src/shaders/SkLocalMatrixShader.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/core/SkTLazy.h"
#include "src/shaders/SkLocalMatrixShader.h"

#if SK_SUPPORT_GPU
#include "src/gpu/GrFragmentProcessor.h"
#endif

#if SK_SUPPORT_GPU
std::unique_ptr<GrFragmentProcessor> SkLocalMatrixShader::asFragmentProcessor(
        const GrFPArgs& args) const {
    return as_SB(fProxyShader)->asFragmentProcessor(
        GrFPArgs::WithPreLocalMatrix(args, this->getLocalMatrix()));
}
#endif

sk_sp<SkFlattenable> SkLocalMatrixShader::CreateProc(SkReadBuffer& buffer) {
    SkMatrix lm;
    buffer.readMatrix(&lm);
    auto baseShader(buffer.readShader());
    if (!baseShader) {
        return nullptr;
    }
    return baseShader->makeWithLocalMatrix(lm);
}

void SkLocalMatrixShader::flatten(SkWriteBuffer& buffer) const {
    buffer.writeMatrix(this->getLocalMatrix());
    buffer.writeFlattenable(fProxyShader.get());
}

#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
SkShaderBase::Context* SkLocalMatrixShader::onMakeContext(
    const ContextRec& rec, SkArenaAlloc* alloc) const
{
    SkTCopyOnFirstWrite<SkMatrix> lm(this->getLocalMatrix());
    if (rec.fLocalMatrix) {
        lm.writable()->preConcat(*rec.fLocalMatrix);
    }

    ContextRec newRec(rec);
    newRec.fLocalMatrix = lm;

    return as_SB(fProxyShader)->makeContext(newRec, alloc);
}
#endif

SkImage* SkLocalMatrixShader::onIsAImage(SkMatrix* outMatrix, SkTileMode* mode) const {
    SkMatrix imageMatrix;
    SkImage* image = fProxyShader->isAImage(&imageMatrix, mode);
    if (image && outMatrix) {
        // Local matrix must be applied first so it is on the right side of the concat.
        *outMatrix = SkMatrix::Concat(imageMatrix, this->getLocalMatrix());
    }

    return image;
}

bool SkLocalMatrixShader::onAppendStages(const SkStageRec& rec) const {
    SkTCopyOnFirstWrite<SkMatrix> lm(this->getLocalMatrix());
    if (rec.fLocalM) {
        lm.writable()->preConcat(*rec.fLocalM);
    }

    SkStageRec newRec = rec;
    newRec.fLocalM = lm;
    return as_SB(fProxyShader)->appendStages(newRec);
}

sk_sp<SkShader> SkShader::makeWithLocalMatrix(const SkMatrix& localMatrix) const {
    if (localMatrix.isIdentity()) {
        return sk_ref_sp(const_cast<SkShader*>(this));
    }

    const SkMatrix* lm = &localMatrix;

    sk_sp<SkShader> baseShader;
    SkMatrix otherLocalMatrix;
    sk_sp<SkShader> proxy(as_SB(this)->makeAsALocalMatrixShader(&otherLocalMatrix));
    if (proxy) {
        otherLocalMatrix.preConcat(localMatrix);
        lm = &otherLocalMatrix;
        baseShader = proxy;
    } else {
        baseShader = sk_ref_sp(const_cast<SkShader*>(this));
    }

    return sk_make_sp<SkLocalMatrixShader>(std::move(baseShader), *lm);
}

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

/**
 *  Replaces the CTM when used. Created to support clipShaders, which have to be evaluated
 *  using the CTM that was present at the time they were specified (which may be different
 *  from the CTM at the time something is drawn through the clip.
 */
class SkCTMShader final : public SkShaderBase {
public:
    SkCTMShader(sk_sp<SkShader> proxy, const SkMatrix& ctm)
    : fProxyShader(std::move(proxy))
    , fCTM(ctm)
    {}

    GradientType asAGradient(GradientInfo* info) const override {
        return fProxyShader->asAGradient(info);
    }

#if SK_SUPPORT_GPU
    std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const override;
#endif

protected:
    void flatten(SkWriteBuffer&) const override { SkASSERT(false); }

#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
    Context* onMakeContext(const ContextRec&, SkArenaAlloc*) const override { return nullptr; }
#endif

    bool onAppendStages(const SkStageRec&) const override;

private:
    SK_FLATTENABLE_HOOKS(SkCTMShader)

    sk_sp<SkShader> fProxyShader;
    SkMatrix        fCTM;

    typedef SkShaderBase INHERITED;
};


#if SK_SUPPORT_GPU
std::unique_ptr<GrFragmentProcessor> SkCTMShader::asFragmentProcessor(
        const GrFPArgs& args) const {
    return as_SB(fProxyShader)->asFragmentProcessor(
        GrFPArgs::WithPreLocalMatrix(args, this->getLocalMatrix()));
}
#endif

sk_sp<SkFlattenable> SkCTMShader::CreateProc(SkReadBuffer& buffer) {
    SkASSERT(false);
    return nullptr;
}

bool SkCTMShader::onAppendStages(const SkStageRec& rec) const {
    SkStageRec newRec = {
        rec.fPipeline,
        rec.fAlloc,
        rec.fDstColorType,
        rec.fDstCS,
        rec.fPaint,
        rec.fLocalM,
        fCTM,
    };
    return as_SB(fProxyShader)->appendStages(newRec);
}

sk_sp<SkShader> SkShaderBase::makeWithCTM(const SkMatrix& postM) const {
    return postM.isIdentity() ? sk_ref_sp(this)
                              : sk_sp<SkShader>(new SkCTMShader(sk_ref_sp(this), postM));
}