2 files changed, 51 insertions, 12 deletions

diff --git a/include/gpu/GrTextureAccess.h b/include/gpu/GrTextureAccess.h
index 124a75aabc..e3ded34ff8 100644
--- a/include/gpu/GrTextureAccess.h
+++ b/include/gpu/GrTextureAccess.h
@@ -14,33 +14,60 @@
 #include "SkRefCnt.h"
 #include "SkShader.h"
 
-/** 
- * Used to represent a texture that is required by a GrProcessor. It holds a GrTexture along with
- * an associated GrTextureParams
+/** A class representing the swizzle access pattern for a texture. Note that if the texture is
+ *  an alpha-only texture then the alpha channel is substituted for other components. Any mangling
+ *  to handle the r,g,b->a conversions for alpha textures is automatically included in the stage
+ *  key. However, if a GrProcessor uses different swizzles based on its input then it must
+ *  consider that variation in its key-generation.
  */
 class GrTextureAccess : public SkNoncopyable {
 public:
     /**
-     * Must be initialized before adding to a GrProcessor's texture access list.
+     * A default GrTextureAccess must have reset() called on it in a GrProcessor subclass's
+     * constructor if it will be accessible via GrProcessor::textureAccess().
      */
     GrTextureAccess();
 
+    /**
+     * Uses the default swizzle, "rgba".
+     */
     GrTextureAccess(GrTexture*, const GrTextureParams&);
-
     explicit GrTextureAccess(GrTexture*,
                              GrTextureParams::FilterMode = GrTextureParams::kNone_FilterMode,
                              SkShader::TileMode tileXAndY = SkShader::kClamp_TileMode);
 
+    /**
+     * swizzle must be a string between one and four (inclusive) characters containing only 'r',
+     * 'g', 'b',  and/or 'a'.
+     */
+    GrTextureAccess(GrTexture*, const char* swizzle, const GrTextureParams&);
+    GrTextureAccess(GrTexture*,
+                    const char* swizzle,
+                    GrTextureParams::FilterMode = GrTextureParams::kNone_FilterMode,
+                    SkShader::TileMode tileXAndY = SkShader::kClamp_TileMode);
+
     void reset(GrTexture*, const GrTextureParams&);
     void reset(GrTexture*,
                GrTextureParams::FilterMode = GrTextureParams::kNone_FilterMode,
                SkShader::TileMode tileXAndY = SkShader::kClamp_TileMode);
+    void reset(GrTexture*, const char* swizzle, const GrTextureParams&);
+    void reset(GrTexture*,
+               const char* swizzle,
+               GrTextureParams::FilterMode = GrTextureParams::kNone_FilterMode,
+               SkShader::TileMode tileXAndY = SkShader::kClamp_TileMode);
 
-    bool operator==(const GrTextureAccess& that) const {
-        return this->getTexture() == that.getTexture() && fParams == that.fParams;
+    bool operator== (const GrTextureAccess& other) const {
+#ifdef SK_DEBUG
+        // below assumes all chars in fSwizzle are initialized even if string is < 4 chars long.
+        SkASSERT(memcmp(fSwizzle, other.fSwizzle, sizeof(fSwizzle)-1) ==
+                 strcmp(fSwizzle, other.fSwizzle));
+#endif
+        return fParams == other.fParams &&
+               (this->getTexture() == other.getTexture()) &&
+               (0 == memcmp(fSwizzle, other.fSwizzle, sizeof(fSwizzle)-1));
     }
 
-    bool operator!=(const GrTextureAccess& other) const { return !(*this == other); }
+    bool operator!= (const GrTextureAccess& other) const { return !(*this == other); }
 
     GrTexture* getTexture() const { return fTexture.get(); }
 
@@ -49,14 +76,26 @@ public:
      */
     const GrGpuResourceRef* getProgramTexture() const { return &fTexture; }
 
+    /**
+     * Returns a string representing the swizzle. The string is is null-terminated.
+     */
+    const char* getSwizzle() const { return fSwizzle; }
+
+    /** Returns a mask indicating which components are referenced in the swizzle. The return
+        is a bitfield of GrColorComponentFlags. */
+    uint32_t swizzleMask() const { return fSwizzleMask; }
+
     const GrTextureParams& getParams() const { return fParams; }
 
 private:
+    void setSwizzle(const char*);
 
     typedef GrTGpuResourceRef<GrTexture> ProgramTexture;
 
     ProgramTexture                  fTexture;
     GrTextureParams                 fParams;
+    uint32_t                        fSwizzleMask;
+    char                            fSwizzle[5];
 
     typedef SkNoncopyable INHERITED;
 };
diff --git a/include/gpu/GrTypesPriv.h b/include/gpu/GrTypesPriv.h
index 491b23b37b..16e2b0bc56 100644
--- a/include/gpu/GrTypesPriv.h
+++ b/include/gpu/GrTypesPriv.h
@@ -12,10 +12,10 @@
 #include "SkTArray.h"
 #include "SkRect.h"
 
- /**
-  * Types of shader-language-specific boxed variables we can create. (Currently only GrGLShaderVars,
-  * but should be applicable to other shader languages.)
-  */
+/**
+ * Types of shader-language-specific boxed variables we can create. (Currently only GrGLShaderVars,
+ * but should be applicable to other shader languages.)
+ */
 enum GrSLType {
     kVoid_GrSLType,
     kFloat_GrSLType,