gtk_window_set_role (GTK_WINDOW (preferences), "preferences");
gtk_window_set_position (GTK_WINDOW (preferences),
GTK_WIN_POS_CENTER_ON_PARENT);
gtk_window_set_role (GTK_WINDOW (preferences), "preferences");
gtk_window_set_position (GTK_WINDOW (preferences),
GTK_WIN_POS_CENTER_ON_PARENT);