Help with investigating a bug in the LightDM/logind/DDX stack

[Yves-Alexis Perez]

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Hi systemd/logind maintainers.

I'm reaching out to you about a bug (#1038611) reported in LightDM which is
likely somewhere else in the stack (maybe in logind or maybe in Xorg or the
DDX).

With the update to 1.32 some people experienced an issue where LightDM
wouldn't start. At first it seemed linked to people using NVidia binary
driver, but we also had one user on a RaspberryPi 4.

Some investigation linked that to a option in lightdm.conf whose default value
changed with 1.32. That option is `login-check-graphical` and seems to check
if the seat (reported by logind) is marked as graphical or not.

Adilson checked and indeed on their installation seat0 is not marked as
graphical:

> logind-check-graphical=true
> loginctl show-seat seat0
> Id=seat0
> CanTTY=yes
> CanGraphical=no
> Sessions=
> IdleHint=yes
> IdleSinceHint=0
> IdleSinceHintMonotonic=0

I'm not sure why and I guess it's a bad interaction between logind and the
graphical system or something, but I'm not too sure how to investigate more,
so I'm adding you to the loop in case you can shine some light.

At this point I don't think it's a bug in LightDM but since I'm not sure where
the bug is, let's not reassign just yet.

Regards,
- -- 
Yves-Alexis
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