[Oneiric-Topic] LightDM for display management

[Robert Ancell]

Last cycle I proposed using LightDM to replace GDM [1].  It was deferred
due to the Unity work, so time to repropose!

The main reasons for switching are:
- Simpler code to maintain (GDM is a huge ~50,000 line C program and we
carry 36 patches.  LightDM is nearer 10,000 lines of C).
- More flexible greeter development - greeters are as easy as X
applications to write, which means we can have an Ubuntu specific
greeter that without branching the rest of the code
- Speed improvements - we can run a greeter without running a full GNOME
session
- Display manager can be shared with Kubuntu, Xubuntu, Lubuntu etc but
still allow each distro to have their own greeter.

The current state of LightDM is "80% done" I would say.  The core
architecture is all there, and it just needs a few weeks of solid work
to make it shine.

[1]
https://blueprints.launchpad.net/ubuntu/+spec/packageselection-desktop-n-display-manager