C++ GrGLFragmentBuilder::fragmentPosition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 GLAARectEffect::emitCode(EmitArgs& args) {
    const AARectEffect& aare = args.fFp.cast<AARectEffect>();
    const char *rectName;
    // The rect uniform's xyzw refer to (left + 0.5, top + 0.5, right - 0.5, bottom - 0.5),
    // respectively.
    fRectUniform = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                       kVec4f_GrSLType,
                                       kDefault_GrSLPrecision,
                                       "rect",
                                       &rectName);

    GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
    const char* fragmentPos = fsBuilder->fragmentPosition();
    if (GrProcessorEdgeTypeIsAA(aare.getEdgeType())) {
        // The amount of coverage removed in x and y by the edges is computed as a pair of negative
        // numbers, xSub and ySub.
        fsBuilder->codeAppend("\t\tfloat xSub, ySub;\n");
        fsBuilder->codeAppendf("\t\txSub = min(%s.x - %s.x, 0.0);\n", fragmentPos, rectName);
        fsBuilder->codeAppendf("\t\txSub += min(%s.z - %s.x, 0.0);\n", rectName, fragmentPos);
        fsBuilder->codeAppendf("\t\tySub = min(%s.y - %s.y, 0.0);\n", fragmentPos, rectName);
        fsBuilder->codeAppendf("\t\tySub += min(%s.w - %s.y, 0.0);\n", rectName, fragmentPos);
        // Now compute coverage in x and y and multiply them to get the fraction of the pixel
        // covered.
        fsBuilder->codeAppendf("\t\tfloat alpha = (1.0 + max(xSub, -1.0)) * (1.0 + max(ySub, -1.0));\n");
    } else {
        fsBuilder->codeAppendf("\t\tfloat alpha = 1.0;\n");
        fsBuilder->codeAppendf("\t\talpha *= (%s.x - %s.x) > -0.5 ? 1.0 : 0.0;\n", fragmentPos, rectName);
        fsBuilder->codeAppendf("\t\talpha *= (%s.z - %s.x) > -0.5 ? 1.0 : 0.0;\n", rectName, fragmentPos);
        fsBuilder->codeAppendf("\t\talpha *= (%s.y - %s.y) > -0.5 ? 1.0 : 0.0;\n", fragmentPos, rectName);
        fsBuilder->codeAppendf("\t\talpha *= (%s.w - %s.y) > -0.5 ? 1.0 : 0.0;\n", rectName, fragmentPos);
    }

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

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());
}