Re: New module proposal: LightDM

[Robert Ancell <robert ancell gmail com>]

Thanks for the feedback Ray,

I hadn't considered if GNOME recommend more than one display manager?
I don't know.  I'm trying to align LightDM as a freedesktop.org
project closely related to the X server (and thus an external
dependency) with a GNOME greeter developed as a full GNOME project.

For some background, LightDM came from a weekend project after trying
to document the greeter<->daemon interface and I was trying to better
understand the interactions in GDM.

While I appreciate the use of a full session for the greeter has it's
advantages, I'm not sure they're all necessary for the limited GUI
required in a greeter.  It really comes down to flexibility - I think
any capable application developer should be able to develop a greeter
(with a full session if required) without needing detailed knowledge
of how the display manager works.  I had been trying to get this
interface into GDM, but I'd come to the conclusion that the
architecture of GDM is overly complex and that holds back innovation.
The weekend project confirmed to me that we can have all the same
features without the complexity.

I am talking with other projects and trying to get people working
together.  I'd like to see the fragmentation in display managers
reduce so we can look at the daemon as the boring reliable bit and
have people go wild designing new interfaces!


On 22 October 2010 16:17, Ray Strode <halfline gmail com> wrote:
> Hi,
>
> (speaking as one of the 3 maintainers of GDM)
>
> On Thu, Oct 21, 2010 at 12:02 AM, Robert Ancell <robert ancell gmail com> wrote:
>> - The GDM greeter is slow due to it loading the GNOME session, the
>> example GTK+ LightDM greeter is very lightweight (so is comparable to
>> the speed of the old GDM and newer display managers like LXDM).
> Using GNOME session / g-s-d /etc  is one of GDMs main features.  The
> point is for there to be consistent experience on the login screen and
> in the session.
> If GDM is too slow because of GNOME session then GNOME session needs
> to be fixed, otherwise login after GDM will be too slow too.  Anyway,
> if gnome-session is slow on your machine we should start by profiling
> it and figuring out why.
>
>> - The GDM greeter has very limited themeing capabilities.  A
>> contributor to LightDM (PCMan) was able to quickly write a new greeter
>> that used GtkBuilder and provided comparable themeing support to the
>> old GDM.
> GDM uses the standard theming mechanism as the rest of GNOME.  This a
> good thing.
>
> Making GDM use GNOME components and integrate with GNOME is not a bad
> thing. It used to not do that and was explicitly changed...
>
> Of course, things will need to be rethought about in a post- GNOME 3
> world (use mutter / clutter?)
>
>> - While it is technically possible to write an alternate greeter for
>> GDM, in practise it is too difficult.  LightDM has been designed from
>> the start to make writing a greeter no harder than a standard X
>> application.
> Granted, the interface between greeter and daemon isn't
> as clean as it could be.  Still,
>
> 1) it's obviously not too difficult, or there couldn't be one
> functioning greeter
> 2) When writing a new greeter becomes a priority to someone, the
> interface is completely changeable. It's a private interface so it can
> be changed in any way that's needed.
>
>> - All X server users have pretty much the same requirements beyond the
>> login GUI.  By using LightDM the development effort of maintaining the
>> display manager can be shared between projects (GNOME, KDE, LXDE,
>> XFCE).
> So you're not proposing LightDM to become part of GNOME, you're just
> proposing GDM get dropped and LightDM become an external dependency?
>
> Have you talked to the other projects about this?  We had some
> discussions some time back with Oswald (KDE developer) about
> standardizing on one display manager a few years ago:
>
> http://mail.gnome.org/archives/gdm-list/2007-October/msg00013.html
> (added him to cc list)
>
> Anyway, I'm obviously in favor of keeping GDM in GNOME.  I admit it
> has some baggage (some of it removed and added back later by popular
> demand), but overall GDM is in really good shape as a project.. FWIW,
> your various patches over the years have been a part of getting GDM to
> where it is.
>
> --Ray
>