User bus conclusion

[Thiago Macieira]

Em Quarta-feira, 10 de Novembro de 2010, às 16:40:12, Lennart Poettering 
escreveu:
> > For example, my workstation in the office keeps my KDE session running
> > all the  time. Sometimes, I need to get a password from the KWallet, so
> > I'll ssh -X in and run kwalletmanager. That currently starts a local
> > D-Bus session and kwalletd, which in turn shows the password dialog.
> 
> local to which side? You are not sharing the dbus session across the
> network, are you? So nothing really changes here. THis will continue to
> work.

Local display, as in the monitor connected to the computer.

Whereas I am logging in remotely, from my laptop, at home, several kilometres 
(sometimes thousands of them) away.

Right now, a new session is started by my starting of any KDE application. 
This session is tied to the triad (user, machine, X display). The important 
thing to note is that the X display is "localhost:10.0", a forwarded X11 
session over SSH. When moving to the user bus, we drop the X display from the 
equation, so a new session isn't started. Instead, my applications join the 
already-running session, the user session.

> > With the user bus proposal, there would be no local D-Bus session.
> > Instead,  the launched kwalletmanager application would be talking to
> > the kwalletd running on my local display. And that would then proceed to
> > show the password dialog in the wrong screen.
> 
> I am a bit confused what you mean by "local".

Sorry. In this case I meant "local to the ssh login".

> > > I guess, if we continue to honour $DBUS_SESSION_BUS_ADDRESS, however
> > > just not set it anymore in modern sessions (gnome, kde) then this and
> > > similar use cases should not be much of a headache.
> >
> > 
> >
> > I didn't get this part. Can you clarify what you meant?
> 
> Well, if sombody does dbus_bus_get(DBUS_BUS_SESSION) what he gets is a
> connection to $DBUS_SESSION_BUS_ADDRESS if that is set, and to if it
> isn't to $XDG_RUNTIME_DIR/dbus/dbus_user_bus. GNOME would then not set
> this env var anymore and we would benefit from clear semantics and full
> parallelization. However, KDE could continue to set it, and would
> continue with the old semantics.

That would not entirely work for the autostart mechanism. This is changing 
that behaviour.

I'd much rather that non-simultaneous login systems set 
DBUS_SESSION_BUS_ADDRESS to the unique user bus and leave the current 
functionality as it is.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358
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