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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      * Should rendering be gamma-correct, end-to-end. Causes sRGB render targets to behave
     74      * as such (with linear blending), and sRGB inputs to be filtered and decoded correctly.
     75      */
     76     void setGammaCorrect(bool gammaCorrect) {
     77         this->setDisableOutputConversionToSRGB(!gammaCorrect);
     78         this->setAllowSRGBInputs(gammaCorrect);
     79     }
     80 
     81     void setXPFactory(const GrXPFactory* xpFactory) {
     82         fXPFactory = xpFactory;
     83         fTrivial &= !SkToBool(xpFactory);
     84     }
     85 
     86     void setPorterDuffXPFactory(SkBlendMode mode);
     87 
     88     void setCoverageSetOpXPFactory(SkRegion::Op, bool invertCoverage = false);
     89 
     90     /**
     91      * Appends an additional color processor to the color computation.
     92      */
     93     void addColorFragmentProcessor(sk_sp<GrFragmentProcessor> fp) {
     94         SkASSERT(fp);
     95         fColorFragmentProcessors.push_back(std::move(fp));
     96         fTrivial = false;
     97     }
     98 
     99     /**
    100      * Appends an additional coverage processor to the coverage computation.
    101      */
    102     void addCoverageFragmentProcessor(sk_sp<GrFragmentProcessor> fp) {
    103         SkASSERT(fp);
    104         fCoverageFragmentProcessors.push_back(std::move(fp));
    105         fTrivial = false;
    106     }
    107 
    108     /**
    109      * Helpers for adding color or coverage effects that sample a texture. The matrix is applied
    110      * to the src space position to compute texture coordinates.
    111      */
    112     void addColorTextureProcessor(sk_sp<GrTextureProxy>,
    113                                   sk_sp<GrColorSpaceXform>, const SkMatrix&);
    114     void addColorTextureProcessor(sk_sp<GrTextureProxy>,
    115                                   sk_sp<GrColorSpaceXform>, const SkMatrix&,
    116                                   const GrSamplerParams&);
    117 
    118     void addCoverageTextureProcessor(sk_sp<GrTextureProxy>, const SkMatrix&);
    119     void addCoverageTextureProcessor(sk_sp<GrTextureProxy>,
    120                                      const SkMatrix&, const GrSamplerParams&);
    121 
    122     int numColorFragmentProcessors() const { return fColorFragmentProcessors.count(); }
    123     int numCoverageFragmentProcessors() const { return fCoverageFragmentProcessors.count(); }
    124     int numTotalFragmentProcessors() const { return this->numColorFragmentProcessors() +
    125                                               this->numCoverageFragmentProcessors(); }
    126 
    127     const GrXPFactory* getXPFactory() const { return fXPFactory; }
    128 
    129     GrFragmentProcessor* getColorFragmentProcessor(int i) const {
    130         return fColorFragmentProcessors[i].get();
    131     }
    132     GrFragmentProcessor* getCoverageFragmentProcessor(int i) const {
    133         return fCoverageFragmentProcessors[i].get();
    134     }
    135 
    136     /**
    137      * Returns true if the paint's output color will be constant after blending. If the result is
    138      * true, constantColor will be updated to contain the constant color. Note that we can conflate
    139      * coverage and color, so the actual values written to pixels with partial coverage may still
    140      * not seem constant, even if this function returns true.
    141      */
    142     bool isConstantBlendedColor(GrColor* constantColor) const;
    143 
    144     /**
    145      * A trivial paint is one that uses src-over and has no fragment processors.
    146      * It may have variable sRGB settings.
    147      **/
    148     bool isTrivial() const { return fTrivial; }
    149 
    150 private:
    151     template <bool> class MoveOrImpl;
    152 
    153 public:
    154     /**
    155      * A temporary instance of this class can be used to select between moving an existing paint or
    156      * a temporary copy of an existing paint into a call site. MoveOrClone(paint, false) is a rvalue
    157      * reference to paint while MoveOrClone(paint, true) is a rvalue reference to a copy of paint.
    158      */
    159     using MoveOrClone = MoveOrImpl<true>;
    160 
    161     /**
    162      * A temporary instance of this class can be used to select between moving an existing or a
    163      * newly default constructed paint into a call site. MoveOrNew(paint, false) is a rvalue
    164      * reference to paint while MoveOrNew(paint, true) is a rvalue reference to a default paint.
    165      */
    166     using MoveOrNew = MoveOrImpl<false>;
    167 
    168 private:
    169     GrPaint& operator=(const GrPaint&) = delete;
    170 
    171     friend class GrProcessorSet;
    172 
    173     const GrXPFactory* fXPFactory = nullptr;
    174     SkSTArray<4, sk_sp<GrFragmentProcessor>>  fColorFragmentProcessors;
    175     SkSTArray<2, sk_sp<GrFragmentProcessor>>  fCoverageFragmentProcessors;
    176     bool fDisableOutputConversionToSRGB = false;
    177     bool fAllowSRGBInputs = false;
    178     bool fTrivial = true;
    179     GrColor4f fColor = GrColor4f::OpaqueWhite();
    180 };
    181 
    182 /** This is the implementation of MoveOrCopy and MoveOrNew. */
    183 template <bool COPY_IF_NEW>
    184 class GrPaint::MoveOrImpl {
    185 public:
    186     MoveOrImpl(GrPaint& paint, bool newPaint) {
    187         if (newPaint) {
    188             if (COPY_IF_NEW) {
    189                 fStorage.init(paint);
    190             } else {
    191                 fStorage.init();
    192             };
    193             fPaint = fStorage.get();
    194         } else {
    195             fPaint = &paint;
    196         }
    197     }
    198 
    199     operator GrPaint&&() && { return std::move(*fPaint); }
    200     GrPaint& paint() { return *fPaint; }
    201 
    202 private:
    203     SkTLazy<GrPaint> fStorage;
    204     GrPaint* fPaint;
    205 };
    206 
    207 #endif
    208