Add perspective shadows

Bug: skia:
Change-Id: I1972f85f593828c982ea08143e1ed7eb70345eaa
Reviewed-on: https://skia-review.googlesource.com/10296
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

1 files changed, 32 insertions, 3 deletions

diff --git a/src/utils/SkInsetConvexPolygon.h b/src/utils/SkInsetConvexPolygon.h
index 3ab7558a25..1d5a19c176 100755
--- a/src/utils/SkInsetConvexPolygon.h
+++ b/src/utils/SkInsetConvexPolygon.h
@@ -8,20 +8,49 @@
 #ifndef SkInsetConvexPolygon_DEFINED
 #define SkInsetConvexPolygon_DEFINED
 
+#include <functional>
+
 #include "SkTDArray.h"
 #include "SkPoint.h"
 
- /**
+/**
  * Generates a polygon that is inset a given distance from the boundary of a given convex polygon.
  *
  * @param inputPolygonVerts  Array of points representing the vertices of the original polygon.
  *  It should be convex and have no coincident points.
  * @param inputPolygonSize  Number of vertices in the original polygon.
- * @param insetDistance  How far we wish to inset the polygon. This should be a positive value.
+ * @param insetDistanceFunc  How far we wish to inset the polygon for a given index in the array.
+ *  This should return a positive value.
  * @param insetPolygon  The resulting inset polygon, if any.
  * @return true if an inset polygon exists, false otherwise.
  */
 bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize,
-                          SkScalar insetDistance, SkTDArray<SkPoint>* insetPolygon);
+                          std::function<SkScalar(int index)> insetDistanceFunc,
+                          SkTDArray<SkPoint>* insetPolygon);
+
+inline bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize,
+                                 SkScalar inset,
+                                 SkTDArray<SkPoint>* insetPolygon) {
+    return SkInsetConvexPolygon(inputPolygonVerts, inputPolygonSize,
+                                [inset](int) { return inset; },
+                                insetPolygon);
+}
+
+/**
+ * Offset a segment by the given distance at each point.
+ * Uses the outer tangents of two circles centered on each endpoint.
+ * See: https://en.wikipedia.org/wiki/Tangent_lines_to_circles
+ *
+ * @param p0  First endpoint.
+ * @param p1  Second endpoint.
+ * @param d0  Offset distance from first endpoint.
+ * @param d1  Offset distance from second endpoint.
+ * @param side  Indicates whether we want to offset to the left (1) or right (-1) side of segment.
+ * @param offset0  First endpoint of offset segment.
+ * @param offset1  Second endpoint of offset segment.
+ * @return true if an offset segment exists, false otherwise.
+ */
+bool SkOffsetSegment(const SkPoint& p0, const SkPoint& p1, SkScalar d0, SkScalar d1,
+                     int side, SkPoint* offset0, SkPoint* offset1);
 
 #endif