Add LCD support for distance field text

src/gpu/effects/GrDistanceFieldTextureEffect.cpp

Index: src/gpu/effects/GrDistanceFieldTextureEffect.cpp
diff --git a/src/gpu/effects/GrDistanceFieldTextureEffect.cpp b/src/gpu/effects/GrDistanceFieldTextureEffect.cpp
index dd370b6d4e66e32e37ff4f638c50d66015be1087..8a023cd1d08073ddc5c0fecb42b45a619d4a87ce 100755
--- a/src/gpu/effects/GrDistanceFieldTextureEffect.cpp
+++ b/src/gpu/effects/GrDistanceFieldTextureEffect.cpp
@@ -66,7 +66,7 @@ public:
         builder->fsCodeAppendf("\tvec2 uv = %s;\n", fsCoordName.c_str());
         builder->fsCodeAppendf("\tvec2 st = uv*%s;\n", textureSizeUniName);
         builder->fsCodeAppend("\tfloat afwidth;\n");
-        if (dfTexEffect.isUniformScale()) {
+        if (dfTexEffect.isSimilarity()) {
             // this gives us a smooth step across approximately one fragment
             // (assuming a radius of the diagonal of the fragment, hence a factor of sqrt(2)/2)
             builder->fsCodeAppend("\tafwidth = 0.7071*dFdx(st.x);\n");
@@ -118,7 +118,7 @@ public:
         const GrDistanceFieldTextureEffect& dfTexEffect =
                                               drawEffect.castEffect<GrDistanceFieldTextureEffect>();
 
-        return dfTexEffect.isUniformScale() ? 0x1 : 0x0;
+        return dfTexEffect.isSimilarity() ? 0x1 : 0x0;
     }
 
 private:
@@ -132,9 +132,9 @@ private:
 
 GrDistanceFieldTextureEffect::GrDistanceFieldTextureEffect(GrTexture* texture,
                                                            const GrTextureParams& params,
-                                                           bool uniformScale)
+                                                           bool similarity)
     : fTextureAccess(texture, params)
-    , fUniformScale(uniformScale) {
+    , fIsSimilarity(similarity) {
     this->addTextureAccess(&fTextureAccess);
     this->addVertexAttrib(kVec2f_GrSLType);
 }
@@ -180,5 +180,210 @@ GrEffectRef* GrDistanceFieldTextureEffect::TestCreate(SkRandom* random,
     GrTextureParams params(tileModes, random->nextBool() ? GrTextureParams::kBilerp_FilterMode :
                                                            GrTextureParams::kNone_FilterMode);
 
-    return GrDistanceFieldTextureEffect::Create(textures[texIdx], params, random->nextBool());
+    return GrDistanceFieldTextureEffect::Create(textures[texIdx], params,
+                                                random->nextBool());
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+class GrGLDistanceFieldLCDTextureEffect : public GrGLVertexEffect {
+public:
+    GrGLDistanceFieldLCDTextureEffect(const GrBackendEffectFactory& factory,
+                                      const GrDrawEffect& drawEffect)
+    : INHERITED (factory)
+    , fTextureSize(SkISize::Make(-1,-1)) {}
+
+    virtual void emitCode(GrGLFullShaderBuilder* builder,
+                          const GrDrawEffect& drawEffect,
+                          EffectKey key,
+                          const char* outputColor,
+                          const char* inputColor,
+                          const TransformedCoordsArray&,
+                          const TextureSamplerArray& samplers) SK_OVERRIDE {
+        SkASSERT(1 == drawEffect.castEffect<GrDistanceFieldLCDTextureEffect>().numVertexAttribs());
+
+        SkAssertResult(builder->enableFeature(GrGLShaderBuilder::kStandardDerivatives_GLSLFeature));
+        const GrDistanceFieldLCDTextureEffect& dfTexEffect =
+                                           drawEffect.castEffect<GrDistanceFieldLCDTextureEffect>();
+
+        SkString fsCoordName;
+        const char* vsCoordName;
+        const char* fsCoordNamePtr;
+        builder->addVarying(kVec2f_GrSLType, "textureCoords", &vsCoordName, &fsCoordNamePtr);
+        fsCoordName = fsCoordNamePtr;
+
+        const char* attrName0 =
+        builder->getEffectAttributeName(drawEffect.getVertexAttribIndices()[0])->c_str();
+        builder->vsCodeAppendf("\t%s = %s;\n", vsCoordName, attrName0);
+
+        const char* textureSizeUniName = NULL;
+        // width, height, 1/(3*width)
+        fTextureSizeUni = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
+                                              kVec3f_GrSLType, "TextureSize",
+                                              &textureSizeUniName);
+
+        // create LCD offset adjusted by inverse of transform
+        builder->fsCodeAppendf("\tvec2 uv = %s;\n", fsCoordName.c_str());
+        builder->fsCodeAppendf("\tvec2 st = uv*%s.xy;\n", textureSizeUniName);
+        if (dfTexEffect.isUniformScale()) {
+            builder->fsCodeAppend("\tfloat dx = dFdx(st.x);\n");
+            builder->fsCodeAppendf("\tvec2 offset = vec2(dx*%s.z, 0.0);\n", textureSizeUniName);
+        } else {
+            builder->fsCodeAppend("\tvec2 Jdx = dFdx(st);\n");
+            builder->fsCodeAppend("\tvec2 Jdy = dFdy(st);\n");
+            builder->fsCodeAppendf("\tvec2 offset = %s.z*Jdx;\n", textureSizeUniName);
+        }
+
+        // green is distance to uv center
+        builder->fsCodeAppend("\tvec4 texColor = ");
+        builder->fsAppendTextureLookup(samplers[0], "uv", kVec2f_GrSLType);
+        builder->fsCodeAppend(";\n");
+        builder->fsCodeAppend("\tvec3 distance;\n");
+        builder->fsCodeAppend("\tdistance.y = " MULTIPLIER "*(texColor.r - " THRESHOLD ");\n");
+        // red is distance to left offset
+        builder->fsCodeAppend("\tvec2 uv_adjusted = uv - offset;\n");
+        builder->fsCodeAppend("\ttexColor = ");
+        builder->fsAppendTextureLookup(samplers[0], "uv_adjusted", kVec2f_GrSLType);
+        builder->fsCodeAppend(";\n");
+        builder->fsCodeAppend("\tdistance.x = " MULTIPLIER "*(texColor.r - " THRESHOLD ");\n");
+        // blue is distance to right offset
+        builder->fsCodeAppend("\tuv_adjusted = uv + offset;\n");
+        builder->fsCodeAppend("\ttexColor = ");
+        builder->fsAppendTextureLookup(samplers[0], "uv_adjusted", kVec2f_GrSLType);
+        builder->fsCodeAppend(";\n");
+        builder->fsCodeAppend("\tdistance.z = " MULTIPLIER "*(texColor.r - " THRESHOLD ");\n");
+
+        // 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.
+
+        // 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.
+        builder->fsCodeAppend("\tfloat afwidth;\n");
+        if (dfTexEffect.isUniformScale()) {
+            // this gives us a smooth step across approximately one fragment
+            // (assuming a radius of the diagonal of the fragment, hence a factor of sqrt(2)/2)
+            builder->fsCodeAppend("\tafwidth = 0.7071*dx;\n");
+        } else {
+            builder->fsCodeAppend("\tvec2 uv_grad;\n");
+            if (builder->ctxInfo().caps()->dropsTileOnZeroDivide()) {
+                // this is to compensate for the Adreno, which likes to drop tiles on division by 0
+                builder->fsCodeAppend("\tfloat uv_len2 = dot(uv, uv);\n");
+                builder->fsCodeAppend("\tif (uv_len2 < 0.0001) {\n");
+                builder->fsCodeAppend("\t\tuv_grad = vec2(0.7071, 0.7071);\n");
+                builder->fsCodeAppend("\t} else {\n");
+                builder->fsCodeAppend("\t\tuv_grad = uv*inversesqrt(uv_len2);\n");
+                builder->fsCodeAppend("\t}\n");
+            } else {
+                builder->fsCodeAppend("\tuv_grad = normalize(uv);\n");
+            }
+            builder->fsCodeAppend("\tvec2 grad = vec2(uv_grad.x*Jdx.x + uv_grad.y*Jdy.x,\n");
+            builder->fsCodeAppend("\t                 uv_grad.x*Jdx.y + uv_grad.y*Jdy.y);\n");
+
+            // this gives us a smooth step across approximately one fragment
+            // (assuming a radius of the diagonal of the fragment, hence a factor of sqrt(2)/2)
+            builder->fsCodeAppend("\tafwidth = 0.7071*length(grad);\n");
+        }
+
+        builder->fsCodeAppend("\tvec4 val = vec4(smoothstep(vec3(-afwidth), vec3(afwidth), distance), 1.0);\n");
+
+        builder->fsCodeAppendf("\t%s = %s;\n", outputColor,
+                               (GrGLSLExpr4(inputColor) * GrGLSLExpr4("val")).c_str());
+    }
+
+    virtual void setData(const GrGLUniformManager& uman,
+                         const GrDrawEffect& drawEffect) SK_OVERRIDE {
+        SkASSERT(fTextureSizeUni.isValid());
+
+        GrTexture* texture = drawEffect.effect()->get()->texture(0);
+        if (texture->width() != fTextureSize.width() ||
+            texture->height() != fTextureSize.height()) {
+            const GrDistanceFieldLCDTextureEffect& dfTexEffect =
+                                           drawEffect.castEffect<GrDistanceFieldLCDTextureEffect>();
+            fTextureSize = SkISize::Make(texture->width(), texture->height());
+            float delta = 1.0f/(3.0f*texture->width());
+            if (dfTexEffect.useBGR()) {
+                delta = -delta;
+            }
+            uman.set3f(fTextureSizeUni,
+                       SkIntToScalar(fTextureSize.width()),
+                       SkIntToScalar(fTextureSize.height()),
+                       delta);
+        }
+    }
+
+    static inline EffectKey GenKey(const GrDrawEffect& drawEffect, const GrGLCaps&) {
+        const GrDistanceFieldLCDTextureEffect& dfTexEffect =
+                                           drawEffect.castEffect<GrDistanceFieldLCDTextureEffect>();
+
+        int uniformScale = dfTexEffect.isUniformScale() ? 0x01 : 0x00;
+        int useBGR = dfTexEffect.useBGR() ? 0x10 : 0x00;
+        return uniformScale | useBGR;
+    }
+
+private:
+    GrGLUniformManager::UniformHandle fTextureSizeUni;
+    SkISize                           fTextureSize;
+
+    typedef GrGLVertexEffect INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+GrDistanceFieldLCDTextureEffect::GrDistanceFieldLCDTextureEffect(GrTexture* texture,
+                                                                 const GrTextureParams& params,
+                                                                 bool uniformScale,
+                                                                 bool useBGR)
+    : fTextureAccess(texture, params)
+    , fUniformScale(uniformScale)
+    , fUseBGR(useBGR) {
+    this->addTextureAccess(&fTextureAccess);
+    this->addVertexAttrib(kVec2f_GrSLType);
+}
+
+bool GrDistanceFieldLCDTextureEffect::onIsEqual(const GrEffect& other) const {
+    const GrDistanceFieldLCDTextureEffect& cte = CastEffect<GrDistanceFieldLCDTextureEffect>(other);
+    return fTextureAccess == cte.fTextureAccess;
+}
+
+void GrDistanceFieldLCDTextureEffect::getConstantColorComponents(GrColor* color,
+                                                                 uint32_t* validFlags) const {
+    if ((*validFlags & kA_GrColorComponentFlag) && 0xFF == GrColorUnpackA(*color) &&
+        GrPixelConfigIsOpaque(this->texture(0)->config())) {
+        *validFlags = kA_GrColorComponentFlag;
+    } else {
+        *validFlags = 0;
+    }
+}
+
+const GrBackendEffectFactory& GrDistanceFieldLCDTextureEffect::getFactory() const {
+    return GrTBackendEffectFactory<GrDistanceFieldLCDTextureEffect>::getInstance();
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+GR_DEFINE_EFFECT_TEST(GrDistanceFieldLCDTextureEffect);
+
+GrEffectRef* GrDistanceFieldLCDTextureEffect::TestCreate(SkRandom* random,
+                                                         GrContext*,
+                                                         const GrDrawTargetCaps&,
+                                                         GrTexture* textures[]) {
+    int texIdx = random->nextBool() ? GrEffectUnitTest::kSkiaPMTextureIdx :
+    GrEffectUnitTest::kAlphaTextureIdx;
+    static const SkShader::TileMode kTileModes[] = {
+        SkShader::kClamp_TileMode,
+        SkShader::kRepeat_TileMode,
+        SkShader::kMirror_TileMode,
+    };
+    SkShader::TileMode tileModes[] = {
+        kTileModes[random->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
+        kTileModes[random->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
+    };
+    GrTextureParams params(tileModes, random->nextBool() ? GrTextureParams::kBilerp_FilterMode :
+                           GrTextureParams::kNone_FilterMode);
+
+    return GrDistanceFieldLCDTextureEffect::Create(textures[texIdx], params,
+                                                   random->nextBool(), random->nextBool());
 }