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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef GrOptDrawState_DEFINED
      9 #define GrOptDrawState_DEFINED
     10 
     11 #include "GrDrawState.h"
     12 #include "GrRODrawState.h"
     13 
     14 /**
     15  * Subclass of GrRODrawState that holds an optimized version of a GrDrawState. Like it's parent
     16  * it is meant to be an immutable class, and simply adds a few helpful data members not in the
     17  * base class.
     18  */
     19 class GrOptDrawState : public GrRODrawState {
     20 public:
     21     bool operator== (const GrOptDrawState& that) const;
     22 
     23     bool inputColorIsUsed() const { return fInputColorIsUsed; }
     24     bool inputCoverageIsUsed() const { return fInputCoverageIsUsed; }
     25 
     26     bool readsDst() const { return fReadsDst; }
     27     bool readsFragPosition() const { return fReadsFragPosition; }
     28     bool requiresLocalCoordAttrib() const { return fRequiresLocalCoordAttrib; }
     29 
     30     ///////////////////////////////////////////////////////////////////////////
     31     /// @name Stage Output Types
     32     ////
     33 
     34     enum PrimaryOutputType {
     35         // Modulate color and coverage, write result as the color output.
     36         kModulate_PrimaryOutputType,
     37         // Combines the coverage, dst, and color as coverage * color + (1 - coverage) * dst. This
     38         // can only be set if fDstReadKey is non-zero.
     39         kCombineWithDst_PrimaryOutputType,
     40 
     41         kPrimaryOutputTypeCnt,
     42     };
     43 
     44     enum SecondaryOutputType {
     45         // There is no secondary output
     46         kNone_SecondaryOutputType,
     47         // Writes coverage as the secondary output. Only set if dual source blending is supported
     48         // and primary output is kModulate.
     49         kCoverage_SecondaryOutputType,
     50         // Writes coverage * (1 - colorA) as the secondary output. Only set if dual source blending
     51         // is supported and primary output is kModulate.
     52         kCoverageISA_SecondaryOutputType,
     53         // Writes coverage * (1 - colorRGBA) as the secondary output. Only set if dual source
     54         // blending is supported and primary output is kModulate.
     55         kCoverageISC_SecondaryOutputType,
     56 
     57         kSecondaryOutputTypeCnt,
     58     };
     59 
     60     PrimaryOutputType getPrimaryOutputType() const { return fPrimaryOutputType; }
     61     SecondaryOutputType getSecondaryOutputType() const { return fSecondaryOutputType; }
     62 
     63     /// @}
     64 
     65 private:
     66     /**
     67      * Constructs and optimized drawState out of a GrRODrawState.
     68      */
     69     GrOptDrawState(const GrDrawState& drawState, BlendOptFlags blendOptFlags,
     70                    GrBlendCoeff optSrcCoeff, GrBlendCoeff optDstCoeff,
     71                    const GrDrawTargetCaps& caps);
     72 
     73     /**
     74      * Loops through all the color stage effects to check if the stage will ignore color input or
     75      * always output a constant color. In the ignore color input case we can ignore all previous
     76      * stages. In the constant color case, we can ignore all previous stages and
     77      * the current one and set the state color to the constant color. Once we determine the so
     78      * called first effective stage, we copy all the effective stages into our optimized
     79      * state.
     80      */
     81     void copyEffectiveColorStages(const GrDrawState& ds);
     82 
     83     /**
     84      * Loops through all the coverage stage effects to check if the stage will ignore color input.
     85      * If a coverage stage will ignore input, then we can ignore all coverage stages before it. We
     86      * loop to determine the first effective coverage stage, and then copy all of our effective
     87      * coverage stages into our optimized state.
     88      */
     89     void copyEffectiveCoverageStages(const GrDrawState& ds);
     90 
     91     /**
     92      * This function takes in a flag and removes the corresponding fixed function vertex attributes.
     93      * The flags are in the same order as GrVertexAttribBinding array. If bit i of removeVAFlags is
     94      * set, then vertex attributes with binding (GrVertexAttribute)i will be removed.
     95      */
     96     void removeFixedFunctionVertexAttribs(uint8_t removeVAFlags);
     97 
     98     /**
     99      * Alter the OptDrawState (adjusting stages, vertex attribs, flags, etc.) based on the
    100      * BlendOptFlags.
    101      */
    102     void adjustFromBlendOpts();
    103 
    104     /**
    105      * Loop over the effect stages to determine various info like what data they will read and what
    106      * shaders they require.
    107      */
    108     void getStageStats();
    109 
    110     /**
    111      * Calculates the primary and secondary output types of the shader. For certain output types
    112      * the function may adjust the blend coefficients. After this function is called the src and dst
    113      * blend coeffs will represent those used by backend API.
    114      */
    115     void setOutputStateInfo(const GrDrawTargetCaps&);
    116 
    117     // These flags are needed to protect the code from creating an unused uniform color/coverage
    118     // which will cause shader compiler errors.
    119     bool            fInputColorIsUsed;
    120     bool            fInputCoverageIsUsed;
    121 
    122     // These flags give aggregated info on the effect stages that are used when building programs.
    123     bool            fReadsDst;
    124     bool            fReadsFragPosition;
    125     bool            fRequiresLocalCoordAttrib;
    126 
    127     SkAutoSTArray<4, GrVertexAttrib> fOptVA;
    128 
    129     BlendOptFlags   fBlendOptFlags;
    130 
    131     // Fragment shader color outputs
    132     PrimaryOutputType  fPrimaryOutputType : 8;
    133     SecondaryOutputType  fSecondaryOutputType : 8;
    134 
    135     friend GrOptDrawState* GrDrawState::createOptState(const GrDrawTargetCaps&) const;
    136     typedef GrRODrawState INHERITED;
    137 };
    138 
    139 #endif
    140