Extend SkTrimPathEffect semantics

Add support for multiple contours, and an explicit "inverted" mode.

Bug: skia:
Change-Id: Iafadbbe9d4692f2467a4ef8585f7fcd9cee9566a
Reviewed-on: https://skia-review.googlesource.com/113270
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/include/effects/SkTrimPathEffect.h b/include/effects/SkTrimPathEffect.h
index d40c9e2..e96b94f 100644
--- a/include/effects/SkTrimPathEffect.h
+++ b/include/effects/SkTrimPathEffect.h
@@ -12,6 +12,11 @@
 
 class SK_API SkTrimPathEffect {
 public:
+    enum class Mode {
+        kNormal,   // return the subset path [start,stop]
+        kInverted, // return the complement/subset paths [0,start] + [stop,1]
+    };
+
     /**
      *  Take start and stop "t" values (values between 0...1), and return a path that is that
      *  subset of the original path.
@@ -26,11 +31,11 @@
      *  startT and stopT must be 0..1 inclusive. If they are outside of that interval, they will
      *  be pinned to the nearest legal value. If either is NaN, null will be returned.
      *
-     *  Note: if startT < stopT, this will return one (logical) segment (even if it is spread
-     *        across multiple contours). If startT > stopT, then this will return 2 logical
+     *  Note: for Mode::kNormal, this will return one (logical) segment (even if it is spread
+     *        across multiple contours). For Mode::kInverted, this will return 2 logical
      *        segments: 0...stopT and startT...1
      */
-    static sk_sp<SkPathEffect> Make(SkScalar startT, SkScalar stopT);
+    static sk_sp<SkPathEffect> Make(SkScalar startT, SkScalar stopT, Mode = Mode::kNormal);
 };
 
 #endif