ListBox DoubleTapped event has inconsistent SelectedIndex

[pygmypenguin]

Describe the bug

When double tapping a listboxitem with a mouse, the SelectedIndex of the sender is the index of the item that was tapped. When this same item is double tapped with a pen or other touch input, though, the SelectedIndex is -1, as if the item had been deselected just before firing the DoubleTapped event.

To Reproduce

Create the following types and compose an avalonia demo app. Then, double tap with a mouse and touch device on any ListBoxItem.

MyControl.axaml

<UserControl xmlns="https://github.com/avaloniaui"
                      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                      xmlns:local="using:Demo"
                      mc:Ignorable="d"
                      x:Class="Demo.MyControl"
                      x:DataType="local:DemoViewModel">
    <StackPanel Orientation="Vertical">
        <ListBox DoubleTapped="MyListBox_DoubleTapped" ItemsSource="{Binding Items}">
            <ListBox.ItemTemplate>
                <DataTemplate x:DataType="local:DemoItem">
                    <Border>
                        <TextBlock Text="{Binding Content}" />
                    </Border>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
        <TextBlock x:Name="ResultText" />
    </StackPanel>
</UserControl>

MyControl.axaml.cs

using Avalonia.Controls;
using Avalonia.Input;

namespace Demo;

public partial class MyControl : UserControl {
    public MyControl() {
        InitializeComponent();
    }

    public void MyListBox_DoubleTapped(object? sender, TappedEventArgs e) {
        if (sender is not ListBox lb) return;
        if (lb.SelectedIndex < 0) {
            ResultText.Text = "No Index Selected on DoubleTap";
        }
        else {
            ResultText.Text = $"Selected Index {e.SelectedIndex} with DoubleTap";
        }
    }
}

DemoViewModel.cs

using System.Collections.ObjectModel;

namespace Demo;

public record Item(string Content);

public class DemoViewModel {
    public ObservableCollection<Item> Items { get; } = [
        new Item("Item 1"),
        new Item("Item 2")
    ];
}

Expected behavior

The ResultText TextBlock should show "Selected Index with DoubleTap" with both a mouse selection and a touch device selection.

Avalonia version

11.3.9

OS

Windows

Additional context

No response

[pygmypenguin]

Correction: this occurs with some odd event handling. Edit MyControl.axaml to the following:

<UserControl xmlns="https://github.com/avaloniaui"
                      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                      xmlns:local="using:Demo"
                      mc:Ignorable="d"
                      x:Class="Demo.MyControl"
                      x:DataType="local:DemoViewModel"
                      PointerPressed="OnBackgroundClicked">
    <StackPanel Orientation="Vertical">
        <ListBox x:Name="SelectionListBox" DoubleTapped="MyListBox_DoubleTapped" ItemsSource="{Binding Items}">
            <ListBox.ItemTemplate>
                <DataTemplate x:DataType="local:DemoItem">
                    <Border>
                        <TextBlock Text="{Binding Content}" />
                    </Border>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
        <TextBlock x:Name="ResultText" />
    </StackPanel>
</UserControl>

and MyControl.axaml.cs:

using Avalonia.Controls;
using Avalonia.Input;

namespace Demo;

public partial class MyControl : UserControl {
    public MyControl() {
        InitializeComponent();
    }

    public void OnBackgroundClicked(object? sender, PointerPressedEventArgs e) {
        SelectionListBox.SelectedIndex = -1;
    }

    public void MyListBox_DoubleTapped(object? sender, TappedEventArgs e) {
        if (sender is not ListBox lb) return;
        if (lb.SelectedIndex < 0) {
            ResultText.Text = "No Index Selected on DoubleTap";
        }
        else {
            ResultText.Text = $"Selected Index {e.SelectedIndex} with DoubleTap";
        }
    }
}

The behavior occurs when you press and hold on a ListBoxItem:
With a stylus, SelectedIndex is set to -1 on PointerPressed, then n on PointerReleased. PointerReleased is triggered after the DoubleTapped event, leaving the SelectedIndex in a limbo state of -1.
With a mouse, PointerPressed never sets the listbox's SelectedIndex as the event is actually Handled by the ListBoxItem and never bubbles, leaving the SelectedIndex in a clean state after the first PointerReleased and before the DoubleTapped.

[pygmypenguin]

Confirmed that this remains an issue in Avalonia 12.0.2