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      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 GrGLSLFragmentShaderBuilder_DEFINED
      9 #define GrGLSLFragmentShaderBuilder_DEFINED
     10 
     11 #include "GrBlend.h"
     12 #include "GrGLSLShaderBuilder.h"
     13 #include "GrProcessor.h"
     14 
     15 class GrRenderTarget;
     16 class GrGLSLVarying;
     17 
     18 /*
     19  * This base class encapsulates the common functionality which all processors use to build fragment
     20  * shaders.
     21  */
     22 class GrGLSLFragmentBuilder : public GrGLSLShaderBuilder {
     23 public:
     24     GrGLSLFragmentBuilder(GrGLSLProgramBuilder* program) : INHERITED(program) {}
     25     virtual ~GrGLSLFragmentBuilder() {}
     26 
     27     /**
     28      * Use of these features may require a GLSL extension to be enabled. Shaders may not compile
     29      * if code is added that uses one of these features without calling enableFeature()
     30      */
     31     enum GLSLFeature {
     32         kMultisampleInterpolation_GLSLFeature
     33     };
     34 
     35     /**
     36      * If the feature is supported then true is returned and any necessary #extension declarations
     37      * are added to the shaders. If the feature is not supported then false will be returned.
     38      */
     39     virtual bool enableFeature(GLSLFeature) = 0;
     40 
     41     /**
     42      * This returns a variable name to access the 2D, perspective correct version of the coords in
     43      * the fragment shader. The passed in coordinates must either be of type kVec2f or kVec3f. If
     44      * the coordinates are 3-dimensional, it a perspective divide into is emitted into the
     45      * fragment shader (xy / z) to convert them to 2D.
     46      */
     47     virtual SkString ensureCoords2D(const GrShaderVar&) = 0;
     48 
     49     // TODO: remove this method.
     50     void declAppendf(const char* fmt, ...);
     51 
     52 private:
     53     typedef GrGLSLShaderBuilder INHERITED;
     54 };
     55 
     56 /*
     57  * This class is used by fragment processors to build their fragment code.
     58  */
     59 class GrGLSLFPFragmentBuilder : virtual public GrGLSLFragmentBuilder {
     60 public:
     61     /** Appease the compiler; the derived class initializes GrGLSLFragmentBuilder. */
     62     GrGLSLFPFragmentBuilder() : GrGLSLFragmentBuilder(nullptr) {}
     63 
     64     enum Coordinates {
     65         kSkiaDevice_Coordinates,
     66         kGLSLWindow_Coordinates,
     67 
     68         kLast_Coordinates = kGLSLWindow_Coordinates
     69     };
     70 
     71     /**
     72      * Appends the offset from the center of the pixel to a specified sample.
     73      *
     74      * @param sampleIdx      GLSL expression of the sample index.
     75      * @param Coordinates    Coordinate space in which to emit the offset.
     76      *
     77      * A processor must call setWillUseSampleLocations in its constructor before using this method.
     78      */
     79     virtual void appendOffsetToSample(const char* sampleIdx, Coordinates) = 0;
     80 
     81     /**
     82      * Subtracts sample coverage from the fragment. Any sample whose corresponding bit is not found
     83      * in the mask will not be written out to the framebuffer.
     84      *
     85      * @param mask      int that contains the sample mask. Bit N corresponds to the Nth sample.
     86      * @param invert    perform a bit-wise NOT on the provided mask before applying it?
     87      *
     88      * Requires GLSL support for sample variables.
     89      */
     90     virtual void maskSampleCoverage(const char* mask, bool invert = false) = 0;
     91 
     92     /**
     93      * Overrides the default precision for the entire fragment program. Processors that require
     94      * high precision input (eg from incoming texture samples) may use this. For calculations that
     95      * are limited to a single processor's code, it is better to annotate individual declarations.
     96      */
     97     virtual void elevateDefaultPrecision(GrSLPrecision) = 0;
     98 
     99     /**
    100      * Fragment procs with child procs should call these functions before/after calling emitCode
    101      * on a child proc.
    102      */
    103     virtual void onBeforeChildProcEmitCode() = 0;
    104     virtual void onAfterChildProcEmitCode() = 0;
    105 
    106     virtual const SkString& getMangleString() const = 0;
    107 };
    108 
    109 /*
    110  * This class is used by primitive processors to build their fragment code.
    111  */
    112 class GrGLSLPPFragmentBuilder : public GrGLSLFPFragmentBuilder {
    113 public:
    114     /** Appease the compiler; the derived class initializes GrGLSLFragmentBuilder. */
    115     GrGLSLPPFragmentBuilder() : GrGLSLFragmentBuilder(nullptr) {}
    116 
    117     /**
    118      * Overrides the fragment's sample coverage. The provided mask determines which samples will now
    119      * be written out to the framebuffer. Note that this mask can be reduced by a future call to
    120      * maskSampleCoverage.
    121      *
    122      * If a primitive processor uses this method, it must guarantee that every codepath through the
    123      * shader overrides the sample mask at some point.
    124      *
    125      * @param mask    int that contains the new coverage mask. Bit N corresponds to the Nth sample.
    126      *
    127      * Requires NV_sample_mask_override_coverage.
    128      */
    129     virtual void overrideSampleCoverage(const char* mask) = 0;
    130 };
    131 
    132 /*
    133  * This class is used by Xfer processors to build their fragment code.
    134  */
    135 class GrGLSLXPFragmentBuilder : virtual public GrGLSLFragmentBuilder {
    136 public:
    137     /** Appease the compiler; the derived class initializes GrGLSLFragmentBuilder. */
    138     GrGLSLXPFragmentBuilder() : GrGLSLFragmentBuilder(nullptr) {}
    139 
    140     virtual bool hasCustomColorOutput() const = 0;
    141     virtual bool hasSecondaryOutput() const = 0;
    142 
    143     /** Returns the variable name that holds the color of the destination pixel. This may be nullptr
    144      * if no effect advertised that it will read the destination. */
    145     virtual const char* dstColor() = 0;
    146 
    147     /** Adds any necessary layout qualifiers in order to legalize the supplied blend equation with
    148         this shader. It is only legal to call this method with an advanced blend equation, and only
    149         if these equations are supported. */
    150     virtual void enableAdvancedBlendEquationIfNeeded(GrBlendEquation) = 0;
    151 };
    152 
    153 /*
    154  * This class implements the various fragment builder interfaces.
    155  */
    156 class GrGLSLFragmentShaderBuilder : public GrGLSLPPFragmentBuilder, public GrGLSLXPFragmentBuilder {
    157 public:
    158    /** Returns a nonzero key for a surface's origin. This should only be called if a processor will
    159        use the fragment position and/or sample locations. */
    160     static uint8_t KeyForSurfaceOrigin(GrSurfaceOrigin);
    161 
    162     GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program);
    163 
    164     // Shared GrGLSLFragmentBuilder interface.
    165     bool enableFeature(GLSLFeature) override;
    166     virtual SkString ensureCoords2D(const GrShaderVar&) override;
    167 
    168     // GrGLSLFPFragmentBuilder interface.
    169     void appendOffsetToSample(const char* sampleIdx, Coordinates) override;
    170     void maskSampleCoverage(const char* mask, bool invert = false) override;
    171     void overrideSampleCoverage(const char* mask) override;
    172     void elevateDefaultPrecision(GrSLPrecision) override;
    173     const SkString& getMangleString() const override { return fMangleString; }
    174     void onBeforeChildProcEmitCode() override;
    175     void onAfterChildProcEmitCode() override;
    176 
    177     // GrGLSLXPFragmentBuilder interface.
    178     bool hasCustomColorOutput() const override { return fHasCustomColorOutput; }
    179     bool hasSecondaryOutput() const override { return fHasSecondaryOutput; }
    180     const char* dstColor() override;
    181     void enableAdvancedBlendEquationIfNeeded(GrBlendEquation) override;
    182 
    183 private:
    184     // Private public interface, used by GrGLProgramBuilder to build a fragment shader
    185     void enableCustomOutput();
    186     void enableSecondaryOutput();
    187     const char* getPrimaryColorOutputName() const;
    188     const char* getSecondaryColorOutputName() const;
    189 
    190 #ifdef SK_DEBUG
    191     // As GLSLProcessors emit code, there are some conditions we need to verify.  We use the below
    192     // state to track this.  The reset call is called per processor emitted.
    193     GrProcessor::RequiredFeatures usedProcessorFeatures() const { return fUsedProcessorFeatures; }
    194     bool hasReadDstColor() const { return fHasReadDstColor; }
    195     void resetVerification() {
    196         fUsedProcessorFeatures = GrProcessor::kNone_RequiredFeatures;
    197         fHasReadDstColor = false;
    198     }
    199 #endif
    200 
    201     static const char* DeclaredColorOutputName() { return "sk_FragColor"; }
    202     static const char* DeclaredSecondaryColorOutputName() { return "fsSecondaryColorOut"; }
    203 
    204     GrSurfaceOrigin getSurfaceOrigin() const;
    205 
    206     void onFinalize() override;
    207     void defineSampleOffsetArray(const char* name, const SkMatrix&);
    208 
    209     static const char* kDstColorName;
    210 
    211     /*
    212      * State that tracks which child proc in the proc tree is currently emitting code.  This is
    213      * used to update the fMangleString, which is used to mangle the names of uniforms and functions
    214      * emitted by the proc.  fSubstageIndices is a stack: its count indicates how many levels deep
    215      * we are in the tree, and its second-to-last value is the index of the child proc at that
    216      * level which is currently emitting code. For example, if fSubstageIndices = [3, 1, 2, 0], that
    217      * means we're currently emitting code for the base proc's 3rd child's 1st child's 2nd child.
    218      */
    219     SkTArray<int> fSubstageIndices;
    220 
    221     /*
    222      * The mangle string is used to mangle the names of uniforms/functions emitted by the child
    223      * procs so no duplicate uniforms/functions appear in the generated shader program. The mangle
    224      * string is simply based on fSubstageIndices. For example, if fSubstageIndices = [3, 1, 2, 0],
    225      * then the manglestring will be "_c3_c1_c2", and any uniform/function emitted by that proc will
    226      * have "_c3_c1_c2" appended to its name, which can be interpreted as "base proc's 3rd child's
    227      * 1st child's 2nd child".
    228      */
    229     SkString fMangleString;
    230 
    231     bool          fSetupFragPosition;
    232     bool          fHasCustomColorOutput;
    233     int           fCustomColorOutputIndex;
    234     bool          fHasSecondaryOutput;
    235     uint8_t       fUsedSampleOffsetArrays;
    236     bool          fHasInitializedSampleMask;
    237     GrSLPrecision fDefaultPrecision;
    238 
    239 #ifdef SK_DEBUG
    240     // some state to verify shaders and effects are consistent, this is reset between effects by
    241     // the program creator
    242     GrProcessor::RequiredFeatures fUsedProcessorFeatures;
    243     bool fHasReadDstColor;
    244 #endif
    245 
    246     friend class GrGLSLProgramBuilder;
    247     friend class GrGLProgramBuilder;
    248 };
    249 
    250 #endif
    251