Use dFdx in Vulkan to address distance field issues.

src/gpu/effects/GrDistanceFieldGeoProc.cpp

 /*
  * 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 "GrInvariantOutput.h"
 #include "GrTexture.h"
@@ skipping 101 matching lines @@
 #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.
-            // 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("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) {");
@@ skipping 216 matching lines @@
         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.
-            // 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->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.
-            // 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->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) {");
@@ skipping 209 matching lines @@
         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);");
-            fragBuilder->codeAppend("vec2 offset = delta*vec2(st_grad.y, -st_grad.x);");
         } 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 = ");
@@ skipping 182 matching lines @@
         flags |= d->fRandom->nextBool() ? kScaleOnly_DistanceFieldEffectFlag : 0;
     }
     flags |= d->fRandom->nextBool() ? kBGR_DistanceFieldEffectFlag : 0;
     return GrDistanceFieldLCDTextGeoProc::Make(GrRandomColor(d->fRandom),
                                                GrTest::TestMatrix(d->fRandom),
                                                d->fTextures[texIdx], params,
                                                wa,
                                                flags,
                                                d->fRandom->nextBool());
 }