[cups.development] Backend signal handling

[Michael R Sweet]

Thomas Küstermann wrote:
> Hello!
> 
> 
> I'm working on a backend-wrapper that does some accounting before
> starting the 'socket' backend. It works very fine. Now, I have some
> questions:
> 
> 1. What is expected from a backend when the print job is canceled or
> the printer queue is stopped?

It should collect the remaining output from the upstream filters and
send it to the device, then exit.  Otherwise the printer can be left
in an undefined state.

> 2. Imagine a backend that handles SIGTERM to print out the job even
> when the print queue is stopped or the job is canceled. How to tell
> CUPS to drop the print job out of the print queue?

There is no way to do this - about all you can do is write PAGE:
messages (PAGE: 123 total) to tell the scheduler how many pages were
printed in total.  You can also try canceling the job via IPP
operation, however that may not always work if authentication is
required.

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Michael R Sweet                        Senior Printing System Engineer