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

include/effects/SkTransparentShader.h

Index: include/effects/SkTransparentShader.h
diff --git a/include/effects/SkTransparentShader.h b/include/effects/SkTransparentShader.h
index 2b3f99814aa2139df38d3c9c721f80e33ae1bf34..7c0b0c90d9f1780ec4fa2a7fc4b6f36c507e70c3 100644
--- a/include/effects/SkTransparentShader.h
+++ b/include/effects/SkTransparentShader.h
@@ -14,20 +14,34 @@ 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) {}