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 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).


AUTHOR

John M Collins, Xi Software Ltd.