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

include/gpu/GrFragmentProcessor.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 GrFragmentProcessor_DEFINED
 #define GrFragmentProcessor_DEFINED
 
@@ skipping 47 matching lines @@
      * series. The original input is passed to the first, the first's output is passed to the
      * second, etc. The output of the returned processor is the output of the last processor of the
      * series.
      *
      * The array elements with be moved.
      */
     static sk_sp<GrFragmentProcessor> RunInSeries(sk_sp<GrFragmentProcessor>*, int cnt);
 
     GrFragmentProcessor()
         : INHERITED()
+        , fUsesDistanceVectorField(false)
         , fUsesLocalCoords(false)
         , fNumTexturesExclChildren(0)
         , fNumBuffersExclChildren(0)
         , fNumTransformsExclChildren(0) {}
 
     ~GrFragmentProcessor() override;
 
     GrGLSLFragmentProcessor* createGLSLInstance() const;
 
     void getGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const {
@@ skipping 25 matching lines @@
         }
     }
 
     int numChildProcessors() const { return fChildProcessors.count(); }
 
     const GrFragmentProcessor& childProcessor(int index) const { return *fChildProcessors[index]; }
 
     /** Do any of the coordtransforms for this processor require local coords? */
     bool usesLocalCoords() const { return fUsesLocalCoords; }
 
+    /** Does this FP need a vector to the nearest edge? */
+    bool usesDistanceVectorField() const { return fUsesDistanceVectorField; }
+
     /** Returns true if this and other processor conservatively draw identically. It can only return
         true when the two processor are of the same subclass (i.e. they return the same object from
         from getFactory()).
 
         A return value of true from isEqual() should not be used to test whether the processor would
         generate the same shader code. To test for identical code generation use getGLSLProcessorKey
      */
     bool isEqual(const GrFragmentProcessor& that, bool ignoreCoordTransforms) const;
 
     /**
@@ skipping 43 matching lines @@
     int registerChildProcessor(sk_sp<GrFragmentProcessor> child);
 
     /**
      * Subclass implements this to support getConstantColorComponents(...).
      *
      * Note: it's up to the subclass implementation to do any recursive call to compute the child
      * procs' output invariants; computeInvariantOutput will not be recursive.
      */
     virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const = 0;
 
+    /* Sub-classes should set this to true in their constructors if they need access to a distance
+     * vector field to the nearest edge
+     */
+    bool fUsesDistanceVectorField;
+
 private:
     void notifyRefCntIsZero() const final;
 
     /** Returns a new instance of the appropriate *GL* implementation class
         for the given GrFragmentProcessor; caller is responsible for deleting
         the object. */
     virtual GrGLSLFragmentProcessor* onCreateGLSLInstance() const = 0;
 
     /** Implemented using GLFragmentProcessor::GenKey as described in this class's comment. */
     virtual void onGetGLSLProcessorKey(const GrGLSLCaps& caps,
@@ skipping 42 matching lines @@
     /**
      * This is not SkSTArray<1, sk_sp<GrFragmentProcessor>> because this class holds strong
      * references until notifyRefCntIsZero and then it holds pending executions.
      */
     SkSTArray<1, GrFragmentProcessor*, true>    fChildProcessors;
 
     typedef GrProcessor INHERITED;
 };
 
 #endif