CircleSegment: Add inner_arc and outer_arc

CHANGELOG.md

@@ -21,6 +21,7 @@ This release has an [MSRV][] of 1.65.
 - Add `Rect::overlaps` and `Rect::contains_rect`. ([#347] by [@nils-mathieu])
 - Add `CubicBez::tangents` ([#288] by [@raphlinus])
 - Add `Arc::flipped`. ([#367] by [@waywardmonkeys])
+- Add `CircleSegment::inner_arc` and `CircleSegment::outer_arc` ([#368] by [@waywardmonkeys])
 
 ### Changed
 
@@ -57,6 +58,7 @@ Note: A changelog was not kept for or before this release
 [#356]: https://github.com/linebender/kurbo/pull/356
 [#361]: https://github.com/linebender/kurbo/pull/361
 [#367]: https://github.com/linebender/kurbo/pull/367
+[#368]: https://github.com/linebender/kurbo/pull/368
 
 [Unreleased]: https://github.com/linebender/kurbo/compare/v0.11.0...HEAD
 [0.11.0]: https://github.com/linebender/kurbo/releases/tag/v0.11.0

src/circle.rs

@@ -228,6 +228,38 @@ impl CircleSegment {
         }
     }
 
+    /// Return an arc representing the outer radius.
+    #[must_use]
+    #[inline]
+    pub fn outer_arc(&self) -> Arc {
+        Arc {
+            center: self.center,
+            radii: Vec2::new(self.outer_radius, self.outer_radius),
+            start_angle: self.start_angle,
+            sweep_angle: self.sweep_angle,
+            x_rotation: 0.0,
+        }
+    }
+
+    /// Return an arc representing the inner radius.
+    ///
+    /// This is [flipped] from the outer arc, so that it is in the
+    /// same direction as the arc that would be drawn (as the path
+    /// elements for this circle segment produce a closed path).
+    ///
+    /// [flipped]: Arc::flipped
+    #[must_use]
+    #[inline]
+    pub fn inner_arc(&self) -> Arc {
+        Arc {
+            center: self.center,
+            radii: Vec2::new(self.inner_radius, self.inner_radius),
+            start_angle: self.start_angle + self.sweep_angle,
+            sweep_angle: -self.sweep_angle,
+            x_rotation: 0.0,
+        }
+    }
+
     /// Is this circle segment [finite]?
     ///
     /// [finite]: f64::is_finite
@@ -301,33 +333,15 @@ impl Shape for CircleSegment {
             self.start_angle,
         ))))
         // outer arc
-        .chain(
-            Arc {
-                center: self.center,
-                radii: Vec2::new(self.outer_radius, self.outer_radius),
-                start_angle: self.start_angle,
-                sweep_angle: self.sweep_angle,
-                x_rotation: 0.0,
-            }
-            .append_iter(tolerance),
-        )
+        .chain(self.outer_arc().append_iter(tolerance))
         // second radius
         .chain(iter::once(PathEl::LineTo(point_on_circle(
             self.center,
             self.inner_radius,
             self.start_angle + self.sweep_angle,
         ))))
         // inner arc
-        .chain(
-            Arc {
-                center: self.center,
-                radii: Vec2::new(self.inner_radius, self.inner_radius),
-                start_angle: self.start_angle + self.sweep_angle,
-                sweep_angle: -self.sweep_angle,
-                x_rotation: 0.0,
-            }
-            .append_iter(tolerance),
-        )
+        .chain(self.inner_arc().append_iter(tolerance))
     }
 
     #[inline]