feat: try to setup communication.

src/Ursa/Controls/NavMenu/NavMenu.cs

@@ -1,5 +1,6 @@
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
+using Avalonia.LogicalTree;
 
 namespace Ursa.Controls;
 
@@ -14,4 +15,18 @@ public class NavMenu: SelectingItemsControl
     {
         return new NavMenuItem();
     }
+    
+    internal void SelectItem(NavMenuItem item)
+    {
+        if (item.IsSelected) return;
+        var children = this.LogicalChildren.OfType<NavMenuItem>();
+        foreach (var child in children)
+        {
+            if (child != item)
+            {
+                child.IsSelected = false;
+            }
+        }
+        item.IsSelected = true;
+    }
 }

src/Ursa/Controls/NavMenu/NavMenuItem.cs

@@ -1,11 +1,18 @@
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Controls.Mixins;
 using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Input;
+using Avalonia.LogicalTree;
+using Avalonia.VisualTree;
 
 namespace Ursa.Controls;
 
 public class NavMenuItem: HeaderedSelectingItemsControl
 {
+    private NavMenu? _rootMenu;
+    
     public static readonly StyledProperty<object?> IconProperty = AvaloniaProperty.Register<NavMenuItem, object?>(
         nameof(Icon));
 
@@ -14,6 +21,30 @@ public class NavMenuItem: HeaderedSelectingItemsControl
         get => GetValue(IconProperty);
         set => SetValue(IconProperty, value);
     }
+
+    public static readonly StyledProperty<IDataTemplate?> IconTemplateProperty = AvaloniaProperty.Register<NavMenuItem, IDataTemplate?>(
+        nameof(IconTemplate));
+
+    public IDataTemplate? IconTemplate
+    {
+        get => GetValue(IconTemplateProperty);
+        set => SetValue(IconTemplateProperty, value);
+    }
+
+    public new static readonly StyledProperty<bool> IsSelectedProperty =
+        SelectingItemsControl.IsSelectedProperty.AddOwner<NavMenuItem>();
+
+    public bool IsSelected
+    {
+        get => GetValue(IsSelectedProperty);
+        set => SetValue(IsSelectedProperty, value);
+    }
+
+    static NavMenuItem()
+    {
+        SelectableMixin.Attach<NavMenuItem>(IsSelectedProperty);
+        PressedMixin.Attach<NavMenuItem>();
+    }
     
     protected override bool NeedsContainerOverride(object? item, int index, out object? recycleKey)
     {
@@ -24,4 +55,26 @@ public class NavMenuItem: HeaderedSelectingItemsControl
     {
         return new NavMenuItem();
     }
+
+    protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        base.OnAttachedToVisualTree(e);
+        _rootMenu = GetRootMenu();
+    }
+
+    protected override void OnPointerPressed(PointerPressedEventArgs e)
+    {
+        base.OnPointerPressed(e);
+        _rootMenu?.SelectItem(this);
+    }
+
+    private NavMenu? GetRootMenu()
+    {
+        var root = this.FindAncestorOfType<NavMenu>();
+        if (root is null)
+        {
+            root = this.FindLogicalAncestorOfType<NavMenu>();
+        }
+        return root;
+    }
 }