CUPS Snap - Call for Testing

Fair enough.

Sounds like now this is going to be a completely standalone project rather than a patch ontop of GCC.

I am not familiar with Mohit’s code base (where it is etc) you are referring to. Please can you link to it here please.

Here we go:
The first link points to a branch which has only modifications for the main view (no change on the “Add Printer” part), the second has the same changes in the main view plus the Printer Application support UI in the “Add Printer” part, but this one not yet actually working, only UI demo.

Note that in these branches all commits from Mohit are at the top, so one can easily extract a patch with all changes. This I did for the G-C-C in the PPA.

For Ubuntu Studio, that’s already a non-starter as KDE Plasma is the desktop. For Edubuntu, it uses whatever is provided by the ubuntu-desktop-minimal seed, so I’m not worried there.

For KDE/Qt-based distros, as long as they do not change their printer setup tool (is there one in KDE’s Settings app?) a small separate program, like we had with system-config-printer, would probably the best stop-gab solution. To get this done re-using Mohit Verma’s work on GNOME Control Center would be to get it into a simple GTK application (libgtk would easily happen to be also on KDE/Qt-based distros as many apps use it).

@fossfreedom @rs2009 WDYT? Could we work together with Mohit, to get a simple GTK-based app which does not require significant parts of GNOME and especially not libadwaita?

There is, and I just gave it a test with the CUPS snap. Seems to work, although the driver seemed to default to the wrong tray, but that’s just a configuration error on my end.

EDIT: That might be an error. No matter how much I change the settings in the KDE system settings, they will not take. That’s a problem.

My concern at this point is that there’s no transitional package. The old CUPS .deb package (and its dependencies/recommends) was completely ripped-out of my system dev system without warning instead of transitionally installing the CUPS snap. To get things working again, I had to manually install the CUPS snap. This won’t affect new installations, but upgrades will be affected. I hope this is resolved soon otherwise we’re going to get a lot of bug reports from people who don’t exactly know what’s going on with regards to this thread.

The transitional package is high on my list and for sure Ubuntu 23.10 will come with it. I told earlier in this thread how this package will look like.

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That’s great news, and I indeed saw that above.

My concern isn’t that it won’t happen, my concern is that we get people testing things prematurely and open bug reports and then get anxious when things don’t get fixed in a timely manner and then get concerned that they won’t ever be fixed. Recently, I got a direct email practically scolding me for not attending to a bug (that wasn’t even within my purview to begin with) that was filed in May for something in mantic.

What happens is, when we get something that affects all flavors, people test before beta release and notice issues and file bugs, being unaware of threads like this. Most of the public assumes that official Ubuntu flavors are separate distributions with separate or additional repositories, which we know isn’t true. Theses people wouldn’t even think to look here for information regarding why, when they’re upgrading via do-release-upgrade -d (even though that’s unsupported) that they’re suddenly missing their printing system. This is when we get unnecessary bug reports (death by 1,000 papercuts) and angry direct emails.

My point is that, removing cups from the desktop-common seed prior to the availability of a transitional package was, quite frankly, premature and, to use a colloquialism, “putting the cart before the horse.”

(N.B. The issue about the public assuming that official Ubuntu flavors being separate distributions from Ubuntu is something I’ve been trying to combat for years since becoming a flavor lead. It’s something even my own team had to switch paradigm on.)


If you release an ISO without the old cups but only with the new snap cups it is obvious that users will open bugs because the new cups is incomplete and does not offer all the functions of the old one.

Hmm, there’s an update ?

@fthx OK, I was very busy, thanks for reminding me.

We have decided to revert to DEB-package based printing and move the switchover out to Ubuntu 24.10.

We are now already long after Feature Freeze and shortly before User Interface Freeze and the desktop integration has taken longer than expected. Especially also the needs of printer setup tools for the flavors need some additional time. Also GNOME Control Center is undergoing a major UI modernization and we need to merge with it. And for providing the Common Print Dialog backends in Snap, the session D-Bus support in snapd needs to get finally released.

To not do high-impact changes in an LTS we will skip 24.04 LTS and do the switchover in 24.10 at the earliest. For the time being I keep the DEB package as much in sync as possible with Debian’s packages.

I will continue coordinating the desktop integration on the upstream level with my Google-Summer-of-Code contributors and keep in touch with upstream on upcoming conferences (seems that next year I need to also attend Akademy?).

On the Ubuntu side I will concentrate on Ubuntu Core Desktop. This distribution is an immutable all-Snap distribution and requires printing and scanning support via Snap. In addition, it has no flavors (yet) and its first release is not earlier than the 24.04 classic Ubuntu release. So here we have enough time to finish the “Printers” module in GNOME Control Center (and that is all printer setup tool we need), to add CPDB frontend support to the GNOME content provider Snaps, to get the Chromium print dialog CPDB-enabled (perhaps also some others), to assure that Snaps of apps use the desktop portal for printing whenever possible, have the scanning support for Snap (Scanner Applications) ready, having Snap release automation in place …

Then when Ubuntu Core Desktop does its printing and scanning well, we will look into the classic Ubuntu, …

This way we avoid what we have seen with the Firefox Snap in Ubuntu 22.04 LTS and @local-optimum’s (in)famous 4 posts on the Ubuntu blog, which should not get followed by 4 posts by me.

But please, have the CUPS Snap in mind and in the time being I am on it and regularly publishing new stuff for testing, in my PPA and naturally also in Ubuntu Core Desktop. I will keep you posted in the OpenPrinting News.

Sorry for the inconvenience with this attempt to launch the switchover and for any disappointment that we will move out the switchover to later.


Thanks for these explanations.
So, if I do install snap cups stack along deb stack, the snap stack is preferred?

@fthx If you have both DEB and Snap of CUPS installed, your print environment is managed by the DEB, the Snap switches into the so-called proxy mode, working as a firewall for your DEB CUPS, so that applications installed from the Snap store cannot mess up your system’s CUPS.


I installed Mantic from the new ISO Ubuntu 23.10 “Mantic Minotaur” - Daily amd64 (20230825)
with cups .deb and i’m still unable to install a printer with gnome-control-center.

Problem solved installing from: Ubuntu 23.10 “Mantic Minotaur” - Daily amd64 (20230904.2)

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I may have missed something: every time I remove CUPS snap, it comes back maybe one day or two after. What causes this?

Perhaps it likes you very much ? :joy:


The CUPS Snap is used by any user application Snap which has print functionality, like LibreOffice or the Chromium browser for example. These Snaps plug the cups interface and this interface is provided by the CUPS Snap. Therefore they install the CUPS Snap as a dependency (a so-called content provider Snap, the same mechanism as GNOME or KDE apps install the respective library content provider Snap for GNOME or KDE).

If you have a classic CUPS (in Ubuntu via DEB packages) installed, the auto-added CUPS Snap goes into proxy mode, to work as a firewall to protect your system’s CUPS against user application Snaps doing something nasty (messing up your CUPS queues, spying on print jobs of other users).

So do not worry about a CUPS Snap being installed on your system, it is not your daily-driver CUPS managing your printers.

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Ok! So why my lovely CUPS snap is allowed to be removed?
Maybe it’s a deb-based argument but I don’t understand here why I was allowed to remove CUPS snap since some of my snaps depend on it. Is that what you mean with “content provider” ?

snaps do not have hard dependencies, I could fork and create a cups-ogra snap with a shiny patched cups version inside that magically operates 10x faster… this snap would then be able to be switched out against tills official cups snap without your apps noticing… this concept is for example used in the steam snap where you can replace multiple Mesa versions with different optimizations by switching channels of the graphics-core22 snap that provides the graphics drivers through a content interface.

That removing the last remaining content provider does not at least spill a warning should indeed be treated as a bug though, you should file it…