Re: New module proposal: LightDM

[Ray Strode <halfline gmail com>]

Hi,

(speaking again as one of the three GDM maintainers)

On Fri, May 13, 2011 at 8:59 AM, Robert Ancell <robert ancell gmail com> wrote:
> Why replace GDM?
>
> - LightDM is a cross-platform solution.
What platforms does LightDM support that GDM doesn't?  Are they
platforms GNOME is targetting?  Not sure this is necessarily a win
without knowing more details.

> Ubuntu is planning to switch to it this cycle,
Sure, and I can see how that decision may potentially make sense for
Canonical (you would be able to offer in-house expertise, better
control over unity integration etc etc.)

>  By sharing this piece of infrastructure GNOME can spend
> more time working on important GNOME components.
So you're saying, we could stop working on GDM, Brian, McCann and I
could leave the login screen to you to handle and we could use the
extra time we got to work on other parts of GNOME?  There's no
question that we're all busy, for sure, but let's look at the "big
things" (modulo small patch review, security errata, etc, that would
exist in both projects) needed for GDM:

1) Landing the multiple simultaneous pam conversations branch of GDM
so you get sane behavior in the presence of smartcards, fingerprint
readers, etc.  This lets you swipe your finger, insert your smart
card, or whatever while sitting at a enter password prompt.
2) Giving GDM a more of a GNOME 3 look and feel (as per the mockups
you already mentioned elsewhere in the thread)
3) Better support starting a login screen dynamically a keyboard,
mouse, and display show up ("multi-seat").  Also, see the work Lennart
and Kay are discussing lower in the stack to help facilitate some of
this.
4) Figuring out how GDM,  screen locking, and the shell all fit together

I don't think LightDM will help us with any of these 4, will it?

> - I am confident that the LightDM architecture is simpler than GDM.
There are certainly parts of the architecture of GDM that could be
cleaned up, and that would be a worthwhile thing to do.
I don't see why it should get replaced though.

>  Architecture can be a personal opinion, and I encourage those with
> programming experience to look at the code and decide for themselves.
Right, coding style  is definitely a subjective thing. And everyone will
have their own opinions.

> Note that LightDM is not lighter in features, but in architecture.
And a different focus, right? GDM is firmly a GNOME project, designed
to integrate and work well with GNOME.  LightDM is designed with the
idea of being more generic right?

> - By having a well defined interface between the greeter and daemon,
> it is significantly easier to develop a greeter without knowledge of
> how display management works.  This is useful as the skillset and
> motivations of these two sets of developers are different.
Not sure how much of a selling point "multiple greeters" is, but GDM's
architecture allows for it.

Dr. Mo even did one apparently:
http://doctormo.org/2011/04/12/how-to-make-a-gnome-login-screen-in-python/

Anyway, we own the code. GDM is GNOME's project.   it's imminently
fixable.  If an interface isn't ideal, we can change the interface.
We have the ability to do whatever we want or need to do.

> - LightDM is a platform for future work and is investigating the use
> of new technologies like Wayland.
Wayland is really cool. It has the potential to let us ditch the junk
unix VT system, and potentially to get us away from X.  Krisitian is
an amazing programmer and wayland is no doubt the future in my mind.
GDM will happily jump on that bandwagon when its time to.

Anyway, I'm obviously of the opinion we should stick with GDM.  There
just doesn't seem to be a good reason to switch.

--Ray