Engine.Core/Abstract/IUniverse.cs

@@ -37,11 +37,21 @@ public interface IUniverse : IEntity, IEnumerable<IUniverseObject>
     /// </summary>
     Event<IUniverse> OnPostDraw { get; }
 
+    /// <summary>
+    /// Event triggered when a <see cref="IUniverseObject"/> is about to be registered to the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UniverseObjectRegisteredArguments> OnPreUniverseObjectRegistered { get; }
+
     /// <summary>
     /// Event triggered when a <see cref="IUniverseObject"/> is registered to the <see cref="IUniverse"/>.
     /// </summary>
     Event<IUniverse, UniverseObjectRegisteredArguments> OnUniverseObjectRegistered { get; }
 
+    /// <summary>
+    /// Event triggered when a <see cref="IUniverseObject"/> is about to be unregistered from the <see cref="IUniverse"/>.
+    /// </summary>
+    Event<IUniverse, UniverseObjectUnRegisteredArguments> OnPreUniverseObjectUnRegistered { get; }
+
     /// <summary>
     /// Event triggered when a <see cref="IUniverseObject"/> is unregistered from the <see cref="IUniverse"/>.
     /// </summary>

Engine.Core/Universe.cs

@@ -13,7 +13,9 @@ public class Universe : BaseEntity, IUniverse
     public Event<IUniverse> OnPreDraw { get; } = new();
     public Event<IUniverse> OnDraw { get; } = new();
     public Event<IUniverse> OnPostDraw { get; } = new();
+    public Event<IUniverse, IUniverse.UniverseObjectRegisteredArguments> OnPreUniverseObjectRegistered { get; } = new();
     public Event<IUniverse, IUniverse.UniverseObjectRegisteredArguments> OnUniverseObjectRegistered { get; } = new();
+    public Event<IUniverse, IUniverse.UniverseObjectUnRegisteredArguments> OnPreUniverseObjectUnRegistered { get; } = new();
     public Event<IUniverse, IUniverse.UniverseObjectUnRegisteredArguments> OnUniverseObjectUnRegistered { get; } = new();
     public Event<IUniverse, IUniverse.TimeScaleChangedArguments> OnTimeScaleChanged { get; } = new();
 
@@ -53,6 +55,8 @@ public class Universe : BaseEntity, IUniverse
         if (_universeObjects.Contains(universeObject))
             throw new Exception($"{nameof(IUniverseObject)} named {universeObject.Name} is already registered to the {nameof(Universe)}.");
 
+        OnPreUniverseObjectRegistered?.Invoke(this, new(universeObject));
+
         universeObject.OnFinalized.AddListener(delegateOnUniverseObjectFinalize);
         universeObject.OnExitedUniverse.AddListener(delegateOnUniverseObjectExitedUniverse);
 
@@ -88,6 +92,8 @@ public class Universe : BaseEntity, IUniverse
         if (!_universeObjects.Contains(universeObject))
             throw new Exception($"{nameof(IUniverseObject)} named {universeObject.Name} is not registered to the {nameof(Universe)}.");
 
+        OnPreUniverseObjectUnRegistered?.Invoke(this, new(universeObject));
+
         universeObject.OnFinalized.RemoveListener(delegateOnUniverseObjectFinalize);
         universeObject.OnExitedUniverse.RemoveListener(delegateOnUniverseObjectExitedUniverse);