Add some tests for the MHCurve material

One is failing. Maybe I should use R64 internally, again.

src/geom.rs

@@ -75,6 +75,22 @@ impl Line {
         self.from.x + t * (self.to.x - self.from.x)
     }
 
+    pub fn as_vector(&self) -> Point {
+        self.from + (-self.to)
+    }
+
+    pub fn length_sq(&self) -> f64 {
+        let Point { x, y } = self.as_vector();
+        x*x + y*y
+    }
+
+    pub fn distance_sq(&self, pt: Point) -> f64 {
+        // source: https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line#Line_defined_by_two_points
+        let d = self.as_vector();
+        let twice_area = d.y*pt.x - d.x*pt.y + self.to.x*self.from.y - self.to.y*self.from.x;
+        twice_area * twice_area / self.length_sq()
+    }
+
     pub fn is_ascending(&self) -> bool {
         self.to.y > self.from.y
     }

src/mat.rs

@@ -112,7 +112,8 @@ impl MHCurve {
                 panic!("failed to find segment for h:{}, m:{}, {:?}", h, m, self.geom.segments().collect::<Vec<_>>());
             });
             if line.contains_y(m) && line.is_ascending() == is_ascending {
-                if line.contains_x(h) {
+                if line.contains_x(h) && line.distance_sq(Point::new(h, m)) < 1.0e-6 {
+                    // (h, m) resides on this line
                     break line;
                 } else {
                     // need to move the point toward this line
@@ -198,3 +199,43 @@ impl Default for GenericMaterial {
         Conductor::default().into()
     }
 }
+
+
+mod test {
+    use super::*;
+    fn mh_curve_for_test() -> MHCurve {
+        MHCurve::new(&[
+            // rising
+            Point::new( 10.0,    0.0),
+            Point::new( 20.0,  100.0),
+            Point::new( 30.0,  150.0),
+            // falling
+            Point::new(  0.0,  120.0),
+            // negative rising
+            Point::new(-10.0,    0.0),
+            Point::new(-20.0, -100.0),
+            Point::new(-30.0, -150.0),
+            // negative falling
+            Point::new(  0.0, -120.0),
+        ])
+    }
+
+    #[test]
+    fn mh_curve_move_from_inner_to_inner() {
+        let curve = mh_curve_for_test();
+        assert_eq!(curve.move_to(0.0, 0.0, 5.0), (5.0, 0.0));
+        assert_eq!(curve.move_to(0.0, 5.0, 10.0), (5.0, 5.0));
+
+        assert_eq!(curve.move_to(-5.0, 5.0, -3.0), (-8.0, 5.0));
+        assert_eq!(curve.move_to(-5.0, 5.0, 7.0), (2.0, 5.0));
+
+        assert_eq!(curve.move_to(5.0, -5.0, -3.0), (2.0, -5.0));
+        assert_eq!(curve.move_to(5.0, -5.0, 3.0), (8.0, -5.0));
+    }
+
+    #[test]
+    fn mh_curve_ascend_along_edge() {
+        let curve = mh_curve_for_test();
+        assert_eq!(curve.move_to(10.0, 0.0, 32.0), (12.0, 20.0));
+    }
+}