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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 "GrColorSpaceXform.h"
     15 #include "GrFragmentProcessor.h"
     16 #include "SkBlendMode.h"
     17 #include "SkRefCnt.h"
     18 #include "SkRegion.h"
     19 #include "SkTLazy.h"
     20 
     21 class GrTextureProxy;
     22 class GrXPFactory;
     23 
     24 /**
     25  * The paint describes how color and coverage are computed at each pixel by GrContext draw
     26  * functions and the how color is blended with the destination pixel.
     27  *
     28  * The paint allows installation of custom color and coverage stages. New types of stages are
     29  * created by subclassing GrProcessor.
     30  *
     31  * The primitive color computation starts with the color specified by setColor(). This color is the
     32  * input to the first color stage. Each color stage feeds its output to the next color stage.
     33  *
     34  * Fractional pixel coverage follows a similar flow. The GrGeometryProcessor (specified elsewhere)
     35  * provides the initial coverage which is passed to the first coverage fragment processor, which
     36  * feeds its output to next coverage fragment processor.
     37  *
     38  * setXPFactory is used to control blending between the output color and dest. It also implements
     39  * the application of fractional coverage from the coverage pipeline.
     40  */
     41 class GrPaint {
     42 public:
     43     GrPaint() = default;
     44     explicit GrPaint(const GrPaint&) = default;
     45     ~GrPaint() = default;
     46 
     47     /**
     48      * The initial color of the drawn primitive. Defaults to solid white.
     49      */
     50     void setColor4f(const GrColor4f& color) { fColor = color; }
     51     const GrColor4f& getColor4f() const { return fColor; }
     52 
     53     /**
     54      * Legacy getter, until all code handles 4f directly.
     55      */
     56     GrColor getColor() const { return fColor.toGrColor(); }
     57 
     58     /**
     59      * Should shader output conversion from linear to sRGB be disabled.
     60      * Only relevant if the destination is sRGB. Defaults to false.
     61      */
     62     void setDisableOutputConversionToSRGB(bool srgb) { fDisableOutputConversionToSRGB = srgb; }
     63     bool getDisableOutputConversionToSRGB() const { return fDisableOutputConversionToSRGB; }
     64 
     65     /**
     66      * Should sRGB inputs be allowed to perform sRGB to linear conversion. With this flag
     67      * set to false, sRGB textures will be treated as linear (including filtering).
     68      */
     69     void setAllowSRGBInputs(bool allowSRGBInputs) { fAllowSRGBInputs = allowSRGBInputs; }
     70     bool getAllowSRGBInputs() const { return fAllowSRGBInputs; }
     71 
     72     /**
     73      * Does one of the fragment processors need a field of distance vectors to the nearest edge?
     74      */
     75     bool usesDistanceVectorField() const { return fUsesDistanceVectorField; }
     76 
     77     /**
     78      * Should rendering be gamma-correct, end-to-end. Causes sRGB render targets to behave
     79      * as such (with linear blending), and sRGB inputs to be filtered and decoded correctly.
     80      */
     81     void setGammaCorrect(bool gammaCorrect) {
     82         setDisableOutputConversionToSRGB(!gammaCorrect);
     83         setAllowSRGBInputs(gammaCorrect);
     84     }
     85 
     86     void setXPFactory(const GrXPFactory* xpFactory) { fXPFactory = xpFactory; }
     87 
     88     void setPorterDuffXPFactory(SkBlendMode mode);
     89 
     90     void setCoverageSetOpXPFactory(SkRegion::Op, bool invertCoverage = false);
     91 
     92     /**
     93      * Appends an additional color processor to the color computation.
     94      */
     95     void addColorFragmentProcessor(sk_sp<GrFragmentProcessor> fp) {
     96         SkASSERT(fp);
     97         fUsesDistanceVectorField |= fp->usesDistanceVectorField();
     98         fColorFragmentProcessors.push_back(std::move(fp));
     99     }
    100 
    101     /**
    102      * Appends an additional coverage processor to the coverage computation.
    103      */
    104     void addCoverageFragmentProcessor(sk_sp<GrFragmentProcessor> fp) {
    105         SkASSERT(fp);
    106         fUsesDistanceVectorField |= fp->usesDistanceVectorField();
    107         fCoverageFragmentProcessors.push_back(std::move(fp));
    108     }
    109 
    110     /**
    111      * Helpers for adding color or coverage effects that sample a texture. The matrix is applied
    112      * to the src space position to compute texture coordinates.
    113      */
    114     void addColorTextureProcessor(GrResourceProvider*, sk_sp<GrTextureProxy>,
    115                                   sk_sp<GrColorSpaceXform>, const SkMatrix&);
    116     void addColorTextureProcessor(GrResourceProvider*, sk_sp<GrTextureProxy>,
    117                                   sk_sp<GrColorSpaceXform>, const SkMatrix&,
    118                                   const GrSamplerParams&);
    119 
    120     void addCoverageTextureProcessor(GrResourceProvider*, sk_sp<GrTextureProxy>, const SkMatrix&);
    121     void addCoverageTextureProcessor(GrResourceProvider*, sk_sp<GrTextureProxy>,
    122                                      const SkMatrix&, const GrSamplerParams&);
    123 
    124     int numColorFragmentProcessors() const { return fColorFragmentProcessors.count(); }
    125     int numCoverageFragmentProcessors() const { return fCoverageFragmentProcessors.count(); }
    126     int numTotalFragmentProcessors() const { return this->numColorFragmentProcessors() +
    127                                               this->numCoverageFragmentProcessors(); }
    128 
    129     const GrXPFactory* getXPFactory() const { return fXPFactory; }
    130 
    131     GrFragmentProcessor* getColorFragmentProcessor(int i) const {
    132         return fColorFragmentProcessors[i].get();
    133     }
    134     GrFragmentProcessor* getCoverageFragmentProcessor(int i) const {
    135         return fCoverageFragmentProcessors[i].get();
    136     }
    137 
    138     /**
    139      * Returns true if the paint's output color will be constant after blending. If the result is
    140      * true, constantColor will be updated to contain the constant color. Note that we can conflate
    141      * coverage and color, so the actual values written to pixels with partial coverage may still
    142      * not seem constant, even if this function returns true.
    143      */
    144     bool isConstantBlendedColor(GrColor* constantColor) const;
    145 
    146 private:
    147     template <bool> class MoveOrImpl;
    148 
    149 public:
    150     /**
    151      * A temporary instance of this class can be used to select between moving an existing paint or
    152      * a temporary copy of an existing paint into a call site. MoveOrClone(paint, false) is a rvalue
    153      * reference to paint while MoveOrClone(paint, true) is a rvalue reference to a copy of paint.
    154      */
    155     using MoveOrClone = MoveOrImpl<true>;
    156 
    157     /**
    158      * A temporary instance of this class can be used to select between moving an existing or a
    159      * newly default constructed paint into a call site. MoveOrNew(paint, false) is a rvalue
    160      * reference to paint while MoveOrNew(paint, true) is a rvalue reference to a default paint.
    161      */
    162     using MoveOrNew = MoveOrImpl<false>;
    163 
    164 private:
    165     GrPaint& operator=(const GrPaint&) = delete;
    166 
    167     friend class GrProcessorSet;
    168 
    169     const GrXPFactory* fXPFactory = nullptr;
    170     SkSTArray<4, sk_sp<GrFragmentProcessor>>  fColorFragmentProcessors;
    171     SkSTArray<2, sk_sp<GrFragmentProcessor>>  fCoverageFragmentProcessors;
    172     bool fDisableOutputConversionToSRGB = false;
    173     bool fAllowSRGBInputs = false;
    174     bool fUsesDistanceVectorField = false;
    175     GrColor4f fColor = GrColor4f::OpaqueWhite();
    176 };
    177 
    178 /** This is the implementation of MoveOrCopy and MoveOrNew. */
    179 template <bool COPY_IF_NEW>
    180 class GrPaint::MoveOrImpl {
    181 public:
    182     MoveOrImpl(GrPaint& paint, bool newPaint) {
    183         if (newPaint) {
    184             if (COPY_IF_NEW) {
    185                 fStorage.init(paint);
    186             } else {
    187                 fStorage.init();
    188             };
    189             fPaint = fStorage.get();
    190         } else {
    191             fPaint = &paint;
    192         }
    193     }
    194 
    195     operator GrPaint&&() && { return std::move(*fPaint); }
    196     GrPaint& paint() { return *fPaint; }
    197 
    198 private:
    199     SkTLazy<GrPaint> fStorage;
    200     GrPaint* fPaint;
    201 };
    202 
    203 #endif
    204