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 "include/core/SkBlendMode.h"
14 #include "include/core/SkRefCnt.h"
15 #include "include/core/SkRegion.h"
16 #include "src/core/SkTLazy.h"
17 #include "src/gpu/GrColor.h"
18 #include "src/gpu/GrFragmentProcessor.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 
Clone(const GrPaint & src)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      */
setColor4f(const SkPMColor4f & color)50     void setColor4f(const SkPMColor4f& color) { fColor = color; }
getColor4f()51     const SkPMColor4f& getColor4f() const { return fColor; }
52 
setXPFactory(const GrXPFactory * xpFactory)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      */
addColorFragmentProcessor(std::unique_ptr<GrFragmentProcessor> fp)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      */
addCoverageFragmentProcessor(std::unique_ptr<GrFragmentProcessor> fp)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>, GrColorType srcColorType, const SkMatrix&);
85     void addColorTextureProcessor(sk_sp<GrTextureProxy>, GrColorType srcColorType, const SkMatrix&,
86                                   const GrSamplerState&);
87 
numColorFragmentProcessors()88     int numColorFragmentProcessors() const { return fColorFragmentProcessors.count(); }
numCoverageFragmentProcessors()89     int numCoverageFragmentProcessors() const { return fCoverageFragmentProcessors.count(); }
numTotalFragmentProcessors()90     int numTotalFragmentProcessors() const { return this->numColorFragmentProcessors() +
91                                               this->numCoverageFragmentProcessors(); }
92 
getXPFactory()93     const GrXPFactory* getXPFactory() const { return fXPFactory; }
94 
getColorFragmentProcessor(int i)95     GrFragmentProcessor* getColorFragmentProcessor(int i) const {
96         return fColorFragmentProcessors[i].get();
97     }
getCoverageFragmentProcessor(int i)98     GrFragmentProcessor* getCoverageFragmentProcessor(int i) const {
99         return fCoverageFragmentProcessors[i].get();
100     }
101 
102     /**
103      * Returns true if the paint's output color will be constant after blending. If the result is
104      * true, constantColor will be updated to contain the constant color. Note that we can conflate
105      * coverage and color, so the actual values written to pixels with partial coverage may still
106      * not seem constant, even if this function returns true.
107      */
108     bool isConstantBlendedColor(SkPMColor4f* constantColor) const;
109 
110     /**
111      * A trivial paint is one that uses src-over and has no fragment processors.
112      * It may have variable sRGB settings.
113      **/
isTrivial()114     bool isTrivial() const { return fTrivial; }
115 
assert_alive(GrPaint & p)116     friend void assert_alive(GrPaint& p) {
117         SkASSERT(p.fAlive);
118     }
119 
120 private:
121     // Since paint copying is expensive if there are fragment processors, we require going through
122     // the Clone() method.
123     GrPaint(const GrPaint&);
124     GrPaint& operator=(const GrPaint&) = delete;
125 
126     friend class GrProcessorSet;
127 
128     const GrXPFactory* fXPFactory = nullptr;
129     SkSTArray<4, std::unique_ptr<GrFragmentProcessor>> fColorFragmentProcessors;
130     SkSTArray<2, std::unique_ptr<GrFragmentProcessor>> fCoverageFragmentProcessors;
131     bool fTrivial = true;
132     SkPMColor4f fColor = SK_PMColor4fWHITE;
133     SkDEBUGCODE(bool fAlive = true;)  // Set false after moved from.
134 };
135 
136 #endif
137