CUPS Printers not found in GTK applications

[wkral]

Describe the bug
Printers which are configured and working in CUPS do not show up in the print dialog of GTK applications. Previously there was a Print to file (PDF) printer option which is no longer present. Notably Firefox and Evince are effected.

I am using Sway as my window manager which may be relevant, but printing worked previously.

I tested with Okular a QT application and it does still have all the printers available to it including print to file.

To Reproduce
Steps to reproduce the behavior:

1. Enable printing as configure a printer with CUPS
2. Open a GTK application and attempt to print a document
3. Notice the print dialog has no options to print

Expected behavior
See configured printers in the print dialog as well as the Print to File (PDF) option.

Additional context
Relevant sections of `/etc/nixos/configuration.nix:

  # Enable CUPS to print documents.
  services.printing = {
    enable = true;
    defaultShared = true;
  };
  services.avahi.enable = true;
  services.avahi.nssmdns = true;
  programs.system-config-printer.enable = true;

Metadata

• system: "x86_64-linux"
• host os: Linux 5.2.16, NixOS, 20.03pre193829.f0fec244ca3 (Markhor)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3
• channels(root): "nixos-20.03pre193829.f0fec244ca3"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[matthewbauer]

Perhaps dbus is not started properly? My printers are showing up for firefox & evince when launched through plasma5.

[wkral]

@matthewbauer thanks for the suggestion, unfortunately it didn't solve the issue for me. I just tried running sway with dbus-run-session sway and printers still aren't showing up.

[wkral]

Some further information, I just rebooted into the last configuration I had for NixOS 19.09 on the unstable channel and printing is working again. So this seems to be related to the update to 20.03. Perhaps there was a GTK upgrade or something else major introduced in that time?

[worldofpeace]

#69434 Fixes this

[fx-chun]

I am still experiencing the issue unfortunately :( Printers still do not show up in GTK applications (e.g. firefox, evince), even with #69434 . I am using i3 as my WM, is that relevant?

[worldofpeace]

@noneucat Can you paste nix run nixpkgs.nix-info -c nix-info -m?

Are you using the configuration mentioned in the issue?
This would actually be an issue with the system-config-printer application.
So are you using programs.system-config-printer.enable? Which I believe is the GUI program that also provides the service for other applications for printing. It would also be best to limit tests to that program since evince and firefox are just interacting with it over DBus.

To get the proper info from DBus you can maybe do

 dbus-monitor --session "interface='org.fedoraproject.Config.Printing'"

while you interact with it for some info.

The original report here said

Notice the print dialog has no options to print

So you've established there's no options in here?

[fx-chun]

@worldofpeace Yes -- no options appear in the print dialog for evince or firefox even after setting programs.system-config-printer.enable:

system-config-printer does list the printer as expected:

I am not using the configuration listed in the original report. Relevant part of my config:

  services.printing.enable = true;
  services.printing.browsing = true;
  services.printing.drivers =
      with pkgs; [
      gutenprint
      gutenprintBin
      samsung-unified-linux-driver_1_00_36
      ];
  services.samsung-unified-linux-driver_1_00_36.enable = true;
  programs.system-config-printer.enable = true;

System information:

 - system: `"x86_64-linux"`
 - host os: `Linux 4.19.76, NixOS, 20.03.git.7ff17ce (Markhor)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3`
 - channels(root): `"nixos-19.09pre191505.7d5375ebf4c"`
 - channels(noneucat): `""`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

No activity on DBus related to printing while I interact with it:

~ % dbus-monitor --session "interface='org.fedoraproject.Config.Printing'"
signal time=1570247967.542757 sender=org.freedesktop.DBus -> destination=:1.34 serial=2 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=NameAcquired
   string ":1.34"
signal time=1570247967.542786 sender=org.freedesktop.DBus -> destination=:1.34 serial=4 path=/org/freedesktop/DBus; interface=org.freedesktop.DBus; member=NameLost
   string ":1.34"

[worldofpeace]

@wkral I'm seeing there's an add button. It appears system-config-printer is listing a printer to be setup and configured because it's detected. Have you configured the printer?
I know at least, this can be confusing with NixOS being declarative.
(an aside, we do have declarative printers)

[wkral]

@worldofpeace Yes my system-config-printer app found the printers that were already configured in cups through the web interface as well. The symptoms @noneucat is showing appear to be identical to mine.

I left this issue open because the #69404 fixes haven't made their way into master yet as staging-next hasn't been merged in since you added the fix there. Builds have been failing for trunk-combined for a week and a half or so. I figured with the 19.09 release going on those things would be resolved in time so just being patient.

It might be more urgent for @noneucat but I've just been booting into my earlier config to print, it's not an everyday activity for me.

[wkral]

@worldofpeace Sorry, I think I gave some bad information on Friday. I do see your fix included in master, I was in a detached head position on my repo from working on another issue and didn't realize.

I did a rebuild against my local copy of nixpkgs today and I still have the issue even with your fix in place. So maybe it's something else causing the issue.

system-config-printer has always worked for me though for whatever reason I don't have icons showing in that application, though that's probably a different issue.

If you have any suggestions on how to diagnose the issue I'm happy to help I don't have a great deal of knowledge about the working of dbus, but I can run stuff on this configuration.

As far as the declarative printers goes, I did notice that feature was recently merged as it came up while I was investigating this issue. It doesn't seem to affect printers set up by other means so I was hoping to give it a try after resolving this issue.

[wkral]

Since 19.09 was released today I tried switching to that channel off of unstable and it fixes the issue for me. It would seem something is different between the two channels. Maybe that helps narrow things down but there is already quite a difference between the two. Nothing jumps out doing a git diff 19.09 --stat maybe it would for someone with a bit more knowledge.

[doronbehar]

@worldofpeace thanks for pointing me to this issue from discourse. I'm trying to track this down. It seems cups support is enabled by default for Linux systems:

nixpkgs/pkgs/development/libraries/gtk/2.x.nix

Line 4 in ea79aba

, cupsSupport ? config.gtk2.cups or stdenv.isLinux, cups ? null

However, I've found this interesting Link:

https://wiki.debian.org/CUPSDriverlessPrinting#CUPS_2.2.4_and_the_GTK_Print_Dialog

@wkral do you use a driverless printer setup with cups? I get the following error in CUPS' web interface when adding a printer with a certain PPD file:

The Arch wiki points that this issue is a cause of nss-mdns not configured properly. Although I'm rather sure nss-mdns is configured properly on my machine (as a proof, cups does find my network printer) this troubleshooting hint indicates the debian's wiki page statement:

The print dialog of GTK applications such as firefox and evince does not function in the same way as the Qt and Libreoffice dialogs. It obtains queue and printer information directly from DNS-SD broadcasts and not through CUPS, so it has no knowledge of what CUPS 2.2.4 and later are capable of doing.

Is correct.

Anyway, I didn't figure out yet why / how editing cups-browsed.conf should solve this as debian's wiki explains. I tries using either both / one of:

  services.printing.browsedConf = ''
    CreateIPPPrinterQueues driverless
    CreateRemoteCUPSPrinterQueues No
  '';

But it didn't make any difference.

[doronbehar]

Update: I've found an evidence I'm not the only one experiencing the "Unable to copy PPD file" error:

https://bbs.archlinux.org/viewtopic.php?pid=1861730#p1861730

On NixOS, I've managed to copy the ppd file from the store, gzip --decompress it, and fix it by removing every line containing "Custom" at the beginning of it. I've filled a bug report to hplip: https://bugs.launchpad.net/hplip/+bug/1847563

Never mind that, this doesn't have to do anything with what printer driver / ppd is used..

The problem is that GTK isn't able to locate printers using DNS-SD. It doesn't even use CUPS at all.