ItemsControl: WrapSelection (#6286)

Add support for selection wrapping for ListBox, ItemsControl, ComboBox.
Co-authored-by: Steven Kirk <grokys@users.noreply.github.com>
Co-authored-by: Takoooooo <tako0qq@gmail.com>
Co-authored-by: Steven Kirk <grokys@gmail.com>

samples/ControlCatalog/Pages/ComboBoxPage.xaml

@@ -1,77 +1,95 @@
-<UserControl xmlns="https://github.com/avaloniaui"
-             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             x:Class="ControlCatalog.Pages.ComboBoxPage"
-             xmlns:sys="using:System"
-             xmlns:col="using:System.Collections">
-  <StackPanel Orientation="Vertical" Spacing="4">
-    <TextBlock Classes="h2">A drop-down list.</TextBlock>
+<UserControl
+    x:Class="ControlCatalog.Pages.ComboBoxPage"
+    xmlns="https://github.com/avaloniaui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:col="using:System.Collections"
+    xmlns:sys="using:System">
+    <StackPanel Orientation="Vertical" Spacing="4">
+        <TextBlock Classes="h2">A drop-down list.</TextBlock>
 
-    <WrapPanel HorizontalAlignment="Center" Margin="0 16 0 0"
-               MaxWidth="660">
-      <WrapPanel.Styles>
-        <Style Selector="ComboBox">
-          <Setter Property="Width" Value="250" />
-          <Setter Property="Margin" Value="10" />
-        </Style>
-      </WrapPanel.Styles>
-      <ComboBox PlaceholderText="Pick an Item">
-        <ComboBoxItem>Inline Items</ComboBoxItem>
-        <ComboBoxItem>Inline Item 2</ComboBoxItem>
-        <ComboBoxItem>Inline Item 3</ComboBoxItem>
-        <ComboBoxItem>Inline Item 4</ComboBoxItem>
-      </ComboBox>
+        <StackPanel
+            Margin="0,16,0,0"
+            HorizontalAlignment="Center"
+            Orientation="Horizontal"
+            Spacing="8">
+            <WrapPanel
+                MaxWidth="660"
+                Margin="0,16,0,0"
+                HorizontalAlignment="Center">
+                <WrapPanel.Styles>
+                    <Style Selector="ComboBox">
+                        <Setter Property="Width" Value="250" />
+                        <Setter Property="Margin" Value="10" />
+                    </Style>
+                </WrapPanel.Styles>
 
-      <ComboBox>
-        <ComboBox.Items>
-          <col:ArrayList>
-            <x:Null />
-            <sys:String>Hello</sys:String>
-            <sys:String>World</sys:String>
-          </col:ArrayList>
-        </ComboBox.Items>
-        <ComboBox.ItemTemplate>
-          <DataTemplate>
-            <Panel>
-              <TextBlock Text="{Binding}" />
-              <TextBlock Text="Null object" IsVisible="{Binding Converter={x:Static ObjectConverters.IsNull}}" />
-            </Panel>
-          </DataTemplate>
-        </ComboBox.ItemTemplate>
-      </ComboBox>
+                <ComboBox PlaceholderText="Pick an Item" WrapSelection="{Binding WrapSelection}">
+                    <ComboBoxItem>Inline Items</ComboBoxItem>
+                    <ComboBoxItem>Inline Item 2</ComboBoxItem>
+                    <ComboBoxItem>Inline Item 3</ComboBoxItem>
+                    <ComboBoxItem>Inline Item 4</ComboBoxItem>
+                </ComboBox>
 
-      <ComboBox SelectedIndex="0">
-        <ComboBoxItem>
-          <Panel>
-            <Rectangle Fill="{DynamicResource SystemAccentColor}"/>
-            <TextBlock Margin="8">Control Items</TextBlock>
-          </Panel>
-        </ComboBoxItem>
-        <ComboBoxItem>
-          <Ellipse Width="50" Height="50" Fill="Yellow"/>
-        </ComboBoxItem>
-        <ComboBoxItem>
-          <TextBox Text="TextBox"/>
-        </ComboBoxItem>
-      </ComboBox>
+                <ComboBox WrapSelection="{Binding WrapSelection}">
+                    <ComboBox.Items>
+                        <col:ArrayList>
+                            <x:Null />
+                            <sys:String>Hello</sys:String>
+                            <sys:String>World</sys:String>
+                        </col:ArrayList>
+                    </ComboBox.Items>
+                    <ComboBox.ItemTemplate>
+                        <DataTemplate>
+                            <Panel>
+                                <TextBlock Text="{Binding}" />
+                                <TextBlock IsVisible="{Binding Converter={x:Static ObjectConverters.IsNull}}" Text="Null object" />
+                            </Panel>
+                        </DataTemplate>
+                    </ComboBox.ItemTemplate>
+                </ComboBox>
 
-       <ComboBox x:Name="fontComboBox"  SelectedIndex="0">
-         <ComboBox.ItemTemplate>
-           <DataTemplate>
-             <TextBlock Text="{Binding Name}" FontFamily="{Binding}" />
-           </DataTemplate>
-         </ComboBox.ItemTemplate>
-       </ComboBox>
-      
-      <ComboBox PlaceholderText="Pick an Item">
-        <ComboBoxItem>Inline Items</ComboBoxItem>
-        <ComboBoxItem>Inline Item 2</ComboBoxItem>
-        <ComboBoxItem>Inline Item 3</ComboBoxItem>
-        <ComboBoxItem>Inline Item 4</ComboBoxItem>
-        <DataValidationErrors.Error>
-          <sys:Exception /> 
-        </DataValidationErrors.Error>
-      </ComboBox>
-    </WrapPanel>
+                <ComboBox SelectedIndex="0" WrapSelection="{Binding WrapSelection}">
+                    <ComboBoxItem>
+                        <Panel>
+                            <Rectangle Fill="{DynamicResource SystemAccentColor}" />
+                            <TextBlock Margin="8">Control Items</TextBlock>
+                        </Panel>
+                    </ComboBoxItem>
+                    <ComboBoxItem>
+                        <Ellipse
+                            Width="50"
+                            Height="50"
+                            Fill="Yellow" />
+                    </ComboBoxItem>
+                    <ComboBoxItem>
+                        <TextBox Text="TextBox" />
+                    </ComboBoxItem>
+                </ComboBox>
 
-  </StackPanel>
+                <ComboBox
+                    x:Name="fontComboBox"
+                    SelectedIndex="0"
+                    WrapSelection="{Binding WrapSelection}">
+                    <ComboBox.ItemTemplate>
+                        <DataTemplate>
+                            <TextBlock FontFamily="{Binding}" Text="{Binding Name}" />
+                        </DataTemplate>
+                    </ComboBox.ItemTemplate>
+                </ComboBox>
+
+                <ComboBox PlaceholderText="Pick an Item" WrapSelection="{Binding WrapSelection}">
+                    <ComboBoxItem>Inline Items</ComboBoxItem>
+                    <ComboBoxItem>Inline Item 2</ComboBoxItem>
+                    <ComboBoxItem>Inline Item 3</ComboBoxItem>
+                    <ComboBoxItem>Inline Item 4</ComboBoxItem>
+                    <DataValidationErrors.Error>
+                        <sys:Exception />
+                    </DataValidationErrors.Error>
+                </ComboBox>
+            </WrapPanel>
+
+            <CheckBox IsChecked="{Binding WrapSelection}">WrapSelection</CheckBox>
+
+        </StackPanel>
+    </StackPanel>
 </UserControl>

samples/ControlCatalog/Pages/ComboBoxPage.xaml.cs

@@ -2,6 +2,7 @@ using System.Linq;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
 using Avalonia.Media;
+using ControlCatalog.ViewModels;
 
 namespace ControlCatalog.Pages
 {
@@ -10,6 +11,7 @@ namespace ControlCatalog.Pages
         public ComboBoxPage()
         {
             this.InitializeComponent();
+            DataContext = new ComboBoxPageViewModel();
         }
 
         private void InitializeComponent()

samples/ControlCatalog/Pages/ListBoxPage.xaml

@@ -21,6 +21,7 @@
       <CheckBox IsChecked="{Binding Toggle}">Toggle</CheckBox>
       <CheckBox IsChecked="{Binding AlwaysSelected}">AlwaysSelected</CheckBox>
       <CheckBox IsChecked="{Binding AutoScrollToSelectedItem}">AutoScrollToSelectedItem</CheckBox>
+      <CheckBox IsChecked="{Binding WrapSelection}">WrapSelection</CheckBox>
     </StackPanel>
     <StackPanel DockPanel.Dock="Bottom" Orientation="Horizontal" Margin="4">
       <Button Command="{Binding AddItemCommand}">Add</Button>
@@ -30,6 +31,7 @@
     <ListBox Items="{Binding Items}"
              Selection="{Binding Selection}"
              AutoScrollToSelectedItem="{Binding AutoScrollToSelectedItem}"
-             SelectionMode="{Binding SelectionMode^}"/>
+             SelectionMode="{Binding SelectionMode^}"
+             WrapSelection="{Binding WrapSelection}"/>
   </DockPanel>
 </UserControl>

samples/ControlCatalog/ViewModels/ComboBoxPageViewModel.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Reactive;
+using Avalonia.Controls;
+using Avalonia.Controls.Selection;
+using MiniMvvm;
+
+namespace ControlCatalog.ViewModels
+{
+    public class ComboBoxPageViewModel : ViewModelBase
+    {
+        private bool _wrapSelection;
+
+        public bool WrapSelection
+        {
+            get => _wrapSelection;
+            set => this.RaiseAndSetIfChanged(ref _wrapSelection, value);
+        }
+    }
+}

samples/ControlCatalog/ViewModels/ListBoxPageViewModel.cs

@@ -14,6 +14,7 @@ namespace ControlCatalog.ViewModels
         private bool _toggle;
         private bool _alwaysSelected;
         private bool _autoScrollToSelectedItem = true;
+        private bool _wrapSelection;
         private int _counter;
         private IObservable<SelectionMode> _selectionMode;
 
@@ -85,6 +86,12 @@ namespace ControlCatalog.ViewModels
             set => this.RaiseAndSetIfChanged(ref _autoScrollToSelectedItem, value);
         }
 
+        public bool WrapSelection
+        {
+            get => _wrapSelection;
+            set => this.RaiseAndSetIfChanged(ref _wrapSelection, value);
+        }
+
         public MiniCommand AddItemCommand { get; }
         public MiniCommand RemoveItemCommand { get; }
         public MiniCommand SelectRandomItemCommand { get; }

src/Avalonia.Controls/ComboBox.cs

@@ -10,9 +10,7 @@ using Avalonia.Controls.Templates;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Layout;
-using Avalonia.LogicalTree;
 using Avalonia.Media;
-using Avalonia.Threading;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
@@ -91,7 +89,7 @@ namespace Avalonia.Controls
         {
             ItemsPanelProperty.OverrideDefaultValue<ComboBox>(DefaultPanel);
             FocusableProperty.OverrideDefaultValue<ComboBox>(true);
-            SelectedItemProperty.Changed.AddClassHandler<ComboBox>((x,e) => x.SelectedItemChanged(e));
+            SelectedItemProperty.Changed.AddClassHandler<ComboBox>((x, e) => x.SelectedItemChanged(e));
             KeyDownEvent.AddClassHandler<ComboBox>((x, e) => x.OnKeyDown(e), Interactivity.RoutingStrategies.Tunnel);
             IsTextSearchEnabledProperty.OverrideDefaultValue<ComboBox>(true);
         }
@@ -221,8 +219,9 @@ namespace Avalonia.Controls
                     e.Handled = true;
                 }
             }
+            // This part of code is needed just to acquire initial focus, subsequent focus navigation will be done by ItemsControl.
             else if (IsDropDownOpen && SelectedIndex < 0 && ItemCount > 0 &&
-                      (e.Key == Key.Up || e.Key == Key.Down))
+                      (e.Key == Key.Up || e.Key == Key.Down) && IsFocused == true)
             {
                 var firstChild = Presenter?.Panel?.Children.FirstOrDefault(c => CanFocus(c));
                 if (firstChild != null)
@@ -430,7 +429,18 @@ namespace Avalonia.Controls
             int next = SelectedIndex + 1;
 
             if (next >= ItemCount)
-                next = 0;
+            {
+                if (WrapSelection == true)
+                {
+                    next = 0;
+                }
+                else
+                {
+                    return;
+                }
+            }
+
+
 
             SelectedIndex = next;
         }
@@ -440,7 +450,16 @@ namespace Avalonia.Controls
             int prev = SelectedIndex - 1;
 
             if (prev < 0)
-                prev = ItemCount - 1;
+            {
+                if (WrapSelection == true)
+                {
+                    prev = ItemCount - 1;
+                }
+                else
+                {
+                    return;
+                }
+            }
 
             SelectedIndex = prev;
         }

src/Avalonia.Controls/ItemsControl.cs

@@ -143,6 +143,8 @@ namespace Avalonia.Controls
             protected set;
         }
 
+        private protected bool WrapFocus { get; set; }
+
         event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexChanged
         {
             add => _childIndexChanged += value;
@@ -315,7 +317,7 @@ namespace Avalonia.Controls
                 {
                     if (current.VisualParent == container && current is IInputElement inputElement)
                     {
-                        var next = GetNextControl(container, direction.Value, inputElement, false);
+                        var next = GetNextControl(container, direction.Value, inputElement, WrapFocus);
 
                         if (next != null)
                         {

src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs

@@ -233,11 +233,6 @@ namespace Avalonia.Controls.Presenters
             var itemIndex = generator.IndexFromContainer(from);
             var vertical = VirtualizingPanel.ScrollDirection == Orientation.Vertical;
 
-            if (itemIndex == -1)
-            {
-                return null;
-            }
-
             var newItemIndex = -1;
 
             switch (direction)
@@ -250,6 +245,16 @@ namespace Avalonia.Controls.Presenters
                     newItemIndex = ItemCount - 1;
                     break;
 
+                default:
+                    if (itemIndex == -1)
+                    {
+                        return null;
+                    }
+                    break;
+            }
+
+            switch (direction)
+            {
                 case NavigationDirection.Up:
                     if (vertical)
                     {

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -114,6 +114,12 @@ namespace Avalonia.Controls.Primitives
                 "SelectionChanged",
                 RoutingStrategies.Bubble);
 
+        /// <summary>
+        /// Defines the <see cref="WrapSelection"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> WrapSelectionProperty =
+            AvaloniaProperty.Register<ItemsControl, bool>(nameof(WrapSelection), defaultValue: false);
+
         private static readonly IList Empty = Array.Empty<object>();
         private string _textSearchTerm = string.Empty;
         private DispatcherTimer? _textSearchTimer;
@@ -321,6 +327,16 @@ namespace Avalonia.Controls.Primitives
             set { SetValue(IsTextSearchEnabledProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a value which indicates whether to wrap around when the first
+        /// or last item is reached.
+        /// </summary>
+        public bool WrapSelection
+        {
+            get { return GetValue(WrapSelectionProperty); }
+            set { SetValue(WrapSelectionProperty, value); }
+        }
+
         /// <summary>
         /// Gets or sets the selection mode.
         /// </summary>
@@ -580,6 +596,10 @@ namespace Avalonia.Controls.Primitives
                 var newValue = change.NewValue.GetValueOrDefault<SelectionMode>();
                 _selection.SingleSelect = !newValue.HasAllFlags(SelectionMode.Multiple);
             }
+            else if (change.Property == WrapSelectionProperty)
+            {
+                WrapFocus = WrapSelection;
+            }
         }
 
         /// <summary>

src/Avalonia.Controls/VirtualizingStackPanel.cs

@@ -36,7 +36,7 @@ namespace Avalonia.Controls
         {
             get
             {
-                var bounds = Orientation == Orientation.Horizontal ? 
+                var bounds = Orientation == Orientation.Horizontal ?
                     _availableSpace.Width : _availableSpace.Height;
                 return Math.Max(0, _takenSpace - bounds);
             }
@@ -129,14 +129,11 @@ namespace Avalonia.Controls
 
         protected override IInputElement? GetControlInDirection(NavigationDirection direction, IControl? from)
         {
-            if (from == null)
-                return null;
-
             var logicalScrollable = Parent as ILogicalScrollable;
 
             if (logicalScrollable?.IsLogicalScrollEnabled == true)
             {
-                return logicalScrollable.GetControlInDirection(direction, from);
+                return logicalScrollable.GetControlInDirection(direction, from!);
             }
             else
             {
@@ -145,7 +142,7 @@ namespace Avalonia.Controls
         }
 
         internal override void ArrangeChild(
-            IControl child, 
+            IControl child,
             Rect rect,
             Size panelSize,
             Orientation orientation)

tests/Avalonia.Controls.UnitTests/ListBoxTests.cs

@@ -613,5 +613,54 @@ namespace Avalonia.Controls.UnitTests
             Assert.True(DataValidationErrors.GetHasErrors(target));
             Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
         }
+
+        private 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()
+        {
+            using (UnitTestApplication.Start(TestServices.RealFocus))
+            {
+                var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToArray();
+                var target = new ListBox
+                {
+                    Template = ListBoxTemplate(),
+                    Items = items,
+                    ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
+                    WrapSelection = true
+                };
+
+                Prepare(target);
+
+                var lbItems = target.GetLogicalChildren().OfType<ListBoxItem>().ToArray();
+
+                var first = lbItems.First();
+                var last = lbItems.Last();
+
+                first.Focus();
+
+                RaisePressedEvent(target, first, MouseButton.Left);
+                Assert.Equal(true, first.IsSelected);
+
+                RaiseKeyEvent(target, Key.Up);
+                Assert.Equal(true, last.IsSelected);
+
+                RaiseKeyEvent(target, Key.Down);
+                Assert.Equal(true, first.IsSelected);
+
+                target.WrapSelection = false;
+                RaiseKeyEvent(target, Key.Up);
+
+                Assert.Equal(true, first.IsSelected);
+            }
+        }
     }
 }