lightdm or gdm?

[Sebastien Bacher]

Hey there,

That's a topic that was mentioned during the meeting yesterday and
something we need to decide on early in the cycle since there is going
to be work needed on that front to have a fully working session.

I'm doing a small summary of what I think are the pro (+) and con (-) of
each

* lightdm

+ well tested in Ubuntu
+ we have people in the team knowing the codebase
+ shared with other flavors/greeters selection
+ guest session
- divergence from upstream
- we are the maintainers so it's more work for us
- gnome-shell uses gdm for its lockscreen so work is needed to make it
work with lightdm

* gdm

+ that's the GNOME solution, works today with wayland & gnome-shell
- we started lightdm because we found the gdm codebase not easy to work
on, that might still be true
- ?keeps an active session from the greeter even after logging which
uses resources? (it was mentioned on IRC, to be confirmed, is that
needed due to the lockscreen?)
- no guest session, we need to work on that or decide to drop the
feature from Ubuntu


I talked a bit with Robert yesterday who said he could make lightdm use
the gdm greeter (he has some work started on that a few cycles ago)
which means it could be used as GNOME lockscreen instead of gdm. He's
probably the best placed to comment on the work and pro/con of the
solutions though so I'm going to let him go into the details when he
replies.

Cheers,
Sebastien Bacher