Fix ray-tracing algorithm when ray passes through a vertex

geo/src/algorithm/contains/mod.rs

@@ -184,6 +184,31 @@ mod test {
         assert!(poly.contains(&Point::new(1., 1.)));
     }
     #[test]
+    fn point_in_polygon_with_ray_passing_through_a_vertex_test() {
+        let linestring = LineString::from(vec![
+            (1., 0.),
+            (0., 1.),
+            (-1., 0.),
+            (0., -1.),
+        ]);
+        let poly = Polygon::new(linestring, Vec::new());
+        assert!(poly.contains(&Point::new(0., 0.)));
+    }
+    #[test]
+    fn point_in_polygon_with_ray_passing_through_a_vertex_and_not_crossing() {
+        let linestring = LineString::from(vec![
+            (0., 0.),
+            (2., 0.),
+            (3., 1.),
+            (4., 0.),
+            (4., 2.),
+            (0., 2.),
+            (0., 0.),
+        ]);
+        let poly = Polygon::new(linestring, Vec::new());
+        assert!(poly.contains(&Point::new(1., 1.)));
+    }
+    #[test]
     fn point_out_polygon_test() {
         let linestring = LineString::from(vec![(0., 0.), (2., 0.), (2., 2.), (0., 2.), (0., 0.)]);
         let poly = Polygon::new(linestring, Vec::new());

geo/src/utils.rs

@@ -140,10 +140,19 @@ where
         }
 
         // Ignore if the intersection of the line is
-        // possibly at the beginning of the line. This is to
+        // possibly at the beginning/end of the line, and
+        // the line lies below the ray. This is to
         // prevent a double counting when the ray passes
-        // through a vertex of the plygon
-        if line.start.y == coord.y {
+        // through a vertex of the polygon.
+        //
+        // The below logic handles two cases:
+        //   1. if the ray enters/exits the polygon
+        //      at the point of intersection
+        //   2. if the ray touches a vertex,
+        //      but doesn't enter/exit at that point
+        if (line.start.y == coord.y && line.end.y < coord.y)
+            || (line.end.y == coord.y && line.start.y < coord.y)
+        {
             continue;
         }