Alter shader code for soft light to avoid driver bug.

src/gpu/effects/GrCustomXfermode.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "effects/GrCustomXfermode.h"
 #include "effects/GrCustomXfermodePriv.h"
 
@@ skipping 137 matching lines @@
     // else if (4D < Da)
     fsBuilder->codeAppendf("} else if (4.0 * %s.%c <= %s.a) {",
                            dst, component, dst);
     fsBuilder->codeAppendf("float DSqd = %s.%c * %s.%c;",
                            dst, component, dst, component);
     fsBuilder->codeAppendf("float DCub = DSqd * %s.%c;", dst, component);
     fsBuilder->codeAppendf("float DaSqd = %s.a * %s.a;", dst, dst);
     fsBuilder->codeAppendf("float DaCub = DaSqd * %s.a;", dst);
     // (Da^3 (-S)+Da^2 (S-D (3 Sa-6 S-1))+12 Da D^2 (Sa-2 S)-16 D^3 (Sa-2 S))/Da^2
     fsBuilder->codeAppendf("%s.%c ="
-                           "(-DaCub*%s.%c + DaSqd*(%s.%c - %s.%c * (3.0*%s.a - 6.0*%s.%c - 1.0)) +"
-                           " 12.0*%s.a*DSqd*(%s.a - 2.0*%s.%c) - 16.0*DCub * (%s.a - 2.0*%s.%c)) /"
-                           "DaSqd;",
-                           final, component, src, component, src, component, dst, component,
+                           "(DaSqd*(%s.%c - %s.%c * (3.0*%s.a - 6.0*%s.%c - 1.0)) +"
+                           " 12.0*%s.a*DSqd*(%s.a - 2.0*%s.%c) - 16.0*DCub * (%s.a - 2.0*%s.%c) -"
+                           " DaCub*%s.%c) / DaSqd;",
+                           final, component, src, component, dst, component,
                            src, src, component, dst, src, src, component, src, src,
-                           component);
+                           component, src, component);
     fsBuilder->codeAppendf("} else {");
     // -sqrt(Da * D) (Sa-2 S)-Da S+D (Sa-2 S+1)+S
-    fsBuilder->codeAppendf("%s.%c = -sqrt(%s.a*%s.%c)*(%s.a - 2.0*%s.%c) - %s.a*%s.%c +"
-                                   "%s.%c*(%s.a - 2.0*%s.%c + 1.0) + %s.%c;",
-                           final, component, dst, dst, component, src, src, component, dst,
-                           src, component, dst, component, src, src, component, src,
-                           component);
+    fsBuilder->codeAppendf("%s.%c = %s.%c*(%s.a - 2.0*%s.%c + 1.0) + %s.%c -"
+                           " sqrt(%s.a*%s.%c)*(%s.a - 2.0*%s.%c) - %s.a*%s.%c;",
+                           final, component, dst, component, src, src, component, src, component,
+                           dst, dst, component, src, src, component, dst, src, component);
     fsBuilder->codeAppendf("}");
 }
 
 // Adds a function that takes two colors and an alpha as input. It produces a color with the
 // hue and saturation of the first color, the luminosity of the second color, and the input
 // alpha. It has this signature:
 //      vec3 set_luminance(vec3 hueSatColor, float alpha, vec3 lumColor).
 static void add_lum_function(GrGLFragmentBuilder* fsBuilder, SkString* setLumFunction) {
     // Emit a helper that gets the luminance of a color.
     SkString getFunction;
@@ skipping 635 matching lines @@
 GR_DEFINE_XP_FACTORY_TEST(GrCustomXPFactory);
 GrXPFactory* GrCustomXPFactory::TestCreate(SkRandom* rand,
                                            GrContext*,
                                            const GrCaps&,
                                            GrTexture*[]) {
     int mode = rand->nextRangeU(SkXfermode::kLastCoeffMode + 1, SkXfermode::kLastSeparableMode);
 
     return SkNEW_ARGS(GrCustomXPFactory, (static_cast<SkXfermode::Mode>(mode)));
 }