Does not fail gracefully when lightdm isn't running

[Daniel Gnoutcheff]

To reproduce:
1) install gdm and use it as the display manager
2) install light-locker and xfce (another DE that uses light-locker would
   probably work as well). Observe that the light-locker package does not
   declare lightdm as a dependency, nor does it conflict with gdm.
3) login with xfce
4) lock the screen (e.g. with a suspend/resume cycle or with the command
   'sudo loginctl lock-session $XDG_SESSION_ID')

Expected: one of the following should happen:
  - APT should prohibit me from installing light-locker (i.e. light-locker
    and gdm should be declared as conflicting packages)
-or-
  - light-locker should refuse to run when gdm is the display manager
-or-
  - light-locker should support gdm (i.e. it should get gdm to spawn a login
    screen and display it)

Result:
- light-locker is installable and runnable even when gdm is the display
  manager.
- The screen goes black and displays the message "This session is locked:
  You'll be redirected to the unlock dialog automatically in a few seconds".
  However, the promised redirection never happens, leaving the user with no
  discoverable way to unlock their session.
- If there happens to be a gdm login screen running on another VT, then I
  can unlock the session by manually switching to gdm's VT and trying to
  login as the user to whom the locked session belongs.
- However, it's often the case that no such login screen is running. The
  only way I know how to unlock the session without the login screen is to
  get to a command line somewhere and run
  'sudo loginctl unlock-session [locked session ID]'.
- While the system does start the gdm login screen after the last user
  logs out or when someone uses the "switch user" function in (at least)
  Gnome or Xfce, it does not appear that light-locker ever manages to start
  it when locking a session.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: light-locker 1.4.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-30.54-generic 3.13.11.2
Uname: Linux 3.13.0-30-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: GNOME
Date: Mon Jun 30 13:00:29 2014
SourcePackage: light-locker
UpgradeStatus: Upgraded to trusty on 2014-04-15 (76 days ago)

[Simon Steinbeiß (ochosi)]

I think for starters this should be fixed on the packaging side by making sure that light-locker depends on lightdm.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[kay (kay-diam)]

I have the same problem. When the fix is expected?

[BENOIT Julien (jbenoit-jb)]

I got the same problem. Is it fixed ? If not, when will it be ?

Thanks.

[Gannet (ken20001)]

I got the same too. How to unlock it? o_O