Martin "eto" Misuth:
First, there are two major caveats,
There are actually three. They break scripting. For example: People
cannot use the GNOME Editor as $VISUAL or $EDITOR because one of the
things implicit in the $EDITOR/$VISUAL mechanism is that when the
program that has been invoked exits, the editing is over and the file
being edited has been saved in the desired form. That is not the
behaviour of the "small and lightweight" GNOME Editor, however.
* http://unix.stackexchange.com/questions/201900/
* http://unix.stackexchange.com/a/323700/5132
* https://news.ycombinator.com/item?id=13056252
Other "interesting" problems result from the move that the Desktop Bus
and the Desktop Environment people are making away from per-session
instances of the D-BUS daemon to per-user instances of the same. This
causes fun with deciding what the daemon's $DISPLAY should be set to. A
per-session Desktop Bus obviously has one $DISPLAY by and large. But a
per-user Desktop Bus not only has to handle multiple logins from a
single user, it has to handle that the per-user session management can
be running when there's no X server at all. (systemd starts its
per-user instances via PAM hooks that act upon every login, including
logins over SSH and on terminals.) Even though some daemons try to take
the approach that the daemon supports multiple $DISPLAYs, sent in from
multiple clients as part of the client session, one unfortunately finds
that the daemons themselves still have to have an arbitrary $DISPLAY in
order to start up in their initial, not connected to any clients and
their displays yet, mode. In practice, thus, the implementation of the
user-wide client-server idea is half-hearted and flawed in this respect.
