David Edmundson david at
Tue May 17 23:06:47 UTC 2011

Hey all,

I stumbled upon your blueprint plans for use of LightDM in Kubuntu 11.10,
and as the person who has written most of LightDM-qt so far I wanted to add
some opinions and an update on where the lib is.

Firstly if you're going to discuss LightMD, it would have been nice to have
been notified.
There's so much I intend to get done with it, but I've been really busy
trying to get KDE Telepathy out. It's all already consuming far more time
than I really should let it.

Anyway. What's the current state and what needs to be done:

Robert Ancell (the main LightDM guy) has been refactoring the backend, which
has led to some changes in the Qt lib which I'm not 100% happy with. Instead
of just jumping on dbus, we now have a lot of GTK lib copying+pasting with a
thin Qt wrapper in the main class of the greeter. At a minimum I want this
moved out to a separate private class to give a very clean maintainable
header to the publicly exposed main lib. Ideally we'd want someone like
George Kiagiadis involved who is extremely pro at auto-building Qt bindings
for GTK and get a library that isn't going to fall apart as soon as the GTK
version updates.

I have a far better demo greeter on kde's git repo than the one in bzr repo.
I'll try and merge that.

I want to give it a really significant refactor that switches the lists of
LdmSessions, LdmUsers, and Langauges to be Qt models.  I also want to expose
the power management parts as Q_PROPERTIES.  I did start this a while ago,
it's not finished but if I worked on it, I could get it done. This not only
makes GUI's quite a bit quicker to build, but will make plasma bindings very

It was started by me a year ago, and I wasn't as familiar with KDE
standards/lib consistency as I am now. It's not bad, but it's far from
perfect. I would really appreciate it if you could give me a month to
completely tidy up all the crap up to make it decent ABI stable code.

As for plasma:
With my LibLightDm-Qt hat on, I will absolutely support everything you do
and will do anything I can to make the library really easy for you to use,
let me know and I'll do what I can to update the lib.

With my generic developer hat on, using plasma is an ill-thought through
idea. To me it seems you've jumped to the solution before you've worked out
what problems you're trying to solve are. I also believe it's a security
risk, will lead to slow load times and potentially unstable login screens. I
think it will lead to a lot of future problems. I have an alternate (pure
QML-oriented) scheme in mind that allows for
greater flexibility/theming with a sensible KCM that I think is pretty
solid. However I'm not one for arguments, and LightDM does allow for
multiple greeters (both built off the same greeter lib) really easily so we
can easily do our own thing.


David Edmundson
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