feat: adding event that is invoked when object visibility changes

adding event on NetworkVisibility that can be used to do extra stuff before show, hide or spawn message is sent ot client

Assets/Mirage/Runtime/NetworkVisibility.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using UnityEngine;
 
 namespace Mirage
@@ -12,6 +12,19 @@ namespace Mirage
     [DisallowMultipleComponent]
     public abstract class NetworkVisibility : NetworkBehaviour
     {
+        public delegate void VisibilityChanged(INetworkPlayer player, bool visible);
+
+        /// <summary>
+        /// Invoked on server when visibility changes for player
+        /// <para>Invoked before Show/Hide/Spawn message is sent to client</para>
+        /// </summary>
+        public event VisibilityChanged OnVisibilityChanged;
+
+        internal void InvokeVisibilityChanged(INetworkPlayer player, bool visible)
+        {
+            OnVisibilityChanged?.Invoke(player, visible);
+        }
+
         /// <summary>
         /// Callback used by the visibility system to determine if an observer (player) can see this object.
         /// <para>If this function returns true, the network connection will be added as an observer.</para>

Assets/Mirage/Runtime/ServerObjectManager.cs

@@ -349,13 +349,21 @@ private void Respawn(NetworkIdentity identity)
         /// <param name="player"></param>
         internal void ShowToPlayer(NetworkIdentity identity, INetworkPlayer player)
         {
+            var visiblity = identity.Visibility;
+            if (visiblity != null)
+                visiblity.InvokeVisibilityChanged(player, true);
+
             // dont send if loading scene
             if (player.SceneIsReady)
                 SendSpawnMessage(identity, player);
         }
 
         internal void HideToPlayer(NetworkIdentity identity, INetworkPlayer player)
         {
+            var visiblity = identity.Visibility;
+            if (visiblity != null)
+                visiblity.InvokeVisibilityChanged(player, false);
+
             player.Send(new ObjectHideMessage { netId = identity.NetId });
         }