hbox->pack_start (_btn_open, false, false, 2);
hbox->pack_start (_btn_save, false, false, 2);
hbox->pack_start (_btn_delete, false, false, 2);
hbox->pack_start (_btn_open, false, false, 2);
hbox->pack_start (_btn_save, false, false, 2);
hbox->pack_start (_btn_delete, false, false, 2);