Fix tab navigation in ItemsControl & ListBox

- Don't set `KeyboardNavigationMode.Once` on `ItemsPresenter`
- Instead set it on `ListBox` (more controls to come)
- Make `TabOnceActiveElement` follow `Selection.AnchorIndex` in `SelectingItemsControl` and set it on `ItemsControl` itself

src/Avalonia.Controls/ListBox.cs

@@ -58,6 +58,9 @@ namespace Avalonia.Controls
         static ListBox()
         {
             ItemsPanelProperty.OverrideDefaultValue<ListBox>(DefaultPanel);
+            KeyboardNavigation.TabNavigationProperty.OverrideDefaultValue(
+                typeof(ListBox),
+                KeyboardNavigationMode.Once);
         }
 
         /// <summary>

src/Avalonia.Controls/Presenters/ItemsPresenter.cs

@@ -52,13 +52,6 @@ namespace Avalonia.Controls.Presenters
                 nameof(VerticalSnapPointsChanged),
                 RoutingStrategies.Bubble);
 
-        static ItemsPresenter()
-        {
-            KeyboardNavigation.TabNavigationProperty.OverrideDefaultValue(
-                typeof(ItemsPresenter),
-                KeyboardNavigationMode.Once);
-        }
-
         event EventHandler? ILogicalScrollable.ScrollInvalidated
         {
             add => _scrollInvalidated += value;

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -5,6 +5,7 @@ using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Xml.Linq;
 using Avalonia.Controls.Selection;
 using Avalonia.Controls.Utils;
 using Avalonia.Data;
@@ -528,13 +529,6 @@ namespace Avalonia.Controls.Primitives
         protected internal override void ClearContainerForItemOverride(Control element)
         {
             base.ClearContainerForItemOverride(element);
-
-            if (Presenter?.Panel is InputElement panel && 
-                KeyboardNavigation.GetTabOnceActiveElement(panel) == element)
-            {
-                KeyboardNavigation.SetTabOnceActiveElement(panel, null);
-            }
-
             element.ClearValue(IsSelectedProperty);
         }
 
@@ -834,12 +828,6 @@ namespace Avalonia.Controls.Primitives
                 Selection.Clear();
                 Selection.Select(index);
             }
-
-            if (Presenter?.Panel is { } panel)
-            {
-                var container = ContainerFromIndex(index);
-                KeyboardNavigation.SetTabOnceActiveElement(panel, container);
-            }
         }
 
         /// <summary>
@@ -928,6 +916,7 @@ namespace Avalonia.Controls.Primitives
             if (e.PropertyName == nameof(ISelectionModel.AnchorIndex))
             {
                 _hasScrolledToSelectedItem = false;
+                KeyboardNavigation.SetTabOnceActiveElement(this, ContainerFromIndex(Selection.AnchorIndex));
                 AutoScrollToSelectedItemIfNecessary();
             }
             else if (e.PropertyName == nameof(ISelectionModel.SelectedIndex) && _oldSelectedIndex != SelectedIndex)

tests/Avalonia.Controls.UnitTests/ListBoxTests.cs

@@ -752,16 +752,6 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{10 - x}"), realized);
         }
 
-        private static void RaiseKeyEvent(ListBox listBox, Key key, KeyModifiers inputModifiers = 0)
-        {
-            listBox.RaiseEvent(new KeyEventArgs
-            {
-                RoutedEvent = InputElement.KeyDownEvent,
-                KeyModifiers = inputModifiers,
-                Key = key
-            });
-        }
-
         [Fact]
         public void WrapSelection_Should_Wrap()
         {
@@ -948,6 +938,117 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(1, raised);
         }
 
+        [Fact]
+        public void Tab_Navigation_Should_Move_To_First_Item_When_No_Anchor_Element_Selected()
+        {
+            var services = TestServices.StyledWindow.With(
+                focusManager: new FocusManager(),
+                keyboardDevice: () => new KeyboardDevice());
+            using var app = UnitTestApplication.Start(services);
+
+            var target = new ListBox
+            {
+                Template = ListBoxTemplate(),
+                Items = { "Foo", "Bar", "Baz" },
+            };
+
+            var button = new Button 
+            { 
+                Content = "Button",
+                [DockPanel.DockProperty] = Dock.Top,
+            };
+
+            var root = new TestRoot
+            {
+                Child = new DockPanel
+                {
+                    Children =
+                    {
+                        button,
+                        target,
+                    }
+                }
+            };
+
+            var navigation = new KeyboardNavigationHandler();
+            navigation.SetOwner(root);
+
+            root.LayoutManager.ExecuteInitialLayoutPass();
+
+            button.Focus();
+            RaiseKeyEvent(button, Key.Tab);
+
+            var item = target.ContainerFromIndex(0);
+            Assert.Same(item, FocusManager.Instance.Current);
+        }
+
+        [Fact]
+        public void Tab_Navigation_Should_Move_To_Anchor_Element()
+        {
+            var services = TestServices.StyledWindow.With(
+                focusManager: new FocusManager(),
+                keyboardDevice: () => new KeyboardDevice());
+            using var app = UnitTestApplication.Start(services);
+
+            var target = new ListBox
+            {
+                Template = ListBoxTemplate(),
+                Items = { "Foo", "Bar", "Baz" },
+            };
+
+            var button = new Button
+            {
+                Content = "Button",
+                [DockPanel.DockProperty] = Dock.Top,
+            };
+
+            var root = new TestRoot
+            {
+                Width = 1000,
+                Height = 1000,
+                Child = new DockPanel
+                {
+                    Children =
+                    {
+                        button,
+                        target,
+                    }
+                }
+            };
+
+            var navigation = new KeyboardNavigationHandler();
+            navigation.SetOwner(root);
+
+            root.LayoutManager.ExecuteInitialLayoutPass();
+
+            button.Focus();
+            target.Selection.AnchorIndex = 1;
+            RaiseKeyEvent(button, Key.Tab);
+
+            var item = target.ContainerFromIndex(1);
+            Assert.Same(item, FocusManager.Instance.Current);
+
+            RaiseKeyEvent(item, Key.Tab);
+
+            Assert.Same(button, FocusManager.Instance.Current);
+
+            target.Selection.AnchorIndex = 2;
+            RaiseKeyEvent(button, Key.Tab);
+
+            item = target.ContainerFromIndex(2);
+            Assert.Same(item, FocusManager.Instance.Current);
+        }
+
+        private static void RaiseKeyEvent(Control target, Key key, KeyModifiers inputModifiers = 0)
+        {
+            target.RaiseEvent(new KeyEventArgs
+            {
+                RoutedEvent = InputElement.KeyDownEvent,
+                KeyModifiers = inputModifiers,
+                Key = key
+            });
+        }
+
         private record ItemViewModel(string Caption);
 
         private class ResettingCollection : List<string>, INotifyCollectionChanged

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs

@@ -1236,13 +1236,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 Prepare(target);
-                _helper.Down((Interactive)target.Presenter.Panel.Children[1]);
+
+                var container = target.ContainerFromIndex(1)!;
+                _helper.Down(container);
 
                 var panel = target.Presenter.Panel;
 
-                Assert.Equal(
-                    KeyboardNavigation.GetTabOnceActiveElement((InputElement)panel),
-                    panel.Children[1]);
+                Assert.Same(container, KeyboardNavigation.GetTabOnceActiveElement(target));
             }
         }