INotifyCollectionChanged is implemented inconsistently for Move and Replace operations.

[mpylon]

Describe the bug

Various INotifyCollectionChanged.CollectionChanged event handlers in Avalonia have an off-by-one error and / or fail to correctly respond to multi-item change events. For example, the following event handler does not respond to multi-item Move or Replace operations correctly.

Avalonia/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs

Lines 95 to 99 in 981f47f

	case NotifyCollectionChangedAction.Replace:
	case NotifyCollectionChangedAction.Move:
	Remove(e.OldStartingIndex, e.OldItems!.Count);
	Add(e.NewStartingIndex, e.NewItems!);
	break;

To correctly implement this type of behavior, we should follow the example of MAUI.

https://github.com/dotnet/maui/blob/cc683f0e99547c2ed4875296d7451332ef64ca73/src/Controls/src/Core/Internals/NotifyCollectionChangedEventArgsExtensions.cs#L47-L61

Furthermore, the event publishers are not consistent in their interpretations of INotifyCollectionChanged. For example, the AvaloniaList.Move and AvaloniaList.MoveRange methods produce different events for the same mutation (or, equivalently, the same events for different mutations). See the below unit test reflecting this incongruity.

[TestFixture]
public class Tests
{
    [Test]
    public void Move()
    {
        AvaloniaList<int> items = [1, 2, 3];

        using (new AssertionScope())
        {
            AssertEvent(items, () => items.Move(0, 1), new NotifyCollectionChangedEventArgs(
                action: NotifyCollectionChangedAction.Move,
                changedItems: new[] { 1 },
                index: 1,
                oldIndex: 0));

            items.ToArray().Should().BeEquivalentTo(new[] { 2, 1, 3 }, o => o.WithStrictOrdering());
        }
    }

    [Test]
    public void MoveRange()
    {
        AvaloniaList<int> items = [1, 2, 3];

        using (new AssertionScope())
        {
            AssertEvent(items, () => items.MoveRange(0, 1, 1), new NotifyCollectionChangedEventArgs(
                action: NotifyCollectionChangedAction.Move,
                changedItems: new[] { 1 },
                index: 1,
                oldIndex: 0));

            items.ToArray().Should().BeEquivalentTo(new[] { 2, 1, 3 }, o => o.WithStrictOrdering());
        }
    }

    private static void AssertEvent(INotifyCollectionChanged items, Action action, NotifyCollectionChangedEventArgs expectedEvent)
    {
        items.CollectionChanged += OnCollectionChanged;

        try
        {
            action();
        }
        finally
        {
            items.CollectionChanged -= OnCollectionChanged;
        }

        return;

        void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs actualEvent)
        {
            actualEvent.Should().BeEquivalentTo(expectedEvent);
        }
    }
}

To Reproduce

To reproduce one of these behaviors, call AvaloniaList.MoveRange and verify that it successfully mutates the list, but fails to correctly update the PanelContainerGenerator.

[AvaloniaTest]
public void MoveRange()
{
    // Arrange

    AvaloniaList<int> items = [1];

    var itemsControl = new ItemsControl
    {
        ItemsPanel = new FuncTemplate<Panel?>(() => new Panel()),
        ItemsSource = items
    };

    var window = new Window
    {
        Content = itemsControl,
        Height = 768,
        Width = 1024
    };

    window.Show();

    // Act

    items.MoveRange(0, 1, 1);

    // Assert

    var actualContents = itemsControl
        .ItemsPanelRoot!
        .GetVisualChildren()
        .Cast<ContentPresenter>()
        .Select(x => x.Content);

    actualContents
        .Should()
        .BeEquivalentTo(items, o => o.WithStrictOrdering());
}

Expected behavior

• The AvaloniaList.Move and AvaloniaList.MoveRange operations should throw exceptions before emitting events that will cause subsequent listeners to throw exceptions due to mismatched indices.
• Move(X, Y) should have the same meaning as MoveRange(X, 1, Y).
• INotifyCollectionChanged handlers throughout Avalonia should interpret indices in the same way.

Avalonia version

11.2.0-beta2

OS

Windows

Additional context

No response