[Bug 87960] installing compiz will make using metacity impossible (even after uninstalling)

[Jeff Fortin]

Public bug reported:

Binary package hint: gnome-session

It seems that debian & ubuntu include a patched /usr/bin/gnome-wm file,
which is part of the gnome-session package.

The comment at the top says:
# The user can specify his prefered WM by setting the WINDOW_MANAGER
# environment variable or setting the
# /desktop/gnome/applications/window_manager/default gconf key.
#
# If this is not set, we search a list of known windowmanagers and use
# the first one that is found in the users's PATH

The big problem is this: it will prevent metacity from being used if compiz is not avaible. To reproduce:
1- install compiz
2- use compiz, a gconf key /desktop/gnome/applications/window_manager/default will be set to "/usr/bin/compiz"
3- uninstall/purge the compiz packages
4- logout and try loggin into gnome: metacity will never start no matter what you do with your session

Looking at .xsession_errors, you see the reason: gnome-wm tries to call
compiz because it read the gconf key and did not check the binary
actually existed. This is completely crazy. If the binary is not
present, don't try running it, fallback to metacity! Actually, if
*anything* goes wrong, fallback to metacity!

Note: this hack is not present in "vanilla" gnome it seems:
http://svn.gnome.org/viewcvs/gnome-session/trunk/gnome-session/gnome-
wm?revision=4186&view=markup

Users can be locked out of their sessions because of this. I was lucky
to have nautilus-open-terminal and #gnome at gimpnet around.

** Affects: gnome-session (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed
** Affects: gnome-session (Debian)
     Importance: Undecided
         Status: Unconfirmed

** Also affects: gnome-session (Debian)
   Importance: Undecided
       Status: Unconfirmed

** Visibility changed to: Public

-- 
installing compiz will make using metacity impossible (even after uninstalling)
https://launchpad.net/bugs/87960