synchronized public void writeEnableContinuousUpdates(boolean enable,
                                           int x, int y, int w, int h)
  {
    if (!cp.supportsContinuousUpdates)
      throw new ErrorException("Server does not support continuous updates");

    startMsg(MsgTypes.msgTypeEnableContinuousUpdates);

    os.writeU8((enable?1:0));

    os.writeU16(x);
    os.writeU16(y);
    os.writeU16(w);
    os.writeU16(h);

    endMsg();
  }