepGradient_DEFINED
 
 #include "SkGradientShaderPriv.h"
 
 class SkSweepGradient : public SkGradientShaderBase {
 public:
     SkSweepGradient(SkScalar cx, SkScalar cy, const Descriptor&);
-    virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
-    virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count) SK_OVERRIDE;
+
+    virtual SkShader::Context* createContext(const SkBitmap&, const SkPaint&, const SkMatrix&,
+                                             void* storage) const SK_OVERRIDE;
+    virtual size_t contextSize() const SK_OVERRIDE;
+
+    class SweepGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
+    public:
+        SweepGradientContext(const SkSweepGradient& shader, const SkBitmap& device,
+                             const SkPaint& paint, const SkMatrix& matrix);
+        ~SweepGradientContext() {}
+
+        virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
+        virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count) SK_OVERRIDE;
+
+    private:
+        typedef SkGradientShaderBase::GradientShaderBaseContext INHERITED;
+    };
 
     virtual BitmapType asABitmap(SkBitmap* bitmap,
                                  SkMatrix* matrix,
                                  TileMode* xy) const SK_OVERRIDE;
 
     virtual GradientType asAGradient(GradientInfo* info) const SK_OVERRIDE;
 
     virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint&) const SK_OVERRIDE;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkSweepGradient)
 
 protected:
     SkSweepGradient(SkReadBuffer& buffer);
     virtual void flatten(SkWriteBuffer& buffer) const SK_OVERRIDE;
 
 private:
+    const SkPoint fCenter;
+
     typedef SkGradientShaderBase INHERITED;
-    const SkPoint fCenter;
 };
 
 #endif