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      1 /*
      2  * Copyright 2012 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 GrProcessor_DEFINED
      9 #define GrProcessor_DEFINED
     10 
     11 #include "GrBackendProcessorFactory.h"
     12 #include "GrColor.h"
     13 #include "GrProcessorUnitTest.h"
     14 #include "GrProgramElement.h"
     15 #include "GrShaderVar.h"
     16 #include "GrTextureAccess.h"
     17 #include "GrTypesPriv.h"
     18 #include "SkString.h"
     19 
     20 class GrBackendProcessorFactory;
     21 class GrContext;
     22 class GrCoordTransform;
     23 
     24 /** Provides custom vertex shader, fragment shader, uniform data for a particular stage of the
     25     Ganesh shading pipeline.
     26     Subclasses must have a function that produces a human-readable name:
     27         static const char* Name();
     28     GrProcessor objects *must* be immutable: after being constructed, their fields may not change.
     29 
     30     Dynamically allocated GrProcessors are managed by a per-thread memory pool. The ref count of an
     31     effect must reach 0 before the thread terminates and the pool is destroyed. To create a static
     32     effect use the macro GR_CREATE_STATIC_EFFECT declared below.
     33   */
     34 class GrProcessor : public GrProgramElement {
     35 public:
     36     SK_DECLARE_INST_COUNT(GrProcessor)
     37 
     38     virtual ~GrProcessor();
     39 
     40     /**
     41      * This function is used to perform optimizations. When called the color and validFlags params
     42      * indicate whether the input components to this effect in the FS will have known values.
     43      * validFlags is a bitfield of GrColorComponentFlags. The function updates both params to
     44      * indicate known values of its output. A component of the color param only has meaning if the
     45      * corresponding bit in validFlags is set.
     46      */
     47     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const = 0;
     48 
     49     /** This object, besides creating back-end-specific helper objects, is used for run-time-type-
     50         identification. The factory should be an instance of templated class,
     51         GrTBackendEffectFactory. It is templated on the subclass of GrProcessor. The subclass must
     52         have a nested type (or typedef) named GLProcessor which will be the subclass of
     53         GrGLProcessor created by the factory.
     54 
     55         Example:
     56         class MyCustomEffect : public GrProcessor {
     57         ...
     58             virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
     59                 return GrTBackendEffectFactory<MyCustomEffect>::getInstance();
     60             }
     61         ...
     62         };
     63      */
     64     virtual const GrBackendProcessorFactory& getFactory() const = 0;
     65 
     66     /** Returns true if this and other effect conservatively draw identically. It can only return
     67         true when the two effects are of the same subclass (i.e. they return the same object from
     68         from getFactory()).
     69 
     70         A return value of true from isEqual() should not be used to test whether the effects would
     71         generate the same shader code. To test for identical code generation use the effects' keys
     72         computed by the GrBackendEffectFactory.
     73      */
     74     bool isEqual(const GrProcessor& other) const {
     75         if (&this->getFactory() != &other.getFactory()) {
     76             return false;
     77         }
     78         bool result = this->onIsEqual(other);
     79 #ifdef SK_DEBUG
     80         if (result) {
     81             this->assertEquality(other);
     82         }
     83 #endif
     84         return result;
     85     }
     86 
     87     /** Human-meaningful string to identify this effect; may be embedded
     88         in generated shader code. */
     89     const char* name() const;
     90 
     91     int numTransforms() const { return fCoordTransforms.count(); }
     92 
     93     /** Returns the coordinate transformation at index. index must be valid according to
     94         numTransforms(). */
     95     const GrCoordTransform& coordTransform(int index) const { return *fCoordTransforms[index]; }
     96 
     97     int numTextures() const { return fTextureAccesses.count(); }
     98 
     99     /** Returns the access pattern for the texture at index. index must be valid according to
    100         numTextures(). */
    101     const GrTextureAccess& textureAccess(int index) const { return *fTextureAccesses[index]; }
    102 
    103     /** Shortcut for textureAccess(index).texture(); */
    104     GrTexture* texture(int index) const { return this->textureAccess(index).getTexture(); }
    105 
    106     /** Will this effect read the fragment position? */
    107     bool willReadFragmentPosition() const { return fWillReadFragmentPosition; }
    108 
    109     void* operator new(size_t size);
    110     void operator delete(void* target);
    111 
    112     void* operator new(size_t size, void* placement) {
    113         return ::operator new(size, placement);
    114     }
    115     void operator delete(void* target, void* placement) {
    116         ::operator delete(target, placement);
    117     }
    118 
    119     /**
    120       * Helper for down-casting to a GrProcessor subclass
    121       */
    122     template <typename T> const T& cast() const { return *static_cast<const T*>(this); }
    123 
    124 protected:
    125     /**
    126      * Subclasses call this from their constructor to register coordinate transformations. The
    127      * effect subclass manages the lifetime of the transformations (this function only stores a
    128      * pointer). The GrCoordTransform is typically a member field of the GrProcessor subclass. When
    129      * the matrix has perspective, the transformed coordinates will have 3 components. Otherwise
    130      * they'll have 2. This must only be called from the constructor because GrProcessors are
    131      * immutable.
    132      */
    133     void addCoordTransform(const GrCoordTransform* coordTransform);
    134 
    135     /**
    136      * Subclasses call this from their constructor to register GrTextureAccesses. The effect
    137      * subclass manages the lifetime of the accesses (this function only stores a pointer). The
    138      * GrTextureAccess is typically a member field of the GrProcessor subclass. This must only be
    139      * called from the constructor because GrProcessors are immutable.
    140      */
    141     void addTextureAccess(const GrTextureAccess* textureAccess);
    142 
    143     GrProcessor()
    144         : fWillReadFragmentPosition(false) {}
    145 
    146     /**
    147      * If the effect will generate a backend-specific effect that will read the fragment position
    148      * in the FS then it must call this method from its constructor. Otherwise, the request to
    149      * access the fragment position will be denied.
    150      */
    151     void setWillReadFragmentPosition() { fWillReadFragmentPosition = true; }
    152 
    153 private:
    154     SkDEBUGCODE(void assertEquality(const GrProcessor& other) const;)
    155 
    156     /** Subclass implements this to support isEqual(). It will only be called if it is known that
    157         the two effects are of the same subclass (i.e. they return the same object from
    158         getFactory()).*/
    159     virtual bool onIsEqual(const GrProcessor& other) const = 0;
    160 
    161     friend class GrGeometryProcessor; // to set fRequiresVertexShader and build fVertexAttribTypes.
    162 
    163     SkSTArray<4, const GrCoordTransform*, true>  fCoordTransforms;
    164     SkSTArray<4, const GrTextureAccess*, true>   fTextureAccesses;
    165     bool                                         fWillReadFragmentPosition;
    166 
    167     typedef GrProgramElement INHERITED;
    168 };
    169 
    170 class GrFragmentProcessor : public GrProcessor {
    171 public:
    172     GrFragmentProcessor()
    173         : INHERITED()
    174         , fWillReadDstColor(false)
    175         , fWillUseInputColor(true) {}
    176 
    177     virtual const GrBackendFragmentProcessorFactory& getFactory() const = 0;
    178 
    179     /** Will this effect read the destination pixel value? */
    180     bool willReadDstColor() const { return fWillReadDstColor; }
    181 
    182     /** Will this effect read the source color value? */
    183     bool willUseInputColor() const { return fWillUseInputColor; }
    184 
    185 protected:
    186     /**
    187      * If the effect subclass will read the destination pixel value then it must call this function
    188      * from its constructor. Otherwise, when its generated backend-specific effect class attempts
    189      * to generate code that reads the destination pixel it will fail.
    190      */
    191     void setWillReadDstColor() { fWillReadDstColor = true; }
    192 
    193     /**
    194      * If the effect will generate a result that does not depend on the input color value then it
    195      * must call this function from its constructor. Otherwise, when its generated backend-specific
    196      * code might fail during variable binding due to unused variables.
    197      */
    198     void setWillNotUseInputColor() { fWillUseInputColor = false; }
    199 
    200 private:
    201     bool                                         fWillReadDstColor;
    202     bool                                         fWillUseInputColor;
    203 
    204     typedef GrProcessor INHERITED;
    205 };
    206 
    207 /**
    208  * This creates an effect outside of the effect memory pool. The effect's destructor will be called
    209  * at global destruction time. NAME will be the name of the created GrProcessor.
    210  */
    211 #define GR_CREATE_STATIC_FRAGMENT_PROCESSOR(NAME, EFFECT_CLASS, ARGS)                             \
    212 static SkAlignedSStorage<sizeof(EFFECT_CLASS)> g_##NAME##_Storage;                                \
    213 static GrFragmentProcessor*                                                                       \
    214 NAME SkNEW_PLACEMENT_ARGS(g_##NAME##_Storage.get(), EFFECT_CLASS, ARGS);                          \
    215 static SkAutoTDestroy<GrFragmentProcessor> NAME##_ad(NAME);
    216 
    217 #endif
    218