Feat: Preserve editor state via CachedTabControl

AssetEditor/Views/CachedTabControl.cs

@@ -0,0 +1,90 @@
+using System.Collections.Specialized;
+using System.Windows;
+using System.Windows.Controls;
+
+namespace AssetEditor.Views
+{
+    [TemplatePart(Name = "PART_ItemsHolder", Type = typeof(Panel))]
+    public class CachedTabControl : TabControl
+    {
+        private Panel _itemsHolderPanel = null;
+
+        public override void OnApplyTemplate()
+        {
+            base.OnApplyTemplate();
+
+            // Retrieve the container defined in XAML
+            _itemsHolderPanel = GetTemplateChild("PART_ItemsHolder") as Panel;
+            UpdateSelectedItem();
+        }
+
+        protected override void OnSelectionChanged(SelectionChangedEventArgs e)
+        {
+            base.OnSelectionChanged(e);
+            UpdateSelectedItem();
+        }
+
+        private void UpdateSelectedItem()
+        {
+            if (_itemsHolderPanel == null) return;
+
+            object selectedItem = this.SelectedItem;
+            if (selectedItem == null) return;
+
+            ContentPresenter cp = FindChildContentPresenter(selectedItem);
+            if (cp == null)
+            {
+                cp = new ContentPresenter
+                {
+                    Content = selectedItem,
+                    ContentTemplate = this.SelectedContentTemplate,
+                    ContentTemplateSelector = this.ContentTemplateSelector,
+                    ContentStringFormat = this.SelectedContentStringFormat,
+                    // Force stretch to fill the entire container to prevent layout collapsing
+                    HorizontalAlignment = HorizontalAlignment.Stretch,
+                    VerticalAlignment = VerticalAlignment.Stretch
+                };
+                _itemsHolderPanel.Children.Add(cp);
+            }
+
+            // Core caching logic: Show the selected item and hide the unselected ones
+            foreach (ContentPresenter child in _itemsHolderPanel.Children)
+            {
+                child.Visibility = (child.Content == selectedItem) ? Visibility.Visible : Visibility.Collapsed;
+            }
+        }
+
+        protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
+        {
+            base.OnItemsChanged(e);
+            if (_itemsHolderPanel == null) return;
+
+            // Handle tab closure to prevent memory leaks
+            if (e.Action == NotifyCollectionChangedAction.Remove || e.Action == NotifyCollectionChangedAction.Replace)
+            {
+                if (e.OldItems != null)
+                {
+                    foreach (var item in e.OldItems)
+                    {
+                        var cp = FindChildContentPresenter(item);
+                        if (cp != null) _itemsHolderPanel.Children.Remove(cp);
+                    }
+                }
+            }
+            else if (e.Action == NotifyCollectionChangedAction.Reset)
+            {
+                _itemsHolderPanel.Children.Clear();
+            }
+        }
+
+        private ContentPresenter FindChildContentPresenter(object data)
+        {
+            if (_itemsHolderPanel == null) return null;
+            foreach (ContentPresenter cp in _itemsHolderPanel.Children)
+            {
+                if (cp.Content == data) return cp;
+            }
+            return null;
+        }
+    }
+}