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.fFPCoordTransformHandler);
// set up varyings
bool isUniformScale = (dfTexEffect.getFlags() & kUniformScale_DistanceFieldEffectMask) ==
kUniformScale_DistanceFieldEffectMask;
bool isSimilarity = SkToBool(dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag);
bool isGammaCorrect =
SkToBool(dfTexEffect.getFlags() & kGammaCorrect_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->appendPrecisionModifier(kHigh_GrSLPrecision);
fragBuilder->codeAppendf("vec2 uv = %s;\n", uv.fsIn());
fragBuilder->appendPrecisionModifier(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) {
#ifdef SK_VULKAN
fragBuilder->codeAppendf("float st_grad_len = abs(dFdx(%s.x));", st.fsIn());
#else
// We use the y gradient because there is a bug in the Mali 400 in the x direction.
fragBuilder->codeAppendf("float st_grad_len = abs(dFdy(%s.y));", st.fsIn());
#endif
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.
#ifdef SK_VULKAN
fragBuilder->codeAppendf("vec2 st_grad = dFdx(%s);", st.fsIn());
fragBuilder->codeAppend("vec2 offset = delta*st_grad;");
#else
// 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("vec2 offset = delta*vec2(st_grad.y, -st_grad.x);");
#endif
fragBuilder->codeAppend("float st_grad_len = length(st_grad);");
} 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.fTexSamplers[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.fTexSamplers[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");
fragBuilder->codeAppend("\ttexColor = ");
fragBuilder->appendTextureLookup(args.fTexSamplers[0], "uv_adjusted", kVec2f_GrSLType);
fragBuilder->codeAppend(";\n");
fragBuilder->codeAppend("\tdistance.z = texColor.r;\n");
fragBuilder->codeAppend("\tdistance = "
"vec3(" SK_DistanceFieldMultiplier ")*(distance - vec3(" SK_DistanceFieldThreshold"));");
// adjust width based on gamma
const char* distanceAdjustUniName = nullptr;
fDistanceAdjustUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
kVec3f_GrSLType, kDefault_GrSLPrecision,
"DistanceAdjust", &distanceAdjustUniName);
fragBuilder->codeAppendf("distance -= %s;", distanceAdjustUniName);
// To be strictly correct, we should compute the anti-aliasing factor separately
// for each color component. However, this is only important when using perspective
// transformations, and even then using a single factor seems like a reasonable
// trade-off between quality and speed.
fragBuilder->codeAppend("float afwidth;");
if (isSimilarity) {
// For similarity transform (uniform scale-only is a subset of this), 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 = " 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.r), dFdy(distance.r));");
// 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 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);");
}
// The smoothstep falloff compensates for the non-linear sRGB response curve. If we are
// doing gamma-correct rendering (to an sRGB or F16 buffer), then we actually want distance
// mapped linearly to coverage, so use a linear step:
if (isGammaCorrect) {
fragBuilder->codeAppend("vec4 val = "
"vec4(clamp(distance + vec3(afwidth) / vec3(2.0 * afwidth), 0.0, 1.0), 1.0);");
} else {
fragBuilder->codeAppend(
"vec4 val = vec4(smoothstep(vec3(-afwidth), vec3(afwidth), distance), 1.0);");
}
// set alpha to be max of rgb coverage
fragBuilder->codeAppend("val.a = max(max(val.r, val.g), val.b);");
fragBuilder->codeAppendf("%s = val;", args.fOutputCoverage);
}
void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override{
const GrDistanceFieldA8TextGeoProc& dfTexEffect =
args.fGP.cast<GrDistanceFieldA8TextGeoProc>();
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);
#ifdef SK_GAMMA_APPLY_TO_A8
// adjust based on gamma
const char* distanceAdjustUniName = nullptr;
// width, height, 1/(3*width)
fDistanceAdjustUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
kFloat_GrSLType, kDefault_GrSLPrecision,
"DistanceAdjust", &distanceAdjustUniName);
#endif
// 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.fFPCoordTransformHandler);
// add varyings
GrGLSLVertToFrag recipScale(kFloat_GrSLType);
GrGLSLVertToFrag uv(kVec2f_GrSLType);
bool isUniformScale = (dfTexEffect.getFlags() & kUniformScale_DistanceFieldEffectMask) ==
kUniformScale_DistanceFieldEffectMask;
bool isSimilarity = SkToBool(dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag);
bool isGammaCorrect =
SkToBool(dfTexEffect.getFlags() & kGammaCorrect_DistanceFieldEffectFlag);
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);
// Use highp to work around aliasing issues
fragBuilder->appendPrecisionModifier(kHigh_GrSLPrecision);
fragBuilder->codeAppendf("vec2 uv = %s;\n", uv.fsIn());
fragBuilder->codeAppend("\tfloat texColor = ");
fragBuilder->appendTextureLookup(args.fTexSamplers[0],
"uv",
kVec2f_GrSLType);
fragBuilder->codeAppend(".r;\n");
fragBuilder->codeAppend("\tfloat distance = "
SK_DistanceFieldMultiplier "*(texColor - " SK_DistanceFieldThreshold ");");
#ifdef SK_GAMMA_APPLY_TO_A8
// adjust width based on gamma
fragBuilder->codeAppendf("distance -= %s;", distanceAdjustUniName);
#endif
fragBuilder->codeAppend("float afwidth;");
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->codeAppendf("afwidth = abs(" SK_DistanceFieldAAFactor "*dFdx(%s.x));",
st.fsIn());
#else
// We use the y gradient because there is a bug in the Mali 400 in the x direction.
fragBuilder->codeAppendf("afwidth = abs(" SK_DistanceFieldAAFactor "*dFdy(%s.y));",
st.fsIn());
#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.
// We use the y gradient because there is a bug in the Mali 400 in the x direction.
// this gives us a smooth step across approximately one fragment
#ifdef SK_VULKAN
fragBuilder->codeAppendf("float st_grad_len = length(dFdx(%s));", st.fsIn());
#else
// We use the y gradient because there is a bug in the Mali 400 in the x direction.
fragBuilder->codeAppendf("float st_grad_len = length(dFdy(%s));", st.fsIn());
#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 {");
fragBuilder->codeAppend("dist_grad = dist_grad*inversesqrt(dg_len2);");
fragBuilder->codeAppend("}");
fragBuilder->codeAppendf("vec2 Jdx = dFdx(%s);", st.fsIn());
fragBuilder->codeAppendf("vec2 Jdy = dFdy(%s);", st.fsIn());
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);");
}
// The smoothstep falloff compensates for the non-linear sRGB response curve. If we are
// doing gamma-correct rendering (to an sRGB or F16 buffer), then we actually want distance
// mapped linearly to coverage, so use a linear step:
if (isGammaCorrect) {
fragBuilder->codeAppend(
"float val = clamp(distance + afwidth / (2.0 * afwidth), 0.0, 1.0);");
} else {
fragBuilder->codeAppend("float val = smoothstep(-afwidth, afwidth, distance);");
}
fragBuilder->codeAppendf("%s = vec4(val);", args.fOutputCoverage);
}
