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      1 
      2 /*
      3  * Copyright 2011 Google Inc.
      4  *
      5  * Use of this source code is governed by a BSD-style license that can be
      6  * found in the LICENSE file.
      7  */
      8 
      9 
     10 #ifndef GrPaint_DEFINED
     11 #define GrPaint_DEFINED
     12 
     13 #include "GrColor.h"
     14 #include "GrFragmentProcessor.h"
     15 #include "SkBlendMode.h"
     16 #include "SkRefCnt.h"
     17 #include "SkRegion.h"
     18 #include "SkTLazy.h"
     19 
     20 class GrTextureProxy;
     21 class GrXPFactory;
     22 
     23 /**
     24  * The paint describes how color and coverage are computed at each pixel by GrContext draw
     25  * functions and the how color is blended with the destination pixel.
     26  *
     27  * The paint allows installation of custom color and coverage stages. New types of stages are
     28  * created by subclassing GrProcessor.
     29  *
     30  * The primitive color computation starts with the color specified by setColor(). This color is the
     31  * input to the first color stage. Each color stage feeds its output to the next color stage.
     32  *
     33  * Fractional pixel coverage follows a similar flow. The GrGeometryProcessor (specified elsewhere)
     34  * provides the initial coverage which is passed to the first coverage fragment processor, which
     35  * feeds its output to next coverage fragment processor.
     36  *
     37  * setXPFactory is used to control blending between the output color and dest. It also implements
     38  * the application of fractional coverage from the coverage pipeline.
     39  */
     40 class GrPaint {
     41 public:
     42     GrPaint() = default;
     43     ~GrPaint() = default;
     44 
     45     static GrPaint Clone(const GrPaint& src) { return GrPaint(src); }
     46 
     47     /**
     48      * The initial color of the drawn primitive. Defaults to solid white.
     49      */
     50     void setColor4f(const SkPMColor4f& color) { fColor = color; }
     51     const SkPMColor4f& getColor4f() const { return fColor; }
     52 
     53     void setXPFactory(const GrXPFactory* xpFactory) {
     54         fXPFactory = xpFactory;
     55         fTrivial &= !SkToBool(xpFactory);
     56     }
     57 
     58     void setPorterDuffXPFactory(SkBlendMode mode);
     59 
     60     void setCoverageSetOpXPFactory(SkRegion::Op, bool invertCoverage = false);
     61 
     62     /**
     63      * Appends an additional color processor to the color computation.
     64      */
     65     void addColorFragmentProcessor(std::unique_ptr<GrFragmentProcessor> fp) {
     66         SkASSERT(fp);
     67         fColorFragmentProcessors.push_back(std::move(fp));
     68         fTrivial = false;
     69     }
     70 
     71     /**
     72      * Appends an additional coverage processor to the coverage computation.
     73      */
     74     void addCoverageFragmentProcessor(std::unique_ptr<GrFragmentProcessor> fp) {
     75         SkASSERT(fp);
     76         fCoverageFragmentProcessors.push_back(std::move(fp));
     77         fTrivial = false;
     78     }
     79 
     80     /**
     81      * Helpers for adding color or coverage effects that sample a texture. The matrix is applied
     82      * to the src space position to compute texture coordinates.
     83      */
     84     void addColorTextureProcessor(sk_sp<GrTextureProxy>, const SkMatrix&);
     85     void addColorTextureProcessor(sk_sp<GrTextureProxy>, const SkMatrix&, const GrSamplerState&);
     86 
     87     void addCoverageTextureProcessor(sk_sp<GrTextureProxy>, const SkMatrix&);
     88     void addCoverageTextureProcessor(sk_sp<GrTextureProxy>, const SkMatrix&, const GrSamplerState&);
     89 
     90     int numColorFragmentProcessors() const { return fColorFragmentProcessors.count(); }
     91     int numCoverageFragmentProcessors() const { return fCoverageFragmentProcessors.count(); }
     92     int numTotalFragmentProcessors() const { return this->numColorFragmentProcessors() +
     93                                               this->numCoverageFragmentProcessors(); }
     94 
     95     const GrXPFactory* getXPFactory() const { return fXPFactory; }
     96 
     97     GrFragmentProcessor* getColorFragmentProcessor(int i) const {
     98         return fColorFragmentProcessors[i].get();
     99     }
    100     GrFragmentProcessor* getCoverageFragmentProcessor(int i) const {
    101         return fCoverageFragmentProcessors[i].get();
    102     }
    103 
    104     /**
    105      * Returns true if the paint's output color will be constant after blending. If the result is
    106      * true, constantColor will be updated to contain the constant color. Note that we can conflate
    107      * coverage and color, so the actual values written to pixels with partial coverage may still
    108      * not seem constant, even if this function returns true.
    109      */
    110     bool isConstantBlendedColor(SkPMColor4f* constantColor) const;
    111 
    112     /**
    113      * A trivial paint is one that uses src-over and has no fragment processors.
    114      * It may have variable sRGB settings.
    115      **/
    116     bool isTrivial() const { return fTrivial; }
    117 
    118     friend void assert_alive(GrPaint& p) {
    119         SkASSERT(p.fAlive);
    120     }
    121 
    122 private:
    123     // Since paint copying is expensive if there are fragment processors, we require going through
    124     // the Clone() method.
    125     GrPaint(const GrPaint&);
    126     GrPaint& operator=(const GrPaint&) = delete;
    127 
    128     friend class GrProcessorSet;
    129 
    130     const GrXPFactory* fXPFactory = nullptr;
    131     SkSTArray<4, std::unique_ptr<GrFragmentProcessor>> fColorFragmentProcessors;
    132     SkSTArray<2, std::unique_ptr<GrFragmentProcessor>> fCoverageFragmentProcessors;
    133     bool fTrivial = true;
    134     SkPMColor4f fColor = SK_PMColor4fWHITE;
    135     SkDEBUGCODE(bool fAlive = true;)  // Set false after moved from.
    136 };
    137 
    138 #endif
    139