[Development] Volunteer wanted: update use of CUPS API

[Michael Weghorn]

On 04/05/2020 09.15, Lars Knoll wrote:
>> On 4 May 2020, at 09:08, Albert Astals Cid via Development <development at qt-project.org> wrote:
>>
>> El diumenge, 3 de maig de 2020, a les 3:35:01 CEST, Thiago Macieira va 
>> escriure:
>>> We have plenty of warnings when building the CUPS plugin to QtPrintSupport
>>> about deprecated methods. See attached.
>>>
>>> Any volunteers to go fix this?
>>
>> This is https://bugreports.qt.io/browse/QTBUG-56545
>>
>> As mentioned there a few years ago I don't think there is a CUPS way to do 
>> stuff like "printer supports stapling" using non deprecated functions.
> 
> So CUPS deprecated API without providing any (non-deprecated) replacement? That makes this somewhat difficult.

Well, as far as I can tell, the so-called "Job Ticket API" is a
replacement that does generally provide the required functionality.
The problem is that many printers (even relatively new models) e.g. use
PPD files with vendor-specific keywords for some funcationality and
don't support the same functionality using IPP (Internet Printing
Protocol) even though equivalents would exist, meaning the functionality
is not available via the "new API".

Some more information also in CUPS issue [1]. I'll also post a link to
this discussion and QTBUG-56545 there, in case anybody from the CUPS
community wants to join...

As far as I know, the plan is to develop/use so-called "Printer
Applications" to allow using such functionality to work with new new API
without having to be done in CUPS itself, but that needs more work
elsewhere and does not "just work out of the box", so it would IMHO
still be a bit over-hasty to drop the use of the PPD API functions right
now, breaking existing printing use cases in practice.

Regards,
Michael

[1] https://github.com/apple/cups/issues/5271