From 2cb3ec6b36427037cd5ada74d34bb56b20eede10 Mon Sep 17 00:00:00 2001
From: Bruce Mitchener <bruce.mitchener@gmail.com>
Date: Wed, 4 Sep 2024 22:00:47 +0700
Subject: [PATCH] Add `Line::reversed`, `Line::midpoint`, rename `Arc::flipped`
 (#375)

---
 CHANGELOG.md  |  4 +++-
 src/arc.rs    | 12 ++++++------
 src/circle.rs |  4 ++--
 src/line.rs   | 39 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1e60845..900a16d3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,9 +20,10 @@ This release has an [MSRV][] of 1.65.
 - Add `From (f32, f32)` for `Point`. ([#339] by [@rsheeter])
 - Add `Rect::overlaps` and `Rect::contains_rect`. ([#347] by [@nils-mathieu])
 - Add `CubicBez::tangents` ([#288] by [@raphlinus])
-- Add `Arc::flipped`. ([#367] by [@waywardmonkeys])
+- Add `Arc::reversed`. ([#367] by [@waywardmonkeys])
 - Add `CircleSegment::inner_arc` and `CircleSegment::outer_arc` ([#368] by [@waywardmonkeys])
 - Add `Rect::is_zero_area` and `Size::is_zero_area` and deprecate their `is_empty` methods. ([#370] by [@waywardmonkeys])
+- Add `Line::reversed` and `Line::midpoint`. ([#375] by [@waywardmonkeys])
 
 ### Changed
 
@@ -67,6 +68,7 @@ Note: A changelog was not kept for or before this release
 [#367]: https://github.com/linebender/kurbo/pull/367
 [#368]: https://github.com/linebender/kurbo/pull/368
 [#370]: https://github.com/linebender/kurbo/pull/370
+[#375]: https://github.com/linebender/kurbo/pull/375
 
 [Unreleased]: https://github.com/linebender/kurbo/compare/v0.11.0...HEAD
 [0.11.0]: https://github.com/linebender/kurbo/releases/tag/v0.11.0
diff --git a/src/arc.rs b/src/arc.rs
index fd903c32..9ac642be 100644
--- a/src/arc.rs
+++ b/src/arc.rs
@@ -49,13 +49,13 @@ impl Arc {
         }
     }
 
-    /// Return a copy of this `Arc` in the opposite direction.
+    /// Returns a copy of this `Arc` in the opposite direction.
     ///
     /// The new `Arc` will sweep towards the original `Arc`s
     /// start angle.
     #[must_use]
     #[inline]
-    pub fn flipped(&self) -> Arc {
+    pub fn reversed(&self) -> Arc {
         Self {
             center: self.center,
             radii: self.radii,
@@ -227,9 +227,9 @@ impl Mul<Arc> for Affine {
 mod tests {
     use super::*;
     #[test]
-    fn flipped_arc() {
+    fn reversed_arc() {
         let a = Arc::new((0., 0.), (1., 0.), 0., PI, 0.);
-        let f = a.flipped();
+        let f = a.reversed();
 
         // Most fields should be unchanged:
         assert_eq!(a.center, f.center);
@@ -239,7 +239,7 @@ mod tests {
         // Sweep angle should be in reverse
         assert_eq!(a.sweep_angle, -f.sweep_angle);
 
-        // Flipping it again should result in the original arc
-        assert_eq!(a, f.flipped());
+        // Reversing it again should result in the original arc
+        assert_eq!(a, f.reversed());
     }
 }
diff --git a/src/circle.rs b/src/circle.rs
index c340a42b..969bd619 100644
--- a/src/circle.rs
+++ b/src/circle.rs
@@ -243,11 +243,11 @@ impl CircleSegment {
 
     /// Return an arc representing the inner radius.
     ///
-    /// This is [flipped] from the outer arc, so that it is in the
+    /// This is [reversed] 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
+    /// [reversed]: Arc::reversed
     #[must_use]
     #[inline]
     pub fn inner_arc(&self) -> Arc {
diff --git a/src/line.rs b/src/line.rs
index edd4aeac..b7a8c586 100644
--- a/src/line.rs
+++ b/src/line.rs
@@ -34,12 +34,33 @@ impl Line {
         }
     }
 
+    /// Returns a copy of this `Line` with the end points swapped so that it
+    /// points in the opposite direction.
+    #[must_use]
+    #[inline]
+    pub fn reversed(&self) -> Line {
+        Self {
+            p0: self.p1,
+            p1: self.p0,
+        }
+    }
+
     /// The length of the line.
     #[inline]
     pub fn length(self) -> f64 {
         self.arclen(DEFAULT_ACCURACY)
     }
 
+    /// The midpoint of the line.
+    ///
+    /// This is the same as calling [`Point::midpoint`] with
+    /// the endpoints of this line.
+    #[must_use]
+    #[inline]
+    pub fn midpoint(&self) -> Point {
+        self.p0.midpoint(self.p1)
+    }
+
     /// Computes the point where two lines, if extended to infinity, would cross.
     pub fn crossing_point(self, other: Line) -> Option<Point> {
         let ab = self.p1 - self.p0;
@@ -302,6 +323,18 @@ impl Iterator for LinePathIter {
 mod tests {
     use crate::{Line, ParamCurveArclen, Point};
 
+    #[test]
+    fn line_reversed() {
+        let l = Line::new((0.0, 0.0), (1.0, 1.0));
+        let f = l.reversed();
+
+        assert_eq!(l.p0, f.p1);
+        assert_eq!(l.p1, f.p0);
+
+        // Reversing it again should result in the original line
+        assert_eq!(l, f.reversed());
+    }
+
     #[test]
     fn line_arclen() {
         let l = Line::new((0.0, 0.0), (1.0, 1.0));
@@ -313,6 +346,12 @@ mod tests {
         assert!((t - 1.0 / 3.0).abs() < epsilon);
     }
 
+    #[test]
+    fn line_midpoint() {
+        let l = Line::new((0.0, 0.0), (2.0, 4.0));
+        assert_eq!(l.midpoint(), Point::new(1.0, 2.0));
+    }
+
     #[test]
     fn line_is_finite() {
         assert!((Line {