Actually cancelling a print job ?

[Michael Sweet]

beavis at snet.net wrote:
> Hi list.  I have an older priner ( HP IIIP ) for which I ocassionally
> want to cancel a print job.  When I do so within CUPS and then reset
> the printer ( flusing the printer's memory ) the job continues to be
> sent data as indicated by the I/O light on printer and soon after
> come more printed pages.  Shouldn't my actions prevent the printing
> of any more pages ? If so, any ideas as to why this is happening ?

Normally when you cancel a job, the driver filter will send a
series of "abort job" commands/characters so that the printer will
be left in a known state.  The parallel backend and parallel port
driver will still have this data waiting to be sent to the printer.

We can detect errors if the parallel port driver returns them and
stop automatically, however if there is a pending write and the
driver gets "stuck" waiting for an "ack" from the printer, then
you'll still get the remaining buffered information...

We're experimenting with some possible fixes for this (basically to
poll the printer status bits before each write and abort if we see
the printer is turned off/off-line and the job has been cancelled)
to be included in CUPS 1.2, but for now there is no clean solution
other than waiting for the rest of the print data to come out.

-- 
______________________________________________________________________
Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Document Software          http://www.easysw.com