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 GrGLFragmentShaderBuilder_DEFINED
9#define GrGLFragmentShaderBuilder_DEFINED
10
11#include "GrGLShaderBuilder.h"
12
13class GrGLVarying;
14
15/*
16 * This base class encapsulates the functionality which the GP uses to build fragment shaders
17 */
18class GrGLFragmentBuilder : public GrGLShaderBuilder {
19public:
20    GrGLFragmentBuilder(GrGLProgramBuilder* program) : INHERITED(program) {}
21    virtual ~GrGLFragmentBuilder() {}
22    /**
23     * Use of these features may require a GLSL extension to be enabled. Shaders may not compile
24     * if code is added that uses one of these features without calling enableFeature()
25     */
26    enum GLSLFeature {
27        kStandardDerivatives_GLSLFeature = 0,
28        kLastGLSLFeature = kStandardDerivatives_GLSLFeature
29    };
30
31    /**
32     * If the feature is supported then true is returned and any necessary #extension declarations
33     * are added to the shaders. If the feature is not supported then false will be returned.
34     */
35    virtual bool enableFeature(GLSLFeature) = 0;
36
37    /**
38     * This returns a variable name to access the 2D, perspective correct version of the coords in
39     * the fragment shader. If the coordinates at index are 3-dimensional, it immediately emits a
40     * perspective divide into the fragment shader (xy / z) to convert them to 2D.
41     */
42    virtual SkString ensureFSCoords2D(const GrGLProcessor::TransformedCoordsArray& coords,
43                                      int index) = 0;
44
45
46    /** Returns a variable name that represents the position of the fragment in the FS. The position
47        is in device space (e.g. 0,0 is the top left and pixel centers are at half-integers). */
48    virtual const char* fragmentPosition() = 0;
49
50private:
51    friend class GrGLPathProcessor;
52
53    typedef GrGLShaderBuilder INHERITED;
54};
55
56/*
57 * Fragment processor's, in addition to all of the above, may need to use dst color so they use
58 * this builder to create their shader.  Because this is the only shader builder the FP sees, we
59 * just call it FPShaderBuilder
60 */
61class GrGLXPFragmentBuilder : public GrGLFragmentBuilder {
62public:
63    GrGLXPFragmentBuilder(GrGLProgramBuilder* program) : INHERITED(program) {}
64
65    /** Returns the variable name that holds the color of the destination pixel. This may be NULL if
66        no effect advertised that it will read the destination. */
67    virtual const char* dstColor() = 0;
68
69    /** Adds any necessary layout qualifiers in order to legalize the supplied blend equation with
70        this shader. It is only legal to call this method with an advanced blend equation, and only
71        if these equations are supported. */
72    virtual void enableAdvancedBlendEquationIfNeeded(GrBlendEquation) = 0;
73
74private:
75    typedef GrGLFragmentBuilder INHERITED;
76};
77
78// TODO rename to Fragment Builder
79class GrGLFragmentShaderBuilder : public GrGLXPFragmentBuilder {
80public:
81    typedef uint8_t DstReadKey;
82    typedef uint8_t FragPosKey;
83
84    /**  Returns a key for adding code to read the copy-of-dst color in service of effects that
85        require reading the dst. It must not return 0 because 0 indicates that there is no dst
86        copy read at all (in which case this function should not be called). */
87    static DstReadKey KeyForDstRead(const GrTexture* dstCopy, const GrGLCaps&);
88
89    /** Returns a key for reading the fragment location. This should only be called if there is an
90       effect that will requires the fragment position. If the fragment position is not required,
91       the key is 0. */
92    static FragPosKey KeyForFragmentPosition(const GrRenderTarget* dst, const GrGLCaps&);
93
94    GrGLFragmentShaderBuilder(GrGLProgramBuilder* program, uint8_t fragPosKey);
95
96    // true public interface, defined explicitly in the abstract interfaces above
97    bool enableFeature(GLSLFeature) override;
98    virtual SkString ensureFSCoords2D(const GrGLProcessor::TransformedCoordsArray& coords,
99                                      int index) override;
100    const char* fragmentPosition() override;
101    const char* dstColor() override;
102
103    void enableAdvancedBlendEquationIfNeeded(GrBlendEquation) override;
104
105private:
106    // Private public interface, used by GrGLProgramBuilder to build a fragment shader
107    void enableCustomOutput();
108    void enableSecondaryOutput();
109    const char* getPrimaryColorOutputName() const;
110    const char* getSecondaryColorOutputName() const;
111    bool compileAndAttachShaders(GrGLuint programId, SkTDArray<GrGLuint>* shaderIds);
112    void bindFragmentShaderLocations(GrGLuint programID);
113
114    // As GLProcessors emit code, there are some conditions we need to verify.  We use the below
115    // state to track this.  The reset call is called per processor emitted.
116    bool hasReadDstColor() const { return fHasReadDstColor; }
117    bool hasReadFragmentPosition() const { return fHasReadFragmentPosition; }
118    void reset() {
119        fHasReadDstColor = false;
120        fHasReadFragmentPosition = false;
121    }
122
123    /*
124     * An internal call for GrGLProgramBuilder to use to add varyings to the vertex shader
125     */
126    void addVarying(GrGLVarying*, GrSLPrecision);
127
128    /**
129     * Features that should only be enabled by GrGLFragmentShaderBuilder itself.
130     */
131    enum GLSLPrivateFeature {
132        kFragCoordConventions_GLSLPrivateFeature = kLastGLSLFeature + 1,
133        kBlendEquationAdvanced_GLSLPrivateFeature,
134        kLastGLSLPrivateFeature = kBlendEquationAdvanced_GLSLPrivateFeature
135    };
136
137    // Interpretation of DstReadKey when generating code
138    enum {
139        kNoDstRead_DstReadKey           = 0,
140        kYesDstRead_DstReadKeyBit       = 0x1, // Set if we do a dst-copy-read.
141        kUseAlphaConfig_DstReadKeyBit   = 0x2, // Set if dst-copy config is alpha only.
142        kTopLeftOrigin_DstReadKeyBit    = 0x4, // Set if dst-copy origin is top-left.
143    };
144
145    // Interpretation of FragPosKey when generating code
146    enum {
147        kNoFragPosRead_FragPosKey           = 0,  // The fragment positition will not be needed.
148        kTopLeftFragPosRead_FragPosKey      = 0x1,// Read frag pos relative to top-left.
149        kBottomLeftFragPosRead_FragPosKey   = 0x2,// Read frag pos relative to bottom-left.
150    };
151
152    static const char* kDstCopyColorName;
153
154    bool fHasCustomColorOutput;
155    bool fHasSecondaryOutput;
156    bool fSetupFragPosition;
157    bool fTopLeftFragPosRead;
158    int  fCustomColorOutputIndex;
159
160    // some state to verify shaders and effects are consistent, this is reset between effects by
161    // the program creator
162    bool fHasReadDstColor;
163    bool fHasReadFragmentPosition;
164
165    friend class GrGLProgramBuilder;
166
167    typedef GrGLXPFragmentBuilder INHERITED;
168};
169
170#endif
171