NetworkConnection.observing sorted by distance to NetworkConnection's main player

Assets/Mirror/Runtime/NetworkConnection.cs

@@ -10,8 +10,10 @@ public abstract class NetworkConnection
         public const int LocalConnectionId = 0;
 
         // NetworkIdentities that this connection can see
+        // sorted by distance to the main player object,
+        // which is necessary for priority based WorldState sync
         // TODO move to server's NetworkConnectionToClient?
-        internal readonly HashSet<NetworkIdentity> observing = new HashSet<NetworkIdentity>();
+        internal readonly SortedSet<NetworkIdentity> observing;
 
         // TODO this is NetworkServer.handlers on server and NetworkClient.handlers on client.
         //      maybe use them directly. avoid extra state.
@@ -52,6 +54,9 @@ public abstract class NetworkConnection
 
         internal NetworkConnection()
         {
+            // initialize 'observing' with the custom comparer
+            observing = new SortedSet<NetworkIdentity>(new ObservingComparer(this));
+
             // set lastTime to current time when creating connection to make
             // sure it isn't instantly kicked for inactivity
             lastMessageTime = Time.time;

Assets/Mirror/Runtime/ObservingComparer.cs

@@ -0,0 +1,30 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace Mirror
+{
+    // Comparer for our observing sorted set
+    internal class ObservingComparer : IComparer<NetworkIdentity>
+    {
+        // need to know the main player object's position
+        NetworkConnection owner;
+        internal ObservingComparer(NetworkConnection owner)
+        {
+            this.owner = owner;
+        }
+
+        public int Compare(NetworkIdentity a, NetworkIdentity b)
+        {
+            // does owner connection have a player?
+            if (owner.identity != null)
+            {
+                // calculate both identity's distances to the player
+                Vector3 ownerPosition = owner.identity.transform.position;
+                float distanceA = Vector3.Distance(ownerPosition, a.transform.position);
+                float distanceB = Vector3.Distance(ownerPosition, b.transform.position);
+                return Comparer<float>.Default.Compare(distanceA, distanceB);
+            }
+            return 0;
+        }
+    }
+}

Assets/Mirror/Runtime/ObservingComparer.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 9e677be00d394c8a8f6a74c26dfe2502
+timeCreated: 1620986031