From 3902f1caca2c7f3f8b69b1ba7239c5cc2dff5af5 Mon Sep 17 00:00:00 2001
From: Syntriax <syntriax@gmail.com>
Date: Tue, 6 Feb 2024 12:15:45 +0300
Subject: [PATCH] feat: Parent Change Propagation to Children

---
 Engine.Core/Transform.cs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Engine.Core/Transform.cs b/Engine.Core/Transform.cs
index 6007b34..394c788 100644
--- a/Engine.Core/Transform.cs
+++ b/Engine.Core/Transform.cs
@@ -133,6 +133,7 @@ public class Transform : ITransform
             Parent.OnPositionChanged -= RecalculatePosition;
             Parent.OnScaleChanged -= RecalculateScale;
             Parent.OnRotationChanged -= RecalculateRotation;
+            Parent.OnParentChanged -= NotifyChildrenOnParentChange;
         }
 
         Parent = transform;
@@ -143,6 +144,7 @@ public class Transform : ITransform
             transform.OnPositionChanged += RecalculatePosition;
             transform.OnScaleChanged += RecalculateScale;
             transform.OnRotationChanged += RecalculateRotation;
+            transform.OnParentChanged += NotifyChildrenOnParentChange;
         }
 
         UpdateLocalPosition();
@@ -174,6 +176,14 @@ public class Transform : ITransform
     public IEnumerator<ITransform> GetEnumerator() => _children.GetEnumerator();
     IEnumerator IEnumerable.GetEnumerator() => _children.GetEnumerator();
 
+    private void NotifyChildrenOnParentChange(ITransform transform, ITransform? previousParent)
+    {
+        // 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?
+        foreach (var child in Children)
+            child.OnParentChanged?.Invoke(transform, previousParent);
+    }
+
     private void RecalculatePosition(ITransform _)
     {
         if (Parent is null)