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

src/core/SkNormalSource.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkNormalSource_DEFINED
 #define SkNormalSource_DEFINED
 
@@ skipping 93 matching lines @@
          *
          * Mathematical details:
          * This bevel follows the only quadratic bezier curve whose start point is at (w, 0, 0),
          * control point is at (0, 0, 0), and end point is at (0, 0, h).
          */
         kRoundedIn
     };
     /** Returns a normal source that generates a bevel for the given shape. UNIMPLEMENTED: Will
         return straight-up normals only.
 
-        @param  type   the type of bevel to add
+        @param  type   the type of bevel to add.
         @param  width  the width of the bevel, in source space. Must be positive.
         @param  height the height of the plateau, in source space. Can be positive, negative,
                        or zero. A negative height means the simulated bevels slope downwards.
     */
     static sk_sp<SkNormalSource> MakeBevel(BevelType, SkScalar width, SkScalar height);
 
     SK_DEFINE_FLATTENABLE_TYPE(SkNormalSource)
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 };
 
 #endif