src/gpu/effects/GrCoverageSetOpXP.cpp

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

#include "src/gpu/GrCaps.h"
#include "src/gpu/GrColor.h"
#include "src/gpu/GrPipeline.h"
#include "src/gpu/GrProcessor.h"
#include "src/gpu/GrRenderTargetContext.h"
#include "src/gpu/effects/GrCoverageSetOpXP.h"
#include "src/gpu/glsl/GrGLSLBlend.h"
#include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
#include "src/gpu/glsl/GrGLSLUniformHandler.h"
#include "src/gpu/glsl/GrGLSLXferProcessor.h"

class CoverageSetOpXP : public GrXferProcessor {
public:
    CoverageSetOpXP(SkRegion::Op regionOp, bool invertCoverage)
            : INHERITED(kCoverageSetOpXP_ClassID)
            , fRegionOp(regionOp)
            , fInvertCoverage(invertCoverage) {}

    const char* name() const override { return "Coverage Set Op"; }

    GrGLSLXferProcessor* createGLSLInstance() const override;

    bool invertCoverage() const { return fInvertCoverage; }

private:

    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override;

    void onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const override;

    bool onIsEqual(const GrXferProcessor& xpBase) const override {
        const CoverageSetOpXP& xp = xpBase.cast<CoverageSetOpXP>();
        return (fRegionOp == xp.fRegionOp &&
                fInvertCoverage == xp.fInvertCoverage);
    }

    SkRegion::Op fRegionOp;
    bool         fInvertCoverage;

    typedef GrXferProcessor INHERITED;
};

///////////////////////////////////////////////////////////////////////////////

class GLCoverageSetOpXP : public GrGLSLXferProcessor {
public:
    GLCoverageSetOpXP(const GrProcessor&) {}

    ~GLCoverageSetOpXP() override {}

    static void GenKey(const GrProcessor& processor, const GrShaderCaps& caps,
                       GrProcessorKeyBuilder* b) {
        const CoverageSetOpXP& xp = processor.cast<CoverageSetOpXP>();
        uint32_t key = xp.invertCoverage() ?  0x0 : 0x1;
        b->add32(key);
    }

private:
    void emitOutputsForBlendState(const EmitArgs& args) override {
        const CoverageSetOpXP& xp = args.fXP.cast<CoverageSetOpXP>();
        GrGLSLXPFragmentBuilder* fragBuilder = args.fXPFragBuilder;

        if (xp.invertCoverage()) {
            fragBuilder->codeAppendf("%s = 1.0 - %s;", args.fOutputPrimary, args.fInputCoverage);
        } else {
            fragBuilder->codeAppendf("%s = %s;", args.fOutputPrimary, args.fInputCoverage);
        }
    }

    void onSetData(const GrGLSLProgramDataManager&, const GrXferProcessor&) override {}

    typedef GrGLSLXferProcessor INHERITED;
};

///////////////////////////////////////////////////////////////////////////////

void CoverageSetOpXP::onGetGLSLProcessorKey(const GrShaderCaps& caps,
                                            GrProcessorKeyBuilder* b) const {
    GLCoverageSetOpXP::GenKey(*this, caps, b);
}

GrGLSLXferProcessor* CoverageSetOpXP::createGLSLInstance() const {
    return new GLCoverageSetOpXP(*this);
}

void CoverageSetOpXP::onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const {
    switch (fRegionOp) {
        case SkRegion::kReplace_Op:
            blendInfo->fSrcBlend = kOne_GrBlendCoeff;
            blendInfo->fDstBlend = kZero_GrBlendCoeff;
            break;
        case SkRegion::kIntersect_Op:
            blendInfo->fSrcBlend = kDC_GrBlendCoeff;
            blendInfo->fDstBlend = kZero_GrBlendCoeff;
            break;
        case SkRegion::kUnion_Op:
            blendInfo->fSrcBlend = kOne_GrBlendCoeff;
            blendInfo->fDstBlend = kISC_GrBlendCoeff;
            break;
        case SkRegion::kXOR_Op:
            blendInfo->fSrcBlend = kIDC_GrBlendCoeff;
            blendInfo->fDstBlend = kISC_GrBlendCoeff;
            break;
        case SkRegion::kDifference_Op:
            blendInfo->fSrcBlend = kZero_GrBlendCoeff;
            blendInfo->fDstBlend = kISC_GrBlendCoeff;
            break;
        case SkRegion::kReverseDifference_Op:
            blendInfo->fSrcBlend = kIDC_GrBlendCoeff;
            blendInfo->fDstBlend = kZero_GrBlendCoeff;
            break;
    }
    blendInfo->fBlendConstant = SK_PMColor4fTRANSPARENT;
}

///////////////////////////////////////////////////////////////////////////////

constexpr GrCoverageSetOpXPFactory::GrCoverageSetOpXPFactory(SkRegion::Op regionOp,
                                                             bool invertCoverage)
        : fRegionOp(regionOp), fInvertCoverage(invertCoverage) {}

const GrXPFactory* GrCoverageSetOpXPFactory::Get(SkRegion::Op regionOp, bool invertCoverage) {
    // If these objects are constructed as static constexpr by cl.exe (2015 SP2) the vtables are
    // null.
#ifdef SK_BUILD_FOR_WIN
#define _CONSTEXPR_
#else
#define _CONSTEXPR_ constexpr
#endif
    switch (regionOp) {
        case SkRegion::kReplace_Op: {
            if (invertCoverage) {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gReplaceCDXPFI(
                        SkRegion::kReplace_Op, true);
                return &gReplaceCDXPFI;
            } else {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gReplaceCDXPF(
                        SkRegion::kReplace_Op, false);
                return &gReplaceCDXPF;
            }
        }
        case SkRegion::kIntersect_Op: {
            if (invertCoverage) {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gIntersectCDXPFI(
                        SkRegion::kIntersect_Op, true);
                return &gIntersectCDXPFI;
            } else {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gIntersectCDXPF(
                        SkRegion::kIntersect_Op, false);
                return &gIntersectCDXPF;
            }
        }
        case SkRegion::kUnion_Op: {
            if (invertCoverage) {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gUnionCDXPFI(SkRegion::kUnion_Op,
                                                                               true);
                return &gUnionCDXPFI;
            } else {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gUnionCDXPF(SkRegion::kUnion_Op,
                                                                              false);
                return &gUnionCDXPF;
            }
        }
        case SkRegion::kXOR_Op: {
            if (invertCoverage) {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gXORCDXPFI(SkRegion::kXOR_Op,
                                                                             true);
                return &gXORCDXPFI;
            } else {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gXORCDXPF(SkRegion::kXOR_Op,
                                                                            false);
                return &gXORCDXPF;
            }
        }
        case SkRegion::kDifference_Op: {
            if (invertCoverage) {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gDifferenceCDXPFI(
                        SkRegion::kDifference_Op, true);
                return &gDifferenceCDXPFI;
            } else {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gDifferenceCDXPF(
                        SkRegion::kDifference_Op, false);
                return &gDifferenceCDXPF;
            }
        }
        case SkRegion::kReverseDifference_Op: {
            if (invertCoverage) {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gRevDiffCDXPFI(
                        SkRegion::kReverseDifference_Op, true);
                return &gRevDiffCDXPFI;
            } else {
                static _CONSTEXPR_ const GrCoverageSetOpXPFactory gRevDiffCDXPF(
                        SkRegion::kReverseDifference_Op, false);
                return &gRevDiffCDXPF;
            }
        }
    }
#undef _CONSTEXPR_
    SK_ABORT("Unknown region op.");
}

sk_sp<const GrXferProcessor> GrCoverageSetOpXPFactory::makeXferProcessor(
        const GrProcessorAnalysisColor&,
        GrProcessorAnalysisCoverage,
        bool hasMixedSamples,
        const GrCaps& caps,
        GrClampType) const {
    // We don't support inverting coverage with mixed samples. We don't expect to ever want this in
    // the future, however we could at some point make this work using an inverted coverage
    // modulation table. Note that an inverted table still won't work if there are coverage procs.
    if (fInvertCoverage && hasMixedSamples) {
        SkASSERT(false);
        return nullptr;
    }

    return sk_sp<GrXferProcessor>(new CoverageSetOpXP(fRegionOp, fInvertCoverage));
}

GR_DEFINE_XP_FACTORY_TEST(GrCoverageSetOpXPFactory);

#if GR_TEST_UTILS
const GrXPFactory* GrCoverageSetOpXPFactory::TestGet(GrProcessorTestData* d) {
    SkRegion::Op regionOp = SkRegion::Op(d->fRandom->nextULessThan(SkRegion::kLastOp + 1));
    bool invertCoverage = d->fRandom->nextBool();
    return GrCoverageSetOpXPFactory::Get(regionOp, invertCoverage);
}
#endif