C++ GrGLFragmentBuilder类代码示例

void GrGLCubicEffect::onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) {
    GrGLVertexBuilder* vsBuilder = args.fPB->getVertexShaderBuilder();
    const GrCubicEffect& gp = args.fGP.cast<GrCubicEffect>();
    const CubicBatchTracker& local = args.fBT.cast<CubicBatchTracker>();

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

    GrGLVertToFrag v(kVec4f_GrSLType);
    args.fPB->addVarying("CubicCoeffs", &v, kHigh_GrSLPrecision);
    vsBuilder->codeAppendf("%s = %s;", v.vsOut(), gp.inCubicCoeffs()->fName);

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

    // Setup position
    this->setupPosition(args.fPB, gpArgs, gp.inPosition()->fName, gp.viewMatrix());

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

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

    GrGLShaderVar edgeAlpha("edgeAlpha", kFloat_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar dklmdx("dklmdx", kVec3f_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar dklmdy("dklmdy", kVec3f_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar dfdx("dfdx", kFloat_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar dfdy("dfdy", kFloat_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar gF("gF", kVec2f_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar gFM("gFM", kFloat_GrSLType, 0, kHigh_GrSLPrecision);
    GrGLShaderVar func("func", kFloat_GrSLType, 0, kHigh_GrSLPrecision);

    fsBuilder->declAppend(edgeAlpha);
    fsBuilder->declAppend(dklmdx);
    fsBuilder->declAppend(dklmdy);
    fsBuilder->declAppend(dfdx);
    fsBuilder->declAppend(dfdy);
    fsBuilder->declAppend(gF);
    fsBuilder->declAppend(gFM);
    fsBuilder->declAppend(func);

    switch (fEdgeType) {
        case kHairlineAA_GrProcessorEdgeType: {
            SkAssertResult(fsBuilder->enableFeature(
                    GrGLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));
            fsBuilder->codeAppendf("%s = dFdx(%s.xyz);", dklmdx.c_str(), v.fsIn());
            fsBuilder->codeAppendf("%s = dFdy(%s.xyz);", dklmdy.c_str(), v.fsIn());
            fsBuilder->codeAppendf("%s = 3.0 * %s.x * %s.x * %s.x - %s.y * %s.z - %s.z * %s.y;",
                                   dfdx.c_str(), v.fsIn(), v.fsIn(), dklmdx.c_str(), v.fsIn(),
                                   dklmdx.c_str(), v.fsIn(), dklmdx.c_str());
            fsBuilder->codeAppendf("%s = 3.0 * %s.x * %s.x * %s.x - %s.y * %s.z - %s.z * %s.y;",
                                   dfdy.c_str(), v.fsIn(), v.fsIn(), dklmdy.c_str(), v.fsIn(),
                                   dklmdy.c_str(), v.fsIn(), dklmdy.c_str());
            fsBuilder->codeAppendf("%s = vec2(%s, %s);", gF.c_str(), dfdx.c_str(), dfdy.c_str());
            fsBuilder->codeAppendf("%s = sqrt(dot(%s, %s));", gFM.c_str(), gF.c_str(), gF.c_str());
            fsBuilder->codeAppendf("%s = %s.x * %s.x * %s.x - %s.y * %s.z;",
                                   func.c_str(), v.fsIn(), v.fsIn(), v.fsIn(), v.fsIn(), v.fsIn());
            fsBuilder->codeAppendf("%s = abs(%s);", func.c_str(), func.c_str());
            fsBuilder->codeAppendf("%s = %s / %s;",
                                   edgeAlpha.c_str(), func.c_str(), gFM.c_str());
            fsBuilder->codeAppendf("%s = max(1.0 - %s, 0.0);",
                                   edgeAlpha.c_str(), edgeAlpha.c_str());
            // Add line below for smooth cubic ramp
            // fsBuilder->codeAppendf("%s = %s * %s * (3.0 - 2.0 * %s);",
            //                        edgeAlpha.c_str(), edgeAlpha.c_str(), edgeAlpha.c_str(),
            //                        edgeAlpha.c_str());
            break;
        }
        case kFillAA_GrProcessorEdgeType: {
            SkAssertResult(fsBuilder->enableFeature(
                    GrGLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));
            fsBuilder->codeAppendf("%s = dFdx(%s.xyz);", dklmdx.c_str(), v.fsIn());
            fsBuilder->codeAppendf("%s = dFdy(%s.xyz);", dklmdy.c_str(), v.fsIn());
            fsBuilder->codeAppendf("%s ="
                                   "3.0 * %s.x * %s.x * %s.x - %s.y * %s.z - %s.z * %s.y;",
                                   dfdx.c_str(), v.fsIn(), v.fsIn(), dklmdx.c_str(), v.fsIn(),
                                   dklmdx.c_str(), v.fsIn(), dklmdx.c_str());
            fsBuilder->codeAppendf("%s = 3.0 * %s.x * %s.x * %s.x - %s.y * %s.z - %s.z * %s.y;",
                                   dfdy.c_str(), v.fsIn(), v.fsIn(), dklmdy.c_str(), v.fsIn(),
                                   dklmdy.c_str(), v.fsIn(), dklmdy.c_str());
            fsBuilder->codeAppendf("%s = vec2(%s, %s);", gF.c_str(), dfdx.c_str(), dfdy.c_str());
            fsBuilder->codeAppendf("%s = sqrt(dot(%s, %s));", gFM.c_str(), gF.c_str(), gF.c_str());
            fsBuilder->codeAppendf("%s = %s.x * %s.x * %s.x - %s.y * %s.z;",
                                   func.c_str(), v.fsIn(), v.fsIn(), v.fsIn(), v.fsIn(), v.fsIn());
            fsBuilder->codeAppendf("%s = %s / %s;",
                                   edgeAlpha.c_str(), func.c_str(), gFM.c_str());
            fsBuilder->codeAppendf("%s = clamp(1.0 - %s, 0.0, 1.0);",
                                   edgeAlpha.c_str(), edgeAlpha.c_str());
            // Add line below for smooth cubic ramp
            // fsBuilder->codeAppendf("%s = %s * %s * (3.0 - 2.0 * %s);",
            //                        edgeAlpha.c_str(), edgeAlpha.c_str(), edgeAlpha.c_str(),
            //                        edgeAlpha.c_str());
            break;
        }
        case kFillBW_GrProcessorEdgeType: {
            fsBuilder->codeAppendf("%s = %s.x * %s.x * %s.x - %s.y * %s.z;",
                                   edgeAlpha.c_str(), v.fsIn(), v.fsIn(), v.fsIn(), v.fsIn(), v.fsIn());
            fsBuilder->codeAppendf("%s = float(%s < 0.0);", edgeAlpha.c_str(), edgeAlpha.c_str());
//.........这里部分代码省略.........

void GLEllipticalRRectEffect::emitCode(GrGLFPBuilder* builder,
                                       const GrFragmentProcessor& effect,
                                       const char* outputColor,
                                       const char* inputColor,
                                       const TransformedCoordsArray&,
                                       const TextureSamplerArray& samplers) {
    const EllipticalRRectEffect& erre = effect.cast<EllipticalRRectEffect>();
    const char *rectName;
    // The inner rect is the rrect bounds inset by the x/y radii
    fInnerRectUniform = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                            kVec4f_GrSLType, kDefault_GrSLPrecision,
                                            "innerRect",
                                            &rectName);

    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
    const char* fragmentPos = fsBuilder->fragmentPosition();
    // At each quarter-ellipse corner we compute a vector that is the offset of the fragment pos
    // to the ellipse center. The vector is pinned in x and y to be in the quarter-plane relevant
    // to that corner. This means that points near the interior near the rrect top edge will have
    // a vector that points straight up for both the TL left and TR corners. Computing an
    // alpha from this vector at either the TR or TL corner will give the correct result. Similarly,
    // fragments near the other three edges will get the correct AA. Fragments in the interior of
    // the rrect will have a (0,0) vector at all four corners. So long as the radii > 0.5 they will
    // correctly produce an alpha value of 1 at all four corners. We take the min of all the alphas.
    // The code below is a simplified version of the above that performs maxs on the vector
    // components before computing distances and alpha values so that only one distance computation
    // need be computed to determine the min alpha.
    fsBuilder->codeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
    fsBuilder->codeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
    switch (erre.getRRect().getType()) {
        case SkRRect::kSimple_Type: {
            const char *invRadiiXYSqdName;
            fInvRadiiSqdUniform = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                      kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                      "invRadiiXY",
                                                      &invRadiiXYSqdName);
            fsBuilder->codeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
            // Z is the x/y offsets divided by squared radii.
            fsBuilder->codeAppendf("\t\tvec2 Z = dxy * %s;\n", invRadiiXYSqdName);
            break;
        }
        case SkRRect::kNinePatch_Type: {
            const char *invRadiiLTRBSqdName;
            fInvRadiiSqdUniform = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                      kVec4f_GrSLType, kDefault_GrSLPrecision,
                                                      "invRadiiLTRB",
                                                      &invRadiiLTRBSqdName);
            fsBuilder->codeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
            // Z is the x/y offsets divided by squared radii. We only care about the (at most) one
            // corner where both the x and y offsets are positive, hence the maxes. (The inverse
            // squared radii will always be positive.)
            fsBuilder->codeAppendf("\t\tvec2 Z = max(max(dxy0 * %s.xy, dxy1 * %s.zw), 0.0);\n",
                                   invRadiiLTRBSqdName, invRadiiLTRBSqdName);
            break;
        }
        default:
            SkFAIL("RRect should always be simple or nine-patch.");
    }
    // implicit is the evaluation of (x/a)^2 + (y/b)^2 - 1.
    fsBuilder->codeAppend("\t\tfloat implicit = dot(Z, dxy) - 1.0;\n");
    // grad_dot is the squared length of the gradient of the implicit.
    fsBuilder->codeAppendf("\t\tfloat grad_dot = 4.0 * dot(Z, Z);\n");
    // avoid calling inversesqrt on zero.
    fsBuilder->codeAppend("\t\tgrad_dot = max(grad_dot, 1.0e-4);\n");
    fsBuilder->codeAppendf("\t\tfloat approx_dist = implicit * inversesqrt(grad_dot);\n");

    if (kFillAA_GrProcessorEdgeType == erre.getEdgeType()) {
        fsBuilder->codeAppend("\t\tfloat alpha = clamp(0.5 - approx_dist, 0.0, 1.0);\n");
    } else {
        fsBuilder->codeAppend("\t\tfloat alpha = clamp(0.5 + approx_dist, 0.0, 1.0);\n");
    }

    fsBuilder->codeAppendf("\t\t%s = %s;\n", outputColor,
                           (GrGLSLExpr4(inputColor) * GrGLSLExpr1("alpha")).c_str());
}

void GrGLMagnifierEffect::emitCode(GrGLFPBuilder* builder,
                                   const GrFragmentProcessor&,
                                   const char* outputColor,
                                   const char* inputColor,
                                   const TransformedCoordsArray& coords,
                                   const TextureSamplerArray& samplers) {
    fOffsetVar = builder->addUniform(
        GrGLProgramBuilder::kFragment_Visibility |
        GrGLProgramBuilder::kVertex_Visibility,
        kVec2f_GrSLType, kDefault_GrSLPrecision, "Offset");
    fInvZoomVar = builder->addUniform(
        GrGLProgramBuilder::kFragment_Visibility |
        GrGLProgramBuilder::kVertex_Visibility,
        kVec2f_GrSLType, kDefault_GrSLPrecision, "InvZoom");
    fInvInsetVar = builder->addUniform(
        GrGLProgramBuilder::kFragment_Visibility |
        GrGLProgramBuilder::kVertex_Visibility,
        kVec2f_GrSLType, kDefault_GrSLPrecision, "InvInset");
    fBoundsVar = builder->addUniform(
        GrGLProgramBuilder::kFragment_Visibility |
        GrGLProgramBuilder::kVertex_Visibility,
        kVec4f_GrSLType, kDefault_GrSLPrecision, "Bounds");

    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
    SkString coords2D = fsBuilder->ensureFSCoords2D(coords, 0);
    fsBuilder->codeAppendf("\t\tvec2 coord = %s;\n", coords2D.c_str());
    fsBuilder->codeAppendf("\t\tvec2 zoom_coord = %s + %s * %s;\n",
                           builder->getUniformCStr(fOffsetVar),
                           coords2D.c_str(),
                           builder->getUniformCStr(fInvZoomVar));
    const char* bounds = builder->getUniformCStr(fBoundsVar);
    fsBuilder->codeAppendf("\t\tvec2 delta = (coord - %s.xy) * %s.zw;\n", bounds, bounds);
    fsBuilder->codeAppendf("\t\tdelta = min(delta, vec2(1.0, 1.0) - delta);\n");
    fsBuilder->codeAppendf("\t\tdelta = delta * %s;\n", builder->getUniformCStr(fInvInsetVar));

    fsBuilder->codeAppend("\t\tfloat weight = 0.0;\n");
    fsBuilder->codeAppend("\t\tif (delta.s < 2.0 && delta.t < 2.0) {\n");
    fsBuilder->codeAppend("\t\t\tdelta = vec2(2.0, 2.0) - delta;\n");
    fsBuilder->codeAppend("\t\t\tfloat dist = length(delta);\n");
    fsBuilder->codeAppend("\t\t\tdist = max(2.0 - dist, 0.0);\n");
    fsBuilder->codeAppend("\t\t\tweight = min(dist * dist, 1.0);\n");
    fsBuilder->codeAppend("\t\t} else {\n");
    fsBuilder->codeAppend("\t\t\tvec2 delta_squared = delta * delta;\n");
    fsBuilder->codeAppend("\t\t\tweight = min(min(delta_squared.x, delta_squared.y), 1.0);\n");
    fsBuilder->codeAppend("\t\t}\n");

    fsBuilder->codeAppend("\t\tvec2 mix_coord = mix(coord, zoom_coord, weight);\n");
    fsBuilder->codeAppend("\t\tvec4 output_color = ");
    fsBuilder->appendTextureLookup(samplers[0], "mix_coord");
    fsBuilder->codeAppend(";\n");

    fsBuilder->codeAppendf("\t\t%s = output_color;", outputColor);
    SkString modulate;
    GrGLSLMulVarBy4f(&modulate, outputColor, inputColor);
    fsBuilder->codeAppend(modulate.c_str());
}

    virtual void emitCode(EmitArgs& args) 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(args.fBuilder->ctxInfo(), &tmpDecl);

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

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

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

        if (GrConfigConversionEffect::kNone_PMConversion == fPMConversion) {
            SkASSERT(fSwapRedAndBlue);
            fsBuilder->codeAppendf("%s = %s.bgra;", args.fOutputColor, 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;", args.fOutputColor, tmpVar.c_str());
        }
        SkString modulate;
        GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
        fsBuilder->codeAppend(modulate.c_str());
    }

 virtual void emitCode(EmitArgs& args) override {
     // pass through
     GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
     fsBuilder->codeAppendf("%s = %s;\n", args.fOutputColor, args.fInputColor);
 }

void GLEllipseEffect::emitCode(EmitArgs& args) {
    const EllipseEffect& ee = args.fFp.cast<EllipseEffect>();
    const char *ellipseName;
    // The ellipse uniform is (center.x, center.y, 1 / rx^2, 1 / ry^2)
    // The last two terms can underflow on mediump, so we use highp.
    fEllipseUniform = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                         kVec4f_GrSLType, kHigh_GrSLPrecision,
                                         "ellipse",
                                         &ellipseName);

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

    // d is the offset to the ellipse center
    fsBuilder->codeAppendf("\t\tvec2 d = %s.xy - %s.xy;\n", fragmentPos, ellipseName);
    fsBuilder->codeAppendf("\t\tvec2 Z = d * %s.zw;\n", ellipseName);
    // implicit is the evaluation of (x/rx)^2 + (y/ry)^2 - 1.
    fsBuilder->codeAppend("\t\tfloat implicit = dot(Z, d) - 1.0;\n");
    // grad_dot is the squared length of the gradient of the implicit.
    fsBuilder->codeAppendf("\t\tfloat grad_dot = 4.0 * dot(Z, Z);\n");
    // avoid calling inversesqrt on zero.
    fsBuilder->codeAppend("\t\tgrad_dot = max(grad_dot, 1.0e-4);\n");
    fsBuilder->codeAppendf("\t\tfloat approx_dist = implicit * inversesqrt(grad_dot);\n");

    switch (ee.getEdgeType()) {
        case kFillAA_GrProcessorEdgeType:
            fsBuilder->codeAppend("\t\tfloat alpha = clamp(0.5 - approx_dist, 0.0, 1.0);\n");
            break;
        case kInverseFillAA_GrProcessorEdgeType:
            fsBuilder->codeAppend("\t\tfloat alpha = clamp(0.5 + approx_dist, 0.0, 1.0);\n");
            break;
        case kFillBW_GrProcessorEdgeType:
            fsBuilder->codeAppend("\t\tfloat alpha = approx_dist > 0.0 ? 0.0 : 1.0;\n");
            break;
        case kInverseFillBW_GrProcessorEdgeType:
            fsBuilder->codeAppend("\t\tfloat alpha = approx_dist > 0.0 ? 1.0 : 0.0;\n");
            break;
        case kHairlineAA_GrProcessorEdgeType:
            SkFAIL("Hairline not expected here.");
    }

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

void GrGLPerlinNoise::emitCode(GrGLFPBuilder* builder,
                               const GrFragmentProcessor&,
                               const char* outputColor,
                               const char* inputColor,
                               const TransformedCoordsArray& coords,
                               const TextureSamplerArray& samplers) {
    sk_ignore_unused_variable(inputColor);

    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
    SkString vCoords = fsBuilder->ensureFSCoords2D(coords, 0);

    fBaseFrequencyUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                            kVec2f_GrSLType, kDefault_GrSLPrecision,
                                            "baseFrequency");
    const char* baseFrequencyUni = builder->getUniformCStr(fBaseFrequencyUni);
    fAlphaUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                    kFloat_GrSLType, kDefault_GrSLPrecision,
                                    "alpha");
    const char* alphaUni = builder->getUniformCStr(fAlphaUni);

    const char* stitchDataUni = NULL;
    if (fStitchTiles) {
        fStitchDataUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                             kVec2f_GrSLType, kDefault_GrSLPrecision,
                                             "stitchData");
        stitchDataUni = builder->getUniformCStr(fStitchDataUni);
    }

    // There are 4 lines, so the center of each line is 1/8, 3/8, 5/8 and 7/8
    const char* chanCoordR  = "0.125";
    const char* chanCoordG  = "0.375";
    const char* chanCoordB  = "0.625";
    const char* chanCoordA  = "0.875";
    const char* chanCoord   = "chanCoord";
    const char* stitchData  = "stitchData";
    const char* ratio       = "ratio";
    const char* noiseVec    = "noiseVec";
    const char* noiseSmooth = "noiseSmooth";
    const char* floorVal    = "floorVal";
    const char* fractVal    = "fractVal";
    const char* uv          = "uv";
    const char* ab          = "ab";
    const char* latticeIdx  = "latticeIdx";
    const char* bcoords     = "bcoords";
    const char* lattice     = "lattice";
    const char* inc8bit     = "0.00390625";  // 1.0 / 256.0
    // This is the math to convert the two 16bit integer packed into rgba 8 bit input into a
    // [-1,1] vector and perform a dot product between that vector and the provided vector.
    const char* dotLattice  = "dot(((%s.ga + %s.rb * vec2(%s)) * vec2(2.0) - vec2(1.0)), %s);";

    // Add noise function
    static const GrGLShaderVar gPerlinNoiseArgs[] =  {
        GrGLShaderVar(chanCoord, kFloat_GrSLType),
        GrGLShaderVar(noiseVec, kVec2f_GrSLType)
    };

    static const GrGLShaderVar gPerlinNoiseStitchArgs[] =  {
        GrGLShaderVar(chanCoord, kFloat_GrSLType),
        GrGLShaderVar(noiseVec, kVec2f_GrSLType),
        GrGLShaderVar(stitchData, kVec2f_GrSLType)
    };

    SkString noiseCode;

    noiseCode.appendf("\tvec4 %s;\n", floorVal);
    noiseCode.appendf("\t%s.xy = floor(%s);\n", floorVal, noiseVec);
    noiseCode.appendf("\t%s.zw = %s.xy + vec2(1.0);\n", floorVal, floorVal);
    noiseCode.appendf("\tvec2 %s = fract(%s);\n", fractVal, noiseVec);

    // smooth curve : t * t * (3 - 2 * t)
    noiseCode.appendf("\n\tvec2 %s = %s * %s * (vec2(3.0) - vec2(2.0) * %s);",
        noiseSmooth, fractVal, fractVal, fractVal);

    // Adjust frequencies if we're stitching tiles
    if (fStitchTiles) {
        noiseCode.appendf("\n\tif(%s.x >= %s.x) { %s.x -= %s.x; }",
            floorVal, stitchData, floorVal, stitchData);
        noiseCode.appendf("\n\tif(%s.y >= %s.y) { %s.y -= %s.y; }",
            floorVal, stitchData, floorVal, stitchData);
        noiseCode.appendf("\n\tif(%s.z >= %s.x) { %s.z -= %s.x; }",
            floorVal, stitchData, floorVal, stitchData);
        noiseCode.appendf("\n\tif(%s.w >= %s.y) { %s.w -= %s.y; }",
            floorVal, stitchData, floorVal, stitchData);
    }

    // Get texture coordinates and normalize
    noiseCode.appendf("\n\t%s = fract(floor(mod(%s, 256.0)) / vec4(256.0));\n",
        floorVal, floorVal);

    // Get permutation for x
    {
        SkString xCoords("");
        xCoords.appendf("vec2(%s.x, 0.5)", floorVal);

        noiseCode.appendf("\n\tvec2 %s;\n\t%s.x = ", latticeIdx, latticeIdx);
        fsBuilder->appendTextureLookup(&noiseCode, samplers[0], xCoords.c_str(), kVec2f_GrSLType);
        noiseCode.append(".r;");
    }

    // Get permutation for x + 1
//.........这里部分代码省略.........

    void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override{
        const GrDistanceFieldA8TextGeoProc& dfTexEffect =
                args.fGP.cast<GrDistanceFieldA8TextGeoProc>();
        GrGLGPBuilder* pb = args.fPB;
        GrGLFragmentBuilder* fsBuilder = args.fPB->getFragmentShaderBuilder();
        SkAssertResult(fsBuilder->enableFeature(
                GrGLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));

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

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

#ifdef SK_GAMMA_APPLY_TO_A8
        // adjust based on gamma
        const char* distanceAdjustUniName = NULL;
        // width, height, 1/(3*width)
        fDistanceAdjustUni = args.fPB->addUniform(GrGLProgramBuilder::kFragment_Visibility,
            kFloat_GrSLType, kDefault_GrSLPrecision,
            "DistanceAdjust", &distanceAdjustUniName);
#endif

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

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

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

        // add varyings
        GrGLVertToFrag recipScale(kFloat_GrSLType);
        GrGLVertToFrag st(kVec2f_GrSLType);
        bool isSimilarity = SkToBool(dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag);
        args.fPB->addVarying("IntTextureCoords", &st, kHigh_GrSLPrecision);
        vsBuilder->codeAppendf("%s = %s;", st.vsOut(), dfTexEffect.inTextureCoords()->fName);

        // compute numbers to be hardcoded to convert texture coordinates from int to float
        SkASSERT(dfTexEffect.numTextures() == 1);
        GrTexture* atlas = dfTexEffect.textureAccess(0).getTexture();
        SkASSERT(atlas && SkIsPow2(atlas->width()) && SkIsPow2(atlas->height()));
        SkScalar recipWidth = 1.0f / atlas->width();
        SkScalar recipHeight = 1.0f / atlas->height();

        GrGLVertToFrag uv(kVec2f_GrSLType);
        args.fPB->addVarying("TextureCoords", &uv, kHigh_GrSLPrecision);
        vsBuilder->codeAppendf("%s = vec2(%.*f, %.*f) * %s;", uv.vsOut(),
                               GR_SIGNIFICANT_POW2_DECIMAL_DIG, recipWidth,
                               GR_SIGNIFICANT_POW2_DECIMAL_DIG, recipHeight,
                               dfTexEffect.inTextureCoords()->fName);
        
        // Use highp to work around aliasing issues
        fsBuilder->codeAppend(GrGLShaderVar::PrecisionString(kHigh_GrSLPrecision,
                                                             pb->ctxInfo().standard()));
        fsBuilder->codeAppendf("vec2 uv = %s;\n", uv.fsIn());

        fsBuilder->codeAppend("\tfloat texColor = ");
        fsBuilder->appendTextureLookup(args.fSamplers[0],
                                       "uv",
                                       kVec2f_GrSLType);
        fsBuilder->codeAppend(".r;\n");
        fsBuilder->codeAppend("\tfloat distance = "
                       SK_DistanceFieldMultiplier "*(texColor - " SK_DistanceFieldThreshold ");");
#ifdef SK_GAMMA_APPLY_TO_A8
        // adjust width based on gamma
        fsBuilder->codeAppendf("distance -= %s;", distanceAdjustUniName);
#endif

        fsBuilder->codeAppend("float afwidth;");
        if (isSimilarity) {
            // For uniform scale, we adjust for the effect of the transformation on the distance
            // by using the length of the gradient of the texture coordinates. We use st coordinates
            // to ensure we're mapping 1:1 from texel space to pixel space.

            // this gives us a smooth step across approximately one fragment
            // we use y to work around a Mali400 bug in the x direction
            fsBuilder->codeAppendf("afwidth = abs(" SK_DistanceFieldAAFactor "*dFdy(%s.y));",
                                       st.fsIn());
        } else {
            // For general transforms, to determine the amount of correction we multiply a unit
            // vector pointing along the SDF gradient direction by the Jacobian of the st coords
            // (which is the inverse transform for this fragment) and take the length of the result.
            fsBuilder->codeAppend("vec2 dist_grad = vec2(dFdx(distance), dFdy(distance));");
            // the length of the gradient may be 0, so we need to check for this
            // this also compensates for the Adreno, which likes to drop tiles on division by 0
            fsBuilder->codeAppend("float dg_len2 = dot(dist_grad, dist_grad);");
            fsBuilder->codeAppend("if (dg_len2 < 0.0001) {");
            fsBuilder->codeAppend("dist_grad = vec2(0.7071, 0.7071);");
            fsBuilder->codeAppend("} else {");
            fsBuilder->codeAppend("dist_grad = dist_grad*inversesqrt(dg_len2);");
            fsBuilder->codeAppend("}");
//.........这里部分代码省略.........

void GrGLConvexPolyEffect::emitCode(EmitArgs& args) {
    const GrConvexPolyEffect& cpe = args.fFp.cast<GrConvexPolyEffect>();

    const char *edgeArrayName;
    fEdgeUniform = args.fBuilder->addUniformArray(GrGLProgramBuilder::kFragment_Visibility,
                                            kVec3f_GrSLType,
                                             kDefault_GrSLPrecision,
                                             "edges",
                                            cpe.getEdgeCount(),
                                            &edgeArrayName);
    GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
    fsBuilder->codeAppend("\t\tfloat alpha = 1.0;\n");
    fsBuilder->codeAppend("\t\tfloat edge;\n");
    const char* fragmentPos = fsBuilder->fragmentPosition();
    for (int i = 0; i < cpe.getEdgeCount(); ++i) {
        fsBuilder->codeAppendf("\t\tedge = dot(%s[%d], vec3(%s.x, %s.y, 1));\n",
                               edgeArrayName, i, fragmentPos, fragmentPos);
        if (GrProcessorEdgeTypeIsAA(cpe.getEdgeType())) {
            fsBuilder->codeAppend("\t\tedge = clamp(edge, 0.0, 1.0);\n");
        } else {
            fsBuilder->codeAppend("\t\tedge = edge >= 0.5 ? 1.0 : 0.0;\n");
        }
        fsBuilder->codeAppend("\t\talpha *= edge;\n");
    }

    // Woe is me. See skbug.com/2149.
    if (kTegra2_GrGLRenderer == args.fBuilder->ctxInfo().renderer()) {
        fsBuilder->codeAppend("\t\tif (-1.0 == alpha) {\n\t\t\tdiscard;\n\t\t}\n");
    }

    if (GrProcessorEdgeTypeIsInverseFill(cpe.getEdgeType())) {
        fsBuilder->codeAppend("\talpha = 1.0 - alpha;\n");
    }
    fsBuilder->codeAppendf("\t%s = %s;\n", args.fOutputColor,
                           (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
}

        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);
        }

void GrGLDisplacementMapEffect::emitCode(GrGLFPBuilder* builder,
                                         const GrFragmentProcessor& fp,
                                         const char* outputColor,
                                         const char* inputColor,
                                         const TransformedCoordsArray& coords,
                                         const TextureSamplerArray& samplers) {
    const GrTextureDomain& domain = fp.cast<GrDisplacementMapEffect>().domain();
    sk_ignore_unused_variable(inputColor);

    fScaleUni = builder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                    kVec2f_GrSLType, kDefault_GrSLPrecision, "Scale");
    const char* scaleUni = builder->getUniformCStr(fScaleUni);
    const char* dColor = "dColor";
    const char* cCoords = "cCoords";
    const char* nearZero = "1e-6"; // Since 6.10352e−5 is the smallest half float, use
                                   // a number smaller than that to approximate 0, but
                                   // leave room for 32-bit float GPU rounding errors.

    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
    fsBuilder->codeAppendf("\t\tvec4 %s = ", dColor);
    fsBuilder->appendTextureLookup(samplers[0], coords[0].c_str(), coords[0].getType());
    fsBuilder->codeAppend(";\n");

    // Unpremultiply the displacement
    fsBuilder->codeAppendf("\t\t%s.rgb = (%s.a < %s) ? vec3(0.0) : clamp(%s.rgb / %s.a, 0.0, 1.0);",
                           dColor, dColor, nearZero, dColor, dColor);
    SkString coords2D = fsBuilder->ensureFSCoords2D(coords, 1);
    fsBuilder->codeAppendf("\t\tvec2 %s = %s + %s*(%s.",
                           cCoords, coords2D.c_str(), scaleUni, dColor);

    switch (fXChannelSelector) {
      case SkDisplacementMapEffect::kR_ChannelSelectorType:
        fsBuilder->codeAppend("r");
        break;
      case SkDisplacementMapEffect::kG_ChannelSelectorType:
        fsBuilder->codeAppend("g");
        break;
      case SkDisplacementMapEffect::kB_ChannelSelectorType:
        fsBuilder->codeAppend("b");
        break;
      case SkDisplacementMapEffect::kA_ChannelSelectorType:
        fsBuilder->codeAppend("a");
        break;
      case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
      default:
        SkDEBUGFAIL("Unknown X channel selector");
    }

    switch (fYChannelSelector) {
      case SkDisplacementMapEffect::kR_ChannelSelectorType:
        fsBuilder->codeAppend("r");
        break;
      case SkDisplacementMapEffect::kG_ChannelSelectorType:
        fsBuilder->codeAppend("g");
        break;
      case SkDisplacementMapEffect::kB_ChannelSelectorType:
        fsBuilder->codeAppend("b");
        break;
      case SkDisplacementMapEffect::kA_ChannelSelectorType:
        fsBuilder->codeAppend("a");
        break;
      case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
      default:
        SkDEBUGFAIL("Unknown Y channel selector");
    }
    fsBuilder->codeAppend("-vec2(0.5));\t\t");

    fGLDomain.sampleTexture(fsBuilder, domain, outputColor, SkString(cCoords), samplers[1]);
    fsBuilder->codeAppend(";\n");
}

void GrGLMorphologyEffect::emitCode(EmitArgs& args) {
    fPixelSizeUni = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                            kFloat_GrSLType, kDefault_GrSLPrecision,
                                            "PixelSize");
    const char* pixelSizeInc = args.fBuilder->getUniformCStr(fPixelSizeUni);
    fRangeUni = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                            kVec2f_GrSLType, kDefault_GrSLPrecision,
                                            "Range");
    const char* range = args.fBuilder->getUniformCStr(fRangeUni);

    GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
    SkString coords2D = fsBuilder->ensureFSCoords2D(args.fCoords, 0);
    const char* func;
    switch (fType) {
        case GrMorphologyEffect::kErode_MorphologyType:
            fsBuilder->codeAppendf("\t\t%s = vec4(1, 1, 1, 1);\n", args.fOutputColor);
            func = "min";
            break;
        case GrMorphologyEffect::kDilate_MorphologyType:
            fsBuilder->codeAppendf("\t\t%s = vec4(0, 0, 0, 0);\n", args.fOutputColor);
            func = "max";
            break;
        default:
            SkFAIL("Unexpected type");
            func = ""; // suppress warning
            break;
    }

    const char* dir;
    switch (fDirection) {
        case Gr1DKernelEffect::kX_Direction:
            dir = "x";
            break;
        case Gr1DKernelEffect::kY_Direction:
            dir = "y";
            break;
        default:
            SkFAIL("Unknown filter direction.");
            dir = ""; // suppress warning
    }

    // vec2 coord = coord2D;
    fsBuilder->codeAppendf("\t\tvec2 coord = %s;\n", coords2D.c_str());
    // coord.x -= radius * pixelSize;
    fsBuilder->codeAppendf("\t\tcoord.%s -= %d.0 * %s; \n", dir, fRadius, pixelSizeInc);
    if (fUseRange) {
        // highBound = min(highBound, coord.x + (width-1) * pixelSize);
        fsBuilder->codeAppendf("\t\tfloat highBound = min(%s.y, coord.%s + %f * %s);",
                               range, dir, float(width() - 1), pixelSizeInc);
        // coord.x = max(lowBound, coord.x);
        fsBuilder->codeAppendf("\t\tcoord.%s = max(%s.x, coord.%s);", dir, range, dir);
    }
    fsBuilder->codeAppendf("\t\tfor (int i = 0; i < %d; i++) {\n", width());
    fsBuilder->codeAppendf("\t\t\t%s = %s(%s, ", args.fOutputColor, func, args.fOutputColor);
    fsBuilder->appendTextureLookup(args.fSamplers[0], "coord");
    fsBuilder->codeAppend(");\n");
    // coord.x += pixelSize;
    fsBuilder->codeAppendf("\t\t\tcoord.%s += %s;\n", dir, pixelSizeInc);
    if (fUseRange) {
        // coord.x = min(highBound, coord.x);
        fsBuilder->codeAppendf("\t\t\tcoord.%s = min(highBound, coord.%s);", dir, dir);
    }
    fsBuilder->codeAppend("\t\t}\n");
    SkString modulate;
    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
    fsBuilder->codeAppend(modulate.c_str());
}

void GrGLFragmentProcessor::emitChild(int childIndex, const char* inputColor,
                                      const char* outputColor, EmitArgs& args) {
    GrGLFragmentBuilder* fb = args.fBuilder->getFragmentShaderBuilder();
    fb->onBeforeChildProcEmitCode();  // call first so mangleString is updated

    const GrFragmentProcessor& childProc = args.fFp.childProcessor(childIndex);

    /*
     * We now want to find the subset of coords and samplers that belong to the child and its
     * descendants and put that into childCoords and childSamplers. To do so, we'll do a forwards
     * linear search.
     *
     * Explanation:
     * Each GrFragmentProcessor has a copy of all the transforms and textures of itself and
     * all procs in its subtree. For example, suppose we have frag proc A, who has two children B
     * and D. B has a child C, and D has two children E and F. Each frag proc's transforms array
     * contains its own transforms, followed by the transforms of all its descendants (i.e. preorder
     * traversal). Suppose procs A, B, C, D, E, F have 1, 2, 1, 1, 3, 2 transforms respectively.
     *
     *                                   (A)
     *                        [a1,b1,b2,c1,d1,e1,e2,e3,f1,f2]
     *                                  /    \
     *                                /        \
     *                            (B)           (D)
     *                        [b1,b2,c1]   [d1,e1,e2,e3,f1,f2]
     *                          /             /    \
     *                        /             /        \
     *                      (C)          (E)          (F)
     *                     [c1]      [e1,e2,e3]      [f1,f2]
     *
     * So if we're inside proc A's emitCode, and A is about to call emitCode on proc D, we want the
     * EmitArgs that's passed onto D to only contain its and its descendants' coords. The
     * EmitArgs given to A would contain the transforms [a1,b1,b2,c1,d1,e1,e2,e3,f1,f2], and we want
     * to extract the subset [d1,e1,e2,e3,f1,f2] to pass on to D. We can do this with a linear
     * search since we know that A has 1 transform (using A.numTransformsExclChildren()), and B's
     * subtree has 3 transforms (using B.numTransforms()), so we know the start of D's transforms is
     * 4 after the start of A's transforms.
     * Textures work the same way as transforms.
     */
    int firstCoordAt = args.fFp.numTransformsExclChildren();
    int firstSamplerAt = args.fFp.numTexturesExclChildren();
    for (int i = 0; i < childIndex; ++i) {
        firstCoordAt += args.fFp.childProcessor(i).numTransforms();
        firstSamplerAt += args.fFp.childProcessor(i).numTextures();
    }
    TransformedCoordsArray childCoords;
    TextureSamplerArray childSamplers;
    if (childProc.numTransforms() > 0) {
        childCoords.push_back_n(childProc.numTransforms(), &args.fCoords[firstCoordAt]);
    }
    if (childProc.numTextures() > 0) {
        childSamplers.push_back_n(childProc.numTextures(), &args.fSamplers[firstSamplerAt]);
    }

    // emit the code for the child in its own scope
    fb->codeAppend("{\n");
    fb->codeAppendf("// Child Index %d (mangle: %s): %s\n", childIndex,
                    fb->getMangleString().c_str(), childProc.name());
    EmitArgs childArgs(args.fBuilder,
                       childProc,
                       outputColor,
                       inputColor,
                       childCoords,
                       childSamplers);
    this->childProcessor(childIndex)->emitCode(childArgs);
    fb->codeAppend("}\n");

    fb->onAfterChildProcEmitCode();
}

        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 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);
}