refactor: Improved & Fixed Issues with Transforms with Parents

Engine.Core/Abstract/ITransform.cs

@@ -99,7 +99,7 @@ public interface ITransform : IAssignableGameObject, IEnumerable<ITransform>
     delegate void OnPositionChangedDelegate(ITransform sender);
     delegate void OnScaleChangedDelegate(ITransform sender);
     delegate void OnRotationChangedDelegate(ITransform sender);
-    delegate void OnParentChangedDelegate(ITransform sender, ITransform? newParent);
+    delegate void OnParentChangedDelegate(ITransform sender, ITransform? previousParent, ITransform? newParent);
     delegate void OnChildrenAddedDelegate(ITransform sender, ITransform childrenAdded);
     delegate void OnChildrenRemovedDelegate(ITransform sender, ITransform childrenRemoved);
 }

Engine.Core/GameManager.cs

@@ -140,6 +140,9 @@ public class GameManager : BaseEntity, IGameManager
         gameObject.OnFinalized += OnGameObjectFinalize;
         gameObject.OnExitedHierarchy += OnGameObjectExitedHierarchy;
 
+        foreach (ITransform child in gameObject.Transform.Children)
+            Register(child.GameObject);
+
         if (!gameObject.Initialize())
             throw new Exception($"{nameof(gameObject)} can't be initialized");
 
@@ -161,6 +164,9 @@ public class GameManager : BaseEntity, IGameManager
         gameObject.OnFinalized -= OnGameObjectFinalize;
         gameObject.OnExitedHierarchy -= OnGameObjectExitedHierarchy;
 
+        foreach (ITransform child in gameObject.Transform.Children)
+            Unregister(child.GameObject);
+
         _gameObjects.Remove(gameObject);
         _hierarchyObjects.Remove(gameObject);
 

Engine.Core/GameObject.cs

@@ -71,6 +71,8 @@ public class GameObject : BaseEntity, IGameObject
 
         _transform = transform;
         OnTransformAssigned?.Invoke(this);
+        transform.OnParentChanged += OnParentChangedInternal;
+        OnParentChangedInternal(transform, null, transform.Parent);
         return true;
     }
 
@@ -88,6 +90,8 @@ public class GameObject : BaseEntity, IGameObject
     {
         base.UnassignInternal();
 
+        _transform.OnParentChanged -= OnParentChangedInternal;
+        OnParentChangedInternal(_transform, _transform.Parent, null);
         _transform = null!;
         _behaviourController = null!;
         _gameManager = null!;
@@ -103,6 +107,25 @@ public class GameObject : BaseEntity, IGameObject
     private void OnBehaviourRemoved(IBehaviourController _, IBehaviour behaviour) { if (IsInitialized) behaviour.Finalize(); }
     private void OnBehaviourAdded(IBehaviourController _, IBehaviour behaviour) { if (!IsInitialized) behaviour.Initialize(); }
 
+    private void OnParentChangedInternal(ITransform sender, ITransform? previousParent, ITransform? newParent)
+    {
+        if (previousParent is not null)
+        {
+            previousParent.OnParentChanged -= OnParentChangedInternal;
+            previousParent.GameObject.OnEnteredHierarchy -= EnterHierarchyInternal;
+            previousParent.GameObject.OnExitedHierarchy -= ExitHierarchyInternal;
+        }
+        if (newParent is not null)
+        {
+            newParent.OnParentChanged += OnParentChangedInternal;
+            newParent.GameObject.OnEnteredHierarchy += EnterHierarchyInternal;
+            newParent.GameObject.OnExitedHierarchy += ExitHierarchyInternal;
+        }
+    }
+
+    private void EnterHierarchyInternal(IHierarchyObject sender, IGameManager gameManager) => ((IHierarchyObject)this).EnterHierarchy(gameManager);
+    private void ExitHierarchyInternal(IHierarchyObject sender, IGameManager gameManager) => ((IHierarchyObject)this).ExitHierarchy();
+
     bool IHierarchyObject.EnterHierarchy(IGameManager gameManager)
     {
         if (IsInHierarchy)

Engine.Core/Transform.cs

@@ -150,7 +150,7 @@ public class Transform : ITransform
         UpdateLocalScale();
         UpdateLocalRotation();
 
-        OnParentChanged?.Invoke(this, previousParent);
+        OnParentChanged?.Invoke(this, previousParent, transform);
     }
 
     public void AddChild(ITransform transform)
@@ -175,7 +175,7 @@ public class Transform : ITransform
     public IEnumerator<ITransform> GetEnumerator() => _children.GetEnumerator();
     IEnumerator IEnumerable.GetEnumerator() => _children.GetEnumerator();
 
-    private void NotifyChildrenOnParentChange(ITransform transform, ITransform? previousParent)
+    private void NotifyChildrenOnParentChange(ITransform transform, ITransform? previousParent, ITransform? newParent)
     {
         // TODO No idea how logical this is to propagate this to the children the way I'm doing right now.
         // I was originally gonna just call `child.OnParentChanged?.Invoke(child, child.Parent);` but seems an unnecessary call too?

Engine.Physics2D/Collider2DBehaviourBase.cs

@@ -46,7 +46,7 @@ public abstract class Collider2DBehaviourBase : Behaviour, ICollider2D
         Transform.OnParentChanged += UpdateRigidBody2D;
     }
 
-    private void UpdateRigidBody2D(ITransform _1, ITransform? _2)
+    private void UpdateRigidBody2D(ITransform sender, ITransform? previousParent, ITransform? newParent)
     {
         BehaviourController.TryGetBehaviourInParent(out _rigidBody2D);
     }