Avalonia/samples/ControlCatalog/Pages/OpenGlPage.xaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ControlCatalog.Pages.OpenGlPage"
             xmlns:pages="using:ControlCatalog.Pages"
             xmlns:openGl="clr-namespace:ControlCatalog.Pages.OpenGl">
  <Grid x:Name="MainGrid">
    <pages:OpenGlPageControl x:Name="GL"/>
    <openGl:GlPageKnobs x:Name="Knobs" />
    <Button x:Name="Snapshot"
            IsVisible="False"
            VerticalAlignment="Bottom" HorizontalAlignment="Right"  Click="SnapshotClick">Snapshot</Button>
  </Grid>
</UserControl>