Is Selector in Avalonia Style

Question

I have a baseButtonStyle, which should apply to all Buttons and all derived types. It works well for all Buttons (excluding derived).

<Style x:Key="BaseButtonStyle" Selector="is Button" >
    <Setter Property="BorderThickness" Value="1"/>
    <Setter Property="Foreground" Value="{StaticResource SecondaryFontBrush}"/>
    <Setter Property="BorderBrush" Value="{StaticResource BlueButtonNormalBorderBrush}"/>
    <Setter Property="Background" Value="{StaticResource BlueButtonNormalBackgroundBrush}"/>
    <Setter Property="UseLayoutRounding" Value="True"/>
    <Setter Property="Padding" Value="10"/>
    <Setter Property="Margin" Value="10"/>
</Style>

Now I have an AdditionalTextButton derived from Button.

using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;
using System;

namespace VW7OrbMachineAvalonia1.Components.Controls
{

    public class AdditionalTextButton : Button
    {

        Type IStyleable.StyleKey => typeof(AdditionalTextButton);

        /// <summary>
        /// Bottom left displayed Text
        /// </summary>
        public string BottomLeftText
        {
            get { return (string)GetValue(BottomLeftTextProperty); }
            set { SetValue(BottomLeftTextProperty, value); }
        }

        public static readonly StyledProperty<String> BottomLeftTextProperty =
            AvaloniaProperty.Register<AdditionalTextButton, String>("BottomLeftText");
    }
}

My understanding of the style behavior of Avalonia is, that the BaseButtonStyle should apply to to AdditionalTextButton because of the is Button Selector. But this does not happen.

Beside that, I have another style which should apply to all AdditionaltextButtons. This also works fine.

<Style x:Key="additionalTextButtonStyle" Selector="is vwaui:Additionaltextbutton">
    <Setter Property="FontSize" Value="22"/>
    <Setter Property="Template">
      <Setter.Value>
        <ControlTemplate>
          <Grid Width="{TemplateBinding Width}" Height="{TemplateBinding Height}">
                <TextBlock HorizontalAlignment="Left" VerticalAlignment="Bottom"  TextWrapping="Wrap" Text="{TemplateBinding BottomLeftText}"/>
                <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center"  TextWrapping="Wrap" Text="{TemplateBinding Content}"/>
          </Grid>
        </ControlTemplate>
      </Setter.Value>
    </Setter>
</Style>

How can I get the result, that the AdditionalTextButton is styled by the BaseButtonStyle AND by the AdditionalTextButtonStyle? Setters from AdditionalTextButtonStyle should overwrite setters from BaseButtonStyle.

Answer 1

The problem is that your is selector syntax is wrong. If you change it to be:

Selector=":is(Button)"

and

Selector=":is(vwaui|Additionaltextbutton)"

Then this should work as expected.