Fix edge case for mindist (#334)

This is fix for  #218.  

Depends on orientation of curves, function fails if curves have
different order. Check, detecting end-points as closest points, returns
false positives here. This is caused by small typo in implementation
where check takes order of first curve instead of order from second
curve.

PR consist of test case from
#218 and replacement of `n`
order to `m` in that specific check.

src/mindist.rs

@@ -85,7 +85,7 @@ pub(crate) fn min_dist_param(
             if dij < dkj {
                 at_boundary0on_bez2 = false;
             }
-            let dkj = D_rk(i, 2 * n, bez1, bez2);
+            let dkj = D_rk(i, 2 * m, bez1, bez2);
             if dij < dkj {
                 at_boundary1on_bez2 = false;
             }
@@ -234,6 +234,7 @@ fn choose(n: usize, k: usize) -> u32 {
 mod tests {
     use crate::mindist::A_r;
     use crate::mindist::{choose, D_rk};
+    use crate::param_curve::ParamCurve;
     use crate::{CubicBez, Line, PathSeg, Vec2};
 
     #[test]
@@ -307,4 +308,26 @@ mod tests {
         let mindist2 = bez2.min_dist(bez1, 0.5);
         assert!((mindist1.distance - mindist2.distance).abs() < 0.5);
     }
+
+    #[test]
+    fn test_line_curve() {
+        let line = PathSeg::Line(Line::new((929.0, 335.0), (911.0, 340.0)));
+
+        let line_as_bez = PathSeg::Cubic(CubicBez::new(
+            line.eval(0.0),
+            line.eval(1.0 / 3.0),
+            line.eval(2.0 / 3.0),
+            line.eval(1.0),
+        ));
+
+        let bez2 = PathSeg::Cubic(CubicBez::new(
+            (1052.0, 401.0),
+            (1048.0, 305.0),
+            (1046.0, 216.0),
+            (1054.0, 146.0),
+        ));
+        let mindist_as_bez = line_as_bez.min_dist(bez2, 0.5);
+        let mindist_as_line = line.min_dist(bez2, 0.5);
+        assert!((mindist_as_line.distance - mindist_as_bez.distance).abs() < 0.5);
+    }
 }