GrXferProcessor.h

/*
 * Copyright 2014 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrXferProcessor_DEFINED
#define GrXferProcessor_DEFINED

#include "GrBlend.h"
#include "GrColor.h"
#include "GrProcessor.h"
#include "GrTexture.h"
#include "GrTypes.h"
#include "SkXfermode.h"

class GrShaderCaps;
class GrGLSLCaps;
class GrGLSLXferProcessor;
class GrProcOptInfo;
struct GrPipelineOptimizations;

enum GrXferBarrierType {
    kNone_GrXferBarrierType = 0, //<! No barrier is required
    kTexture_GrXferBarrierType,  //<! Required when a shader reads and renders to the same texture.
    kBlend_GrXferBarrierType,    //<! Required by certain blend extensions.
};
GR_STATIC_ASSERT(SkToBool(kNone_GrXferBarrierType) == false);

class GrXferProcessor : public GrProcessor {
public:
    class DstTexture {
    public:
        DstTexture() { fOffset.set(0, 0); }

        DstTexture(const DstTexture& other) {
            *this = other;
        }

        DstTexture(GrTexture* texture, const SkIPoint& offset)
            : fTexture(SkSafeRef(texture))
            , fOffset(offset) {
        }

        DstTexture& operator=(const DstTexture& other) {
            fTexture.reset(SkSafeRef(other.fTexture.get()));
            fOffset = other.fOffset;
            return *this;
        }

        const SkIPoint& offset() const { return fOffset; }

        void setOffset(const SkIPoint& offset) { fOffset = offset; }
        void setOffset(int ox, int oy) { fOffset.set(ox, oy); }

        GrTexture* texture() const { return fTexture.get(); }

        GrTexture* setTexture(GrTexture* texture) {
            fTexture.reset(SkSafeRef(texture));
            return texture;
        }

    private:
        SkAutoTUnref<GrTexture> fTexture;
        SkIPoint                fOffset;
    };

    void getGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const;

    virtual GrGLSLXferProcessor* createGLSLInstance() const = 0;

    enum OptFlags {
        kSkipDraw_OptFlag                 = 0x1,
        kIgnoreColor_OptFlag              = 0x2,
        kIgnoreCoverage_OptFlag           = 0x4,
        kOverrideColor_OptFlag            = 0x8,
        kCanTweakAlphaForCoverage_OptFlag = 0x20,
    };

    static const OptFlags kNone_OptFlags = (OptFlags)0;

    GR_DECL_BITFIELD_OPS_FRIENDS(OptFlags);

    OptFlags getOptimizations(const GrPipelineOptimizations& optimizations,
                              bool doesStencilWrite,
                              GrColor* overrideColor,
                              const GrCaps& caps) const;

    GrXferBarrierType xferBarrierType(const GrRenderTarget* rt, const GrCaps& caps) const;

    struct BlendInfo {
        void reset() {
            fEquation = kAdd_GrBlendEquation;
            fSrcBlend = kOne_GrBlendCoeff;
            fDstBlend = kZero_GrBlendCoeff;
            fBlendConstant = 0;
            fWriteColor = true;
        }

        SkDEBUGCODE(SkString dump() const;)

        GrBlendEquation fEquation;
        GrBlendCoeff    fSrcBlend;
        GrBlendCoeff    fDstBlend;
        GrColor         fBlendConstant;
        bool            fWriteColor;
    };

    void getBlendInfo(BlendInfo* blendInfo) const;

    bool willReadDstColor() const { return fWillReadDstColor; }

    const GrTexture* getDstTexture() const { return fDstTexture.getTexture(); }

    const SkIPoint& dstTextureOffset() const {
        SkASSERT(this->getDstTexture());
        return fDstTextureOffset;
    }

    bool dstReadUsesMixedSamples() const { return fDstReadUsesMixedSamples; }

    bool hasSecondaryOutput() const;

    bool isEqual(const GrXferProcessor& that) const {
        if (this->classID() != that.classID()) {
            return false;
        }
        if (this->fWillReadDstColor != that.fWillReadDstColor) {
            return false;
        }
        if (this->fDstTexture.getTexture() != that.fDstTexture.getTexture()) {
            return false;
        }
        if (this->fDstTextureOffset != that.fDstTextureOffset) {
            return false;
        }
        if (this->fDstReadUsesMixedSamples != that.fDstReadUsesMixedSamples) {
            return false;
        }
        return this->onIsEqual(that);
    }
   
protected:
    GrXferProcessor();
    GrXferProcessor(const DstTexture*, bool willReadDstColor, bool hasMixedSamples);

private:
    void notifyRefCntIsZero() const final {}

    virtual OptFlags onGetOptimizations(const GrPipelineOptimizations& optimizations,
                                        bool doesStencilWrite,
                                        GrColor* overrideColor,
                                        const GrCaps& caps) const = 0;

    virtual void onGetGLSLProcessorKey(const GrGLSLCaps& caps,
                                       GrProcessorKeyBuilder* b) const = 0;

    virtual GrXferBarrierType onXferBarrier(const GrRenderTarget*, const GrCaps&) const {
        return kNone_GrXferBarrierType;
    }

    virtual bool onHasSecondaryOutput() const { return false; }

    virtual void onGetBlendInfo(BlendInfo*) const {}

    virtual bool onIsEqual(const GrXferProcessor&) const = 0;

    bool                    fWillReadDstColor;
    bool                    fDstReadUsesMixedSamples;
    SkIPoint                fDstTextureOffset;
    GrTextureAccess         fDstTexture;

    typedef GrFragmentProcessor INHERITED;
};

GR_MAKE_BITFIELD_OPS(GrXferProcessor::OptFlags);


class GrXPFactory : public SkRefCnt {
public:
    typedef GrXferProcessor::DstTexture DstTexture;
    GrXferProcessor* createXferProcessor(const GrPipelineOptimizations& optimizations,
                                         bool hasMixedSamples,
                                         const DstTexture*,
                                         const GrCaps& caps) const;
    struct InvariantBlendedColor {
        bool                     fWillBlendWithDst;
        GrColor                  fKnownColor;
        GrColorComponentFlags    fKnownColorFlags;
    };

    virtual void getInvariantBlendedColor(const GrProcOptInfo& colorPOI,
                                          InvariantBlendedColor*) const = 0;

    bool willNeedDstTexture(const GrCaps& caps, const GrPipelineOptimizations& optimizations) const;

    bool isEqual(const GrXPFactory& that) const {
        if (this->classID() != that.classID()) {
            return false;
        }
        return this->onIsEqual(that);
    }

    template <typename T> const T& cast() const { return *static_cast<const T*>(this); }

    uint32_t classID() const { SkASSERT(kIllegalXPFClassID != fClassID); return fClassID; }

protected:
    GrXPFactory() : fClassID(kIllegalXPFClassID) {}

    template <typename XPF_SUBCLASS> void initClassID() {
         static uint32_t kClassID = GenClassID();
         fClassID = kClassID;
    }

    uint32_t fClassID;

private:
    virtual GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
                                                   const GrPipelineOptimizations& optimizations,
                                                   bool hasMixedSamples,
                                                   const DstTexture*) const = 0;

    virtual bool onIsEqual(const GrXPFactory&) const = 0;

    bool willReadDstColor(const GrCaps&, const GrPipelineOptimizations&) const;
    virtual bool onWillReadDstColor(const GrCaps&, const GrPipelineOptimizations&) const = 0;

    static uint32_t GenClassID() {
        // fCurrXPFactoryID has been initialized to kIllegalXPFactoryID. The
        // atomic inc returns the old value not the incremented value. So we add
        // 1 to the returned value.
        uint32_t id = static_cast<uint32_t>(sk_atomic_inc(&gCurrXPFClassID)) + 1;
        if (!id) {
            SkFAIL("This should never wrap as it should only be called once for each GrXPFactory "
                   "subclass.");
        }
        return id;
    }

    enum {
        kIllegalXPFClassID = 0,
    };
    static int32_t gCurrXPFClassID;

    typedef GrProgramElement INHERITED;
};

#endif