public typealias Window = Gtk.Window
    public typealias Widget = Gtk.Widget

    var gtkApp: Application

    /// A window to be returned on the next call to ``GtkBackend/createWindow``.
    /// This is necessary because Gtk creates a root window no matter what, and
    /// this needs to be returned on the first call to `createWindow`.
    var precreatedWindow: Window?

    public init(appIdentifier: String) {
        gtkApp = Application(applicationId: appIdentifier)
    }