feat: add selection list.

src/Ursa/Controls/SelectionList/SelectionListItem.cs

@@ -0,0 +1,38 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Mixins;
+using Avalonia.Controls.Primitives;
+using Avalonia.Input;
+
+namespace Ursa.Controls;
+
+public class SelectionListItem: ContentControl, ISelectable
+{
+    static SelectionListItem()
+    {
+        SelectableMixin.Attach<SelectionListItem>(IsSelectedProperty);
+        PressedMixin.Attach<SelectionListItem>();
+        FocusableProperty.OverrideDefaultValue<SelectionListItem>(true);
+    }
+    
+    private static readonly Point s_invalidPoint = new Point(double.NaN, double.NaN);
+    private Point _pointerDownPoint = s_invalidPoint;
+
+    public static readonly StyledProperty<bool> IsSelectedProperty = SelectingItemsControl.IsSelectedProperty.AddOwner<ListBoxItem>();
+
+    public bool IsSelected
+    {
+        get => GetValue(IsSelectedProperty);
+        set => SetValue(IsSelectedProperty, value);
+    }
+
+    protected override void OnPointerPressed(PointerPressedEventArgs e)
+    {
+        base.OnPointerPressed(e);
+        if (ItemsControl.ItemsControlFromItemContaner(this) is SelectionList list)
+        {
+            int index = list.IndexFromContainer(this);
+            list.SelectByIndex(index);
+        }
+    }
+}