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

src/effects/gradients/SkTwoPointRadialGradient.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 SkTwoPointRadialGradient_DEFINED
  #define SkTwoPointRadialGradient_DEFINED
 
  #include "SkGradientShaderPriv.h"
 
 class SkTwoPointRadialGradient : public SkGradientShaderBase {
 public:
     SkTwoPointRadialGradient(const SkPoint& start, SkScalar startRadius,
                               const SkPoint& end, SkScalar endRadius,
                               const Descriptor&);
 
     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;
 
-    virtual void shadeSpan(int x, int y, SkPMColor* dstCParam,
-                           int count) SK_OVERRIDE;
-    virtual bool setContext(const SkBitmap& device,
-                            const SkPaint& paint,
-                            const SkMatrix& matrix) SK_OVERRIDE;
+
+    virtual size_t contextSize() const SK_OVERRIDE;
+    bool validContext(const SkBitmap&, const SkPaint&, const SkMatrix&) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(const SkBitmap&, const SkPaint&, const SkMatrix&,
+                                             void* storage) const SK_OVERRIDE;
+
+    class TwoPointRadialGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
+    public:
+        TwoPointRadialGradientContext(const SkTwoPointRadialGradient& shader,
+                                      const SkBitmap& device,
+                                      const SkPaint& paint,
+                                      const SkMatrix& matrix);
+        ~TwoPointRadialGradientContext() {}
+
+        virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
+
+        typedef SkGradientShaderBase::GradientShaderBaseContext INHERITED;
+    };
 
     SkScalar getCenterX1() const { return fDiff.length(); }
     SkScalar getStartRadius() const { return fStartRadius; }
     SkScalar getDiffRadius() const { return fDiffRadius; }
 
     SK_DEVELOPER_TO_STRING()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkTwoPointRadialGradient)
 
 protected:
     SkTwoPointRadialGradient(SkReadBuffer& buffer);
     virtual void flatten(SkWriteBuffer& buffer) const SK_OVERRIDE;
 
 private:
     typedef SkGradientShaderBase INHERITED;
     const SkPoint fCenter1;
     const SkPoint fCenter2;
     const SkScalar fRadius1;
     const SkScalar fRadius2;
     SkPoint fDiff;
     SkScalar fStartRadius, fDiffRadius, fSr2D2, fA, fOneOverTwoA;
 
     void init();
 };
 
 #endif