Calculate Primary and Secondary output types in the GrOptDrawState

src/gpu/GrOptDrawState.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrOptDrawState_DEFINED
 #define GrOptDrawState_DEFINED
 
@@ skipping 10 matching lines @@
     bool operator== (const GrOptDrawState& that) const;
 
     bool inputColorIsUsed() const { return fInputColorIsUsed; }
     bool inputCoverageIsUsed() const { return fInputCoverageIsUsed; }
 
     bool readsDst() const { return fReadsDst; }
     bool readsFragPosition() const { return fReadsFragPosition; }
     bool requiresVertexShader() const { return fRequiresVertexShader; }
     bool requiresLocalCoordAttrib() const { return fRequiresLocalCoordAttrib; }
 
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Stage Output Types
+    ////
+
+    enum PrimaryOutputType {
+        // Modulate color and coverage, write result as the color output.
+        kModulate_PrimaryOutputType,
+        // Combines the coverage, dst, and color as coverage * color + (1 - coverage) * dst. This
+        // can only be set if fDstReadKey is non-zero.
+        kCombineWithDst_PrimaryOutputType,
+
+        kPrimaryOutputTypeCnt,
+    };
+
+    enum SecondaryOutputType {
+        // There is no secondary output
+        kNone_SecondaryOutputType,
+        // Writes coverage as the secondary output. Only set if dual source blending is supported
+        // and primary output is kModulate.
+        kCoverage_SecondaryOutputType,
+        // Writes coverage * (1 - colorA) as the secondary output. Only set if dual source blending
+        // is supported and primary output is kModulate.
+        kCoverageISA_SecondaryOutputType,
+        // Writes coverage * (1 - colorRGBA) as the secondary output. Only set if dual source
+        // blending is supported and primary output is kModulate.
+        kCoverageISC_SecondaryOutputType,
+
+        kSecondaryOutputTypeCnt,
+    };
+
+    PrimaryOutputType getPrimaryOutputType() const { return fPrimaryOutputType; }
+    SecondaryOutputType getSecondaryOutputType() const { return fSecondaryOutputType; }
+
+    /// @}
+
 private:
     /**
      * Constructs and optimized drawState out of a GrRODrawState.
      */
     GrOptDrawState(const GrDrawState& drawState, BlendOptFlags blendOptFlags,
-                   GrBlendCoeff optSrcCoeff, GrBlendCoeff optDstCoeff);
+                   GrBlendCoeff optSrcCoeff, GrBlendCoeff optDstCoeff,
+                   const GrDrawTargetCaps& caps);
 
     /**
      * Loops through all the color stage effects to check if the stage will ignore color input or
      * always output a constant color. In the ignore color input case we can ignore all previous
      * stages. In the constant color case, we can ignore all previous stages and
      * the current one and set the state color to the constant color. Once we determine the so
      * called first effective stage, we copy all the effective stages into our optimized
      * state.
      */
     void copyEffectiveColorStages(const GrDrawState& ds);
@@ skipping 18 matching lines @@
      * BlendOptFlags.
      */
     void adjustFromBlendOpts();
 
     /**
      * Loop over the effect stages to determine various info like what data they will read and what
      * shaders they require.
      */
     void getStageStats();
 
+    /**
+     * Calculates the primary and secondary output types of the shader. For certain output types
+     * the function may adjust the blend coefficients. After this function is called the src and dst
+     * blend coeffs will represent those used by backend API.
+     */
+    void setOutputStateInfo(const GrDrawTargetCaps&);
+
     // These flags are needed to protect the code from creating an unused uniform color/coverage
     // which will cause shader compiler errors.
     bool            fInputColorIsUsed;
     bool            fInputCoverageIsUsed;
 
     // These flags give aggregated info on the effect stages that are used when building programs.
     bool            fReadsDst;
     bool            fReadsFragPosition;
     bool            fRequiresVertexShader;
     bool            fRequiresLocalCoordAttrib;
 
     SkAutoSTArray<4, GrVertexAttrib> fOptVA;
 
     BlendOptFlags   fBlendOptFlags;
 
-    friend GrOptDrawState* GrDrawState::createOptState() const;
+    // Fragment shader color outputs
+    PrimaryOutputType  fPrimaryOutputType : 8;
+    SecondaryOutputType  fSecondaryOutputType : 8;
+
+    friend GrOptDrawState* GrDrawState::createOptState(const GrDrawTargetCaps&) const;
     typedef GrRODrawState INHERITED;
 };
 
 #endif