[Pkg-xfce-devel] Bug#780025: Bug#780025: dm-tool: lock locks a new VT instead of current VT

Ben Armstrong synrg at sanctuary.nslug.ns.ca
Sun Mar 8 14:46:54 UTC 2015

On 08/03/15 10:25 AM, Yves-Alexis Perez wrote:
> Actually that's not what happens. dm-tool locks will just call the
> Lock() dbus method on the current seat. In response to that, lightdm
> will emit a dbus signal for locking, then switch vt to display a login
> screen.

Sure. Makes sense. And aligns with my second comment on this bug.

> See the following thread [1] where I raised exactly those issues. There
> are other threads on this, for example about lxsession [2].

OK. Read them. So to sum up, the way the system is architected now,
there's really no way for lightdm to know if a lock actually occurred or

Once I discovered light-locker needed to be installed, which took in
excess of an hour of investigation to discover, I got it sorted out, so
I guess in absence of fixing this at the architecture level (which I
understand won't be cheap), just a little bit of doc will go a long way
to at least help the users who are observant enough to notice the screen
isn't actually being locked, or who go looking to see if disabling
xscreensaver needs anything else to keep locking working.

> That's because you don't have anything waiting for the dbus signal. If
> you really want to use dm-tool lock (or switch-to-greeter), you need a
> locker running on the session, like light-locker or the GNOME ones
> (gnome-shell, unity or whatever).

Yep, that's all it took. But wow, what a big accident waiting to happen
for unsuspecting users! Some time ago, I had disabled xscreensaver to
keep my session as light as possible, and the session appeared to be
getting locked by lightdm anyway, so I didn't think anything of it. It
was not until lxlock failed to produce any visible result when I pressed
the "Lock Screen" button that I went looking and found this issue, so I
don't know how long it has been that my session was not actually being

I'm happy to leave this one on the books as a pair of minor doc bugs to
xref the relevant man pages. But I earnestly hope that upstream sorts
this out in the next release.


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