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Re: Buster/XFCE unlock screen is blank

On Sat, Jun 01, 2019 at 11:06:42AM +0200, Andreas Tille wrote:
> > This appears to be a bug in light-locker specifically, which is the
> > default screen lock program with XFCE with lightdm.  See, for instance:
> > 
> > https://github.com/the-cavalry/light-locker/issues/114
> > 
> > Switching to another greeter from the default gtk-greeter appears to help
> > according to that bug, which may mean that the bug is actually in
> > lightdm-gtk-greeter.  There doesn't appear to be a Debian bug for this; it
> > might be a good idea to open one against light-locker (or, if you confirm
> > switching to slick-greeter per that bug, lightdm-gtk-greeter).
> Yes, please file the bug (and may be report the bug number here).  We
> should not release with a broken greeter as default since we can not
> assume that normal users will find out the "switch VT trick" and instead
> will assume the box is frozen. 

While I greatly prefer slick-greeter (I use it exclusively since the first
day I reviewed+sponsored the package), I recall it doesn't support a11y
anywhere as well as the default greeter.  This is old data, though -- as my
wetware doesn't require a11y, I wouldn't even know what to look at.

But, the culprit is light-locker.  In general, it's in such a buggy state
that I believe it shouldn't be in the distribution at all, much less a
default of any kind.  After it replaced xscreensaver[1] as the xfce's
dependency, I went into some pretty heated arguments, but then stormed off
and ignored the issue.

Just some issues with light-locker.  INACCURATE, BASED ON AN OLD VERSION,
AND NOT RESEARCHED WELL AT ALL.  (Ie, areas to look at, not proper reports)
* it doesn't show anyone is logged in -- lock screen is pixel-to-pixel
  identical as the login screen
* breaks when the *DM is not lightdm.  A package dependency doesn't mean
  that lightdm is running or used to start that session.
* breaks with multiseat (as in: concurrent same-uid logins from different
  seats, not the systemd meaning)
* breaks if ssh -X into the box is used with some programs
* breaks with any non-standard VT assignment
(Some of the issues might have been already fixed.)

At the time of the xscreensaver debacle, there was no sane alternative
(candidates depended on 80% of GNOME, offered no feedback nor discoverable
controls to the user, etc).  There _is_ a wonderful alternative now:
xfce4-screensaver, which seems to work perfectly[2] -- but alas, it's not in

Using unstable myself, I'm not sure what to recommend for Buster.  But if
the bugs can't get fixed in late freeze, and slick-greeter is not enough,
I's light-locker not the greeter I'd propose switching out of.


[1]. When jwz planted a time-bomb in xscreensaver.
[2]. There was an issue with taking lots of CPU even when the monitor has
     been long since powered down, but that's now fixed.
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