[gdm-list] Future of multi-display support in GDM

[Brian Cameron <Brian Cameron Sun COM>]

I know that Sun is very interested to integrate the new GDM rewrite into
Solaris/OpenSolaris in GNOME 2.26.  However, one feature that is missing
that needs to be addressed before GDM can integrate into Solaris is how
multi-display should work.  By multi-display I mean making GDM support
management of multiple displays with separate login prompts.  This used
to be supported in the old GDM by adding lines like the following to the
configuration file:

[servers]
0=Standard
1=Standard
2=Standard
[...]

Since this is a fairly serious regression, I expect that some solution
will eventually come into place.  But, I and others here at Sun would
like to help do the work once we agree how it should work.

Currently with the new GDM, the only way to get multi-display support
is to use the gdmdynamic patch that was written by Simon Zheng at Sun.

  http://bugzilla.gnome.org/show_bug.cgi?id=536355

It seems to work pretty well already in our testing.

Perhaps it would be a nice solution for GDM to take this sort of
approach and provide a CLI for starting any such displays.  This makes
it easy to launch displays via scripting as needed, and avoids needing
to complicate configuration files.  Though we could also enhance the
new GDM rewrite so if the config file has a [servers] section, it could
just call such a script in the background and "just work" without users
needing to change their configuration.  That might be nice.

Since the existing patch uses D-Bus to communicate with the GDM server,
other frontends could also be written to make GDM respond to HAL events
or other mechanisms for starting displays as needed.

However, I am not sure the existing design is the best approach, and
some thought may be needed to make sure that GDM and ConsoleKit talk
to each other properly when displays are added in any sort of dynamic
fashion.  Perhaps instead of a gdmdynamic script there should be a
ck-dynamic script so the flow of events is that ConsoleKit drives
the addition of new consoles and informs GDM rather than the other
way around.

Thoughts?

--

Brian