src/gpu/effects/GrGradientEffects.cpp

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "GrGradientEffects.h"
#include "gl/GrGLProgramStage.h"
#include "GrProgramStageFactory.h"

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

class GrGLRadialGradient : public GrGLProgramStage {

public:

    GrGLRadialGradient(const GrProgramStageFactory& factory,
                       const GrCustomStage&) : INHERITED (factory) { }
    virtual ~GrGLRadialGradient() { }

    virtual void emitVS(GrGLShaderBuilder* state,
                        const char* vertexCoords) SK_OVERRIDE { }
    virtual void emitFS(GrGLShaderBuilder* state,
                        const char* outputColor,
                        const char* inputColor,
                        const char* samplerName) SK_OVERRIDE;

    static StageKey GenKey(const GrCustomStage& s) { return 0; }

private:

    typedef GrGLProgramStage INHERITED;

};

void GrGLRadialGradient::emitFS(GrGLShaderBuilder* state,
                        const char* outputColor,
                        const char* inputColor,
                        const char* samplerName) {
    state->fSampleCoords.printf("vec2(length(%s.xy), 0.5)",
                                state->fSampleCoords.c_str());
    state->fComplexCoord = true;

    state->emitDefaultFetch(outputColor, samplerName);
}


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


GrRadialGradient::GrRadialGradient() {

}

GrRadialGradient::~GrRadialGradient() {

}


const GrProgramStageFactory& GrRadialGradient::getFactory() const {
    return GrTProgramStageFactory<GrRadialGradient>::getInstance();
}

bool GrRadialGradient::isEqual(const GrCustomStage& sBase) const {
    return true;
}

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

class GrGLRadial2Gradient : public GrGLProgramStage {

public:

    GrGLRadial2Gradient(const GrProgramStageFactory& factory,
                        const GrCustomStage&);
    virtual ~GrGLRadial2Gradient() { }

    virtual void setupVariables(GrGLShaderBuilder* state,
                                int stage) SK_OVERRIDE;
    virtual void emitVS(GrGLShaderBuilder* state,
                        const char* vertexCoords) SK_OVERRIDE;
    virtual void emitFS(GrGLShaderBuilder* state,
                        const char* outputColor,
                        const char* inputColor,
                        const char* samplerName) SK_OVERRIDE;
    virtual void initUniforms(const GrGLInterface*, int programID) SK_OVERRIDE;
    virtual void setData(const GrGLInterface*,
                         const GrGLTexture&,
                         const GrCustomStage&,
                         int stageNum) SK_OVERRIDE;

    static StageKey GenKey(const GrCustomStage& s) {
        return (static_cast<const GrRadial2Gradient&>(s).isDegenerate());
    }

protected:

    const GrGLShaderVar* fParamVar;
    GrGLint fParamLocation;

    const char* fVSVaryingName;
    const char* fFSVaryingName;

    bool fIsDegenerate;

    // @{
    /// Values last uploaded as uniforms

    GrScalar fCachedCenter;
    GrScalar fCachedRadius;
    SkBool8  fCachedPosRoot;

    // @}

private:

    typedef GrGLProgramStage INHERITED;

};

GrGLRadial2Gradient::GrGLRadial2Gradient(
        const GrProgramStageFactory& factory,
        const GrCustomStage& baseData)
    : INHERITED(factory)
    , fParamVar(NULL)
    , fVSVaryingName(NULL)
    , fFSVaryingName(NULL)
    , fCachedCenter(GR_ScalarMax)
    , fCachedRadius(-GR_ScalarMax)
    , fCachedPosRoot(0) {

    const GrRadial2Gradient& data =
        static_cast<const GrRadial2Gradient&>(baseData);
    fIsDegenerate = data.isDegenerate();
}

void GrGLRadial2Gradient::setupVariables(GrGLShaderBuilder* state, int stage) {
    fParamVar = &state->addUniform(
        GrGLShaderBuilder::kBoth_VariableLifetime,
        kFloat_GrSLType, "uRadial2Params", stage, 6);

    fParamLocation = GrGLProgramStage::kUseUniform;

    // For radial gradients without perspective we can pass the linear
    // part of the quadratic as a varying.
    if (state->fVaryingDims == state->fCoordDims) {
        state->addVarying(kFloat_GrSLType, "Radial2BCoeff", stage,
                          &fVSVaryingName, &fFSVaryingName);
    }
}

void GrGLRadial2Gradient::emitVS(GrGLShaderBuilder* state,
                        const char* vertexCoords) {
    GrStringBuilder* code = &state->fVSCode;
    GrStringBuilder p2;
    GrStringBuilder p3;
    fParamVar->appendArrayAccess(2, &p2);
    fParamVar->appendArrayAccess(3, &p3);

    // For radial gradients without perspective we can pass the linear
    // part of the quadratic as a varying.
    if (state->fVaryingDims == state->fCoordDims) {
        // r2Var = 2 * (r2Parm[2] * varCoord.x - r2Param[3])
        code->appendf("\t%s = 2.0 *(%s * %s.x - %s);\n",
                      fVSVaryingName, p2.c_str(),
                      vertexCoords, p3.c_str());
    }
}

void GrGLRadial2Gradient::emitFS(GrGLShaderBuilder* state,
                        const char* outputColor,
                        const char* inputColor,
                        const char* samplerName) {
    GrStringBuilder* code = &state->fFSCode;
    GrStringBuilder cName("c");
    GrStringBuilder ac4Name("ac4");
    GrStringBuilder rootName("root");
    GrStringBuilder p0;
    GrStringBuilder p1;
    GrStringBuilder p2;
    GrStringBuilder p3;
    GrStringBuilder p4;
    GrStringBuilder p5;
    fParamVar->appendArrayAccess(0, &p0);
    fParamVar->appendArrayAccess(1, &p1);
    fParamVar->appendArrayAccess(2, &p2);
    fParamVar->appendArrayAccess(3, &p3);
    fParamVar->appendArrayAccess(4, &p4);
    fParamVar->appendArrayAccess(5, &p5);

    // If we we're able to interpolate the linear component,
    // bVar is the varying; otherwise compute it
    GrStringBuilder bVar;
    if (state->fCoordDims == state->fVaryingDims) {
        bVar = fFSVaryingName;
        GrAssert(2 == state->fVaryingDims);
    } else {
        GrAssert(3 == state->fVaryingDims);
        bVar = "b";
        //bVar.appendS32(stageNum);
        code->appendf("\tfloat %s = 2.0 * (%s * %s.x - %s);\n",
                      bVar.c_str(), p2.c_str(),
                      state->fSampleCoords.c_str(), p3.c_str());
    }

    // c = (x^2)+(y^2) - params[4]
    code->appendf("\tfloat %s = dot(%s, %s) - %s;\n",
                  cName.c_str(), state->fSampleCoords.c_str(),
                  state->fSampleCoords.c_str(),
                  p4.c_str());

    // If we aren't degenerate, emit some extra code, and accept a slightly
    // more complex coord.
    if (fIsDegenerate) {

        // ac4 = 4.0 * params[0] * c
        code->appendf("\tfloat %s = %s * 4.0 * %s;\n",
                      ac4Name.c_str(), p0.c_str(),
                      cName.c_str());

        // root = sqrt(b^2-4ac)
        // (abs to avoid exception due to fp precision)
        code->appendf("\tfloat %s = sqrt(abs(%s*%s - %s));\n",
                      rootName.c_str(), bVar.c_str(), bVar.c_str(),
                      ac4Name.c_str());

        // x coord is: (-b + params[5] * sqrt(b^2-4ac)) * params[1]
        // y coord is 0.5 (texture is effectively 1D)
        state->fSampleCoords.printf("vec2((-%s + %s * %s) * %s, 0.5)",
                            bVar.c_str(), p5.c_str(),
                            rootName.c_str(), p1.c_str());
    } else {
        // x coord is: -c/b
        // y coord is 0.5 (texture is effectively 1D)
        state->fSampleCoords.printf("vec2((-%s / %s), 0.5)",
                            cName.c_str(), bVar.c_str());
    }
    state->fComplexCoord = true;

    state->emitDefaultFetch(outputColor, samplerName);
}

void GrGLRadial2Gradient::initUniforms(const GrGLInterface* gl, int programID) {
    GR_GL_CALL_RET(gl, fParamLocation,
        GetUniformLocation(programID, fParamVar->getName().c_str()));
}

void GrGLRadial2Gradient::setData(const GrGLInterface* gl,
                                 const GrGLTexture& texture,
                                 const GrCustomStage& baseData,
                                 int stageNum) {
    const GrRadial2Gradient& data =
        static_cast<const GrRadial2Gradient&>(baseData);
    GrAssert(data.isDegenerate() == fIsDegenerate);
    GrScalar centerX1 = data.center();
    GrScalar radius0 = data.radius();
    if (fCachedCenter != centerX1 ||
        fCachedRadius != radius0 ||
        fCachedPosRoot != data.isPosRoot()) {

        GrScalar a = GrMul(centerX1, centerX1) - GR_Scalar1;

        // When we're in the degenerate (linear) case, the second
        // value will be INF but the program doesn't read it. (We
        // use the same 6 uniforms even though we don't need them
        // all in the linear case just to keep the code complexity
        // down).
        float values[6] = {
            GrScalarToFloat(a),
            1 / (2.f * GrScalarToFloat(a)),
            GrScalarToFloat(centerX1),
            GrScalarToFloat(radius0),
            GrScalarToFloat(GrMul(radius0, radius0)),
            data.isPosRoot() ? 1.f : -1.f
        };

        GR_GL_CALL(gl, Uniform1fv(fParamLocation, 6, values));
        fCachedCenter = centerX1;
        fCachedRadius = radius0;
        fCachedPosRoot = data.isPosRoot();
    }
}


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

GrRadial2Gradient::GrRadial2Gradient(GrScalar center,
                                     GrScalar radius,
                                     bool posRoot)
    : fCenterX1 (center)
    , fRadius0 (radius)
    , fPosRoot (posRoot) {

}

GrRadial2Gradient::~GrRadial2Gradient() {

}


const GrProgramStageFactory& GrRadial2Gradient::getFactory() const {
    return GrTProgramStageFactory<GrRadial2Gradient>::getInstance();
}

bool GrRadial2Gradient::isEqual(const GrCustomStage& sBase) const {
    const GrRadial2Gradient& s = static_cast<const GrRadial2Gradient&>(sBase);
    return (this->isDegenerate() == s.isDegenerate());
}

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

class GrGLSweepGradient : public GrGLProgramStage {

public:

    GrGLSweepGradient(const GrProgramStageFactory& factory,
                      const GrCustomStage&) : INHERITED (factory) { }
    virtual ~GrGLSweepGradient() { }

    virtual void emitVS(GrGLShaderBuilder* state,
                        const char* vertexCoords) SK_OVERRIDE { }
    virtual void emitFS(GrGLShaderBuilder* state,
                        const char* outputColor,
                        const char* inputColor,
                        const char* samplerName) SK_OVERRIDE;

    static StageKey GenKey(const GrCustomStage& s) { return 0; }

private:

    typedef GrGLProgramStage INHERITED;

};

void GrGLSweepGradient::emitFS(GrGLShaderBuilder* state,
                              const char* outputColor,
                              const char* inputColor,
                              const char* samplerName) {
    state->fSampleCoords.printf(
        "vec2(atan(- %s.y, - %s.x) * 0.1591549430918 + 0.5, 0.5)",
        state->fSampleCoords.c_str(), state->fSampleCoords.c_str());
    state->fComplexCoord = true;

    state->emitDefaultFetch(outputColor, samplerName);
}

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

GrSweepGradient::GrSweepGradient() {

}

GrSweepGradient::~GrSweepGradient() {

}

const GrProgramStageFactory& GrSweepGradient::getFactory() const {
    return GrTProgramStageFactory<GrSweepGradient>::getInstance();
}

bool GrSweepGradient::isEqual(const GrCustomStage& sBase) const {
    return true;
}