fix(dock): address reviewer feedback on tree renderer

src/Editor/Ghost.Editor/View/Controls/DockLayout.cs

@@ -1,11 +1,22 @@
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Diagnostics;
 using Ghost.Editor.Core.Controls.Internal.Docking;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
+using Microsoft.UI.Xaml.Data;
 
 namespace Ghost.Editor.View.Controls;
 
+/// <summary>
+/// A control that renders a docking layout tree.
+/// </summary>
+[TemplatePart(Name = PART_ROOT_GRID, Type = typeof(Grid))]
 public sealed partial class DockLayout : Control
 {
+    private const string PART_ROOT_GRID = "PART_RootGrid";
+
     public DockLayout()
     {
         DefaultStyleKey = typeof(DockLayout);
@@ -24,13 +35,79 @@ public sealed partial class DockLayout : Control
     {
         if (d is DockLayout layout)
         {
+            if (e.OldValue is DockGroupNode oldRoot)
+            {
+                layout.UnsubscribeFromNode(oldRoot);
+            }
+
+            if (e.NewValue is DockGroupNode newRoot)
+            {
+                layout.SubscribeToNode(newRoot);
+            }
+
             layout.RenderTree();
         }
     }
 
+    private void SubscribeToNode(DockNode node)
+    {
+        node.PropertyChanged += OnNodePropertyChanged;
+
+        if (node is DockGroupNode groupNode)
+        {
+            ((INotifyCollectionChanged)groupNode.Children).CollectionChanged += OnChildrenCollectionChanged;
+            foreach (var child in groupNode.Children)
+            {
+                SubscribeToNode(child);
+            }
+        }
+    }
+
+    private void UnsubscribeFromNode(DockNode node)
+    {
+        node.PropertyChanged -= OnNodePropertyChanged;
+
+        if (node is DockGroupNode groupNode)
+        {
+            ((INotifyCollectionChanged)groupNode.Children).CollectionChanged -= OnChildrenCollectionChanged;
+            foreach (var child in groupNode.Children)
+            {
+                UnsubscribeFromNode(child);
+            }
+        }
+    }
+
+    private void OnNodePropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        // Re-render on relevant property changes (e.g. Orientation)
+        RenderTree();
+    }
+
+    private void OnChildrenCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        // Handle subscriptions for new/removed children
+        if (e.OldItems != null)
+        {
+            foreach (DockNode oldNode in e.OldItems)
+            {
+                UnsubscribeFromNode(oldNode);
+            }
+        }
+
+        if (e.NewItems != null)
+        {
+            foreach (DockNode newNode in e.NewItems)
+            {
+                SubscribeToNode(newNode);
+            }
+        }
+
+        RenderTree();
+    }
+
     private void RenderTree()
     {
-        if (GetTemplateChild("PART_RootGrid") is Grid rootGrid)
+        if (GetTemplateChild(PART_ROOT_GRID) is Grid rootGrid)
         {
             rootGrid.Children.Clear();
             if (Root != null)
@@ -55,16 +132,32 @@ public sealed partial class DockLayout : Control
         }
         else if (node is DockPanelNode panelNode)
         {
-            // NOTE: NavigationTabView is expected to be implemented in a future task or exists in a namespace not yet fully visible.
-            // For now, we use a placeholder if it's not found, but the task specifies using it.
-            // If it fails to compile, I will check for the correct namespace.
-            return new Ghost.Editor.Controls.NavigationTabView 
+            var tabView = new Ghost.Editor.Controls.NavigationTabView 
             { 
                 TabItemsSource = panelNode.Items,
                 HorizontalAlignment = HorizontalAlignment.Stretch,
                 VerticalAlignment = VerticalAlignment.Stretch
             };
+
+            // Bind selection state
+            tabView.SetBinding(Selector.SelectedIndexProperty, new Binding
+            {
+                Source = panelNode,
+                Path = new PropertyPath(nameof(DockPanelNode.SelectedIndex)),
+                Mode = BindingMode.TwoWay
+            });
+
+            tabView.SetBinding(Selector.SelectedItemProperty, new Binding
+            {
+                Source = panelNode,
+                Path = new PropertyPath(nameof(DockPanelNode.SelectedItem)),
+                Mode = BindingMode.TwoWay
+            });
+
+            return tabView;
         }
+
+        Debug.Fail($"Unsupported node type: {node.GetType().Name}");
         return new Grid(); // Fallback
     }