Fix prefab window performance with large hierarchies

Source/Editor/SceneGraph/GUI/ActorTreeNode.cs

@@ -85,12 +85,20 @@ namespace FlaxEditor.SceneGraph.GUI
         {
             if (Parent is ActorTreeNode parent)
             {
-                for (int i = 0; i < parent.ChildrenCount; i++)
+                var anyChanged = false;
+                var children = parent.Children;
+                for (int i = 0; i < children.Count; i++)
                 {
-                    if (parent.Children[i] is ActorTreeNode child && child.Actor)
-                        child._orderInParent = child.Actor.OrderInParent;
+                    if (children[i] is ActorTreeNode child && child.Actor)
+                    {
+                        var orderInParent = child.Actor.OrderInParent;
+                        anyChanged |= child._orderInParent != orderInParent;
+                        if (anyChanged)
+                            child._orderInParent = orderInParent;
+                    }
                 }
-                parent.SortChildren();
+                if (anyChanged)
+                    parent.SortChildren();
             }
             else if (Actor)
             {

Source/Editor/Windows/Assets/PrefabWindow.Hierarchy.cs

@@ -428,11 +428,9 @@ namespace FlaxEditor.Windows.Assets
 
         private void Update(ActorNode actorNode)
         {
-            if (actorNode.Actor)
-            {
-                actorNode.TreeNode.UpdateText();
-                actorNode.TreeNode.OnOrderInParentChanged();
-            }
+            actorNode.TreeNode.UpdateText();
+            if (actorNode.TreeNode.IsCollapsed)
+                return;
 
             for (int i = 0; i < actorNode.ChildNodes.Count; i++)
             {

Source/Editor/Windows/Assets/PrefabWindow.cs

@@ -440,6 +440,7 @@ namespace FlaxEditor.Windows.Assets
         {
             try
             {
+                FlaxEngine.Profiler.BeginEvent("PrefabWindow.Update");
                 if (Graph.Main != null)
                 {
                     // Due to fact that actors in prefab editor are only created but not added to gameplay 
@@ -468,6 +469,10 @@ namespace FlaxEditor.Windows.Assets
                     Graph.Root.TreeNode.ExpandAll(true);
                 }
             }
+            finally
+            {
+                FlaxEngine.Profiler.EndEvent();
+            }
 
             // Auto fit
             if (_focusCamera && _viewport.Task.FrameCount > 1)