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

with other changes mentioned in comments, I think we should only need
distanceVectorName

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

Done.

+    virtual bool hasDistanceVectorOutput() const = 0;
+
     // 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 92 matching lines @@
    /** Returns a nonzero key for a surface's origin. This should only be called if a processor will
        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;

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

same order as above ?

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

Done.

+    bool hasDistanceVectorOutput() const 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.
     bool hasCustomColorOutput() const override { return fHasCustomColorOutput; }
     bool hasSecondaryOutput() const override { return fHasSecondaryOutput; }
     const char* dstColor() override;
     void enableAdvancedBlendEquationIfNeeded(GrBlendEquation) override;
 
 private:
     // Private public interface, used by GrGLProgramBuilder to build a fragment shader
+    void enableDistanceVector(const SkString& name);
     void enableCustomOutput();
     void enableSecondaryOutput();
     const char* getPrimaryColorOutputName() const;
     const char* getSecondaryColorOutputName() const;
 
 #ifdef SK_DEBUG
     // As GLSLProcessors emit code, there are some conditions we need to verify.  We use the below
     // state to track this.  The reset call is called per processor emitted.
     GrProcessor::RequiredFeatures usedProcessorFeatures() const { return fUsedProcessorFeatures; }
     bool hasReadDstColor() const { return fHasReadDstColor; }
@@ skipping 32 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