Yep, just tested it.
I'm trying to make a wahcade session that loads automatically from gdm for my cabinet. The reason I want to do that is because it shaves a couple of seconds off the boot time and completely hides the OS, so no mouse cursor or anything.
Wahcade loads if you do this but it crashes if you try to go into a menu or start mame.
If anyone else wants to try this for some other program this is how you do it in ubuntu (change name, comment and exec to whatever you want to load):
sudo gedit /usr/share/xsessions/wahcade.desktop
Then add this to the file and save it:
[Desktop Entry]
Encoding=UTF-8
Name=Wahcade
Comment=Arcade Front End
Exec=/usr/bin/wahcade
Terminal=False
Type=Application
Then you should have a new option on the GDM sessions screen.
I don't really know too much about the inner workings of linux so I have no idea if this will actually ever be possible or if there is a better way to do it, but it would definitely be great if it did work.
I currently have gdm automatically log in and load blackbox, which then runs wahcade from its autorun script. It works perfectly fine but the mouse cursor still shows for a couple of seconds.
This is my only niggle with wahcade, other than that it is perfect, so thanks again!