PowerToys/src/modules/poweraccent/PowerAccent.UI/Selector.xaml

<Window
    x:Class="PowerAccent.UI.Selector"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:PowerAccent"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="50"
    Height="50"
    ResizeMode="NoResize"
    ShowInTaskbar="False"
    SizeToContent="WidthAndHeight"
    Visibility="Collapsed"
    WindowStyle="None"
    mc:Ignorable="d">
    <Grid>
        <ListBox
            x:Name="characters"
            HorizontalContentAlignment="Stretch"
            VerticalContentAlignment="Stretch"
            BorderBrush="SlateGray"
            BorderThickness="1"
            IsHitTestVisible="False">
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <VirtualizingStackPanel IsItemsHost="False" Orientation="Horizontal" />
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock
                        VerticalAlignment="Center"
                        FontSize="18"
                        Text="{Binding}"
                        TextAlignment="Center" />
                </DataTemplate>
            </ListBox.ItemTemplate>
            <ListBox.ItemContainerStyle>
                <Style x:Name="ItemStyle" TargetType="ListBoxItem">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type ListBoxItem}">
                                <Border
                                    x:Name="myBorder"
                                    Margin="0"
                                    Padding="0"
                                    SnapsToDevicePixels="true"
                                    Style="{DynamicResource borderContent}">
                                    <ContentPresenter />
                                </Border>
                                <ControlTemplate.Resources>
                                    <Style x:Key="borderContent" TargetType="Border">
                                        <Setter Property="BorderThickness" Value="0" />
                                        <Setter Property="BorderBrush" Value="Transparent" />
                                        <Setter Property="Background" Value="#ECECEC" />
                                        <Setter Property="Width" Value="50" />
                                        <Setter Property="Height" Value="50" />
                                    </Style>
                                </ControlTemplate.Resources>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="IsSelected" Value="true">
                                        <Setter TargetName="myBorder" Property="Background" Value="White" />
                                        <Setter Property="FontWeight" Value="Bold" />
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </ListBox.ItemContainerStyle>
        </ListBox>
    </Grid>
</Window>