Function app_popup 

pub fn app_popup<App: Application>(
    live_settings: impl Fn(&App) -> LiveSettings + Send + Sync + 'static,
    settings: impl Fn(&mut App) -> SctkPopupSettings + Send + Sync + 'static,
    view: Option<Box<dyn Fn(&App) -> Element<'_, Action<<App as Application>::Message>> + Send + Sync + 'static>>,
) -> Action

Available on wayland_platform only.