GPU Gradients

src/effects/gradients/SkGradientShaderPriv.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkGradientShaderPriv_DEFINED
 #define SkGradientShaderPriv_DEFINED
 
@@ skipping 232 matching lines @@
                      const SkMatrix& matrix,
                      SkShader::TileMode tileMode);
 
     virtual ~GrGradientEffect();
 
     bool useAtlas() const { return SkToBool(-1 != fRow); }
     SkScalar getYCoord() const { return fYCoord; };
     const SkMatrix& getMatrix() const { return fMatrix;}
 
     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
+    
+    enum ColorType{
+        kTwo_ColorType,
+        kThree_ColorType,
+        kTexture_ColorType
+    };
+
+    inline int getNumColors() const { return fNumColors; };

[bsalomon, 2013/08/13 21:07:52]

Do we need fNumColors or can we just store ColorType directly? It seems like the
enum is a bit less misleading... it accurately describes the way color lookup is
implemented while fNumColors is only related to the number of colors (and the t
values...)

+    inline ColorType getColorType() const {
+        if (2 == fNumColors) {return kTwo_ColorType;}
+        else if (3 == fNumColors) {return kThree_ColorType;}
+        else {return kTexture_ColorType;}
+    }
 
 protected:
 
     /** Populates a pair of arrays with colors and stop info to construct a random gradient.
         The function decides whether stop values should be used or not. The return value indicates
         the number of colors, which will be capped by kMaxRandomGradientColors. colors should be
         sized to be at least kMaxRandomGradientColors. stops is a pointer to an array of at least
         size kMaxRandomGradientColors. It may be updated to NULL, indicating that NULL should be
         passed to the gradient factory rather than the array.
     */
     static const int kMaxRandomGradientColors = 4;
     static int RandomGradientParams(SkMWCRandom* r,
                                     SkColor colors[kMaxRandomGradientColors],
                                     SkScalar** stops,
                                     SkShader::TileMode* tm);
 
     virtual bool onIsEqual(const GrEffect& effect) const SK_OVERRIDE;
 
 private:
 
     GrTextureAccess fTextureAccess;
     SkScalar fYCoord;
     GrTextureStripAtlas* fAtlas;
     int fRow;
     SkMatrix fMatrix;
     bool fIsOpaque;
+    int fNumColors;
 
     typedef GrEffect INHERITED;
 
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 // Base class for GL gradient effects
 class GrGLGradientEffect : public GrGLEffect {
 public:
     GrGLGradientEffect(const GrBackendEffectFactory& factory);
     virtual ~GrGLGradientEffect();
 
     virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;
 
 protected:
     /**
      * Subclasses must reserve the lower kMatrixKeyBitCnt of their key for use by
      * GrGLGradientEffect.
      */
     enum {
         kMatrixKeyBitCnt = GrGLEffectMatrix::kKeyBits,
         kMatrixKeyMask = (1 << kMatrixKeyBitCnt) - 1,
+
+        kTwoColorKey = 2 << kMatrixKeyBitCnt,
+        kThreeColorKey = 3 << kMatrixKeyBitCnt,
+        kColorKeyMask = kThreeColorKey

[bsalomon, 2013/08/13 21:07:52]

maybe kTwoColorKey | kThreeColorKey... I realize that's identical currently, but
it seems like better documentation of  the intent of kColorKeyMask.

[dierk, 2013/08/14 21:33:15]

Done.

     };
 
+    inline GrGradientEffect::ColorType getColorType(EffectKey key){

[bsalomon, 2013/08/13 21:07:52]

static?

[dierk, 2013/08/14 21:33:15]

Done.

+        if (kTwoColorKey == (key & kColorKeyMask)) {
+            return GrGradientEffect::kTwo_ColorType;
+        } else if (kThreeColorKey == (key & kColorKeyMask)) {
+            return GrGradientEffect::kThree_ColorType;
+        } else {return GrGradientEffect::kTexture_ColorType;}
+    }
+    
     /**
      * Subclasses must call this. It will return a value restricted to the lower kMatrixKeyBitCnt
      * bits.
      */
-    static EffectKey GenMatrixKey(const GrDrawEffect&);
+    static EffectKey GenBaseGradientKey(const GrDrawEffect&);
 
     /**
      * Inserts code to implement the GrGradientEffect's matrix. This should be called before a
      * subclass emits its own code. The name of the 2D coords is output via fsCoordName and already
      * incorporates any perspective division. The caller can also optionally retrieve the name of
      * the varying inserted in the VS and its type, which may be either vec2f or vec3f depending
      * upon whether the matrix has perspective or not. It is not necessary to mask the key before
      * calling.
      */
     void setupMatrix(GrGLShaderBuilder* builder,
                      EffectKey key,
                      const char** fsCoordName,
                      const char** vsVaryingName = NULL,
                      GrSLType* vsVaryingType = NULL);
 
     // Emits the uniform used as the y-coord to texture samples in derived classes. Subclasses
     // should call this method from their emitCode().
-    void emitYCoordUniform(GrGLShaderBuilder* builder);
+    void emitUniforms(GrGLShaderBuilder* builder, EffectKey key);
 
-    // emit code that gets a fragment's color from an expression for t; for now this always uses the
-    // texture, but for simpler cases we'll be able to lerp. Subclasses should call this method from
-    // their emitCode().
-    void emitColorLookup(GrGLShaderBuilder* builder,
-                         const char* gradientTValue,
-                         const char* outputColor,
-                         const char* inputColor,
-                         const GrGLShaderBuilder::TextureSampler&);
+
+    // emit code that gets a fragment's color from an expression for t; Has branches for 3 separate
+    // control flows inside -- 2 color gradients, 3 color symmetric gradients (both using
+    // native GLSL mix), and 4+ color gradients that use the traditional texture lookup.
+    void emitColor(GrGLShaderBuilder* builder,
+                   const char* gradientTValue,
+                   EffectKey key,
+                   const char* outputColor,
+                   const char* inputColor,
+                   const GrGLShaderBuilder::TextureSamplerArray& samplers);
 
 private:
     static const GrEffect::CoordsType kCoordsType = GrEffect::kLocal_CoordsType;
 
     SkScalar fCachedYCoord;
     GrGLUniformManager::UniformHandle fFSYUni;
+    GrGLUniformManager::UniformHandle fColorStartUni;
+    GrGLUniformManager::UniformHandle fColorMidUni;
+    GrGLUniformManager::UniformHandle fColorEndUni;
     GrGLEffectMatrix fEffectMatrix;
 
     typedef GrGLEffect INHERITED;
 };
 
 #endif
 
 #endif