<ResourceDictionary
    x:ClassModifier="internal"
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <ControlTheme TargetType="GridSplitter" x:Key="{x:Type GridSplitter}">
        <Setter Property="Focusable" Value="True" />
        <Setter Property="MinWidth" Value="1" />
        <Setter Property="MinHeight" Value="1" />
        <Setter Property="PreviewContent">
            <Template>
                <Rectangle Fill="Black" />
            </Template>
        </Setter>
        <Setter Property="Template">
            <ControlTemplate>
                <Border
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}"
                    CornerRadius="{TemplateBinding CornerRadius}" />
            </ControlTemplate>
        </Setter>
    </ControlTheme>
</ResourceDictionary>