Add support for reading the dst pixel value in an effect. Use in a new effect for the kDarken xfer …

src/gpu/gl/GrGLShaderBuilder.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 GrGLShaderBuilder_DEFINED
 #define GrGLShaderBuilder_DEFINED
 
 #include "GrAllocator.h"
 #include "GrBackendEffectFactory.h"
 #include "GrColor.h"
 #include "GrEffect.h"
 #include "gl/GrGLSL.h"
 #include "gl/GrGLUniformManager.h"
 
 #include <stdarg.h>
 
 class GrGLContextInfo;
 class GrEffectStage;
+class GrGLProgramDesc;
 
 /**
   Contains all the incremental state of a shader as it is being built,as well as helpers to
   manipulate that state.
 */
 class GrGLShaderBuilder {
 public:
     /**
      * Passed to GrGLEffects to add texture reads to their shader code.
      */
@@ skipping 16 matching lines @@
             fConfigComponentMask = other.fConfigComponentMask;
             fSamplerUniform = other.fSamplerUniform;
             return *this;
         }
 
         // bitfield of GrColorComponentFlags present in the texture's config.
         uint32_t configComponentMask() const { return fConfigComponentMask; }
 
         const char* swizzle() const { return fSwizzle; }
 
+        bool isInitialized() const { return 0 != fConfigComponentMask; }
+
     private:
         // The idx param is used to ensure multiple samplers within a single effect have unique
         // uniform names. swizzle is a four char max string made up of chars 'r', 'g', 'b', and 'a'.
         void init(GrGLShaderBuilder* builder,
                   uint32_t configComponentMask,
                   const char* swizzle,
                   int idx) {
-            GrAssert(0 == fConfigComponentMask);
+            GrAssert(!this->isInitialized());
+            GrAssert(0 != configComponentMask);
             GrAssert(GrGLUniformManager::kInvalidUniformHandle == fSamplerUniform);
 
             GrAssert(NULL != builder);
             SkString name;
             name.printf("Sampler%d_", idx);
             fSamplerUniform = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
                                                   kSampler2D_GrSLType,
                                                   name.c_str());
             GrAssert(GrGLUniformManager::kInvalidUniformHandle != fSamplerUniform);
 
@@ skipping 17 matching lines @@
     };
 
     typedef SkTArray<TextureSampler> TextureSamplerArray;
 
     enum ShaderType {
         kVertex_ShaderType   = 0x1,
         kGeometry_ShaderType = 0x2,
         kFragment_ShaderType = 0x4,
     };
 
-    GrGLShaderBuilder(const GrGLContextInfo&, GrGLUniformManager&, bool explicitLocalCoords);
+    GrGLShaderBuilder(const GrGLContextInfo&, GrGLUniformManager&, const GrGLProgramDesc&);
 
     /**
      * Called by GrGLEffects to add code to one of the shaders.
      */
     void vsCodeAppendf(const char format[], ...) SK_PRINTF_LIKE(2, 3) {
         va_list args;
         va_start(args, format);
         this->codeAppendf(kVertex_ShaderType, format, args);
         va_end(args);
     }
@@ skipping 51 matching lines @@
                       const GrGLShaderVar* args,
                       const char* body,
                       SkString* outName);
 
     /** Generates a EffectKey for the shader code based on the texture access parameters and the
         capabilities of the GL context.  This is useful for keying the shader programs that may
         have multiple representations, based on the type/format of textures used. */
     static GrBackendEffectFactory::EffectKey KeyForTextureAccess(const GrTextureAccess&,
                                                                  const GrGLCaps&);
 
+    typedef uint8_t DstReadKey;
+
+    /**  Returns a key for adding code to read the copy-of-dst color in service of effects that
+         require reading the dst. It must not return 0 because 0 indicates that there is no dst
+         copy read at all. */
+    static DstReadKey KeyForDstRead(const GrTexture* dstCopy, const GrGLCaps&);
+
     /** If texture swizzling is available using tex parameters then it is preferred over mangling
         the generated shader code. This potentially allows greater reuse of cached shaders. */
     static const GrGLenum* GetTexParamSwizzle(GrPixelConfig config, const GrGLCaps& caps);
 
     /** Add a uniform variable to the current program, that has visibility in one or more shaders.
         visibility is a bitfield of ShaderType values indicating from which shaders the uniform
         should be accessible. At least one bit must be set. Geometry shader uniforms are not
         supported at this time. The actual uniform name will be mangled. If outName is not NULL then
         it will refer to the final uniform name after return. Use the addUniformArray variant to add
         an array of uniforms.
@@ skipping 38 matching lines @@
     /** Returns a vertex attribute that represents the vertex position in the VS. This is the
         pre-matrix position and is commonly used by effects to compute texture coords via a matrix.
       */
     const GrGLShaderVar& positionAttribute() const { return *fPositionVar; }
 
     /** Returns a vertex attribute that represents the local coords in the VS. This may be the same
         as positionAttribute() or it may not be. It depends upon whether the rendering code
         specified explicit local coords or not in the GrDrawState. */
     const GrGLShaderVar& localCoordsAttribute() const { return *fLocalCoordsVar; }
 
+    /** Returns the color of the destination pixel. This may be NULL if no effect advertised
+        that it will read the destination. */
+    const char* dstColor() const;
+
     /**
      * Are explicit local coordinates provided as input to the vertex shader.
      */
     bool hasExplicitLocalCoords() const { return (fLocalCoordsVar != fPositionVar); }
 
     /**
      * Interfaces used by GrGLProgram.
      * TODO: Hide these from the GrEffects using friend or splitting this into two related classes.
      * Also, GrGLProgram's shader string construction should be moved to this class.
      */
 
     /** Called after building is complete to get the final shader string. */
     void getShader(ShaderType, SkString*) const;
 
     void setCurrentStage(int stageIdx) { fCurrentStageIdx = stageIdx; }
     void setNonStage() { fCurrentStageIdx = kNonStageIdx; }
     // TODO: move remainder of shader code generation to this class and call this privately
     // Handles of sampler uniforms generated for the effect are appended to samplerHandles.
     GrGLEffect* createAndEmitGLEffect(
                                 const GrEffectStage& stage,
                                 GrBackendEffectFactory::EffectKey key,
                                 const char* fsInColor, // NULL means no incoming color
                                 const char* fsOutColor,
                                 SkTArray<GrGLUniformManager::UniformHandle, true>* samplerHandles);
+
     GrGLUniformManager::UniformHandle getRTHeightUniform() const { return fRTHeightUniform; }
+    GrGLUniformManager::UniformHandle getDstCopyTopLeftUniform() const {
+        return fDstCopyTopLeftUniform;
+    }
+    GrGLUniformManager::UniformHandle getDstCopyScaleUniform() const {
+        return fDstCopyScaleUniform;
+    }
+    GrGLUniformManager::UniformHandle getDstCopySamplerUniform() const {
+        return fDstCopySampler.fSamplerUniform;
+    }
 
     struct AttributePair {
         void set(int index, const SkString& name) {
             fIndex = index; fName = name;
         }
         int      fIndex;
         SkString fName;
     };
-    const SkSTArray<10, AttributePair, true>& getEffectAttributes() const {
+    const SkTArray<AttributePair, true>& getEffectAttributes() const {
         return fEffectAttributes;
     }
     const SkString* getEffectAttributeName(int attributeIndex) const;
 
     // TODO: Make this do all the compiling, linking, etc.
     void finished(GrGLuint programID);
 
     const GrGLContextInfo& ctxInfo() const { return fCtxInfo; }
 
 private:
@@ skipping 12 matching lines @@
 public:
 
     SkString    fHeader; // VS+FS, GLSL version, etc
     VarArray    fVSAttrs;
     VarArray    fVSOutputs;
     VarArray    fGSInputs;
     VarArray    fGSOutputs;
     VarArray    fFSInputs;
     SkString    fGSHeader; // layout qualifiers specific to GS
     VarArray    fFSOutputs;
-    bool        fUsesGS;
 
 private:
     enum {
         kNonStageIdx = -1,
     };
 
+    // Interpretation of DstReadKey when generating code
+    enum {
+        kNoDstRead_DstReadKey         = 0,
+        kYesDstRead_DstReadKeyBit     = 0x1, // Set if we do a dst-copy-read.
+        kUseAlphaConfig_DstReadKeyBit = 0x2, // Set if dst-copy config is alpha only.
+        kTopLeftOrigin_DstReadKeyBit  = 0x4, // Set if dst-copy origin is top-left.
+    };
+
     const GrGLContextInfo&              fCtxInfo;
     GrGLUniformManager&                 fUniformManager;
     int                                 fCurrentStageIdx;
     SkString                            fFSFunctions;
     SkString                            fFSHeader;
 
+    bool                                fUsesGS;
+
     SkString                            fFSCode;
     SkString                            fVSCode;
     SkString                            fGSCode;
 
     bool                                fSetupFragPosition;
+    TextureSampler                      fDstCopySampler;
+
     GrGLUniformManager::UniformHandle   fRTHeightUniform;
+    GrGLUniformManager::UniformHandle   fDstCopyTopLeftUniform;
+    GrGLUniformManager::UniformHandle   fDstCopyScaleUniform;
 
     SkSTArray<10, AttributePair, true>  fEffectAttributes;
 
     GrGLShaderVar*                      fPositionVar;
     GrGLShaderVar*                      fLocalCoordsVar;
 
 };
 
 #endif