Merge pull request #4307 from donandren/issues/4306

Fix multiple selection with keys (shift/ctrl) in ListBox

src/Avalonia.Controls/ItemsControl.cs

@@ -295,7 +295,7 @@ namespace Avalonia.Controls
 
                         if (next != null)
                         {
-                            focus.Focus(next, NavigationMethod.Directional);
+                            focus.Focus(next, NavigationMethod.Directional, e.KeyModifiers);
                             e.Handled = true;
                         }
 

src/Avalonia.Controls/ListBox.cs

@@ -136,7 +136,8 @@ namespace Avalonia.Controls
                 e.Handled = UpdateSelectionFromEventSource(
                     e.Source,
                     true,
-                    (e.KeyModifiers & KeyModifiers.Shift) != 0);
+                    (e.KeyModifiers & KeyModifiers.Shift) != 0,
+                    (e.KeyModifiers & KeyModifiers.Control) != 0);
             }
         }
 

tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs

@@ -0,0 +1,126 @@
+using System.Linq;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
+using Avalonia.Input;
+using Avalonia.Styling;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class ListBoxTests_Multiple
+    {
+        [Fact]
+        public void Focusing_Item_With_Shift_And_Arrow_Key_Should_Add_To_Selection()
+        {
+            var target = new ListBox
+            {
+                Template = new FuncControlTemplate(CreateListBoxTemplate),
+                Items = new[] { "Foo", "Bar", "Baz " },
+                SelectionMode = SelectionMode.Multiple
+            };
+
+            ApplyTemplate(target);
+
+            target.SelectedItem = "Foo";
+
+            target.Presenter.Panel.Children[1].RaiseEvent(new GotFocusEventArgs
+            {
+                RoutedEvent = InputElement.GotFocusEvent,
+                NavigationMethod = NavigationMethod.Directional,
+                KeyModifiers = KeyModifiers.Shift
+            });
+
+            Assert.Equal(new[] { "Foo", "Bar" }, target.SelectedItems);
+        }
+
+        [Fact]
+        public void Focusing_Item_With_Ctrl_And_Arrow_Key_Should_Add_To_Selection()
+        {
+            var target = new ListBox
+            {
+                Template = new FuncControlTemplate(CreateListBoxTemplate),
+                Items = new[] { "Foo", "Bar", "Baz " },
+                SelectionMode = SelectionMode.Multiple
+            };
+
+            ApplyTemplate(target);
+
+            target.SelectedItem = "Foo";
+
+            target.Presenter.Panel.Children[1].RaiseEvent(new GotFocusEventArgs
+            {
+                RoutedEvent = InputElement.GotFocusEvent,
+                NavigationMethod = NavigationMethod.Directional,
+                KeyModifiers = KeyModifiers.Control
+            });
+
+            Assert.Equal(new[] { "Foo", "Bar" }, target.SelectedItems);
+        }
+
+        [Fact]
+        public void Focusing_Selected_Item_With_Ctrl_And_Arrow_Key_Should_Remove_From_Selection()
+        {
+            var target = new ListBox
+            {
+                Template = new FuncControlTemplate(CreateListBoxTemplate),
+                Items = new[] { "Foo", "Bar", "Baz " },
+                SelectionMode = SelectionMode.Multiple
+            };
+
+            ApplyTemplate(target);
+
+            target.SelectedItems.Add("Foo");
+            target.SelectedItems.Add("Bar");
+
+            target.Presenter.Panel.Children[0].RaiseEvent(new GotFocusEventArgs
+            {
+                RoutedEvent = InputElement.GotFocusEvent,
+                NavigationMethod = NavigationMethod.Directional,
+                KeyModifiers = KeyModifiers.Control
+            });
+
+            Assert.Equal(new[] { "Bar" }, target.SelectedItems);
+        }
+
+        private Control CreateListBoxTemplate(ITemplatedControl parent, INameScope scope)
+        {
+            return new ScrollViewer
+            {
+                Template = new FuncControlTemplate(CreateScrollViewerTemplate),
+                Content = new ItemsPresenter
+                {
+                    Name = "PART_ItemsPresenter",
+                    [~ItemsPresenter.ItemsProperty] = parent.GetObservable(ItemsControl.ItemsProperty).ToBinding(),
+                }.RegisterInNameScope(scope)
+            };
+        }
+
+        private Control CreateScrollViewerTemplate(ITemplatedControl parent, INameScope scope)
+        {
+            return new ScrollContentPresenter
+            {
+                Name = "PART_ContentPresenter",
+                [~ContentPresenter.ContentProperty] =
+                    parent.GetObservable(ContentControl.ContentProperty).ToBinding(),
+            }.RegisterInNameScope(scope);
+        }
+
+        private void ApplyTemplate(ListBox target)
+        {
+            // Apply the template to the ListBox itself.
+            target.ApplyTemplate();
+
+            // Then to its inner ScrollViewer.
+            var scrollViewer = (ScrollViewer)target.GetVisualChildren().Single();
+            scrollViewer.ApplyTemplate();
+
+            // Then make the ScrollViewer create its child.
+            ((ContentPresenter)scrollViewer.Presenter).UpdateChild();
+
+            // Now the ItemsPresenter should be reigstered, so apply its template.
+            target.Presenter.ApplyTemplate();
+        }
+    }
+}