[bug#75270] [PATCH 1/3] services: greetd: Improve greeter configurations.

[Nicolas Graves via Guix-patches via <guix-patches@gnu.org>]

On 2025-01-03 20:08, muradm wrote:

> Nicolas Graves <ngraves@ngraves.fr> writes:
>
>> On 2025-01-02 01:53, muradm wrote:
>>
>>> This improvement focuses on providing common user session 
>>> scripts
>>> for use by multiple greeters. It also fixes incorrect use of
>>> `XDG_RUNTIME_DIR` for `wlgreet`. `wlgreet` requires compositor 
>>> to
>>> run. We provide common sway based greeter script, which can be
>>> shared by other graphical greeters.
>>
>> [...]
>>
>>> +(define (make-greetd-sway-greeter-command sway sway-config)
>>> +  (let ((sway-bin (file-append sway "/bin/sway")))
>>> +    (program-file
>>> +     "greeter-sway-command"
>>> +     #~(begin
>>> +         (let* ((username (getenv "USER"))
>>> +                (useruid (passwd:uid (getpwuid username)))
>>> +                (useruid (number->string useruid))
>>> +                ;; /run/user/<greeter-user-uid> won't exist 
>>> yet
>>> +                ;; this will contain WAYLAND_DISPLAY socket 
>>> file
>>> +                ;; and log-file below
>>> +                (user-xdg-runtime-dir "/tmp/greeter-xdg-rt")
>>> +                (log-file (string-append (number->string 
>>> (getpid)) ".log"))
>>> +                (log-file (string-append user-xdg-runtime-dir 
>>> "/"
>>> log-file)))
>>
>> Could you explain why this is necessary?  If I'm not mistaken, 
>> we didn't
>> used a special runtime dir in RDE, and it worked OK.
>>
>
> When you start sway, it has to put WAYLAND_DISPLAY somewhere. By 
> default it is put to `/run/user/<uid>`. However greeter is special 
> limited user which is used to run without logging in. Because of 
> that, `/run/user/<uid>` is not created by PAM mount. For special 
> purpose we can use any XDG_RUNTIME_DIR. Sway does not support 
> specifying location of WAYLAND_DISPLAY as far as I remember (I was 
> opening an issue about it long ago, still was not resolved).

IIUC, it's because of PAM mount execution order that this happens?  So
there's also no need for that for people that don't use PAM mount.
Maybe completing the comment as "/run/user/<greeter-user-uid> won't
exist yet due to PAM mount execution order" comment would make that
clearer?

Is the logfile here the one logging everything Sway?  Could you make the
logfile configurable or is that not possible due to unguaranteed dir
existence due to PAM mount?  We are making an extra effort to locate
logfiles in the same dir in RDE. (I could also try and make a symlink a
posteriori to the right dir).

-- 
Best regards,
Nicolas Graves