When Unity.Session is available, use its API for logging out

[Stephen M. Webb]

[Impact]

The session indicator always uses gnome-session to end the session (log out), but gnome-session is not guaranteed to be available under, for example, a Unity8 desktop preview session. It should use Upstart where available.

[Test Case]

Install unity8-desktop-session and choose to log in to that session from the LightDM login screen. You should be able to select "log out" from the session-indicator indicator and have it bring you back to the login screen.

[Regression Potential]

In the worst case this change could affect log out operations from regular Unity 7 sessions and potentially other sessions that use the session indicator. In such a case, the log out operation would fail necessitating a reboot or manual session kill.

[Other Info]

This change has been in production use on later releases of Ubuntu (14.10 and later) without problems.

Later version of the Unity 8 desktop session do not exit to the LightDM login screen but instead restart Unity 8 and present the Unity 8 login screen. This is a bug in Unity 8 and not related to indicator-session.

[Stephen M. Webb (bregma)]

See the partial (hacked) implementation at lp:~unity8-desktop-session-team/indicator-session/indicator-session-using-upstart and the binary packages at https://launchpad.net/~unity8-desktop-session-team/+archive/custom/+packages for an example.

[Charles Kerr (charlesk)]

See also bug #1302213

[Charles Kerr (charlesk)]

So when the user has prompting disabled, indicator-session can use the Unity API directly, and there's an attached MP for this.

In the default case where prompting is turned on, it looks like UnityCore/GnomeSessionManager.cpp's implementation of org.gnome.SessionManager.EndSessionDialog handles the logout signals on its own instead of returning control to indicator-session. It seems likely that once Unity has control it's irrelevant whether the logout signal emitted is Gnome or Unity, but am adding Treviño here for a sanity check to confirm...

[Charles Kerr (charlesk)]

Raising importance to Critical as per bug #1323992

[Launchpad Janitor (janitor)]

This bug was fixed in the package indicator-session - 12.10.5+14.10.20140620-0ubuntu1

---------------
indicator-session (12.10.5+14.10.20140620-0ubuntu1) utopic; urgency=low

  [ Charles Kerr ]
  * When logging out, prefer com.canonical.Unity.RequestLogout over
    org.gnome.SessionManager.Logout. (LP: #1296814)
 -- Ubuntu daily release <email address hidden> Fri, 20 Jun 2014 15:27:42 +0000

[Stephen M. Webb (bregma)]

This has been fixed and released in the underlying component packages.

[Chris J Arges (arges)]

Hello Stephen, or anyone else affected,

Accepted indicator-session into trusty-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/indicator-session/12.10.5+14.04.20140925-0ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Stephen M. Webb (bregma)]

Verified using unity8-desktop-session-mir on Trusty.

[Chris J Arges (arges)]

The verification of the Stable Release Update for indicator-session has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[Launchpad Janitor (janitor)]

This bug was fixed in the package indicator-session - 12.10.5+14.04.20140925-0ubuntu1

---------------
indicator-session (12.10.5+14.04.20140925-0ubuntu1) trusty; urgency=low

  [ Charles Kerr ]
  * When logging out, prefer com.canonical.Unity.RequestLogout over
    org.gnome.SessionManager.Logout. (LP: #1296814)
  * Install translations into the correct directories. (LP: #1318980)

  [ Sergey "Shnatsel" Davidoff ]
  * Allow Pantheon as a valid show-in target. (LP: #1301699)
 -- Ubuntu daily release <email address hidden> Thu, 25 Sep 2014 15:07:42 +0000