BoxCollider2DGizmo.cs

using System.Linq;
using UnityEditor;
using UnityEngine;

namespace Kogane.Internal
{
    internal static class BoxCollider2DGizmo
    {
        [DrawGizmo
        (
            GizmoType.NotInSelectionHierarchy |
            GizmoType.Selected |
            GizmoType.NonSelected
        )]
        private static void Draw
        (
            BoxCollider2D boxCollider2D,
            GizmoType     gizmoType
        )
        {
            var color = Color.red;
            var width = 8;

            var transform = boxCollider2D.transform;
            var offset    = boxCollider2D.offset;
            var size      = boxCollider2D.size;
            var p1        = offset + new Vector2( -size.x, -size.y ) * 0.5f;
            var p2        = offset + new Vector2( size.x, -size.y ) * 0.5f;
            var p3        = offset + new Vector2( size.x, size.y ) * 0.5f;
            var p4        = offset + new Vector2( -size.x, size.y ) * 0.5f;
            var points    = new[] { p1, p2, p3, p4, p1, p2, };

            Handles.color = color;

            Handles.DrawAAPolyLine
            (
                lineTex: EditorGUIUtility.whiteTexture,
                width: width,
                points: points
                    .Select( x => transform.TransformPoint( x ) )
                    .ToArray()
            );
        }
    }
}