introduce a proper closed polyline abstraction, sub it in

game/src/render/building.rs

@@ -1,7 +1,7 @@
 use crate::helpers::{ColorScheme, ID};
 use crate::render::{DrawCtx, DrawOptions, Renderable, OUTLINE_THICKNESS};
 use ezgui::{Color, GeomBatch, GfxCtx, Line, Text};
-use geom::{Circle, Distance, Line, PolyLine, Polygon, Pt2D};
+use geom::{Circle, Distance, Line, Polygon, Pt2D, Ring};
 use map_model::{Building, BuildingID, Map, LANE_THICKNESS};
 
 pub struct DrawBuilding {
@@ -111,10 +111,7 @@ impl Renderable for DrawBuilding {
     }
 
     fn get_outline(&self, map: &Map) -> Polygon {
-        PolyLine::make_polygons_for_boundary(
-            map.get_b(self.id).polygon.points().clone(),
-            OUTLINE_THICKNESS,
-        )
+        Ring::new(map.get_b(self.id).polygon.points().clone()).make_polygons(OUTLINE_THICKNESS)
     }
 
     fn contains_pt(&self, pt: Pt2D, map: &Map) -> bool {

game/src/render/extra_shape.rs

@@ -3,7 +3,7 @@ use crate::render::{
     DrawCtx, DrawOptions, Renderable, EXTRA_SHAPE_POINT_RADIUS, EXTRA_SHAPE_THICKNESS,
 };
 use ezgui::{Color, Drawable, GeomBatch, GfxCtx, Prerender};
-use geom::{Circle, FindClosest, GPSBounds, PolyLine, Polygon, Pt2D};
+use geom::{Circle, FindClosest, GPSBounds, PolyLine, Polygon, Pt2D, Ring};
 use kml::ExtraShape;
 use map_model::{DirectedRoadID, Map, LANE_THICKNESS};
 use std::collections::BTreeMap;
@@ -54,9 +54,9 @@ impl DrawExtraShape {
         } else if pts[0] == *pts.last().unwrap() {
             // TODO Toggle between these better
             //Polygon::new(&pts)
-            PolyLine::make_polygons_for_boundary(pts, EXTRA_SHAPE_THICKNESS)
+            Ring::new(pts).make_polygons(EXTRA_SHAPE_THICKNESS)
         } else {
-            PolyLine::make_polygons_for_boundary(pts, EXTRA_SHAPE_THICKNESS)
+            PolyLine::new(pts).make_polygons(EXTRA_SHAPE_THICKNESS)
         };
         let mut batch = GeomBatch::new();
         batch.push(

game/src/render/intersection.rs

@@ -5,7 +5,7 @@ use crate::render::{
 };
 use abstutil::Timer;
 use ezgui::{Color, Drawable, GeomBatch, GfxCtx, Prerender};
-use geom::{Angle, Distance, Duration, Line, PolyLine, Polygon, Pt2D, EPSILON_DIST};
+use geom::{Angle, Distance, Duration, Line, PolyLine, Polygon, Pt2D, Ring, EPSILON_DIST};
 use map_model::{
     Intersection, IntersectionID, IntersectionType, Map, Road, RoadWithStopSign, Turn, TurnID,
     TurnType, LANE_THICKNESS,
@@ -170,10 +170,7 @@ impl Renderable for DrawIntersection {
     }
 
     fn get_outline(&self, map: &Map) -> Polygon {
-        PolyLine::make_polygons_for_boundary(
-            map.get_i(self.id).polygon.points().clone(),
-            OUTLINE_THICKNESS,
-        )
+        Ring::new(map.get_i(self.id).polygon.points().clone()).make_polygons(OUTLINE_THICKNESS)
     }
 
     fn contains_pt(&self, pt: Pt2D, map: &Map) -> bool {

geom/src/lib.rs

@@ -9,6 +9,7 @@ mod line;
 mod polygon;
 mod polyline;
 mod pt;
+mod ring;
 mod speed;
 
 pub use crate::angle::Angle;
@@ -22,6 +23,7 @@ pub use crate::line::{InfiniteLine, Line};
 pub use crate::polygon::{Polygon, Triangle};
 pub use crate::polyline::PolyLine;
 pub use crate::pt::{HashablePt2D, Pt2D};
+pub use crate::ring::Ring;
 pub use crate::speed::Speed;
 
 // About 0.4 inches... which is quite tiny on the scale of things. :)

geom/src/polyline.rs

@@ -1,5 +1,5 @@
 use crate::{
-    Angle, Bounds, Distance, HashablePt2D, InfiniteLine, Line, Polygon, Pt2D, EPSILON_DIST,
+    Angle, Bounds, Distance, HashablePt2D, InfiniteLine, Line, Polygon, Pt2D, Ring, EPSILON_DIST,
 };
 use abstutil::Warn;
 use serde_derive::{Deserialize, Serialize};
@@ -27,7 +27,7 @@ impl PolyLine {
         // needs to be squished down, why, and how.
         if pts.windows(2).any(|pair| pair[0] == pair[1]) {
             panic!(
-                "PL with total length {} and {} pts has ~dupe pts: {:?}",
+                "PL with total length {} and {} pts has ~dupe adjacent pts: {:?}",
                 length,
                 pts.len(),
                 pts
@@ -68,7 +68,7 @@ impl PolyLine {
         Some(result)
     }
 
-    pub fn make_polygons_for_boundary(pts: Vec<Pt2D>, thickness: Distance) -> Polygon {
+    pub(crate) fn make_polygons_for_boundary(pts: Vec<Pt2D>, thickness: Distance) -> Polygon {
         // Points WILL repeat -- fast-path some stuff.
         let pl = PolyLine {
             pts,
@@ -77,15 +77,6 @@ impl PolyLine {
         pl.make_polygons(thickness)
     }
 
-    pub fn to_thick_boundary_pts(&self, width: Distance) -> Vec<Pt2D> {
-        let mut side1 = self.shift_with_sharp_angles(width / 2.0);
-        let mut side2 = self.shift_with_sharp_angles(-width / 2.0);
-        side2.reverse();
-        side1.extend(side2);
-        side1.push(side1[0]);
-        side1
-    }
-
     pub fn to_thick_boundary(
         &self,
         self_width: Distance,
@@ -102,7 +93,7 @@ impl PolyLine {
         side1.extend(side2);
         side1.push(side1[0]);
         side1.dedup();
-        Some(PolyLine::make_polygons_for_boundary(side1, boundary_width))
+        Some(Ring::new(side1).make_polygons(boundary_width))
     }
 
     pub fn reversed(&self) -> PolyLine {
@@ -534,17 +525,15 @@ impl PolyLine {
             let angle = slice.last_pt().angle_to(self.last_pt());
             Warn::ok(vec![
                 p,
-                PolyLine::make_polygons_for_boundary(
-                    vec![
-                        self.last_pt(),
-                        self.last_pt()
-                            .project_away(head_size, angle.rotate_degs(-135.0)),
-                        self.last_pt()
-                            .project_away(head_size, angle.rotate_degs(135.0)),
-                        self.last_pt(),
-                    ],
-                    outline_thickness,
-                ),
+                Ring::new(vec![
+                    self.last_pt(),
+                    self.last_pt()
+                        .project_away(head_size, angle.rotate_degs(-135.0)),
+                    self.last_pt()
+                        .project_away(head_size, angle.rotate_degs(135.0)),
+                    self.last_pt(),
+                ])
+                .make_polygons(outline_thickness),
             ])
         } else {
             Warn::warn(

geom/src/ring.rs

@@ -0,0 +1,54 @@
+use crate::{Distance, PolyLine, Polygon, Pt2D};
+use serde_derive::{Deserialize, Serialize};
+use std::collections::HashSet;
+use std::fmt;
+
+// Maybe a misnomer, but like a PolyLine, but closed.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Ring {
+    // first equals last
+    pts: Vec<Pt2D>,
+}
+
+impl Ring {
+    pub fn new(pts: Vec<Pt2D>) -> Ring {
+        assert!(pts.len() >= 3);
+        assert_eq!(pts[0], *pts.last().unwrap());
+
+        // This checks no lines are too small. Could take the other approach and automatically
+        // squish down points here and make sure the final result is at least EPSILON_DIST.
+        // But probably better for the callers to do this -- they have better understanding of what
+        // needs to be squished down, why, and how.
+        if pts.windows(2).any(|pair| pair[0] == pair[1]) {
+            panic!("Ring has ~dupe adjacent pts: {:?}", pts);
+        }
+
+        let result = Ring { pts };
+
+        let mut seen_pts = HashSet::new();
+        for pt in result.pts.iter().skip(1) {
+            seen_pts.insert(pt.to_hashable());
+        }
+        if seen_pts.len() != result.pts.len() - 1 {
+            panic!("Ring has repeat points: {}", result);
+        }
+
+        result
+    }
+
+    pub fn make_polygons(&self, thickness: Distance) -> Polygon {
+        // TODO Has a weird corner. Use the polygon offset thing instead? And move the
+        // implementation here, ideally.
+        PolyLine::make_polygons_for_boundary(self.pts.clone(), thickness)
+    }
+}
+
+impl fmt::Display for Ring {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        writeln!(f, "Ring::new(vec![")?;
+        for pt in &self.pts {
+            writeln!(f, "  Pt2D::new({}, {}),", pt.x(), pt.y())?;
+        }
+        write!(f, "])")
+    }
+}