Introduction of set of functions to manage generation of texture fetch shader code.

A new set of routines have been added to GrGLShaderBuilder to emit texture fetches, taking into consideration the format of the texture to be accessed, and the channel swizzle.  
Review URL: https://codereview.appspot.com/6446072

git-svn-id: http://skia.googlecode.com/svn/trunk@4919 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 45 insertions, 11 deletions

diff --git a/include/gpu/GrCustomStage.h b/include/gpu/GrCustomStage.h
index 906076656a..a13ecd469e 100644
--- a/include/gpu/GrCustomStage.h
+++ b/include/gpu/GrCustomStage.h
@@ -14,6 +14,27 @@
 
 class GrContext;
 class GrTexture;
+class SkString;
+
+/** A class representing the swizzle access pattern for a texture.
+ */
+class GrTextureAccess {
+public:
+    typedef char Swizzle[4];
+
+    GrTextureAccess(const GrTexture* texture, const SkString& swizzle);
+
+    const GrTexture* getTexture() const { return fTexture; }
+    const Swizzle& getSwizzle() const { return fSwizzle; }
+
+    bool referencesAlpha() const {
+        return fSwizzle[0] == 'a' || fSwizzle[1] == 'a' || fSwizzle[2] == 'a' || fSwizzle[3] == 'a';
+    }
+
+private:
+    const GrTexture* fTexture;
+    Swizzle fSwizzle;
+};
 
 /** Provides custom vertex shader, fragment shader, uniform data for a
     particular stage of the Ganesh shading pipeline. 
@@ -74,13 +95,17 @@ public:
      */
     virtual bool isEqual(const GrCustomStage&) const;
 
-     /** Human-meaningful string to identify this effect; may be embedded
-         in generated shader code. */
+    /** Human-meaningful string to identify this effect; may be embedded
+        in generated shader code. */
     const char* name() const { return this->getFactory().name(); }
 
     virtual unsigned int numTextures() const;
     virtual GrTexture* texture(unsigned int index) const;
 
+    /** Returns the access pattern for the texture at index.  Returns NULL if index is
+        unused. */
+    virtual const GrTextureAccess* textureAccess(unsigned int index) const;
+
     void* operator new(size_t size);
     void operator delete(void* target);
 
diff --git a/include/gpu/GrProgramStageFactory.h b/include/gpu/GrProgramStageFactory.h
index f2b4f5fc90..90f6b32851 100644
--- a/include/gpu/GrProgramStageFactory.h
+++ b/include/gpu/GrProgramStageFactory.h
@@ -19,15 +19,18 @@
 
 class GrCustomStage;
 class GrGLProgramStage;
+class GrGLCaps;
 
 class GrProgramStageFactory : public GrNoncopyable {
 public:
-    typedef uint16_t StageKey;
+    typedef uint32_t StageKey;
     enum {
         kProgramStageKeyBits = 10,
+        kTexturingStageKeyBits = 6
     };
 
-    virtual StageKey glStageKey(const GrCustomStage& stage) const = 0;
+    virtual StageKey glStageKey(const GrCustomStage& stage,
+                                const GrGLCaps& caps ) const = 0;
     virtual GrGLProgramStage* createGLInstance(
         const GrCustomStage& stage) const = 0;
 
@@ -68,7 +71,7 @@ template <typename StageClass>
 class GrTProgramStageFactory : public GrProgramStageFactory {
 
 public:
-    typedef typename StageClass::GLProgramStage GLProgramStage; 
+    typedef typename StageClass::GLProgramStage GLProgramStage;
 
     /** Returns a human-readable name that is accessible via GrCustomStage or
         GrGLProgramStage and is consistent between the two of them.
@@ -80,20 +83,26 @@ public:
         id identifies the GrCustomShader subclass. The remainder is based
         on the aspects of the GrCustomStage object's configuration that affect
         GLSL code generation. */
-    virtual StageKey glStageKey(const GrCustomStage& stage) const SK_OVERRIDE {
+    virtual StageKey glStageKey(const GrCustomStage& stage,
+                                const GrGLCaps& caps) const SK_OVERRIDE {
         GrAssert(kIllegalStageClassID != fStageClassID);
-        StageKey stageID = GLProgramStage::GenKey(stage);
+        StageKey stageID = GLProgramStage::GenKey(stage, caps);
+        StageKey textureKey = GLProgramStage::GenTextureKey(stage, caps);
 #if GR_DEBUG
         static const StageKey kIllegalIDMask =
             (uint16_t) (~((1U << kProgramStageKeyBits) - 1));
         GrAssert(!(kIllegalIDMask & stageID));
+
+        static const StageKey kIllegalTextureKeyMask =
+            (uint16_t) (~((1U << kTexturingStageKeyBits) - 1));
+        GrAssert(!(kIllegalTextureKeyMask & textureKey));
 #endif
-        return fStageClassID | stageID;
+        return fStageClassID | (textureKey << kProgramStageKeyBits) | stageID;
     }
 
     /** Returns a new instance of the appropriate *GL* implementation class
-     for the given GrCustomStage; caller is responsible for deleting
-     the object. */
+        for the given GrCustomStage; caller is responsible for deleting
+        the object. */
     virtual GLProgramStage* createGLInstance(
                         const GrCustomStage& stage) const SK_OVERRIDE {
         return SkNEW_ARGS(GLProgramStage, (*this, stage));
@@ -113,7 +122,7 @@ public:
 
 protected:
     GrTProgramStageFactory() {
-        fStageClassID = GenID() << kProgramStageKeyBits;
+        fStageClassID = GenID() << (kProgramStageKeyBits + kTexturingStageKeyBits) ;
     }
 };