Add functions for inspecting SkShader.

include/core/SkShader.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 SkShader_DEFINED
 #define SkShader_DEFINED
 
 #include "SkBitmap.h"
 #include "SkFlattenable.h"
 #include "SkMask.h"
 #include "SkMatrix.h"
 #include "SkPaint.h"
 
 class SkPath;
 class SkPicture;
+class SkXfermode;
 class GrContext;
 class GrEffectRef;
 
 /** \class SkShader
  *
  *  Shaders specify the source color(s) for what is being drawn. If a paint
  *  has no shader, then the paint's color is used. If the paint has a
  *  shader, then the shader's color(s) are use instead, but they are
  *  modulated by the paint's alpha. This makes it easy to create a shader
  *  once (e.g. bitmap tiling or gradient) and then change its transparency
@@ skipping 319 matching lines @@
         SkScalar*   fColorOffsets;  //!< The unit offset for color transitions.
         SkPoint     fPoint[2];      //!< Type specific, see above.
         SkScalar    fRadius[2];     //!< Type specific, see above.
         TileMode    fTileMode;      //!< The tile mode used.
         uint32_t    fGradientFlags; //!< see SkGradientShader::Flags
     };
 
     virtual GradientType asAGradient(GradientInfo* info) const;
 
     /**
+     *  If the shader subclass is composed of two shaders, return true, and if rec is not NULL,
+     *  fill it out with info about the shader.

[reed1, 2014/05/13 18:00:24]

? What is the ownership-rule for the returned pointers? 

I presume the answer is that they are bare-pointers, and that if the caller
wants to retain them, he needs to call ref. But no matter what we should
document this (now or in a later CL).

[scroggo, 2014/05/14 13:51:26]

Uploaded https://codereview.chromium.org/288713002

+     */
+
+    struct ComposeRec {
+        const SkShader*     fShaderA;
+        const SkShader*     fShaderB;
+        const SkXfermode*   fMode;
+    };
+
+    virtual bool asACompose(ComposeRec* rec) const { return false; }
+
+
+    /**
      *  If the shader subclass has a GrEffect implementation, this resturns the effect to install.
      *  The incoming color to the effect has r=g=b=a all extracted from the SkPaint's alpha.
      *  The output color should be the computed SkShader premul color modulated by the incoming
      *  color. The GrContext may be used by the effect to create textures. The GPU device does not
      *  call createContext. Instead we pass the SkPaint here in case the shader needs paint info.
      */
     virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint& paint,
                                      const SkMatrix* localMatrixOrNull) const;
 
+#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
+    /**
+     *  If the shader is a custom shader which has data the caller might want, call this function
+     *  to get that data.
+     */
+    virtual bool asACustomShader(void** customData) const { return false; }
+#endif
+
     //////////////////////////////////////////////////////////////////////////
     //  Factory methods for stock shaders
 
     /**
      *  Call this to create a new "empty" shader, that will not draw anything.
      */
     static SkShader* CreateEmptyShader();
 
     /** Call this to create a new shader that will draw with the specified bitmap.
      *
@@ skipping 58 matching lines @@
      */
     virtual Context* onCreateContext(const ContextRec&, void* storage) const;
 
 private:
     SkMatrix fLocalMatrix;
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif