Calculate stage stats in 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
 
 #include "GrDrawState.h"
 #include "GrRODrawState.h"
 
 /**
  * Subclass of GrRODrawState that holds an optimized version of a GrDrawState. Like it's parent
  * it is meant to be an immutable class, and simply adds a few helpful data members not in the
  * base class.
  */
 class GrOptDrawState : public GrRODrawState {
 public:
     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; }
+
 private:
     /**
      * Constructs and optimized drawState out of a GrRODrawState.
      */
     GrOptDrawState(const GrDrawState& drawState, BlendOptFlags blendOptFlags,
                    GrBlendCoeff optSrcCoeff, GrBlendCoeff optDstCoeff);
 
     /**
      * 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
@@ skipping 18 matching lines @@
      * set, then vertex attributes with binding (GrVertexAttribute)i will be removed.
      */
     void removeFixedFunctionVertexAttribs(uint8_t removeVAFlags);
 
     /**
      * Alter the OptDrawState (adjusting stages, vertex attribs, flags, etc.) based on the
      * 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();
+
     // 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;
+
     SkAutoSTArray<4, GrVertexAttrib> fOptVA;
 
     BlendOptFlags   fBlendOptFlags;
 
     friend GrOptDrawState* GrDrawState::createOptState() const;
     typedef GrRODrawState INHERITED;
 };
 
 #endif