Session management - a question and answer dialogue


Q: What is a session?
A: A session is a set of programs. The set of programs that normally run while
   you're working could be called your "working session". Analogously, there
   may be a "hacking-on-scwm session", etc.

Q: What is session management?
A: Session management tries to preserve the state of your sessions while they
   are not active. That means that the state of all programs belonging to a
   session is saved when you suspend the session, and restored when you
   reactivate it. These actions normally happen on logout/login, but the same
   holds if you want to directly switch from one session A to session B: A is
   suspended, B is reactivated. The net effect is that, whenever you
   reactivate a session, you are in exactly the same environment as when you
   suspended it - the same files are loaded in the editor, the current
   directory in your terminal windows is the same, etc.

Q: But I want my session to on every restart!
A: That was not exactly a question, was it?

Q: Can I reset the session to some sane state?
A: Yes. Since you can save anytime, and to arbitrary session names, the way to 
   go is to checkpoint to another name when your session is in the desired
   "default state", and never write that session again. Whenever you feel the
   need, you can go back to this state of your session and start again from
   there. There is also the possibility not to save on session suspension.
   This gives you back the last saved state on reactivation. So session
   management offers additional options while not taking away behaviour that
   you have get used to.

Q: How does it work?
A: Programs supporting session management are instructed by the session
   manager to load or save their state. Unique IDs are used, so that you can
   have the same program running multiple times in the same or different
   sessions without clashing of save files.

Q: So what programs support this?
A: All Gnome applications should support this. A few programs from the X
   distribution do, too. Unfortunately there are a lot of programs anaware of
   session management. A proxy program is normally used to stand in for these
   applications, so that they can at least be restarted correctly. Internal
   state is not normally preserved in this case.

Q: What should the window manager do?
A: The window manager cares mainly about the state of windows - their
   geometry, whether they're iconified, etc. Exactly this kind of information
   should be preserved by the window manager. Settings internal to the window
   manager (e.g. key bindings) should also be kept across sessions, if
   appropriate.

Q: What is really preserved by scwm?
A: Right now (98-11-16) window geometry, icon position, desk number, and the
   following flags are preserved: iconified, keep-on-top, sticky, sticky-icon,
   winlist-skip, circulate-skip, circulate-skip-icon.

Q: Ok, I want to check it out. What do I do?
A: Edit your "~/.xsession" or "~/.xinitrc". If you don't have one, copy the
   system-default "from /usr/X11R6/lib/X11/xinit/xinitrc". Decide which
   programs should belong to the session. I recommend that you leave all
   programs that only set something (xmodmap, xrdb, ...) alone, and
   concentrate on lingering applications (xterm, emacs, scwm, ...). Move the
   calls of this applications to a new file "~/.xsmstartup". Keep all program
   arguments, but remove backgrounding ampersands. This is now your default
   session. The last line in your .xsession or .xinitrc should be "exec xsm".
   This hands over responsibility to the session manager.

Q: What can I do with xsm then?
A: To end X you have to select "Shutdown". "Shutdown Immediately" does not
   save your session, so you will later resume at the last saved position. If
   you never saved, all you will have to resume is the default session.
   "Shutdown With checkpoint" saves the session to an arbitrary name before
   terminating X. "Checkpoint" saves without termination. "Client list" and
   "Session log" will display some information.

Q: Why is window information not preserved for most clients?
A: These clients probably do not support session management themselves. Be
   sure that you are running a smproxy that provides SM_CLIENT_ID info: The
   standard smproxy programs from the X distribution and from GNOME do *not*
   do this. You'll have to patch gnome-smproxy with the "smproxy.patch"
   found in the same directory as this document.


Q: What should Emacs do with this file?
A: Information for Emacs follows - you can safely ignore this if you're human.
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