GrFP can express distance vector field req., program builder declares variable for it

src/core/SkNormalSource.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkError.h"
 #include "SkErrorInternals.h"
 #include "SkLightingShader.h"
@@ skipping 367 matching lines @@
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "SkGr.h"
 #endif
 
 class NormalBevelFP : public GrFragmentProcessor {
 public:
     NormalBevelFP(SkNormalSource::BevelType type, SkScalar width, SkScalar height)
         : fType(type)
         , fWidth(width)
         , fHeight(height) {
+        fUsesDistanceVectorField = true;
+
         this->initClassID<NormalBevelFP>();
     }
 
     class GLSLNormalBevelFP : public GrGLSLFragmentProcessor {
     public:
         GLSLNormalBevelFP() {}
 
         void emitCode(EmitArgs& args) override {
             GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
 
-            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+            fragBuilder->codeAppendf("if (%s == vec2(0.0, 0.0)) {",
+                    fragBuilder->distanceVectorName());
+            fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, 1.0, 0.0));",
+                    args.fOutputColor);
+            fragBuilder->codeAppend( "} else {");
+            // TODO (dvonbeck): emit normals according to bevel type and distance vector
+            fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, 1.0, 0.0));",
+                    args.fOutputColor);
+            fragBuilder->codeAppend( "}");
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
                            GrProcessorKeyBuilder* b) {
             b->add32(0x0);
         }
 
     protected:
         void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
             const NormalBevelFP& normalBevelFP = proc.cast<NormalBevelFP>();
@@ skipping 97 matching lines @@
 ////////////////////////////////////////////////////////////////////////////
 
 ////////////////////////////////////////////////////////////////////////////
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkNormalSource)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(NormalMapSourceImpl)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(NormalBevelSourceImpl)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ////////////////////////////////////////////////////////////////////////////