xfce4-session: xfwm4 removed from session, not started on login

[Chris Bainbridge]

Hello,

I decided to try and track down the infamous bug that causes xfwm4 to
not be running on login (for details see links at end of email):

XFCE Bug #5379 suggested that it was related to multiple applications
requesting an interact with the session manager. I found the cause of
this (in this particular case) to be that xfwm4-session disconnects
xfwm4 and then the session is recorded with no xfwm4, so on next login
there is no xfwm4. I have posted a patch for this to bug #5379.

Questions:

1) Can someone verify that my patch to #5379 is correct, and if so, commit it?

2) Is there any way to ensure that this never happens again? I'm
thinking that xfwm4 (and perhaps some others) is so important that it
should always be started regardless of the previous session contents,
unless the user has explicitly configured an alternative session
manager. This could be hardcoded in the session init code, but perhaps
XFCE already supports such an "essential apps" list? It seems a poor
design that xfwm4 can be disconnected from the session manager, won't
reconnect, and the user loses window manager forever. If the user is
unable to focus and type on a terminal, then the process to manually
restart is involved (switch to a console, and either rm the session
file and login again, or restart xfwm4, go back to desktop and run
xfwm4 --replace again so this time it picks up the $SESSION_MANAGER
variable and will get stored in the cache on next logout.)

https://bugs.launchpad.net/ubuntu/+source/xfwm4/+bug/495361
https://bugs.launchpad.net/ubuntu/+source/xfwm4/+bug/978333
https://bugzilla.xfce.org/show_bug.cgi?id=8070
https://bugzilla.xfce.org/show_bug.cgi?id=5379
http://forum.xfce.org/viewtopic.php?id=5707 - According to the 'known
bugs in 4.8' thread: "it's by far the most frequent xfce bug as I can
see in help section of different forums. It's very easy to recover
from it but, for users who don't know the xfwm4 magic command, it's
seen as a catastrophe."