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

include/effects/SkTransparentShader.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 SkTransparentShader_DEFINED
 #define SkTransparentShader_DEFINED
 
 #include "SkShader.h"
 
 class SK_API SkTransparentShader : public SkShader {
 public:
     SkTransparentShader() {}
 
-    virtual uint32_t getFlags() SK_OVERRIDE;
-    virtual bool    setContext(const SkBitmap& device,
-                               const SkPaint& paint,
-                               const SkMatrix& matrix) SK_OVERRIDE;
-    virtual void    shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;
-    virtual void    shadeSpan16(int x, int y, uint16_t span[], int count) SK_OVERRIDE;
+    virtual bool validContext(const SkBitmap& device,
+                              const SkPaint& paint,
+                              const SkMatrix& matrix) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(
+        const SkBitmap& device, const SkPaint& paint,

[scroggo, 2014/03/24 21:24:46]

device should be on the same line, assuming it fits. If you go beyond the length
of one line, the next line should either start lined up with the first
parameter, or use an 8 space indent. See
https://sites.google.com/site/skiadocs/developer-documentation/contributing-c...
(at the bottom).

Some other declarations for createContext need to be fixed similarly.

+        const SkMatrix& matrix, void* storage) const SK_OVERRIDE;
+    virtual size_t contextSize() const SK_OVERRIDE;
+
+    class TransparentShaderContext : public SkShader::Context {
+    public:
+        TransparentShaderContext(const SkTransparentShader& shader, const SkBitmap& device,
+                                 const SkPaint& paint, const SkMatrix& matrix);
+        virtual ~TransparentShaderContext();
+
+        virtual uint32_t getFlags() const SK_OVERRIDE;
+        virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;
+        virtual void shadeSpan16(int x, int y, uint16_t span[], int count) SK_OVERRIDE;
+    private:
+        const SkBitmap* fDevice;
+        uint8_t         fAlpha;
+
+        typedef SkShader::Context INHERITED;
+    };
 
     SK_DEVELOPER_TO_STRING()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkTransparentShader)
 
 private:
-    // these are a cache from the call to setContext()
-    const SkBitmap* fDevice;
-    uint8_t         fAlpha;
 
     SkTransparentShader(SkReadBuffer& buffer) : INHERITED(buffer) {}
 
     typedef SkShader INHERITED;
 };
 
 #endif