Make Gizmos::rect_2d and primitive_2d draw the joint of the first corner of closed shapes

crates/bevy_gizmos/src/gizmos.rs

@@ -727,6 +727,46 @@ where
         self.linestrip(positions.into_iter().map(|vec2| vec2.extend(0.)), color);
     }
 
+    /// Draw a line in 2D made of straight segments between the points, with the first and last connected.
+    ///
+    /// # Example
+    /// ```
+    /// # use bevy_gizmos::prelude::*;
+    /// # use bevy_math::prelude::*;
+    /// # use bevy_color::palettes::basic::GREEN;
+    /// fn system(mut gizmos: Gizmos) {
+    ///     gizmos.lineloop_2d([Vec2::ZERO, Vec2::X, Vec2::Y], GREEN);
+    /// }
+    /// # bevy_ecs::system::assert_is_system(system);
+    /// ```
+    #[inline]
+    pub fn lineloop_2d(
+        &mut self,
+        positions: impl IntoIterator<Item = Vec2>,
+        color: impl Into<Color>,
+    ) {
+        if !self.enabled {
+            return;
+        }
+
+        // Loop back to the start; second is needed to ensure that
+        // the joint on the first corner is drawn.
+        let mut positions = positions.into_iter();
+        let first = positions.next();
+        let second = positions.next();
+
+        self.linestrip(
+            first
+                .into_iter()
+                .chain(second)
+                .chain(positions)
+                .chain(first)
+                .chain(second)
+                .map(|vec2| vec2.extend(0.)),
+            color,
+        );
+    }
+
     /// Draw a line in 2D made of straight segments between the points, with a color gradient.
     ///
     /// # Example
@@ -833,7 +873,7 @@ where
         }
         let isometry = isometry.into();
         let [tl, tr, br, bl] = rect_inner(size).map(|vec2| isometry * vec2);
-        self.linestrip_2d([tl, tr, br, bl, tl], color);
+        self.lineloop_2d([tl, tr, br, bl], color);
     }
 
     #[inline]

crates/bevy_gizmos/src/primitives/dim2.rs

@@ -358,8 +358,8 @@ where
                     primitive.half_diagonals.y * sign_y,
                 )
             });
-        let positions = [a, b, c, d, a].map(|vec2| isometry * vec2);
-        self.linestrip_2d(positions, color);
+        let positions = [a, b, c, d].map(|vec2| isometry * vec2);
+        self.lineloop_2d(positions, color);
     }
 }
 
@@ -706,8 +706,8 @@ where
         let isometry = isometry.into();
 
         let [a, b, c] = primitive.vertices;
-        let positions = [a, b, c, a].map(|vec2| isometry * vec2);
-        self.linestrip_2d(positions, color);
+        let positions = [a, b, c].map(|vec2| isometry * vec2);
+        self.lineloop_2d(positions, color);
     }
 }
 
@@ -742,8 +742,8 @@ where
                     primitive.half_size.y * sign_y,
                 )
             });
-        let positions = [a, b, c, d, a].map(|vec2| isometry * vec2);
-        self.linestrip_2d(positions, color);
+        let positions = [a, b, c, d].map(|vec2| isometry * vec2);
+        self.lineloop_2d(positions, color);
     }
 }
 
@@ -771,24 +771,14 @@ where
 
         let isometry = isometry.into();
 
-        // Check if the polygon needs a closing point
-        let closing_point = {
-            let first = primitive.vertices.first();
-            (primitive.vertices.last() != first)
-                .then_some(first)
-                .flatten()
-                .cloned()
+        let vertices = if primitive.vertices.first() == primitive.vertices.last() {
+            // Strip closing point if there is one
+            &primitive.vertices[..primitive.vertices.len() - 1]
+        } else {
+            &primitive.vertices[..]
         };
 
-        self.linestrip_2d(
-            primitive
-                .vertices
-                .iter()
-                .copied()
-                .chain(closing_point)
-                .map(|vec2| isometry * vec2),
-            color,
-        );
+        self.lineloop_2d(vertices.iter().map(|&vec2| isometry * vec2), color);
     }
 }
 
@@ -816,9 +806,9 @@ where
 
         let isometry = isometry.into();
 
-        let points = (0..=primitive.sides)
+        let points = (0..primitive.sides)
             .map(|n| single_circle_coordinate(primitive.circumcircle.radius, primitive.sides, n))
             .map(|vec2| isometry * vec2);
-        self.linestrip_2d(points, color);
+        self.lineloop_2d(points, color);
     }
 }