You wouldn’t expect it to be difficult for a printer driver to detect that the printer is out of paper. Having spent several days trying to work out the Linux usblp kernel driver, I have all but given up trying to fix it myself. Hopefully someone will show interest in the bug report I filed.
Until that’s fixed I’ve had to put a work-around in the CUPS “usb” backend, but at least now it detects paper-out correctly. Today I took a look at the “hal” backend and fixed not only the paper-out detection but something even more basic: retrying the job if the printer isn’t switched on yet(!).