Preprocessor blocks UI

[lastWords]

I noticed the preprocessor only flashes a progress bar after a delay before the "complete" notification is displayed. Looks like the UI is blocked and call to GeneratePreprocessingAsync should be made on a separate thread, i.e.

            line 194: await Task.Run(() => processor.GeneratePreprocessingAsync(preprocessingFile));

Another issue I had at build was a missing resource so I added this to App.xaml:

 <Application.Resources>
    <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
</Application.Resources>

Maybe I am missing some kind of global definition?