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

src/gpu/glsl/GrGLSLFragmentShaderBuilder.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSLFragmentShaderBuilder_DEFINED
 #define GrGLSLFragmentShaderBuilder_DEFINED
 
@@ skipping 35 matching lines @@
      * the fragment shader. If the coordinates at index are 3-dimensional, it immediately emits a
      * perspective divide into the fragment shader (xy / z) to convert them to 2D.
      */
     virtual SkString ensureFSCoords2D(const GrGLSLTransformedCoordsArray& coords, int index) = 0;
 
 
     /** Returns a variable name that represents the position of the fragment in the FS. The position
         is in device space (e.g. 0,0 is the top left and pixel centers are at half-integers). */
     virtual const char* fragmentPosition() = 0;
 
+    /** Returns a variable name that represents a vector to the nearest edge of the shape, in source
+        space coordinates. */
+    virtual const char* distanceVectorName() const = 0;

[egdaniel, 2016/07/14 02:47:47]

I think we can drop this down one level to grglslfpfragmentbuilder. The XP
should never need the distance vector. The gp probably doesn't need it either,
but we don't have anything that is FP only the GP builder inherits from the FP
one.

[dvonbeck, 2016/07/14 13:40:34]

Done.

+
     // TODO: remove this method.
     void declAppendf(const char* fmt, ...);
 
 private:
     typedef GrGLSLShaderBuilder INHERITED;
 };
 
 /*
  * This class is used by fragment processors to build their fragment code.
  */
@@ skipping 93 matching lines @@
        use the fragment position and/or sample locations. */
     static uint8_t KeyForSurfaceOrigin(GrSurfaceOrigin);
 
     GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program);
 
     // Shared GrGLSLFragmentBuilder interface.
     bool enableFeature(GLSLFeature) override;
     virtual SkString ensureFSCoords2D(const GrGLSLTransformedCoordsArray& coords,
                                       int index) override;
     const char* fragmentPosition() override;
+    const char* distanceVectorName() const override;
 
     // GrGLSLFPFragmentBuilder interface.
     void appendOffsetToSample(const char* sampleIdx, Coordinates) override;
     void maskSampleCoverage(const char* mask, bool invert = false) override;
     void overrideSampleCoverage(const char* mask) override;
     const SkString& getMangleString() const override { return fMangleString; }
     void onBeforeChildProcEmitCode() override;
     void onAfterChildProcEmitCode() override;
 
     // GrGLSLXPFragmentBuilder interface.
@@ skipping 49 matching lines @@
      * 1st child's 2nd child".
      */
     SkString fMangleString;
 
     bool       fSetupFragPosition;
     bool       fHasCustomColorOutput;
     int        fCustomColorOutputIndex;
     bool       fHasSecondaryOutput;
     uint8_t    fUsedSampleOffsetArrays;
     bool       fHasInitializedSampleMask;
+    SkString   fDistanceVectorOutput;
 
 #ifdef SK_DEBUG
     // some state to verify shaders and effects are consistent, this is reset between effects by
     // the program creator
     GrProcessor::RequiredFeatures fUsedProcessorFeatures;
     bool fHasReadDstColor;
 #endif
 
     friend class GrGLSLProgramBuilder;
     friend class GrGLProgramBuilder;
 };
 
 #endif