Fixing the Session Manager

There’s lots of talk at the moment about “fixing the session manager”,
a sentiment I agree with, but I worry that if we don’t step back and
look at the big picture a bit we’ll screw things up even more.

To me, “Session Management” is all about providing the ability to take
a snapshot of what you’re doing right now, log out and be able to come
back later, log in and continue where you left off. So if I saved
the state of my session I’d expect following to be remembered:

  • the applications which are running, and the windows belong to
    those applications which are open
  • the size and position of all those windows
  • which documents I have open, the position within those
    documents etc.

Alternatively, people seem to set things up just how they’d like it
when they log in every morning and take a snaphot of the session at
that point.

This is the kind of functionality which XSMP was designed for but it
hasn’t yet worked out very well because most applications don’t do a
good job of implementing it and there’s not a lot of clarity on how
session state differs from application state (e.g. when you close your
browser, should it remember the last position of the window or should
it only remember that when you save your session?)

Anyway, lets forget about this feature for the moment. We do our best
to hide it in GNOME because we know its broken and my impression is
that most people don’t bother with it because of its brokeness. I’m
not too concerned about fixing it right now.

There’s this whole other thing the session manager does, though. It
starts what we think of as the “desktop shell” – the window manager,
panel, nautilus, screensaver daemon, settings daemon etc. etc. I think
most user’s mental model of the desktop would be that all these
components make up a single entity in which different applications
run. Whether the panel is running isn’t a part of transient session
state in the same way as whether the browser is running, its a fixed
part of the desktop.

Making this distinction gives us the ability to treat the session
shell and transient session state differently. But to what end? Well,
there’s a number of thing we can do differently if we treat the
management of the session shell as a different problem:

  1. We stop forcing users to understand that in order to have certain
    desktop services started at login they must run them and then
    save the session.
  2. We consolidate all the hard-coded hacks for starting desktop
    services into a single mechanism whereby desktop services can
    register themselves with the session manager and asked to be
    started up based on a user preference.
  3. We remove the possibility of “losing” important parts of the
    desktop from your session
  4. We can start the session in two stages – the desktop shell
    followed by the applications, perhaps hiding the entire screen
    until the desktop has started
  5. We can remove obtuse terms like “Metacity Window Manager”, “The
    Panel”, “Nautilus” from the splash screen and just have “Starting
  6. Since we won’t have to worry about managing legacy applications,
    we can think about dumping XSMP and coming up with a solution
    specifically designed for starting the desktop itself

Here’s another way to look at it – if you save your session while
you’re running GNOME, wouldn’t it make sense that when you log in to
KDE the same applications are running? If the answer to that is yes, I
think it shows that the question of activating desktop shell
components is orthogonal to the question of restoring session state on