NAME

       gspool_jobmon - set a function to monitor changes to jobs

       gspool_setmon - monitor job and printer list changes on Windows

SYNOPSIS

       #include <gspool.h>

       int gspool_jobmon(const int fd, void (*fn)(const int))

       int gspool_setmon(const int fd, HWND hWnd, UINT wMsg)

       int gspool_procmon(const int fd)

       void gspool_unsetmon(const int fd)

DESCRIPTION

   Unix and GNU/Linux
       The gspool_jobmon() function is used to set the function fn to be called upon notification of any changes
       to the jobs list.

       fd is a file descriptor previously returned by gspool_open.

       fn is a function which must be declared as returning void and taking one "const int" argument.
       Alternatively, this may be "NULL" to cancel monitoring.

       The function fn will be called upon each change to the job list. The argument passed will be fd. Note
       that any changes to the job queue are reported (including changes on other hosts whose details are passed
       through) as the API does not record which jobs the user is interested in.

   Windows
       The gspool_setmon routine may be used to monitor changes to the job queue or printer list. Its parameters
       are as follows.

       fd is a file descriptor previously returned by gspool_open.

       hWnd is a windows handle to which messages should be sent.

       wMsg is the message id to be passed to the window ("WM_USER" or a constant based on this is suggested).

       To decode the message, the gspool_procmon is provided. This returns "XTWINAPI_JOBPROD" to indicate a
       change or changes to the job queue and "XTWINAPI_PTRPROD" to indicate a change or changes to the printer
       list. If there are changes to both, two or more messages will be sent, each of which should be decoded
       via separate gspool_procmon calls.

       To cancel monitoring, invoke the routine

        gspool_unsetmon(fd)

       If no monitoring is in progress, or the descriptor is invalid, this call is just ignored.

RETURN VALUES

       The function gspool_jobmon() returns 0 if successful otherwise the error code "GSPOOL_INVALID_FD" if the
       file descriptor is invalid. Invalid fn parameters will not be detected and the application program will
       probably crash.

SEE ALSO

       gspool_open(3), gspool_close(3), gspool_joblist(3), gspool_ptrlist(3), gspool_ptrmon(3).

COPYRIGHT

       Copyright (c) 2009 Free Software Foundation, Inc.  This is free software. You may redistribute copies of
       it under the terms of the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.  There is NO
       WARRANTY, to the extent permitted by law.

AUTHOR

       John M Collins, Xi Software Ltd.

GNUspool Release 1                                 2009-05-18                                   gspool_jobmon(3)