Added API for Bevel NormalSource.

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
 
 #include "SkFlattenable.h"
+#include "SkShader.h"
+
+class SkMatrix;
+class SkPoint3;
+
+#if SK_SUPPORT_GPU
+class GrFragmentProcessor;
+class GrContext;
+enum SkFilterQuality;
+enum SkSourceGammaTreatment;
+#endif
 
 /** Abstract class that generates or reads in normals for use by SkLightingShader.
 */
 class SK_API SkNormalSource : public SkFlattenable {
 public:
     virtual ~SkNormalSource() override;
 
 #if SK_SUPPORT_GPU
     /** Returns a fragment processor that takes no input and outputs a normal (already rotated)
         as its output color. To be used as a child fragment processor.
@@ skipping 40 matching lines @@
             N.normalize();
         The +Z axis is thus encoded in RGB as (127, 127, 255) while the -Z axis is
         (127, 127, 0).
     */
     static sk_sp<SkNormalSource> MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm);
 
     /** Returns a normal source that provides straight-up normals only (0, 0, 1).
     */
     static sk_sp<SkNormalSource> MakeFlat();
 
+    /** This enum specifies the shape of the bevel.
+     */
+    enum class BevelType {

[egdaniel, 2016/07/25 15:48:00]

Change this to what we just discussed. Make sure to add that any d > width has
normal (0,0,1). 

[dvonbeck, 2016/07/25 20:37:14]

Done.

+        /* This bevel simulates a surface that is slanted from the shape's edges inwards, linearly.
+         * It generates normals perpendicular to a straight line of slope 'height/width' that goes
+         * from the closest edge of the shape to the point being shaded, as long as that point is
+         * less than 'width' away from the closest edge.
+         */
+        kLinear,
+        /* This bevel simulates a surface that rounds off at the shape's edges, smoothly becoming
+         * perpendicular to the x-y plane, starting 'width' units from the edge and following a
+         * quadratic bezier curve.
+         *
+         * It can be more rigorously defined as the top surface of the volume enclosed between the
+         * plane z=0, the plane z='height', and the surface formed by the union of all quadratic
+         * bezier curves defined as follows:
+         *     - The start point is the edge of the shape
+         *     - The end point is 'width' units from the start point in the x-y plane
+         *     - The end point z-coordinate is 'height'.
+         *     - The projection of the curve in the x-y plane is perpendicular to the shape's edge
+         *       at the start point.
+         *     - The control point is the projection of the start point onto the z='height' plane.
+         */
+        kRoundedOut,
+        /* This bevel simulates a surface that sharply becomes perpendicular to the x-y plane at a
+         * distance of 'width' units from the edge, and then smoothly becomes parallel to the x-y
+         * plane following a quadratic bezier curve.
+         *
+         * It can be more rigorously defined as the top surface of the volume enclosed between the
+         * plane z=0, the plane z='height', and the surface formed by the union of all quadratic
+         * bezier curves defined as follows:
+         *     - The start point is the edge of the shape
+         *     - The end point is 'width' units from the start point in the x-y plane
+         *     - The end point z-coordinate is 'height'.
+         *     - The projection of the curve in the x-y plane is perpendicular to the shape's edge
+         *       at the start point.
+         *     - The control point is the projection of the end point onto the z=0 plane.
+         */
+        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  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