C++ GrGLFragmentBuilder::codeAppendf方法代码示例

void GLCircleEffect::emitCode(EmitArgs& args) {
    const CircleEffect& ce = args.fFp.cast<CircleEffect>();
    const char *circleName;
    // The circle uniform is (center.x, center.y, radius + 0.5, 1 / (radius + 0.5)) for regular
    // fills and (..., radius - 0.5, 1 / (radius - 0.5)) for inverse fills.
    fCircleUniform = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                         kVec4f_GrSLType, kDefault_GrSLPrecision,
                                         "circle",
                                         &circleName);

    GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
    const char* fragmentPos = fsBuilder->fragmentPosition();

    SkASSERT(kHairlineAA_GrProcessorEdgeType != ce.getEdgeType());
    // TODO: Right now the distance to circle caclulation is performed in a space normalized to the
    // radius and then denormalized. This is to prevent overflow on devices that have a "real"
    // mediump. It'd be nice to only to this on mediump devices but we currently don't have the
    // caps here.
    if (GrProcessorEdgeTypeIsInverseFill(ce.getEdgeType())) {
        fsBuilder->codeAppendf("\t\tfloat d = (length((%s.xy - %s.xy) * %s.w) - 1.0) * %s.z;\n",
                                circleName, fragmentPos, circleName, circleName);
    } else {
        fsBuilder->codeAppendf("\t\tfloat d = (1.0 - length((%s.xy - %s.xy) *  %s.w)) * %s.z;\n",
                               circleName, fragmentPos, circleName, circleName);
    }
    if (GrProcessorEdgeTypeIsAA(ce.getEdgeType())) {
        fsBuilder->codeAppend("\t\td = clamp(d, 0.0, 1.0);\n");
    } else {
        fsBuilder->codeAppend("\t\td = d > 0.5 ? 1.0 : 0.0;\n");
    }

    fsBuilder->codeAppendf("\t\t%s = %s;\n", args.fOutputColor,
                           (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("d")).c_str());
}

 void emitCode(EmitArgs& args) override {
     GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
     fsBuilder->codeAppendf("vec4 alpha4 = %s.aaaa;", args.fInputColor);
     SkString output;
     this->emitChild(0, "alpha4", &output, args);
     fsBuilder->codeAppendf("%s = %s;", args.fOutputColor, output.c_str());
 }

void GrGLBicubicEffect::emitCode(EmitArgs& args) {
    const GrTextureDomain& domain = args.fFp.cast<GrBicubicEffect>().domain();

    fCoefficientsUni = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                           kMat44f_GrSLType, kDefault_GrSLPrecision,
                                           "Coefficients");
    fImageIncrementUni = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                             kVec2f_GrSLType, kDefault_GrSLPrecision,
                                             "ImageIncrement");

    const char* imgInc = args.fBuilder->getUniformCStr(fImageIncrementUni);
    const char* coeff = args.fBuilder->getUniformCStr(fCoefficientsUni);

    SkString cubicBlendName;

    static const GrGLShaderVar gCubicBlendArgs[] = {
        GrGLShaderVar("coefficients",  kMat44f_GrSLType),
        GrGLShaderVar("t",             kFloat_GrSLType),
        GrGLShaderVar("c0",            kVec4f_GrSLType),
        GrGLShaderVar("c1",            kVec4f_GrSLType),
        GrGLShaderVar("c2",            kVec4f_GrSLType),
        GrGLShaderVar("c3",            kVec4f_GrSLType),
    };
    GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
    SkString coords2D = fsBuilder->ensureFSCoords2D(args.fCoords, 0);
    fsBuilder->emitFunction(kVec4f_GrSLType,
                            "cubicBlend",
                            SK_ARRAY_COUNT(gCubicBlendArgs),
                            gCubicBlendArgs,
                            "\tvec4 ts = vec4(1.0, t, t * t, t * t * t);\n"
                            "\tvec4 c = coefficients * ts;\n"
                            "\treturn c.x * c0 + c.y * c1 + c.z * c2 + c.w * c3;\n",
                            &cubicBlendName);
    fsBuilder->codeAppendf("\tvec2 coord = %s - %s * vec2(0.5);\n", coords2D.c_str(), imgInc);
    // We unnormalize the coord in order to determine our fractional offset (f) within the texel
    // We then snap coord to a texel center and renormalize. The snap prevents cases where the
    // starting coords are near a texel boundary and accumulations of imgInc would cause us to skip/
    // double hit a texel.
    fsBuilder->codeAppendf("\tcoord /= %s;\n", imgInc);
    fsBuilder->codeAppend("\tvec2 f = fract(coord);\n");
    fsBuilder->codeAppendf("\tcoord = (coord - f + vec2(0.5)) * %s;\n", imgInc);
    fsBuilder->codeAppend("\tvec4 rowColors[4];\n");
    for (int y = 0; y < 4; ++y) {
        for (int x = 0; x < 4; ++x) {
            SkString coord;
            coord.printf("coord + %s * vec2(%d, %d)", imgInc, x - 1, y - 1);
            SkString sampleVar;
            sampleVar.printf("rowColors[%d]", x);
            fDomain.sampleTexture(fsBuilder, domain, sampleVar.c_str(), coord, args.fSamplers[0]);
        }
        fsBuilder->codeAppendf("\tvec4 s%d = %s(%s, f.x, rowColors[0], rowColors[1], rowColors[2], rowColors[3]);\n", y, cubicBlendName.c_str(), coeff);
    }
    SkString bicubicColor;
    bicubicColor.printf("%s(%s, f.y, s0, s1, s2, s3)", cubicBlendName.c_str(), coeff);
    fsBuilder->codeAppendf("\t%s = %s;\n", args.fOutputColor,(GrGLSLExpr4(bicubicColor.c_str()) *
                           GrGLSLExpr4(args.fInputColor)).c_str());
}

        void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
            const DefaultGeoProc& gp = args.fGP.cast<DefaultGeoProc>();
            GrGLGPBuilder* pb = args.fPB;
            GrGLVertexBuilder* vsBuilder = pb->getVertexShaderBuilder();
            GrGLFragmentBuilder* fs = args.fPB->getFragmentShaderBuilder();

            // emit attributes
            vsBuilder->emitAttributes(gp);

            // Setup pass through color
            if (!gp.colorIgnored()) {
                if (gp.hasVertexColor()) {
                    pb->addPassThroughAttribute(gp.inColor(), args.fOutputColor);
                } else {
                    this->setupUniformColor(pb, args.fOutputColor, &fColorUniform);
                }
            }

            // Setup position
            this->setupPosition(pb, gpArgs, gp.inPosition()->fName, gp.viewMatrix(),
                                &fViewMatrixUniform);

            if (gp.hasExplicitLocalCoords()) {
                // emit transforms with explicit local coords
                this->emitTransforms(pb, gpArgs->fPositionVar, gp.inLocalCoords()->fName,
                                     gp.localMatrix(), args.fTransformsIn, args.fTransformsOut);
            } else if(gp.hasTransformedLocalCoords()) {
                // transforms have already been applied to vertex attributes on the cpu
                this->emitTransforms(pb, gp.inLocalCoords()->fName,
                                     args.fTransformsIn, args.fTransformsOut);
            } else {
                // emit transforms with position
                this->emitTransforms(pb, gpArgs->fPositionVar, gp.inPosition()->fName,
                                     gp.localMatrix(), args.fTransformsIn, args.fTransformsOut);
            }

            // Setup coverage as pass through
            if (!gp.coverageWillBeIgnored()) {
                if (gp.hasVertexCoverage()) {
                    fs->codeAppendf("float alpha = 1.0;");
                    args.fPB->addPassThroughAttribute(gp.inCoverage(), "alpha");
                    fs->codeAppendf("%s = vec4(alpha);", args.fOutputCoverage);
                } else if (gp.coverage() == 0xff) {
                    fs->codeAppendf("%s = vec4(1);", args.fOutputCoverage);
                } else {
                    const char* fragCoverage;
                    fCoverageUniform = pb->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                      kFloat_GrSLType,
                                                      kDefault_GrSLPrecision,
                                                      "Coverage",
                                                      &fragCoverage);
                    fs->codeAppendf("%s = vec4(%s);", args.fOutputCoverage, fragCoverage);
                }
            }
        }

 void emitCode(EmitArgs& args) override {
     GrGLFragmentBuilder* fpb = args.fBuilder->getFragmentShaderBuilder();
     fpb->codeAppendf("vec2 c = %s;", fpb->ensureFSCoords2D(args.fCoords, 0).c_str());
     fpb->codeAppend("vec2 r = mod(c, vec2(20.0));");
     fpb->codeAppend("vec4 color = vec4(0.5*sin(c.x / 15.0) + 0.5,"
                                         "0.5*cos((c.x + c.y) / 15.0) + 0.5,"
                                         "(r.x + r.y) / 20.0,"
                                         "distance(r, vec2(15.0)) / 20.0 + 0.2);");
     fpb->codeAppendf("color.rgb *= color.a;"
                         "%s = color * %s;",
                         args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str());
 }

    void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override{
        const GrBitmapTextGeoProc& cte = args.fGP.cast<GrBitmapTextGeoProc>();

        GrGLGPBuilder* pb = args.fPB;
        GrGLVertexBuilder* vsBuilder = pb->getVertexShaderBuilder();

        // emit attributes
        vsBuilder->emitAttributes(cte);

        GrGLVertToFrag v(kVec2f_GrSLType);
        pb->addVarying("TextureCoords", &v);
        // this is only used with text, so our texture bounds always match the glyph atlas
        if (cte.maskFormat() == kA8_GrMaskFormat) {
            vsBuilder->codeAppendf("%s = vec2(" GR_FONT_ATLAS_A8_RECIP_WIDTH ", "
                                   GR_FONT_ATLAS_RECIP_HEIGHT ")*%s;", v.vsOut(),
                                   cte.inTextureCoords()->fName);
        } else {
            vsBuilder->codeAppendf("%s = vec2(" GR_FONT_ATLAS_RECIP_WIDTH ", "
                                   GR_FONT_ATLAS_RECIP_HEIGHT ")*%s;", v.vsOut(),
                                   cte.inTextureCoords()->fName);
        }

        // Setup pass through color
        if (!cte.colorIgnored()) {
            if (cte.hasVertexColor()) {
                pb->addPassThroughAttribute(cte.inColor(), args.fOutputColor);
            } else {
                this->setupUniformColor(pb, args.fOutputColor, &fColorUniform);
            }
        }

        // Setup position
        this->setupPosition(pb, gpArgs, cte.inPosition()->fName);

        // emit transforms
        this->emitTransforms(args.fPB, gpArgs->fPositionVar, cte.inPosition()->fName,
                             cte.localMatrix(), args.fTransformsIn, args.fTransformsOut);

        GrGLFragmentBuilder* fsBuilder = pb->getFragmentShaderBuilder();
        if (cte.maskFormat() == kARGB_GrMaskFormat) {
            fsBuilder->codeAppendf("%s = ", args.fOutputColor);
            fsBuilder->appendTextureLookupAndModulate(args.fOutputColor,
                                                      args.fSamplers[0],
                                                      v.fsIn(),
                                                      kVec2f_GrSLType);
            fsBuilder->codeAppend(";");
            fsBuilder->codeAppendf("%s = vec4(1);", args.fOutputCoverage);
        } else {
            fsBuilder->codeAppendf("%s = ", args.fOutputCoverage);
            fsBuilder->appendTextureLookup(args.fSamplers[0], v.fsIn(), kVec2f_GrSLType);
            fsBuilder->codeAppend(";");
        }
    }

    virtual void emitCode(GrGLFPBuilder* builder,
                          const GrFragmentProcessor&,
                          const char* outputColor,
                          const char* inputColor,
                          const TransformedCoordsArray& coords,
                          const TextureSamplerArray& samplers) override {
        // Using highp for GLES here in order to avoid some precision issues on specific GPUs.
        GrGLShaderVar tmpVar("tmpColor", kVec4f_GrSLType, 0, kHigh_GrSLPrecision);
        SkString tmpDecl;
        tmpVar.appendDecl(builder->ctxInfo(), &tmpDecl);

        GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();

        fsBuilder->codeAppendf("%s;", tmpDecl.c_str());

        fsBuilder->codeAppendf("%s = ", tmpVar.c_str());
        fsBuilder->appendTextureLookup(samplers[0], coords[0].c_str(), coords[0].getType());
        fsBuilder->codeAppend(";");

        if (GrConfigConversionEffect::kNone_PMConversion == fPMConversion) {
            SkASSERT(fSwapRedAndBlue);
            fsBuilder->codeAppendf("%s = %s.bgra;", outputColor, tmpVar.c_str());
        } else {
            const char* swiz = fSwapRedAndBlue ? "bgr" : "rgb";
            switch (fPMConversion) {
                case GrConfigConversionEffect::kMulByAlpha_RoundUp_PMConversion:
                    fsBuilder->codeAppendf(
                        "%s = vec4(ceil(%s.%s * %s.a * 255.0) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                    break;
                case GrConfigConversionEffect::kMulByAlpha_RoundDown_PMConversion:
                    // Add a compensation(0.001) here to avoid the side effect of the floor operation.
                    // In Intel GPUs, the integer value converted from floor(%s.r * 255.0) / 255.0
                    // is less than the integer value converted from  %s.r by 1 when the %s.r is
                    // converted from the integer value 2^n, such as 1, 2, 4, 8, etc.
                    fsBuilder->codeAppendf(
                        "%s = vec4(floor(%s.%s * %s.a * 255.0 + 0.001) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                    break;
                case GrConfigConversionEffect::kDivByAlpha_RoundUp_PMConversion:
                    fsBuilder->codeAppendf(
                        "%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(ceil(%s.%s / %s.a * 255.0) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                    break;
                case GrConfigConversionEffect::kDivByAlpha_RoundDown_PMConversion:
                    fsBuilder->codeAppendf(
                        "%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(floor(%s.%s / %s.a * 255.0) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), swiz, tmpVar.c_str(), tmpVar.c_str());
                    break;
                default:
                    SkFAIL("Unknown conversion op.");
                    break;
            }
            fsBuilder->codeAppendf("%s = %s;", outputColor, tmpVar.c_str());
        }
        SkString modulate;
        GrGLSLMulVarBy4f(&modulate, outputColor, inputColor);
        fsBuilder->codeAppend(modulate.c_str());
    }

        virtual void emitCode(EmitArgs& args) override {
            if (nullptr == args.fInputColor) {
                args.fInputColor = "vec4(1)";
            }

            GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
            fsBuilder->codeAppendf("\tfloat luma = dot(vec3(%f, %f, %f), %s.rgb);\n",
                                   SK_ITU_BT709_LUM_COEFF_R,
                                   SK_ITU_BT709_LUM_COEFF_G,
                                   SK_ITU_BT709_LUM_COEFF_B,
                                   args.fInputColor);
            fsBuilder->codeAppendf("\t%s = vec4(0, 0, 0, luma);\n",
                                   args.fOutputColor);

        }

 void emitCode(GrGLFPBuilder* builder,
                 const GrFragmentProcessor& fp,
                 const char* outputColor,
                 const char* inputColor,
                 const TransformedCoordsArray& coords,
                 const TextureSamplerArray& samplers) {
     GrGLFragmentBuilder* fpb = builder->getFragmentShaderBuilder();
     fpb->codeAppendf("vec2 c = %s;", fpb->ensureFSCoords2D(coords, 0).c_str());
     fpb->codeAppend("vec2 r = mod(c, vec2(20.0));");
     fpb->codeAppend("vec4 color = vec4(0.5*sin(c.x / 15.0) + 0.5,"
                                         "0.5*cos((c.x + c.y) / 15.0) + 0.5,"
                                         "(r.x + r.y) / 20.0,"
                                         "distance(r, vec2(15.0)) / 20.0 + 0.2);");
     fpb->codeAppendf("color.rgb *= color.a;"
                         "%s = color * %s;",
                         outputColor, GrGLSLExpr4(inputColor).c_str());
 }

 virtual void emitCode(EmitArgs& args) override {
     GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
     fsBuilder->codeAppendf("\t%s = ", args.fOutputColor);
     fsBuilder->appendTextureLookupAndModulate(args.fInputColor,
                                               args.fSamplers[0],
                                               args.fCoords[0].c_str(),
                                               args.fCoords[0].getType());
     fsBuilder->codeAppend(";\n");
 }

        void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
            const QuadEdgeEffect& qe = args.fGP.cast<QuadEdgeEffect>();
            GrGLGPBuilder* pb = args.fPB;
            GrGLVertexBuilder* vsBuilder = pb->getVertexShaderBuilder();

            // emit attributes
            vsBuilder->emitAttributes(qe);

            GrGLVertToFrag v(kVec4f_GrSLType);
            args.fPB->addVarying("QuadEdge", &v);
            vsBuilder->codeAppendf("%s = %s;", v.vsOut(), qe.inQuadEdge()->fName);

            const BatchTracker& local = args.fBT.cast<BatchTracker>();

            // Setup pass through color
            this->setupColorPassThrough(pb, local.fInputColorType, args.fOutputColor, NULL,
                                        &fColorUniform);

            // Setup position
            this->setupPosition(pb, gpArgs, qe.inPosition()->fName, qe.viewMatrix());

            // emit transforms
            this->emitTransforms(args.fPB, gpArgs->fPositionVar, qe.inPosition()->fName,
                                 qe.localMatrix(), args.fTransformsIn, args.fTransformsOut);

            GrGLFragmentBuilder* fsBuilder = args.fPB->getFragmentShaderBuilder();

            SkAssertResult(fsBuilder->enableFeature(
                    GrGLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));
            fsBuilder->codeAppendf("float edgeAlpha;");

            // keep the derivative instructions outside the conditional
            fsBuilder->codeAppendf("vec2 duvdx = dFdx(%s.xy);", v.fsIn());
            fsBuilder->codeAppendf("vec2 duvdy = dFdy(%s.xy);", v.fsIn());
            fsBuilder->codeAppendf("if (%s.z > 0.0 && %s.w > 0.0) {", v.fsIn(), v.fsIn());
            // today we know z and w are in device space. We could use derivatives
            fsBuilder->codeAppendf("edgeAlpha = min(min(%s.z, %s.w) + 0.5, 1.0);", v.fsIn(),
                                    v.fsIn());
            fsBuilder->codeAppendf ("} else {");
            fsBuilder->codeAppendf("vec2 gF = vec2(2.0*%s.x*duvdx.x - duvdx.y,"
                                   "               2.0*%s.x*duvdy.x - duvdy.y);",
                                   v.fsIn(), v.fsIn());
            fsBuilder->codeAppendf("edgeAlpha = (%s.x*%s.x - %s.y);", v.fsIn(), v.fsIn(),
                                    v.fsIn());
            fsBuilder->codeAppendf("edgeAlpha = "
                                   "clamp(0.5 - edgeAlpha / length(gF), 0.0, 1.0);}");

            fsBuilder->codeAppendf("%s = vec4(edgeAlpha);", args.fOutputCoverage);
        }

        void emitCode(GrGLFPBuilder* builder,
                      const GrFragmentProcessor& fp,
                      const char* outputColor,
                      const char* inputColor,
                      const TransformedCoordsArray& coords,
                      const TextureSamplerArray& samplers) override {

            GrGLFragmentBuilder* fpb = builder->getFragmentShaderBuilder();

            // add uniforms
            const char* lightDirUniName = NULL;
            fLightDirUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                               kVec3f_GrSLType, kDefault_GrSLPrecision,
                                               "LightDir", &lightDirUniName);

            const char* lightColorUniName = NULL;
            fLightColorUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                 kVec4f_GrSLType, kDefault_GrSLPrecision,
                                                 "LightColor", &lightColorUniName);

            const char* ambientColorUniName = NULL;
            fAmbientColorUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                   kVec4f_GrSLType, kDefault_GrSLPrecision,
                                                   "AmbientColor", &ambientColorUniName);

            fpb->codeAppend("vec4 diffuseColor = ");
            fpb->appendTextureLookupAndModulate(inputColor, samplers[0], 
                                                coords[0].c_str(), coords[0].getType());
            fpb->codeAppend(";");

            fpb->codeAppend("vec4 normalColor = ");
            fpb->appendTextureLookup(samplers[1], coords[0].c_str(), coords[0].getType());
            fpb->codeAppend(";");

            fpb->codeAppend("vec3 normal = normalize(2.0*(normalColor.rgb - vec3(0.5)));");
            fpb->codeAppendf("vec3 lightDir = normalize(%s);", lightDirUniName);
            fpb->codeAppend("float NdotL = dot(normal, lightDir);");
            // diffuse light
            fpb->codeAppendf("vec3 result = %s.rgb*diffuseColor.rgb*NdotL;", lightColorUniName);
            // ambient light
            fpb->codeAppendf("result += %s.rgb;", ambientColorUniName);
            fpb->codeAppendf("%s = vec4(result.rgb, diffuseColor.a);", outputColor);
        }

 virtual void emitCode(GrGLFPBuilder* builder,
                       const GrFragmentProcessor& fp,
                       const char* outputColor,
                       const char* inputColor,
                       const TransformedCoordsArray&,
                       const TextureSamplerArray&) {
     // pass through
     GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     fsBuilder->codeAppendf("%s = %s;\n", outputColor, inputColor);
 }

void GrColorCubeEffect::GLProcessor::emitCode(GrGLFPBuilder* builder,
                                              const GrFragmentProcessor&,
                                              const char* outputColor,
                                              const char* inputColor,
                                              const TransformedCoordsArray& coords,
                                              const TextureSamplerArray& samplers) {
    if (NULL == inputColor) {
        inputColor = "vec4(1)";
    }

    fColorCubeSizeUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                            kFloat_GrSLType, kDefault_GrSLPrecision,
                                            "Size");
    const char* colorCubeSizeUni = builder->getUniformCStr(fColorCubeSizeUni);
    fColorCubeInvSizeUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                               kFloat_GrSLType, kDefault_GrSLPrecision,
                                               "InvSize");
    const char* colorCubeInvSizeUni = builder->getUniformCStr(fColorCubeInvSizeUni);

    const char* nonZeroAlpha = "nonZeroAlpha";
    const char* unPMColor = "unPMColor";
    const char* cubeIdx = "cubeIdx";
    const char* cCoords1 = "cCoords1";
    const char* cCoords2 = "cCoords2";

    // Note: if implemented using texture3D in OpenGL ES older than OpenGL ES 3.0,
    //       the shader might need "#extension GL_OES_texture_3D : enable".

    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();

    // Unpremultiply color
    fsBuilder->codeAppendf("\tfloat %s = max(%s.a, 0.00001);\n", nonZeroAlpha, inputColor);
    fsBuilder->codeAppendf("\tvec4 %s = vec4(%s.rgb / %s, %s);\n",
                           unPMColor, inputColor, nonZeroAlpha, nonZeroAlpha);

    // Fit input color into the cube.
    fsBuilder->codeAppendf(
        "vec3 %s = vec3(%s.rg * vec2((%s - 1.0) * %s) + vec2(0.5 * %s), %s.b * (%s - 1.0));\n",
        cubeIdx, unPMColor, colorCubeSizeUni, colorCubeInvSizeUni, colorCubeInvSizeUni,
        unPMColor, colorCubeSizeUni);

    // Compute y coord for for texture fetches.
    fsBuilder->codeAppendf("vec2 %s = vec2(%s.r, (floor(%s.b) + %s.g) * %s);\n",
                           cCoords1, cubeIdx, cubeIdx, cubeIdx, colorCubeInvSizeUni);
    fsBuilder->codeAppendf("vec2 %s = vec2(%s.r, (ceil(%s.b) + %s.g) * %s);\n",
                           cCoords2, cubeIdx, cubeIdx, cubeIdx, colorCubeInvSizeUni);

    // Apply the cube.
    fsBuilder->codeAppendf("%s = vec4(mix(", outputColor);
    fsBuilder->appendTextureLookup(samplers[0], cCoords1);
    fsBuilder->codeAppend(".rgb, ");
    fsBuilder->appendTextureLookup(samplers[0], cCoords2);

    // Premultiply color by alpha. Note that the input alpha is not modified by this shader.
    fsBuilder->codeAppendf(".rgb, fract(%s.b)) * vec3(%s), %s.a);\n",
                           cubeIdx, nonZeroAlpha, inputColor);
}

 void emitCode(EmitArgs& args) override {
     GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
     const char* colorUni;
     fColorUniform = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                         kVec4f_GrSLType, kMedium_GrSLPrecision, "constantColor",
                                         &colorUni);
     switch (args.fFp.cast<GrConstColorProcessor>().inputMode()) {
         case GrConstColorProcessor::kIgnore_InputMode:
             fsBuilder->codeAppendf("%s = %s;", args.fOutputColor, colorUni);
             break;
         case GrConstColorProcessor::kModulateRGBA_InputMode:
             fsBuilder->codeAppendf("%s = %s * %s;", args.fOutputColor, args.fInputColor,
                                    colorUni);
             break;
         case GrConstColorProcessor::kModulateA_InputMode:
             fsBuilder->codeAppendf("%s = %s.a * %s;", args.fOutputColor, args.fInputColor,
                                    colorUni);
             break;
     }
 }