C++ GrGLSLFragmentBuilder::enableFeature方法代码示例

        void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
            const QuadEdgeEffect& qe = args.fGP.cast<QuadEdgeEffect>();
            GrGLSLGPBuilder* pb = args.fPB;
            GrGLSLVertexBuilder* vertBuilder = args.fVertBuilder;
            GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;

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

            GrGLSLVertToFrag v(kVec4f_GrSLType);
            varyingHandler->addVarying("QuadEdge", &v);
            vertBuilder->codeAppendf("%s = %s;", v.vsOut(), qe.inQuadEdge()->fName);

            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
            // Setup pass through color
            if (!qe.colorIgnored()) {
                this->setupUniformColor(pb, fragBuilder, args.fOutputColor, &fColorUniform);
            }

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

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

            SkAssertResult(fragBuilder->enableFeature(
                    GrGLSLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));
            fragBuilder->codeAppendf("float edgeAlpha;");

            // keep the derivative instructions outside the conditional
            fragBuilder->codeAppendf("vec2 duvdx = dFdx(%s.xy);", v.fsIn());
            fragBuilder->codeAppendf("vec2 duvdy = dFdy(%s.xy);", v.fsIn());
            fragBuilder->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
            fragBuilder->codeAppendf("edgeAlpha = min(min(%s.z, %s.w) + 0.5, 1.0);", v.fsIn(),
                                     v.fsIn());
            fragBuilder->codeAppendf ("} else {");
            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->codeAppendf("edgeAlpha = "
                                     "clamp(0.5 - edgeAlpha / length(gF), 0.0, 1.0);}");

            fragBuilder->codeAppendf("%s = vec4(edgeAlpha);", 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);

            GrGLSLFragmentBuilder* 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);

        GrGLSLFragmentBuilder* 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 = SkToBool(dfTexEffect.getFlags() & kUniformScale_DistanceFieldEffectMask);
        GrGLSLVertToFrag recipScale(kFloat_GrSLType);
        GrGLSLVertToFrag st(kVec2f_GrSLType);
        varyingHandler->addVarying("IntTextureCoords", &st, kHigh_GrSLPrecision);
        vertBuilder->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();

        GrGLSLVertToFrag uv(kVec2f_GrSLType);
        varyingHandler->addVarying("TextureCoords", &uv, kHigh_GrSLPrecision);
        vertBuilder->codeAppendf("%s = vec2(%.*f, %.*f) * %s;", uv.vsOut(),
                                 GR_SIGNIFICANT_POW2_DECIMAL_DIG, recipWidth,
                                 GR_SIGNIFICANT_POW2_DECIMAL_DIG, recipHeight,
                                 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 dy = abs(dFdy(%s.y));", st.fsIn());
            fragBuilder->codeAppend("vec2 offset = vec2(dy*delta, 0.0);");
        } 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
        fragBuilder->codeAppend("\tvec2 uv_adjusted = uv - offset;\n");
        fragBuilder->codeAppend("\ttexColor = ");
        fragBuilder->appendTextureLookup(args.fSamplers[0], "uv_adjusted", kVec2f_GrSLType);
        fragBuilder->codeAppend(";\n");
        fragBuilder->codeAppend("\tdistance.x = texColor.r;\n");
        // blue is distance to right offset
        fragBuilder->codeAppend("\tuv_adjusted = uv + offset;\n");
//.........这里部分代码省略.........