LightDM and Xscreensaver

LightDM tweaking (Xubuntu and Vsido)

LightDM tutorials are quite nicely googleable so - the following is simply chaotic list of things I checked and investigated, and not a 'howto'. AND - this time I didn't do almost a thing, so the story is mostly hearsay. (26.04.2013 - a bit less hearsay now, see Edit below. Which is further edited 10.05.13.)

Important places
/etc/X11/default-display-manager - here you can see which display manager is your default. Quite good to know before starting hacking or swapping it to some other one.
/etc/lightdm/lightdm.conf - here you can add allow-guest=false, and very probably something even more interesting ...
/etc/lightdm/lightdm-gtk-greeter.conf greeters' GUI-related things are here, like background picture (png seems to be the only acceptable format).
By default it sits in /lib/plymouth/themes/xubuntu-logo/ for Xubuntu and in /usr/share/images/desktop-base/ in Vsido. It is a symlink managed by update-alternatives. And it is sayeth: 'So, to change the greeter's background, the best way is to find some images that you like from /usr/share/images/desktop-base/, then use update-alternatives to change the desktop-background group: update-alternatives --config desktop-background' ... And I might add, there is also GUI front-end for that tool: 'galternatives' is the name, download & install (less button-pressing compared to CLI-version).
Once more: Removing un-needed sessions from greeters' menu. Sometimes it's not wise to uninstall all your (backup) sessions...
And then I happened to read of someone who had problem with default greeter sessions - it kept hopping back to first installed one. He did so: /usr/share/xsessions/lightdm-xsession.desktop. Edited lightdm-xsession.desktop - changed "exec" from "default" to "startxfce4" - meant that when he had "Default XSession" selected at the login screen, it started then xfce4 instead of "default".

Short look into lightdm-gtk-greeter.conf (Xubuntu):
logo=/usr/share/pixmaps/xubuntu-lightdm-computer.png 
background=/lib/plymouth/themes/xubuntu-logo/xubuntu-greybird.png 
theme-name=Greybird 
icon-theme-name=elementary-xfce 
font-name=Droid Sans 10 
xft-antialias=true 
xft-dpi=96 
xft-hintstyle=slight 
xft-rgba=rgb 
show-language-selector=true
As is seen, there are quite interesting possibilities here ...  
| EDIT (26.04.2013): First line, 'logo' doesn't work in Debian Sid (I do not know about Xubuntu. But probably it does - this bit of code is taken from Xubuntu). In Debian the icon has to be changed in file /usr/share/lightdm-gtk-greeter/greeter.ui
|added: With unfreezing of the Debian came also new version on Lightdm... which doesn't have greeter.ui file anymore. It's told that it's in-built now. Means, you can take source, change glade file and rebuild your Lightdm. A hassle, I would say... Also - latest iterations of Lightdm (Debian Sid) doesn't have session chooser anymore. One can pick them from upper menu, as 'default'. Really idiotic... add ends|
Object is quite at the beginning of file and it's id is image1, icon_name probably 'computer'. Greeter seeks it in usr/share/icons/gnome/256x256/devices/ - put your new icon there and do sudo gtk-update-icon-cache /usr/share/icons/gnome. Edit greeter.ui - replace 'computer' with name of your new icon (NO png!). Save, logout / login.
PS! I found such address: ... icons/hicolor/64x64/devices/ in web. It wasn't so for me, but might be so in some other configuration.
Second line, background, is OK and works. Probably even when you simply stick your new file into proper folder. I did it through 'update alternatives'. The file probably HAS to be png.
Third line, theme. In version of Greybird I have in Debian, things seem to work, but not entirely. Needs further investigation. Xubuntus' lightdm.css under its Greybird, of the contrary, does everything right. EDIT ENDS |

lightdm.conf has only 2 lines by default - and those are  not good to play with. But here goes this added 'quest...'.
[SeatDefaults] 
greeter-session=lightdm-gtk-greeter 
user-session=xubuntu 
allow-guest=false
Playing around  with those things should make something change. Beware.

Xscreensaver

It seems to be very much default in most distros. And its lock screen is ugly like hell.
In Xubuntu it's slightly tweaked, but still ugly.
In Vsido - all natural - it looks like hairy pile of crap.
Unfortunately, it's also quite difficult to tweak - for example, the picture seems to be the holy grail of Xscreensaver dev-people. They do not want it changed and have secreted it away. I didn't find it at all.
What I DID find:
In you home folder is file .xscreensaver... Alas, there isn't anything overly exciting in this one...
What you have to do is: make a new file named .Xdefaults (in Xubuntu you already have it) into home folder. And fill it with Xscreensavers' parameters.
Alas, I am not going to put this file here - it's not short and has silly wide formatting  - but, the best way to proceed is to use Xubuntus' default tweaked file. Simply copy it to your ~/home/username/. It works in Debian without any problems. That I have tested.
And then, having the base file - tweak away. And I haven't tested that yet -very much, except that the code is, of course, nicely touchy for mistakes, and presents interesting yellow error messages.