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

src/gpu/glsl/GrGLSLProgramBuilder.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 "glsl/GrGLSLProgramBuilder.h"
 
 #include "GrPipeline.h"
@@ skipping 69 matching lines @@
 }
 
 void GrGLSLProgramBuilder::emitAndInstallPrimProc(const GrPrimitiveProcessor& proc,
                                                   GrGLSLExpr4* outputColor,
                                                   GrGLSLExpr4* outputCoverage) {
     // Program builders have a bit of state we need to clear with each effect
     AutoStageAdvance adv(this);
     this->nameExpression(outputColor, "outputColor");
     this->nameExpression(outputCoverage, "outputCoverage");
 
+    if (this->fPipeline.usesDistanceVectorField()) {
+        SkString outputDistanceVectorStr;
+        this->nameVariable(&outputDistanceVectorStr, '\0', "outputDistanceVector");

[egdaniel, 2016/07/12 13:46:42]

I think I would prefer hard coding the name we want to use into
GLSLFragmentShaderBuilder instead of us telling the fragment shader what the
name should be.

[dvonbeck, 2016/07/13 15:17:13]

The thing is, the Geometry Processors get their variable names mangled. That's
why I'm running it through the nameVariable method.

[egdaniel, 2016/07/13 15:47:02]

I don't think there is any need for mangling the variable here. We do a similar
thing when we need to declare the the outColor variable. See 
DeclaredColorOutputName()

[dvonbeck, 2016/07/13 16:57:49]

Done.

+        fFS.enableDistanceVector(outputDistanceVectorStr);
+

[robertphillips, 2016/07/11 17:55:40]

Maybe emit a comment:

// Un-normalized vector to the closed geometric edge (in source space)

?

[dvonbeck, 2016/07/13 15:17:13]

Done.

+        fFS.codeAppendf("vec2 %s = vec2(0.0, 0.0);", fFS.distanceVectorName());
+    }
+
     // Enclose custom code in a block to avoid namespace conflicts
     SkString openBrace;
     openBrace.printf("{ // Stage %d, %s\n", fStageIndex, proc.name());
     fFS.codeAppend(openBrace.c_str());
     fVS.codeAppendf("// Primitive Processor %s\n", proc.name());
 
     SkASSERT(!fGeometryProcessor);
     fGeometryProcessor = proc.createGLSLInstance(*this->glslCaps());
 
     SkSTArray<4, SamplerHandle> texSamplers(proc.numTextures());
@@ skipping 301 matching lines @@
         delete fFragmentProcessors[i];
     }
 }
 
 void GrGLSLProgramBuilder::finalizeShaders() {
     this->varyingHandler()->finalize();
     fVS.finalize(kVertex_GrShaderFlag);
     fFS.finalize(kFragment_GrShaderFlag);
 
 }