Correctly check for LineString containment in Polygon

The [DE-9IM specification for [`containment`] (http://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_Transformers/Transformers/spatialrelations.htm#DE9IM_Matrix) states: > The **interiors intersect** and no part of the candidate's interior or boundary intersects the base's exterior. It is possible for the boundaries to intersect. For `intersection`: > The two features are not disjoint For `disjoint` > The boundaries and interiors do not intersect. The current containment check deviates from this, in that it forbids intersection (`!self.intersects(linestring)`), when in fact it should be forbidding intersection with any _interior rings_. This PR fixes that, and adds a test. closes #157
georust · Sep 6, 2017 · d1ba7f4 · d1ba7f4
1 parent 63d54f0
commit d1ba7f4
Showing 1 changed file with 12 additions and 2 deletions.
diff --git a/src/algorithm/contains.rs b/src/algorithm/contains.rs
@@ -215,9 +215,11 @@ impl<T> Contains<LineString<T>> for Polygon<T>
     where T: Float
 {
     fn contains(&self, linestring: &LineString<T>) -> bool {
-        // All points of LineString must be in the polygon ?
+        // All LineString points must be inside the Polygon
         if linestring.0.iter().all(|point| self.contains(point)) {
-            !self.intersects(linestring)
+            // The Polygon interior is allowed to intersect with the LineString
+            // but the Polygon's rings are not
+            !self.interiors.iter().any(|ring| ring.intersects(linestring))
         } else {
             false
         }
@@ -246,6 +248,14 @@ impl<T> Contains<Bbox<T>> for Bbox<T>
 mod test {
     use types::{Coordinate, Point, Line, LineString, Polygon, MultiPolygon, Bbox};
     use algorithm::contains::Contains;
+    #[test]
+    // LineString is fully contained
+    fn linestring_fully_contained_in_polygon() {
+        let p = |x, y| Point(Coordinate { x: x, y: y });
+        let poly = Polygon::new(LineString(vec![p(0., 0.), p(5., 0.), p(5., 6.), p(0., 6.), p(0., 0.)]), vec![]);
+        let ls = LineString(vec![Point::new(3.0, 0.5), Point::new(3.0, 3.5)]);
+        assert_eq!(poly.contains(&ls), true);
+    }
     /// Tests: Point in LineString
     #[test]
     fn empty_linestring_test() {