Re: adding session-management to a wm

[Tom Tromey <tromey cygnus com>]

>>>>> "Chris" == Chris Cannam <cannam@all-day-breakfast.com> writes:

Chris> I'm thinking of making the wmx window manager a bit gnome-aware
Chris> for the wmx-5 release.

Cool.

Chris>  * I've looked at the documents on www.gnome.org and the xsmp
Chris>  specifications, and I'm not quite clear on the role of the wm
Chris>  in the session-management process.

Chris> I had assumed (or hoped) the wm was not supposed to be a
Chris> manager itself, as gnome has a separate process for this.

I agree.  I think this is the way to go because it lets the user
change window managers without exiting the session.

Chris> But if that's the case, I can't see how the wm could save any
Chris> useful state other than the number of virtual desktops
Chris> available, and in particular I don't see how it can ensure that
Chris> a newly-restarted client comes up on the correct desktop next
Chris> time you log in.  The wm surely can't make any association
Chris> between previous and new instantiations of a client application
Chris> unless it is a session manager itself... can it?

Nope, there's no way to do this.  It seems unbelievable to me right
now (maybe it's too late at night?), but there it is.

I guess the answer is that clients should save all the state they care
about, and the window manager should just save the state of those
things it directly controls: various wm-specific options, what desktop
you are looking at by default, geometry of wm-created windows, etc.

Chris> (Maybe there's some sort of idiot's guide on adding
Chris> session-management support to a wm that I've overlooked?  Or
Chris> maybe people who write window managers are just supposed to be
Chris> clever.)

Or choice #3: the people who wrote the X session management stuff
weren't wm implementors and didn't think it all the way through :-)

Chris>  * Do the gnome libraries enable applications to use window
Chris>  groups?  I'd rather like to support them, but I'm too lazy to
Chris>  make the effort unless I know lots of new software is going to
Chris>  make use.

I don't know.  I do know that one other popular X toolkit, Tk, does
let you use window groups.  I've even written Tk applications that do
this.

Tom