C++ GrGLSLPPFragmentBuilder::codeAppend方法代码示例

    void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
        const GrRRectShadowGeoProc& rsgp = args.fGP.cast<GrRRectShadowGeoProc>();
        GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
        GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
        GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
        GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;

        // emit attributes
        varyingHandler->emitAttributes(rsgp);
        fragBuilder->codeAppend("vec4 shadowParams;");
        varyingHandler->addPassThroughAttribute(rsgp.inShadowParams(), "shadowParams");

        // setup pass through color
        varyingHandler->addPassThroughAttribute(rsgp.inColor(), args.fOutputColor);

        // Setup position
        this->setupPosition(vertBuilder, gpArgs, rsgp.inPosition()->fName);

        // emit transforms
        this->emitTransforms(vertBuilder,
                             varyingHandler,
                             uniformHandler,
                             gpArgs->fPositionVar,
                             rsgp.inPosition()->fName,
                             args.fFPCoordTransformHandler);

        fragBuilder->codeAppend("float d = length(shadowParams.xy);");
        fragBuilder->codeAppend("float distance = shadowParams.z * (1.0 - d);");

        fragBuilder->codeAppend("float factor = 1.0 - clamp(distance, 0.0, shadowParams.w);");
        fragBuilder->codeAppend("factor = exp(-factor * factor * 4.0) - 0.018;");
        fragBuilder->codeAppendf("%s = vec4(factor);",
                                 args.fOutputCoverage);
    }

        void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
            const PLSFinishEffect& fe = args.fGP.cast<PLSFinishEffect>();
            GrGLSLVertexBuilder* vsBuilder = args.fVertBuilder;
            GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

            fUseEvenOdd = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                    kFloat_GrSLType, kLow_GrSLPrecision,
                                                    "useEvenOdd");
            const char* useEvenOdd = uniformHandler->getUniformCStr(fUseEvenOdd);

            varyingHandler->emitAttributes(fe);
            this->setupPosition(vsBuilder, gpArgs, fe.inPosition()->fName);
            this->emitTransforms(vsBuilder, varyingHandler, uniformHandler, gpArgs->fPositionVar,
                                 fe.inPosition()->fName, fe.localMatrix(), args.fTransformsIn,
                                 args.fTransformsOut);

            GrGLSLPPFragmentBuilder* fsBuilder = args.fFragBuilder;
            SkAssertResult(fsBuilder->enableFeature(
                           GrGLSLFragmentShaderBuilder::kPixelLocalStorage_GLSLFeature));
            fsBuilder->declAppendf(GR_GL_PLS_PATH_DATA_DECL);
            fsBuilder->codeAppend("float coverage;");
            fsBuilder->codeAppendf("if (%s != 0.0) {", useEvenOdd);
            fsBuilder->codeAppend("coverage = float(abs(pls.windings[0]) % 2) * 0.25;");
            fsBuilder->codeAppend("coverage += float(abs(pls.windings[1]) % 2) * 0.25;");
            fsBuilder->codeAppend("coverage += float(abs(pls.windings[2]) % 2) * 0.25;");
            fsBuilder->codeAppend("coverage += float(abs(pls.windings[3]) % 2) * 0.25;");
            fsBuilder->codeAppend("} else {");
            fsBuilder->codeAppend("coverage = pls.windings[0] != 0 ? 0.25 : 0.0;");
            fsBuilder->codeAppend("coverage += pls.windings[1] != 0 ? 0.25 : 0.0;");
            fsBuilder->codeAppend("coverage += pls.windings[2] != 0 ? 0.25 : 0.0;");
            fsBuilder->codeAppend("coverage += pls.windings[3] != 0 ? 0.25 : 0.0;");
            fsBuilder->codeAppend("}");
            if (!fe.colorIgnored()) {
                this->setupUniformColor(fsBuilder, uniformHandler, args.fOutputColor,
                                        &fColorUniform);
            }
            fsBuilder->codeAppendf("%s = vec4(coverage);", args.fOutputCoverage);
            fsBuilder->codeAppendf("%s = vec4(1.0, 0.0, 1.0, 1.0);", args.fOutputColor);
        }

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

        GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
        GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
        GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

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

        GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;

        // setup pass through color
        if (!dfTexEffect.colorIgnored()) {
            varyingHandler->addPassThroughAttribute(dfTexEffect.inColor(), args.fOutputColor);
        }

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

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

        // set up varyings
        bool isUniformScale = (dfTexEffect.getFlags() & kUniformScale_DistanceFieldEffectMask) ==
                              kUniformScale_DistanceFieldEffectMask;
        bool isSimilarity = SkToBool(dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag);
        GrGLSLVertToFrag recipScale(kFloat_GrSLType);
        GrGLSLVertToFrag uv(kVec2f_GrSLType);
        varyingHandler->addVarying("TextureCoords", &uv, kHigh_GrSLPrecision);
        vertBuilder->codeAppendf("%s = %s;", uv.vsOut(), dfTexEffect.inTextureCoords()->fName);

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

        GrGLSLVertToFrag st(kVec2f_GrSLType);
        varyingHandler->addVarying("IntTextureCoords", &st, kHigh_GrSLPrecision);
        vertBuilder->codeAppendf("%s = vec2(%d, %d) * %s;", st.vsOut(),
                                 atlas->width(), atlas->height(),
                                 dfTexEffect.inTextureCoords()->fName);

        // add frag shader code

        SkAssertResult(fragBuilder->enableFeature(
                GrGLSLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));

        // create LCD offset adjusted by inverse of transform
        // Use highp to work around aliasing issues
        fragBuilder->codeAppend(GrGLSLShaderVar::PrecisionString(args.fGLSLCaps,
                                                                 kHigh_GrSLPrecision));
        fragBuilder->codeAppendf("vec2 uv = %s;\n", uv.fsIn());
        fragBuilder->codeAppend(GrGLSLShaderVar::PrecisionString(args.fGLSLCaps,
                                                                 kHigh_GrSLPrecision));

        SkScalar lcdDelta = 1.0f / (3.0f * atlas->width());
        if (dfTexEffect.getFlags() & kBGR_DistanceFieldEffectFlag) {
            fragBuilder->codeAppendf("float delta = -%.*f;\n", SK_FLT_DECIMAL_DIG, lcdDelta);
        } else {
            fragBuilder->codeAppendf("float delta = %.*f;\n", SK_FLT_DECIMAL_DIG, lcdDelta);
        }
        if (isUniformScale) {
            fragBuilder->codeAppendf("float st_grad_len = abs(dFdy(%s.y));", st.fsIn());
            fragBuilder->codeAppend("vec2 offset = vec2(st_grad_len*delta, 0.0);");
        } else if (isSimilarity) {
            // For a similarity matrix with rotation, the gradient will not be aligned
            // with the texel coordinate axes, so we need to calculate it.
            // We use dFdy because of a Mali 400 bug, and rotate -90 degrees to
            // get the gradient in the x direction.
            fragBuilder->codeAppendf("vec2 st_grad = dFdy(%s);", st.fsIn());
            fragBuilder->codeAppend("float st_grad_len = length(st_grad);");
            fragBuilder->codeAppend("vec2 offset = delta*vec2(st_grad.y, -st_grad.x);");
        } else {
            fragBuilder->codeAppendf("vec2 st = %s;\n", st.fsIn());

            fragBuilder->codeAppend("vec2 Jdx = dFdx(st);");
            fragBuilder->codeAppend("vec2 Jdy = dFdy(st);");
            fragBuilder->codeAppend("vec2 offset = delta*Jdx;");
        }

        // green is distance to uv center
        fragBuilder->codeAppend("\tvec4 texColor = ");
        fragBuilder->appendTextureLookup(args.fSamplers[0], "uv", kVec2f_GrSLType);
        fragBuilder->codeAppend(";\n");
        fragBuilder->codeAppend("\tvec3 distance;\n");
        fragBuilder->codeAppend("\tdistance.y = texColor.r;\n");
        // red is distance to left offset
//.........这里部分代码省略.........

void GrGLQuadEffect::onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) {
    GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
    const GrQuadEffect& gp = args.fGP.cast<GrQuadEffect>();
    GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

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

    GrGLSLVertToFrag v(kVec4f_GrSLType);
    varyingHandler->addVarying("HairQuadEdge", &v);
    vertBuilder->codeAppendf("%s = %s;", v.vsOut(), gp.inHairQuadEdge()->fName);

    GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;
    // Setup pass through color
    this->setupUniformColor(fragBuilder, uniformHandler, args.fOutputColor, &fColorUniform);

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

    // emit transforms with position
    this->emitTransforms(vertBuilder,
                         varyingHandler,
                         uniformHandler,
                         gpArgs->fPositionVar,
                         gp.inPosition()->fName,
                         gp.localMatrix(),
                         args.fFPCoordTransformHandler);

    fragBuilder->codeAppendf("float edgeAlpha;");

    switch (fEdgeType) {
        case kHairlineAA_GrProcessorEdgeType: {
            fragBuilder->codeAppendf("vec2 duvdx = dFdx(%s.xy);", v.fsIn());
            fragBuilder->codeAppendf("vec2 duvdy = dFdy(%s.xy);", v.fsIn());
            fragBuilder->codeAppendf("vec2 gF = vec2(2.0 * %s.x * duvdx.x - duvdx.y,"
                                     "               2.0 * %s.x * duvdy.x - duvdy.y);",
                                     v.fsIn(), v.fsIn());
            fragBuilder->codeAppendf("edgeAlpha = (%s.x * %s.x - %s.y);",
                                     v.fsIn(), v.fsIn(), v.fsIn());
            fragBuilder->codeAppend("edgeAlpha = sqrt(edgeAlpha * edgeAlpha / dot(gF, gF));");
            fragBuilder->codeAppend("edgeAlpha = max(1.0 - edgeAlpha, 0.0);");
            // Add line below for smooth cubic ramp
            // fragBuilder->codeAppend("edgeAlpha = edgeAlpha*edgeAlpha*(3.0-2.0*edgeAlpha);");
            break;
        }
        case kFillAA_GrProcessorEdgeType: {
            fragBuilder->codeAppendf("vec2 duvdx = dFdx(%s.xy);", v.fsIn());
            fragBuilder->codeAppendf("vec2 duvdy = dFdy(%s.xy);", v.fsIn());
            fragBuilder->codeAppendf("vec2 gF = vec2(2.0 * %s.x * duvdx.x - duvdx.y,"
                                     "               2.0 * %s.x * duvdy.x - duvdy.y);",
                                     v.fsIn(), v.fsIn());
            fragBuilder->codeAppendf("edgeAlpha = (%s.x * %s.x - %s.y);",
                                     v.fsIn(), v.fsIn(), v.fsIn());
            fragBuilder->codeAppend("edgeAlpha = edgeAlpha / sqrt(dot(gF, gF));");
            fragBuilder->codeAppend("edgeAlpha = clamp(0.5 - edgeAlpha, 0.0, 1.0);");
            // Add line below for smooth cubic ramp
            // fragBuilder->codeAppend("edgeAlpha = edgeAlpha*edgeAlpha*(3.0-2.0*edgeAlpha);");
            break;
        }
        case kFillBW_GrProcessorEdgeType: {
            fragBuilder->codeAppendf("edgeAlpha = (%s.x * %s.x - %s.y);",
                                     v.fsIn(), v.fsIn(), v.fsIn());
            fragBuilder->codeAppend("edgeAlpha = float(edgeAlpha < 0.0);");
            break;
        }
        default:
            SkFAIL("Shouldn't get here");
    }

    if (0xff != gp.coverageScale()) {
        const char* coverageScale;
        fCoverageScaleUniform = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                           kFloat_GrSLType,
                                                           kDefault_GrSLPrecision,
                                                           "Coverage",
                                                           &coverageScale);
        fragBuilder->codeAppendf("%s = vec4(%s * edgeAlpha);", args.fOutputCoverage, coverageScale);
    } else {
        fragBuilder->codeAppendf("%s = vec4(edgeAlpha);", args.fOutputCoverage);
    }
}

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

        GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
        GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
        GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

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

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

        GrGLSLVertToFrag v(kVec2f_GrSLType);
        varyingHandler->addVarying("TextureCoords", &v, kHigh_GrSLPrecision);
        vertBuilder->codeAppendf("%s = %s;", v.vsOut(),
                                 cte.inTextureCoords()->fName);

        GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;
        // Setup pass through color
        if (!cte.colorIgnored()) {
            if (cte.hasVertexColor()) {
                varyingHandler->addPassThroughAttribute(cte.inColor(), args.fOutputColor);
            } else {
                this->setupUniformColor(fragBuilder, uniformHandler, args.fOutputColor,
                                        &fColorUniform);
            }
        }

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

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

        if (cte.maskFormat() == kARGB_GrMaskFormat) {
            fragBuilder->codeAppendf("%s = ", args.fOutputColor);
            fragBuilder->appendTextureLookupAndModulate(args.fOutputColor,
                                                        args.fTexSamplers[0],
                                                        v.fsIn(),
                                                        kVec2f_GrSLType);
            fragBuilder->codeAppend(";");
            fragBuilder->codeAppendf("%s = vec4(1);", args.fOutputCoverage);
        } else {
            fragBuilder->codeAppendf("%s = ", args.fOutputCoverage);
            fragBuilder->appendTextureLookup(args.fTexSamplers[0], v.fsIn(), kVec2f_GrSLType);
            fragBuilder->codeAppend(";");
            if (cte.maskFormat() == kA565_GrMaskFormat) {
                // set alpha to be max of rgb coverage
                fragBuilder->codeAppendf("%s.a = max(max(%s.r, %s.g), %s.b);",
                                         args.fOutputCoverage, args.fOutputCoverage,
                                         args.fOutputCoverage, args.fOutputCoverage);
            }
        }
    }

void GLSLPathProcessor::onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) {
    using InstanceAttribs = GrCCPRPathProcessor::InstanceAttribs;
    const GrCCPRPathProcessor& proc = args.fGP.cast<GrCCPRPathProcessor>();
    GrGLSLUniformHandler* uniHandler = args.fUniformHandler;
    GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;

    const char* atlasAdjust;
    fAtlasAdjustUniform = uniHandler->addUniform(
            kVertex_GrShaderFlag,
            kVec2f_GrSLType, kHigh_GrSLPrecision, "atlas_adjust", &atlasAdjust);

    varyingHandler->emitAttributes(proc);

    GrGLSLVertToFrag texcoord(kVec2f_GrSLType);
    GrGLSLVertToFrag color(kVec4f_GrSLType);
    varyingHandler->addVarying("texcoord", &texcoord, kHigh_GrSLPrecision);
    varyingHandler->addFlatPassThroughAttribute(&proc.getInstanceAttrib(InstanceAttribs::kColor),
                                                args.fOutputColor, kLow_GrSLPrecision);

    // Vertex shader.
    GrGLSLVertexBuilder* v = args.fVertBuilder;

    // Find the intersections of (bloated) devBounds and devBounds45 in order to come up with an
    // octagon that circumscribes the (bloated) path. A vertex is the intersection of two lines:
    // one edge from the path's bounding box and one edge from its 45-degree bounding box.
    v->codeAppendf("highp mat2 N = mat2(%s);", proc.getEdgeNormsAttrib().fName);

    // N[0] is the normal for the edge we are intersecting from the regular bounding box, pointing
    // out of the octagon.
    v->codeAppendf("highp vec2 refpt = (min(N[0].x, N[0].y) < 0) ? %s.xy : %s.zw;",
                   proc.getInstanceAttrib(InstanceAttribs::kDevBounds).fName,
                   proc.getInstanceAttrib(InstanceAttribs::kDevBounds).fName);
    v->codeAppendf("refpt += N[0] * %f;", kAABloatRadius); // bloat for AA.

    // N[1] is the normal for the edge we are intersecting from the 45-degree bounding box, pointing
    // out of the octagon.
    v->codeAppendf("highp vec2 refpt45 = (N[1].x < 0) ? %s.xy : %s.zw;",
                   proc.getInstanceAttrib(InstanceAttribs::kDevBounds45).fName,
                   proc.getInstanceAttrib(InstanceAttribs::kDevBounds45).fName);
    v->codeAppendf("refpt45 *= mat2(.5,.5,-.5,.5);"); // transform back to device space.
    v->codeAppendf("refpt45 += N[1] * %f;", kAABloatRadius); // bloat for AA.

    v->codeAppend ("highp vec2 K = vec2(dot(N[0], refpt), dot(N[1], refpt45));");
    v->codeAppendf("highp vec2 octocoord = K * inverse(N);");

    gpArgs->fPositionVar.set(kVec2f_GrSLType, "octocoord");

    // Convert to atlas coordinates in order to do our texture lookup.
    v->codeAppendf("highp vec2 atlascoord = octocoord + vec2(%s);",
                   proc.getInstanceAttrib(InstanceAttribs::kAtlasOffset).fName);
    if (kTopLeft_GrSurfaceOrigin == proc.atlas()->origin()) {
        v->codeAppendf("%s = atlascoord * %s;", texcoord.vsOut(), atlasAdjust);
    } else {
        SkASSERT(kBottomLeft_GrSurfaceOrigin == proc.atlas()->origin());
        v->codeAppendf("%s = vec2(atlascoord.x * %s.x, 1 - atlascoord.y * %s.y);",
                       texcoord.vsOut(), atlasAdjust, atlasAdjust);
    }

    // Convert to (local) path cordinates.
    v->codeAppendf("highp vec2 pathcoord = inverse(mat2(%s)) * (octocoord - %s);",
                   proc.getInstanceAttrib(InstanceAttribs::kViewMatrix).fName,
                   proc.getInstanceAttrib(InstanceAttribs::kViewTranslate).fName);

    this->emitTransforms(v, varyingHandler, uniHandler, gpArgs->fPositionVar, "pathcoord",
                         args.fFPCoordTransformHandler);

    // Fragment shader.
    GrGLSLPPFragmentBuilder* f = args.fFragBuilder;

    f->codeAppend ("mediump float coverage_count = ");
    f->appendTextureLookup(args.fTexSamplers[0], texcoord.fsIn(), kVec2f_GrSLType);
    f->codeAppend (".a;");

    if (SkPath::kWinding_FillType == proc.fillType()) {
        f->codeAppendf("%s = vec4(min(abs(coverage_count), 1));", args.fOutputCoverage);
    } else {
        SkASSERT(SkPath::kEvenOdd_FillType == proc.fillType());
        f->codeAppend ("mediump float t = mod(abs(coverage_count), 2);");
        f->codeAppendf("%s = vec4(1 - abs(t - 1));", args.fOutputCoverage);
    }
}

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

        GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;
        SkAssertResult(fragBuilder->enableFeature(
                                     GrGLSLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));

        GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
        GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
        GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

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

        GrGLSLVertToFrag v(kVec2f_GrSLType);
        varyingHandler->addVarying("TextureCoords", &v, kHigh_GrSLPrecision);

        // setup pass through color
        if (!dfTexEffect.colorIgnored()) {
            varyingHandler->addPassThroughAttribute(dfTexEffect.inColor(), args.fOutputColor);
        }
        vertBuilder->codeAppendf("%s = %s;", v.vsOut(), dfTexEffect.inTextureCoords()->fName);

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

        // emit transforms
        this->emitTransforms(vertBuilder,
                             varyingHandler,
                             uniformHandler,
                             gpArgs->fPositionVar,
                             dfTexEffect.inPosition()->fName,
                             args.fFPCoordTransformHandler);

        const char* textureSizeUniName = nullptr;
        fTextureSizeUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                     "TextureSize", &textureSizeUniName);

        // Use highp to work around aliasing issues
        fragBuilder->appendPrecisionModifier(kHigh_GrSLPrecision);
        fragBuilder->codeAppendf("vec2 uv = %s;", v.fsIn());

        fragBuilder->codeAppend("float texColor = ");
        fragBuilder->appendTextureLookup(args.fTexSamplers[0],
                                         "uv",
                                         kVec2f_GrSLType);
        fragBuilder->codeAppend(".r;");
        fragBuilder->codeAppend("float distance = "
            SK_DistanceFieldMultiplier "*(texColor - " SK_DistanceFieldThreshold ");");

        fragBuilder->appendPrecisionModifier(kHigh_GrSLPrecision);
        fragBuilder->codeAppendf("vec2 st = uv*%s;", textureSizeUniName);
        fragBuilder->codeAppend("float afwidth;");
        bool isUniformScale = (dfTexEffect.getFlags() & kUniformScale_DistanceFieldEffectMask) ==
                               kUniformScale_DistanceFieldEffectMask;
        bool isSimilarity = SkToBool(dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag);
        bool isGammaCorrect =
            SkToBool(dfTexEffect.getFlags() & kGammaCorrect_DistanceFieldEffectFlag);
        if (isUniformScale) {
            // For uniform scale, we adjust for the effect of the transformation on the distance
            // by using the length of the gradient of the t coordinate in the y direction.
            // 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
#ifdef SK_VULKAN
            fragBuilder->codeAppend("afwidth = abs(" SK_DistanceFieldAAFactor "*dFdx(st.x));");
#else
            // We use the y gradient because there is a bug in the Mali 400 in the x direction.
            fragBuilder->codeAppend("afwidth = abs(" SK_DistanceFieldAAFactor "*dFdy(st.y));");
#endif
        } else if (isSimilarity) {
            // For similarity transform, we adjust 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
#ifdef SK_VULKAN
            fragBuilder->codeAppend("float st_grad_len = length(dFdx(st));");
#else
            // We use the y gradient because there is a bug in the Mali 400 in the x direction.
            fragBuilder->codeAppend("float st_grad_len = length(dFdy(st));");
#endif
            fragBuilder->codeAppend("afwidth = abs(" SK_DistanceFieldAAFactor "*st_grad_len);");
        } 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.
            fragBuilder->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
            fragBuilder->codeAppend("float dg_len2 = dot(dist_grad, dist_grad);");
            fragBuilder->codeAppend("if (dg_len2 < 0.0001) {");
            fragBuilder->codeAppend("dist_grad = vec2(0.7071, 0.7071);");
            fragBuilder->codeAppend("} else {");
//.........这里部分代码省略.........

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

        GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;
        SkAssertResult(fragBuilder->enableFeature(
                                     GrGLSLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));

        GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
        GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
        GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

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

        GrGLSLVertToFrag v(kVec2f_GrSLType);
        varyingHandler->addVarying("TextureCoords", &v, kHigh_GrSLPrecision);

        // setup pass through color
        if (!dfTexEffect.colorIgnored()) {
            varyingHandler->addPassThroughAttribute(dfTexEffect.inColor(), args.fOutputColor);
        }
        vertBuilder->codeAppendf("%s = %s;", v.vsOut(), dfTexEffect.inTextureCoords()->fName);

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

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

        const char* textureSizeUniName = nullptr;
        fTextureSizeUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                     "TextureSize", &textureSizeUniName);

        // Use highp to work around aliasing issues
        fragBuilder->codeAppend(GrGLSLShaderVar::PrecisionString(args.fGLSLCaps,
                                                                 kHigh_GrSLPrecision));
        fragBuilder->codeAppendf("vec2 uv = %s;", v.fsIn());

        fragBuilder->codeAppend("float texColor = ");
        fragBuilder->appendTextureLookup(args.fSamplers[0],
                                         "uv",
                                         kVec2f_GrSLType);
        fragBuilder->codeAppend(".r;");
        fragBuilder->codeAppend("float distance = "
            SK_DistanceFieldMultiplier "*(texColor - " SK_DistanceFieldThreshold ");");

        fragBuilder->codeAppend(GrGLSLShaderVar::PrecisionString(args.fGLSLCaps,
                                                                 kHigh_GrSLPrecision));
        fragBuilder->codeAppendf("vec2 st = uv*%s;", textureSizeUniName);
        fragBuilder->codeAppend("float afwidth;");
        if (dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag) {
            // 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
            fragBuilder->codeAppend("afwidth = abs(" SK_DistanceFieldAAFactor "*dFdy(st.y));");
        } 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.
            fragBuilder->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
            fragBuilder->codeAppend("float dg_len2 = dot(dist_grad, dist_grad);");
            fragBuilder->codeAppend("if (dg_len2 < 0.0001) {");
            fragBuilder->codeAppend("dist_grad = vec2(0.7071, 0.7071);");
            fragBuilder->codeAppend("} else {");
            fragBuilder->codeAppend("dist_grad = dist_grad*inversesqrt(dg_len2);");
            fragBuilder->codeAppend("}");

            fragBuilder->codeAppend("vec2 Jdx = dFdx(st);");
            fragBuilder->codeAppend("vec2 Jdy = dFdy(st);");
            fragBuilder->codeAppend("vec2 grad = vec2(dist_grad.x*Jdx.x + dist_grad.y*Jdy.x,");
            fragBuilder->codeAppend("                 dist_grad.x*Jdx.y + dist_grad.y*Jdy.y);");

            // this gives us a smooth step across approximately one fragment
            fragBuilder->codeAppend("afwidth = " SK_DistanceFieldAAFactor "*length(grad);");
        }
        fragBuilder->codeAppend("float val = smoothstep(-afwidth, afwidth, distance);");

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