Fix focus issues with combo box #19396 (#19672)

* Fix focus issues with combo box #19396

* add unit tests for combobox focus issue

src/Avalonia.Controls/ComboBox.cs

@@ -276,6 +276,10 @@ namespace Avalonia.Controls
                 SetCurrentValue(IsDropDownOpenProperty, false);
                 e.Handled = true;
             }
+            else if (IsDropDownOpen && e.Key == Key.Tab)
+            {
+                SetCurrentValue(IsDropDownOpenProperty, false);
+            }
             // Ignore key buttons, if they are used for XY focus.
             else if (!IsDropDownOpen
                      && !XYFocusHelpers.IsAllowedXYNavigationMode(this, e.KeyDeviceType))
@@ -717,6 +721,11 @@ namespace Avalonia.Controls
             {
                 _skipNextTextChanged = false;
             }
+
+            //when changing the SelectedIndex it will call: KeyboardNavigation.SetTabOnceActiveElement(this, [combo box item]);
+            //this will then break tab navigation back into this combobox as it will try to focus the combo box item
+            //rather than the combobox or editable text box, so we need to SetTabOnceActiveElement to null
+            KeyboardNavigation.SetTabOnceActiveElement(this, null);
         }
 
         private string GetItemTextValue(object? item) 

tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs

@@ -193,10 +193,6 @@ namespace Avalonia.Controls.UnitTests
                         {
                             [!ContentControl.ContentProperty] = parent[!ComboBox.SelectionBoxItemProperty],
                         },
-                        new ToggleButton
-                        {
-                            Name = "toggle",
-                        }.RegisterInNameScope(scope),
                         new Popup
                         {
                             Name = "PART_Popup",
@@ -212,7 +208,7 @@ namespace Avalonia.Controls.UnitTests
                         }.RegisterInNameScope(scope),
                         new TextBox
                         {
-                            Name = "PART_InputText"
+                            Name = "PART_EditableTextBox"
                         }.RegisterInNameScope(scope)
                     }
                 };
@@ -715,5 +711,132 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(target.SelectedItem, items2[0]);
             Assert.Equal(target.Text, "Value 1");
         }
+
+        private void RaiseTabKeyPress(Control target, bool withShift = false)
+        {
+            target.RaiseEvent(new KeyEventArgs
+            {
+                RoutedEvent = InputElement.KeyDownEvent,
+                Key = Key.Tab,
+                KeyModifiers = withShift ? KeyModifiers.Shift : KeyModifiers.None
+            });
+
+            target.RaiseEvent(new KeyEventArgs
+            {
+                RoutedEvent = InputElement.KeyUpEvent,
+                Key = Key.Tab,
+                KeyModifiers = withShift ? KeyModifiers.Shift : KeyModifiers.None
+            });
+        }
+
+        [Fact]
+        public void When_Tabbing_Out_With_Dropdown_Open_It_Closes()
+        {
+            using var app = UnitTestApplication.Start(TestServices.RealFocus);
+
+            var target = new ComboBox
+            {
+                ItemsSource = new[] { "Foo", "Bar" }
+            };
+            var nextControl = new ComboBox
+            {
+                ItemsSource = new[] { "Baz" }
+            };
+
+            var container = new StackPanel
+            {
+                Children =
+                {
+                    target,
+                    nextControl
+                }
+            };
+            var root = new TestRoot(container);
+            var keyboardNavHandler = new KeyboardNavigationHandler();
+            keyboardNavHandler.SetOwner(root);
+
+            target.Focus();
+            _helper.Down(target);
+            _helper.Up(target);
+            Assert.True(target.IsFocused);
+            Assert.True(target.IsDropDownOpen);
+
+            RaiseTabKeyPress(target);
+
+            Assert.False(target.IsFocused);
+            Assert.True(nextControl.IsFocused);
+            Assert.False(target.IsDropDownOpen);
+        }
+
+        [Fact]
+        public void When_Editable_And_Item_Selected_Via_Text_Then_Focus_Swaps_Via_Tab_Swapping_Back_Should_Focus_TextBox()
+        {
+            using var app = UnitTestApplication.Start(TestServices.RealFocus);
+
+            var items = new[]
+            {
+                new Item("Value 1", "Display 1"),
+                new Item("Value 2", "Display 2")
+            };
+            var target = new ComboBox
+            {
+                DisplayMemberBinding = new Binding("Display"),
+                IsEditable = true,
+                IsTabStop = false,
+                ItemsSource = items,
+                Template = GetTemplate()
+            };
+            TextSearch.SetTextBinding(target, new Binding("Value"));
+            KeyboardNavigation.SetTabNavigation(target, KeyboardNavigationMode.Local);
+
+            var previousControl = new ComboBox
+            {
+                ItemsSource = new[] { "Baz" }
+            };
+
+            var container = new StackPanel
+            {
+                Children =
+                {
+                    previousControl,
+                    target
+                }
+            };
+            var root = new TestRoot(container);
+            var keyboardNavHandler = new KeyboardNavigationHandler();
+            keyboardNavHandler.SetOwner(root);
+
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var containerPanel = target.GetTemplateChildren().OfType<Panel>().FirstOrDefault(x => x.Name == "container");
+            var editableTextBox = containerPanel?.GetVisualDescendants().OfType<TextBox>().FirstOrDefault(x => x.Name == "PART_EditableTextBox");
+            var popup = containerPanel?.GetVisualDescendants().OfType<Popup>().FirstOrDefault(x => x.Name == "PART_Popup");
+            var popupScrollViewer = popup?.Child as ScrollViewer;
+            var scrollViewerItemsPresenter = popupScrollViewer?.Content as ItemsPresenter;
+            var popupVirtualizingStackPanel = scrollViewerItemsPresenter?.GetVisualDescendants().OfType<VirtualizingStackPanel>().FirstOrDefault();
+            Assert.NotNull(popupVirtualizingStackPanel);
+
+            //force the popup to render the ComboBoxItem(s) as they are what get set as "focused" if this test fails
+            popupVirtualizingStackPanel.Measure(Size.Infinity);
+
+            target.Focus();
+            Assert.True(editableTextBox.IsFocused);
+
+            target.Text = "Value 1";
+            Assert.Same(target.SelectedItem, items[0]);
+            var item1 = scrollViewerItemsPresenter.ContainerFromIndex(0);
+            Assert.IsType<ComboBoxItem>(item1);
+
+            RaiseTabKeyPress(target, withShift: true);
+
+            Assert.False(target.IsFocused);
+            Assert.True(previousControl.IsFocused);
+
+            RaiseTabKeyPress(previousControl);
+
+            var focused = root.FocusManager.GetFocusedElement();
+            Assert.Same(editableTextBox, focused);
+        }
     }
 }