text: /*
   * Copyright 2013 Google Inc.
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "GrDistanceFieldGeoProc.h"
  
  #include "GrTexture.h"
  #include "SkDistanceFieldGen.h"
  #include "glsl/GrGLSLFragmentShaderBuilder.h"
  #include "glsl/GrGLSLGeometryProcessor.h"
  #include "glsl/GrGLSLProgramDataManager.h"
  #include "glsl/GrGLSLUniformHandler.h"
  #include "glsl/GrGLSLUtil.h"
  #include "glsl/GrGLSLVarying.h"
  #include "glsl/GrGLSLVertexShaderBuilder.h"
  
  // Assuming a radius of a little less than the diagonal of the fragment
  #define SK_DistanceFieldAAFactor     "0.65"
  
  class GrGLDistanceFieldA8TextGeoProc : public GrGLSLGeometryProcessor {
  public:
      GrGLDistanceFieldA8TextGeoProc()
          : fViewMatrix(SkMatrix::InvalidMatrix())
  #ifdef SK_GAMMA_APPLY_TO_A8
          , fDistanceAdjust(-1.0f)
  #endif
          {}
  
      void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override{
          const GrDistanceFieldA8TextGeoProc& dfTexEffect =
                  args.fGP.cast<GrDistanceFieldA8TextGeoProc>();
          GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;
  
          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
          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.numTextureSamplers() == 1);
          GrTexture* atlas = dfTexEffect.textureSampler(0).texture();
          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->codeAppendf("highp 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);
      }
  
      void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor& proc,
                   FPCoordTransformIter&& transformIter) override {
  #ifdef SK_GAMMA_APPLY_TO_A8
          const GrDistanceFieldA8TextGeoProc& dfTexEffect = proc.cast<GrDistanceFieldA8TextGeoProc>();
          float distanceAdjust = dfTexEffect.getDistanceAdjust();
          if (distanceAdjust != fDistanceAdjust) {
              pdman.set1f(fDistanceAdjustUni, distanceAdjust);
              fDistanceAdjust = distanceAdjust;
          }
  #endif
          const GrDistanceFieldA8TextGeoProc& dfa8gp = proc.cast<GrDistanceFieldA8TextGeoProc>();
  
          if (!dfa8gp.viewMatrix().isIdentity() && !fViewMatrix.cheapEqualTo(dfa8gp.viewMatrix())) {
              fViewMatrix = dfa8gp.viewMatrix();
              float viewMatrix[3 * 3];
              GrGLSLGetMatrix<3>(viewMatrix, fViewMatrix);
              pdman.setMatrix3f(fViewMatrixUniform, viewMatrix);
          }
          this->setTransformDataHelper(SkMatrix::I(), pdman, &transformIter);
      }
  
      static inline void GenKey(const GrGeometryProcessor& gp,
                                const GrShaderCaps&,
                                GrProcessorKeyBuilder* b) {
          const GrDistanceFieldA8TextGeoProc& dfTexEffect = gp.cast<GrDistanceFieldA8TextGeoProc>();
          uint32_t key = dfTexEffect.getFlags();
          key |= ComputePosKey(dfTexEffect.viewMatrix()) << 16;
          b->add32(key);
  
          // Currently we hardcode numbers to convert atlas coordinates to normalized floating point
          SkASSERT(gp.numTextureSamplers() == 1);
          GrTexture* atlas = gp.textureSampler(0).texture();
          SkASSERT(atlas);
          b->add32(atlas->width());
          b->add32(atlas->height());
      }
  
  private:
      SkMatrix      fViewMatrix;
      UniformHandle fViewMatrixUniform;
  #ifdef SK_GAMMA_APPLY_TO_A8
      float         fDistanceAdjust;
      UniformHandle fDistanceAdjustUni;
  #endif
  
      typedef GrGLSLGeometryProcessor INHERITED;
  };
  
  ///////////////////////////////////////////////////////////////////////////////
  
  GrDistanceFieldA8TextGeoProc::GrDistanceFieldA8TextGeoProc(GrResourceProvider* resourceProvider,
                                                             GrColor color,
                                                             const SkMatrix& viewMatrix,
                                                             sk_sp<GrTextureProxy> proxy,
                                                             const GrSamplerParams& params,
  #ifdef SK_GAMMA_APPLY_TO_A8
                                                             float distanceAdjust,
  #endif
                                                             uint32_t flags,
                                                             bool usesLocalCoords)
      : fColor(color)
      , fViewMatrix(viewMatrix)
      , fTextureSampler(resourceProvider, std::move(proxy), params)
  #ifdef SK_GAMMA_APPLY_TO_A8
      , fDistanceAdjust(distanceAdjust)
  #endif
      , fFlags(flags & kNonLCD_DistanceFieldEffectMask)
      , fInColor(nullptr)
      , fUsesLocalCoords(usesLocalCoords) {
      SkASSERT(!(flags & ~kNonLCD_DistanceFieldEffectMask));
      this->initClassID<GrDistanceFieldA8TextGeoProc>();
      fInPosition = &this->addVertexAttrib("inPosition", kVec2f_GrVertexAttribType,
                                           kHigh_GrSLPrecision);
      fInColor = &this->addVertexAttrib("inColor", kVec4ub_GrVertexAttribType);
      fInTextureCoords = &this->addVertexAttrib("inTextureCoords", kVec2us_GrVertexAttribType,
                                                kHigh_GrSLPrecision);
      this->addTextureSampler(&fTextureSampler);
  }
  
  void GrDistanceFieldA8TextGeoProc::getGLSLProcessorKey(const GrShaderCaps& caps,
                                                         GrProcessorKeyBuilder* b) const {
      GrGLDistanceFieldA8TextGeoProc::GenKey(*this, caps, b);
  }
  
  GrGLSLPrimitiveProcessor*
  GrDistanceFieldA8TextGeoProc::createGLSLInstance(const GrShaderCaps&) const {
      return new GrGLDistanceFieldA8TextGeoProc();
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  
  GR_DEFINE_GEOMETRY_PROCESSOR_TEST(GrDistanceFieldA8TextGeoProc);
  
  #if GR_TEST_UTILS
  sk_sp<GrGeometryProcessor> GrDistanceFieldA8TextGeoProc::TestCreate(GrProcessorTestData* d) {
      int texIdx = d->fRandom->nextBool() ? GrProcessorUnitTest::kSkiaPMTextureIdx
                                          : GrProcessorUnitTest::kAlphaTextureIdx;
      sk_sp<GrTextureProxy> proxy = d->textureProxy(texIdx);
  
      static const SkShader::TileMode kTileModes[] = {
          SkShader::kClamp_TileMode,
          SkShader::kRepeat_TileMode,
          SkShader::kMirror_TileMode,
      };
      SkShader::TileMode tileModes[] = {
          kTileModes[d->fRandom->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
          kTileModes[d->fRandom->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
      };
      GrSamplerParams params(tileModes, d->fRandom->nextBool() ? GrSamplerParams::kBilerp_FilterMode
                                                               : GrSamplerParams::kNone_FilterMode);
  
      uint32_t flags = 0;
      flags |= d->fRandom->nextBool() ? kSimilarity_DistanceFieldEffectFlag : 0;
      if (flags & kSimilarity_DistanceFieldEffectFlag) {
          flags |= d->fRandom->nextBool() ? kScaleOnly_DistanceFieldEffectFlag : 0;
      }
  
      return GrDistanceFieldA8TextGeoProc::Make(d->resourceProvider(),
                                                GrRandomColor(d->fRandom),
                                                GrTest::TestMatrix(d->fRandom),
                                                std::move(proxy), params,
  #ifdef SK_GAMMA_APPLY_TO_A8
                                                d->fRandom->nextF(),
  #endif
                                                flags,
                                                d->fRandom->nextBool());
  }
  #endif
  
  ///////////////////////////////////////////////////////////////////////////////
  
  class GrGLDistanceFieldPathGeoProc : public GrGLSLGeometryProcessor {
  public:
      GrGLDistanceFieldPathGeoProc()
          : fViewMatrix(SkMatrix::InvalidMatrix())
          , fTextureSize(SkISize::Make(-1, -1)) {}
  
      void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override{
          const GrDistanceFieldPathGeoProc& dfTexEffect = args.fGP.cast<GrDistanceFieldPathGeoProc>();
  
          GrGLSLPPFragmentBuilder* fragBuilder = args.fFragBuilder;
  
          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
          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->codeAppendf("highp 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->codeAppendf("highp 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 {");
              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);");
          }
          // 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);
      }
  
      void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor& proc,
                   FPCoordTransformIter&& transformIter) override {
          SkASSERT(fTextureSizeUni.isValid());
  
          GrTexture* texture = proc.textureSampler(0).texture();
          if (texture->width() != fTextureSize.width() ||
              texture->height() != fTextureSize.height()) {
              fTextureSize = SkISize::Make(texture->width(), texture->height());
              pdman.set2f(fTextureSizeUni,
                          SkIntToScalar(fTextureSize.width()),
                          SkIntToScalar(fTextureSize.height()));
          }
  
          const GrDistanceFieldPathGeoProc& dfpgp = proc.cast<GrDistanceFieldPathGeoProc>();
  
          if (!dfpgp.viewMatrix().isIdentity() && !fViewMatrix.cheapEqualTo(dfpgp.viewMatrix())) {
              fViewMatrix = dfpgp.viewMatrix();
              float viewMatrix[3 * 3];
              GrGLSLGetMatrix<3>(viewMatrix, fViewMatrix);
              pdman.setMatrix3f(fViewMatrixUniform, viewMatrix);
          }
          this->setTransformDataHelper(SkMatrix::I(), pdman, &transformIter);
      }
  
      static inline void GenKey(const GrGeometryProcessor& gp,
                                const GrShaderCaps&,
                                GrProcessorKeyBuilder* b) {
          const GrDistanceFieldPathGeoProc& dfTexEffect = gp.cast<GrDistanceFieldPathGeoProc>();
  
          uint32_t key = dfTexEffect.getFlags();
          key |= ComputePosKey(dfTexEffect.viewMatrix()) << 16;
          b->add32(key);
      }
  
  private:
      UniformHandle fTextureSizeUni;
      UniformHandle fViewMatrixUniform;
      SkMatrix      fViewMatrix;
      SkISize       fTextureSize;
  
      typedef GrGLSLGeometryProcessor INHERITED;
  };
  
  ///////////////////////////////////////////////////////////////////////////////
  GrDistanceFieldPathGeoProc::GrDistanceFieldPathGeoProc(
          GrResourceProvider* resourceProvider,
          GrColor color,
          const SkMatrix& viewMatrix,
          sk_sp<GrTextureProxy> proxy,
          const GrSamplerParams& params,
          uint32_t flags,
          bool usesLocalCoords)
      : fColor(color)
      , fViewMatrix(viewMatrix)
      , fTextureSampler(resourceProvider, std::move(proxy), params)
      , fFlags(flags & kNonLCD_DistanceFieldEffectMask)
      , fInColor(nullptr)
      , fUsesLocalCoords(usesLocalCoords) {
      SkASSERT(!(flags & ~kNonLCD_DistanceFieldEffectMask));
      this->initClassID<GrDistanceFieldPathGeoProc>();
      fInPosition = &this->addVertexAttrib("inPosition", kVec2f_GrVertexAttribType,
                                           kHigh_GrSLPrecision);
      fInColor = &this->addVertexAttrib("inColor", kVec4ub_GrVertexAttribType);
      fInTextureCoords = &this->addVertexAttrib("inTextureCoords", kVec2us_GrVertexAttribType);
      this->addTextureSampler(&fTextureSampler);
  }
  
  void GrDistanceFieldPathGeoProc::getGLSLProcessorKey(const GrShaderCaps& caps,
                                                       GrProcessorKeyBuilder* b) const {
      GrGLDistanceFieldPathGeoProc::GenKey(*this, caps, b);
  }
  
  GrGLSLPrimitiveProcessor*
  GrDistanceFieldPathGeoProc::createGLSLInstance(const GrShaderCaps&) const {
      return new GrGLDistanceFieldPathGeoProc();
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  
  GR_DEFINE_GEOMETRY_PROCESSOR_TEST(GrDistanceFieldPathGeoProc);
  
  #if GR_TEST_UTILS
  sk_sp<GrGeometryProcessor> GrDistanceFieldPathGeoProc::TestCreate(GrProcessorTestData* d) {
      int texIdx = d->fRandom->nextBool() ? GrProcessorUnitTest::kSkiaPMTextureIdx
                                          : GrProcessorUnitTest::kAlphaTextureIdx;
      sk_sp<GrTextureProxy> proxy = d->textureProxy(texIdx);
  
      static const SkShader::TileMode kTileModes[] = {
          SkShader::kClamp_TileMode,
          SkShader::kRepeat_TileMode,
          SkShader::kMirror_TileMode,
      };
      SkShader::TileMode tileModes[] = {
          kTileModes[d->fRandom->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
          kTileModes[d->fRandom->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
      };
      GrSamplerParams params(tileModes, d->fRandom->nextBool() ? GrSamplerParams::kBilerp_FilterMode
                                                               : GrSamplerParams::kNone_FilterMode);
  
      uint32_t flags = 0;
      flags |= d->fRandom->nextBool() ? kSimilarity_DistanceFieldEffectFlag : 0;
      if (flags & kSimilarity_DistanceFieldEffectFlag) {
          flags |= d->fRandom->nextBool() ? kScaleOnly_DistanceFieldEffectFlag : 0;
      }
  
      return GrDistanceFieldPathGeoProc::Make(d->resourceProvider(),
                                              GrRandomColor(d->fRandom),
                                              GrTest::TestMatrix(d->fRandom),
                                              std::move(proxy),
                                              params,
                                              flags,
                                              d->fRandom->nextBool());
  }
  #endif
  
  ///////////////////////////////////////////////////////////////////////////////
  
  class GrGLDistanceFieldLCDTextGeoProc : public GrGLSLGeometryProcessor {
  public:
      GrGLDistanceFieldLCDTextGeoProc()
          : fViewMatrix(SkMatrix::InvalidMatrix()) {
          fDistanceAdjust = GrDistanceFieldLCDTextGeoProc::DistanceAdjust::Make(1.0f, 1.0f, 1.0f);
      }
  
      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
          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.numTextureSamplers() == 1);
          GrTexture* atlas = dfTexEffect.textureSampler(0).texture();
          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
  
          // create LCD offset adjusted by inverse of transform
          // Use highp to work around aliasing issues
          fragBuilder->codeAppendf("highp vec2 uv = %s;\n", uv.fsIn());
  
          SkScalar lcdDelta = 1.0f / (3.0f * atlas->width());
          if (dfTexEffect.getFlags() & kBGR_DistanceFieldEffectFlag) {
              fragBuilder->codeAppendf("highp float delta = -%.*f;\n", SK_FLT_DECIMAL_DIG, lcdDelta);
          } else {
              fragBuilder->codeAppendf("highp 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 setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor& processor,
                   FPCoordTransformIter&& transformIter) override {
          SkASSERT(fDistanceAdjustUni.isValid());
  
          const GrDistanceFieldLCDTextGeoProc& dflcd = processor.cast<GrDistanceFieldLCDTextGeoProc>();
          GrDistanceFieldLCDTextGeoProc::DistanceAdjust wa = dflcd.getDistanceAdjust();
          if (wa != fDistanceAdjust) {
              pdman.set3f(fDistanceAdjustUni,
                          wa.fR,
                          wa.fG,
                          wa.fB);
              fDistanceAdjust = wa;
          }
  
          if (!dflcd.viewMatrix().isIdentity() && !fViewMatrix.cheapEqualTo(dflcd.viewMatrix())) {
              fViewMatrix = dflcd.viewMatrix();
              float viewMatrix[3 * 3];
              GrGLSLGetMatrix<3>(viewMatrix, fViewMatrix);
              pdman.setMatrix3f(fViewMatrixUniform, viewMatrix);
          }
          this->setTransformDataHelper(SkMatrix::I(), pdman, &transformIter);
      }
  
      static inline void GenKey(const GrGeometryProcessor& gp,
                                const GrShaderCaps&,
                                GrProcessorKeyBuilder* b) {
          const GrDistanceFieldLCDTextGeoProc& dfTexEffect = gp.cast<GrDistanceFieldLCDTextGeoProc>();
  
          uint32_t key = dfTexEffect.getFlags();
          key |= ComputePosKey(dfTexEffect.viewMatrix()) << 16;
          b->add32(key);
  
          // Currently we hardcode numbers to convert atlas coordinates to normalized floating point
          SkASSERT(gp.numTextureSamplers() == 1);
          GrTexture* atlas = gp.textureSampler(0).texture();
          SkASSERT(atlas);
          b->add32(atlas->width());
          b->add32(atlas->height());
      }
  
  private:
      SkMatrix                                     fViewMatrix;
      UniformHandle                                fViewMatrixUniform;
      UniformHandle                                fColorUniform;
      GrDistanceFieldLCDTextGeoProc::DistanceAdjust fDistanceAdjust;
      UniformHandle                                fDistanceAdjustUni;
  
      typedef GrGLSLGeometryProcessor INHERITED;
  };
  
  ///////////////////////////////////////////////////////////////////////////////
  GrDistanceFieldLCDTextGeoProc::GrDistanceFieldLCDTextGeoProc(
                                                    GrResourceProvider* resourceProvider,
                                                    GrColor color, const SkMatrix& viewMatrix,
                                                    sk_sp<GrTextureProxy> proxy,
                                                    const GrSamplerParams& params,
                                                    DistanceAdjust distanceAdjust,
                                                    uint32_t flags, bool usesLocalCoords)
      : fColor(color)
      , fViewMatrix(viewMatrix)
      , fTextureSampler(resourceProvider, std::move(proxy), params)
      , fDistanceAdjust(distanceAdjust)
      , fFlags(flags & kLCD_DistanceFieldEffectMask)
      , fUsesLocalCoords(usesLocalCoords) {
      SkASSERT(!(flags & ~kLCD_DistanceFieldEffectMask) && (flags & kUseLCD_DistanceFieldEffectFlag));
      this->initClassID<GrDistanceFieldLCDTextGeoProc>();
      fInPosition = &this->addVertexAttrib("inPosition", kVec2f_GrVertexAttribType,
                                           kHigh_GrSLPrecision);
      fInColor = &this->addVertexAttrib("inColor", kVec4ub_GrVertexAttribType);
      fInTextureCoords = &this->addVertexAttrib("inTextureCoords", kVec2us_GrVertexAttribType,
                                                kHigh_GrSLPrecision);
      this->addTextureSampler(&fTextureSampler);
  }
  
  void GrDistanceFieldLCDTextGeoProc::getGLSLProcessorKey(const GrShaderCaps& caps,
                                                          GrProcessorKeyBuilder* b) const {
      GrGLDistanceFieldLCDTextGeoProc::GenKey(*this, caps, b);
  }
  
  GrGLSLPrimitiveProcessor* GrDistanceFieldLCDTextGeoProc::createGLSLInstance(const GrShaderCaps&) const {
      return new GrGLDistanceFieldLCDTextGeoProc();
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  
  GR_DEFINE_GEOMETRY_PROCESSOR_TEST(GrDistanceFieldLCDTextGeoProc);
  
  #if GR_TEST_UTILS
  sk_sp<GrGeometryProcessor> GrDistanceFieldLCDTextGeoProc::TestCreate(GrProcessorTestData* d) {
      int texIdx = d->fRandom->nextBool() ? GrProcessorUnitTest::kSkiaPMTextureIdx :
                                            GrProcessorUnitTest::kAlphaTextureIdx;
      sk_sp<GrTextureProxy> proxy = d->textureProxy(texIdx);
  
      static const SkShader::TileMode kTileModes[] = {
          SkShader::kClamp_TileMode,
          SkShader::kRepeat_TileMode,
          SkShader::kMirror_TileMode,
      };
      SkShader::TileMode tileModes[] = {
          kTileModes[d->fRandom->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
          kTileModes[d->fRandom->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
      };
      GrSamplerParams params(tileModes, d->fRandom->nextBool() ? GrSamplerParams::kBilerp_FilterMode
                                                               : GrSamplerParams::kNone_FilterMode);
      DistanceAdjust wa = { 0.0f, 0.1f, -0.1f };
      uint32_t flags = kUseLCD_DistanceFieldEffectFlag;
      flags |= d->fRandom->nextBool() ? kSimilarity_DistanceFieldEffectFlag : 0;
      if (flags & kSimilarity_DistanceFieldEffectFlag) {
          flags |= d->fRandom->nextBool() ? kScaleOnly_DistanceFieldEffectFlag : 0;
      }
      flags |= d->fRandom->nextBool() ? kBGR_DistanceFieldEffectFlag : 0;
      return GrDistanceFieldLCDTextGeoProc::Make(d->resourceProvider(),
                                                 GrRandomColor(d->fRandom),
                                                 GrTest::TestMatrix(d->fRandom),
                                                 std::move(proxy), params,
                                                 wa,
                                                 flags,
                                                 d->fRandom->nextBool());
  }
  #endif
  