Gtk.Window.prototype.set_wmclass

function set_wmclass(wmclass_name:String, wmclass_class:String):void {
    // Gjs wrapper for gtk_window_set_wmclass()
}

Don't use this function. It sets the X Window System "class" and "name" hints for a window. According to the ICCCM, you should always set these to the same value for all windows in an application, and GTK+ sets them to that value by default, so calling this function is sort of pointless. However, you may want to call Gtk.Window.prototype.set_role on each window in your application, for the benefit of the session manager. Setting the role allows the window manager to restore window positions when loading a saved session.