[RFC] Merging LightDM into KDE Workspaces

[David Edmundson]

As you're all probably aware I've been working on a new login manager
for KDE [1]. Currently known as LightDM-KDE, named as it is based on
the display manager backend LightDM [2].

I've just released 0.3, and it's mature enough that Kubuntu are
choosing to have it as their default display manager in their next
release. This isn't a decision forced by Canonical, they just think
it's better, though obviously it helps that the backend is already
tested on Ubuntu. Other distributions have also expressed an interest,
or ship it already. I therefore need to move out of Playground to
somewhere more "official"

It was always my intention to merge into KDE Workspaces, so the
purpose of this thread is to make it clear that I want to do so and to
work out together what steps still need to be done in order for that
to happen.

Obviously replacing any KDE application is a bit of a contentious
issue, especially given that KDM still works adequately, though
obviously I do feel mine is better. What I would like to do is discuss
moving LightDM into KDE workspaces _alongside_ KDM and making
compiling KDM optional, but keeping it enabled by default.


Features LightDM-KDE has that KDM does not:
 - Guest support login
 - Use of plasma components makes it fit in with workspaces better
 - Ability to make customisations such as changing the background
without having to edit XML
 - An easy to use KCM
 - Suspend when lid closed
 - Active development
 - Upstream supported backend with extensive unit tests
 - Wayland support imminent (all done upstream). KDE/Greeter has
_almost_ no X specific code.

Features KDM has that are still missing in LightDM-KDE
 - ability to switch X sessions
 - connect to remote XDMCP sessions
 - Get hot new stuff/theme installer
 - Ability to reboot into a different grub entry(not that that
actually works for me)


What's coming in the future:
 - a big refactor (see branch "big_refactor")
 - making X specific code in the greeter a compile time option, making
us totally Wayland ready (when the backend is)
 - everything important KDM has :)
 - better support for alternate login mechanisms (currently both KDM
and LightDM-KDE suck)

I'm sure many of you will have questions "why was this decision
made?", so I've written out my design rationale on all big topics here
[4] I've put it as a link partly because it's more for documentation
than for discussion as it's all in the past and partly because this
email is already really really long :)

[1] https://projects.kde.org/projects/playground/base/lightdm
[2] http://launchpad.net/lightdm
[3] http://http://www.sharpley.org.uk/blog/lightdm-0_3 ,
http://http://www.sharpley.org.uk/blog/lightdm-0_2,
http://www.sharpley.org.uk/lightdm-google-authentication,
http://www.sharpley.org.uk/blog/an-update-on-lightdm-kde
[4] http://static.davidedmundson.co.uk/lightdm_design_rationale.html

Regards

David Edmundson