Arch Linux

Forgot to mention, Dell Inspiron 7348, fully updated against [testing].

I have no clue how libcups can grab or prevent keyboard input events. Are you sure this is the reason? We had other related updates (libinput/xf86-input-libinput and more).

Yep, totally weird.
Just noticed something else:
With libcups 2.1.4-2 installed, xev (xorg-xev) shows nothing when volume keys are pressed, but volume works.
With libcups 2.2.0-1 installed, xev display the expected keycodes (XF86AudioRaiseVolume, XF86AudioLowerVolume, XF86AudioMute), but nothing happens.
Perhaps some weird Gnome issue?

Only thing I can think of is libcups going into infinite loop. In gnome 3.20 all plugins for gnome-settings-daemon are in-process, so if libcups goes into a loop then the media keys plugin will not work.

Can you please try to downgrade cups-filters from 1.11.3 to 1.11.2 and see if this solves it?

cups-filters wasn't even installed, so I installed the package and all of the following combinations do not work:
- libsups 2.2.0 + no cups-filters
- libcups 2.2.0 + cups-filters 1.11.2
- libcups 2.2.0 + cups-filters 1.11.3

You can try asking on the cups user mailing list what this could be. Maybe running commands with strace might help.

https://github.com/apple/cups/issues/4870
https://bugzilla.redhat.com/show_bug.cgi?id=1366775

Seems libcups goes into endless loop when cups is not running on localhost. This can happen when cups is not installed or when cups is disabled in systemd (systemd will launch cups on connect if it's installed and not disabled).

https://bugs.linuxfoundation.org/show_bug.cgi?id=1376 - not sure if this is the same bug or a different one.

libcups 2.2.0-x breaks libreoffice for me in opening documents and stalls forever.
Seems it goes into a loop there too. Also a machine with no cups server running, only libcups installed.
Other machine with full cups setup does not show this hang. Weird.

libcups-2.2.x removes /etc/cups/client.conf which is needed to launch libreoffice for me.
Why was this file removed?

/etc/cups/client.conf is a deprecated way and not supported and not recommended by upstream. You are highly recommended to run a local cups server on your system if you want to print (also if there's no local printer but only remote printers). This is all in our wiki and in the man pages. There was also some discussion on the cups mailing lists.

Having libcups for dependency without running a local cups server leeds to infinite loops and weird behavior caused by https://github.com/apple/cups/issues/4870. You should be able workaround it with
setting up a local cups server and use cups-filters 1.11.3-2.

Hello Andreas (Radke),

seems you are right. I installed fresh versions of cups (cups 2.2.0-2, libcups 2.2.0-2), cups-filter (1.11.3-2) and ENABLED and STARTED org.cups.cupsd.socket (though I don't have any printer connected to that linux box). After I restarted samba and gnome-settings-daemon (it was affected too) all seems fine, both samba and gsd don't load at very high the CPU.

If I understand your last sentence correctly this configuration (installed both libcups and cups and explicitly enabled and started socket or service for cups) is only a workaround and not standard way to work with cups. Otherwise samba and gnome-settings-daemon have to depend on both libcups and cups and to require to start cups server (either using socket activation or just service).

If this is so why libcups is still used and not replaced by cups itself, with an install message, which shows this change?

This way people are forced to run a service which is not needed at all if you have no printer in your environment.

Please try libcups 2.2.0-3. It should fix the endless loops when not running a local cups server.

On my side:
cups 2.2.0-3, libcups 2.2.0-3, stopped org.cups.cupsd.service, org.cups.cupsd.socket, disable the last one and removed /run/cups/cups.sock. After that I restarted samba service and gnome-settings-daemon, all works fine without high CPU load.

libcups 2.2.0-3 fixes the libreoffice hang for me. Thanks!