private void OnPlusMinusButtonPressEvent(object o, ButtonPressEventArgs args)
{
if(click_id != 0) {
GLib.Source.Remove(click_id);
}
direction = o == minus ? -1 : 1;
click_id = GLib.Timeout.Add(CLICK_TIMEOUT / 2, PlusMinusButtonTimeout);
PlusMinusButtonTimeout();
args.RetVal = true;
}