QuestPDF/Source/QuestPDF.Previewer/PreviewerApp.axaml

<Application x:Class="QuestPDF.Previewer.PreviewerApp"
             xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Name="QuestPDF Document Preview"
             RequestedThemeVariant="Dark">
	<Application.Styles>
		<FluentTheme />
	</Application.Styles>
</Application>