feat: add selection change event.

src/Ursa/Controls/NavMenu/NavMenu.cs

@@ -135,6 +135,14 @@ public class NavMenu: ItemsControl
     public static void SetCanToggle(InputElement obj, bool value) => obj.SetValue(CanToggleProperty, value);
     public static bool GetCanToggle(InputElement obj) => obj.GetValue(CanToggleProperty);
     
+    public static readonly RoutedEvent<SelectionChangedEventArgs> SelectionChangedEvent = RoutedEvent.Register<NavMenu, SelectionChangedEventArgs>(nameof(SelectionChanged), RoutingStrategies.Bubble);
+    
+    public event EventHandler<SelectionChangedEventArgs>? SelectionChanged
+    {
+        add => AddHandler(SelectionChangedEvent, value);
+        remove => RemoveHandler(SelectionChangedEvent, value);
+    }
+    
     static NavMenu()
     {
         SelectedItemProperty.Changed.AddClassHandler<NavMenu, object?>((o, e) => o.OnSelectedItemChange(e));
@@ -169,11 +177,20 @@ public class NavMenu: ItemsControl
     /// <param name="args"></param>
     private void OnSelectedItemChange(AvaloniaPropertyChangedEventArgs<object?> args)
     {
-        if (_updateFromUI) return;
+        SelectionChangedEventArgs a = new SelectionChangedEventArgs(
+            SelectionChangedEvent,
+            new [] { args.OldValue.Value },
+            new [] { args.NewValue.Value });
+        if (_updateFromUI)
+        {
+            RaiseEvent(a);
+            return;
+        }
         var newValue = args.NewValue.Value;
         if (newValue is null)
         {
             ClearAll();
+            RaiseEvent(a);
             return;
         }
         var leaves = GetLeafMenus();
@@ -186,8 +203,11 @@ public class NavMenu: ItemsControl
                 found = true;
             }
         }
-        if (found) return;
+        if (!found)
-        ClearAll();
+        {
+            ClearAll();
+        }
+        RaiseEvent(a);
     }
 
     protected override bool NeedsContainerOverride(object? item, int index, out object? recycleKey)
@@ -205,7 +225,6 @@ public class NavMenu: ItemsControl
     internal void SelectItem(NavMenuItem item, NavMenuItem parent)
     {
         _updateFromUI = true;
-        // if (item.IsSelected) return;
         foreach (var child in LogicalChildren)
         {
             if (child == parent)
@@ -226,7 +245,6 @@ public class NavMenu: ItemsControl
             SelectedItem = item;
         }
         item.BringIntoView();
-        // item.IsSelected = true;
         _updateFromUI = false;
     }
 

src/Ursa/Controls/NavMenu/NavMenuItem.cs

@@ -18,7 +18,7 @@ namespace Ursa.Controls;
 /// Navigation Menu Item
 /// </summary>
 [PseudoClasses(PC_Highlighted, PC_HorizontalCollapsed, PC_VerticalCollapsed, PC_FirstLevel, PC_Selector)]
-public class NavMenuItem: HeaderedSelectingItemsControl
+public class NavMenuItem: HeaderedItemsControl
 {
     public const string PC_Highlighted = ":highlighted";
     public const string PC_FirstLevel = ":first-level";
@@ -30,7 +30,6 @@ public class NavMenuItem: HeaderedSelectingItemsControl
     private Panel? _popupPanel;
     private Popup? _popup;
     private Panel? _overflowPanel;
-    private Border? _border;
     
     public static readonly StyledProperty<object?> IconProperty = AvaloniaProperty.Register<NavMenuItem, object?>(
         nameof(Icon));
@@ -67,7 +66,7 @@ public class NavMenuItem: HeaderedSelectingItemsControl
         set => SetValue(CommandParameterProperty, value);
     }
 
-    public new static readonly StyledProperty<bool> IsSelectedProperty =
+    public static readonly StyledProperty<bool> IsSelectedProperty =
         SelectingItemsControl.IsSelectedProperty.AddOwner<NavMenuItem>();
 
     public bool IsSelected
@@ -75,6 +74,8 @@ public class NavMenuItem: HeaderedSelectingItemsControl
         get => GetValue(IsSelectedProperty);
         set => SetValue(IsSelectedProperty, value);
     }
+    
+    public static readonly RoutedEvent<RoutedEventArgs> IsSelectedChangedEvent = RoutedEvent.Register<SelectingItemsControl, RoutedEventArgs>("IsSelectedChanged", RoutingStrategies.Bubble);
 
     private bool _isHighlighted;
 
@@ -192,7 +193,6 @@ public class NavMenuItem: HeaderedSelectingItemsControl
         SetCurrentValue(LevelProperty,CalculateDistanceFromLogicalParent<NavMenu>(this));
         _popup = e.NameScope.Find<Popup>("PART_Popup");
         _overflowPanel = e.NameScope.Find<Panel>("PART_OverflowPanel");
-        _border = e.NameScope.Find<Border>("PART_Border");
         if (_rootMenu is not null)
         {
             if (_rootMenu.IconBinding is not null)

src/Ursa/Controls/NavMenu/OverflowStackPanel.cs

@@ -10,8 +10,8 @@ public class OverflowStackPanel: StackPanel
         var children = this.Children.ToList();
         foreach (var child in children)
         {
-            this.Children.Remove(child);
+            Children.Remove(child);
-            this.OverflowPanel?.Children.Add(child);
+            OverflowPanel?.Children.Add(child);
         }
     }
     
@@ -22,8 +22,8 @@ public class OverflowStackPanel: StackPanel
         {
             foreach (var child in children)
             {
-                this.OverflowPanel?.Children.Remove(child);
+                OverflowPanel?.Children.Remove(child);
-                this.Children.Add(child);
+                Children.Add(child);
             }
         }
     }