libs/kworkspace/kdisplaymanager.cpp mess

[Martin Briza]

Well, as I said last week, I started working on it.
First few commits are in branch mbriza/kdisplaymanager-split.
Currently, PLEASE, don't judge me for the KDMBackendPrivate class stuff.  
:) I have just cut that out of KDisplayManager, not really knowing what to  
do with it further. I'll try to merge it in the code tomorrow in a fashion  
that doesn't look so horrible and is shared only for the classes which  
really do need it.

I'm pretty sure it doesn't work in this state because all the  
initializations (and static storage of the pointers to the backends)  
aren't complete yet. But it at least compiles.

Regarding design:
I removed all OldGDM and OldKDM code.
In the end, it seems two backends will be needed:
  * One to communicate with something that manages sessions  
(systemd-logind, CK, the DM itself) to be able to switch them. I'm naming  
the classes <something>SMBackend - SM as for Session Manager.
  * The second to be able to control the DM to make it possible to command  
it to create a new greeter on an other VT. The classes are called  
<something>DMBackend - as for Display Manager.

Currently, I have added the following SM Backends: Null, Login1,  
ConsoleKit and Basic (contains all the previous code) and the following DM  
Backends: Null, DBus (previously called LightDM), Basic (again, with the  
old code).

What I'm not sure about are inheritance chains. I think it would be nice  
to be able to use multiple backends when it's possible, for example we can  
try to shut down the computer using systemd-logind, if it fails, there  
still can be CK and when both fail, there's still possibility to call  
shutdown directly.

Of course there's still a lot of mess left and coding standards aren't  
exactly followed but I'll fix that when the work is done completely.