Support ListBox.HorizontalContentAlignment

Vanilla WPF has ListBox.HorizontalContentAlignment. In the following scenario:

xaml:

<ListBox ItemsSource="{Binding Items}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding .}" MouseDown="TextBlock_MouseDown"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

xaml.cs:

private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
{
    Debug.WriteLine("Mouse Down!");
}

The “Mouse Down!” text will be printed only if the text in the TextBox is clicked, as the TextBox “shrinks” its bounds to the size of the text. But, if we add HorizontalContentAlignment="Stretch" to the ListBox declaration, then the TextBox will fill the horizontal space and accept the click event anywhere on the ListBoxItem (even outside the text).

Avalonia does not currently support ListBox.HorizontalContentAlignment - the ask is to add it. Is there currently a workaround? Maybe using styles?

[jp2masa]

I think it works if you set Background="Transparent" on the TextBlock and this style:

<Style Selector="ListBoxItem">
    <Setter Property="HorizontalContentAlignment" Value="Stretch" />
</Style>

Also, this seems to be a problem on fluent theme only:

https://github.com/AvaloniaUI/Avalonia/blob/d53920bc99fab3b0aaeb8c2f065096c071d2c388/src/Avalonia.Themes.Fluent/Controls/ListBoxItem.xaml#L21

Default theme doesn’t set HorizontalContentAlignment (I think the default is Stretch).

[maxkatz6]

If ListBoxItem is already stretched, you need to check the same property on your CheckBox. I am also not sure right now if it has Transparent (clickable) background.