Call POLL_oob() with a pointer to a non-zero integer to check and dispatch PEN events. Notice that if you implements a low level PEN routine (see section 11.7.1), you might not need to use this function. Otherwise, if you have a higher level user interface and are using high level PENs (see section 11.7.1), you should call this function whenever the file handle returned by PEN_GET_HANDLE() is ``readable''.