Steps to reproduce:
* Install lightdm
* Install another display manager that lists sessions based on
/usr/share/xsessions/*.desktop
- currently this means: gdm3 | sddm | slim | lxdm
* Use dpkg-reconfigure to select the other display manager to be used
* Reboot
Expected result:
* The sessions listed by the other display manager are not affected by
having installed lightdm
Actual result:
* The other display manager now lists "Default Xsession" as an option
* Users cannot predict what desktop environment will result from choosing
this option
* This is particularly confusing in display managers like gdm3 where the
default is something different (e.g. gdm3 defaults to GNOME-on-Wayland),
so "Default Xsession" is in fact a non-default X session :-)
----
I suspect this might be the root cause of #973812.
I personally think this "Default Xsession" option is more confusing than
it is useful, even for lightdm-only systems, because users cannot predict
from its name what it will do. Older versions of gdm3 had a similar
option, but I removed it from the versions in testing/unstable. Instead,
gdm3 now ships /usr/share/doc/gdm3/examples/custom-x11-session.desktop,
which sysadmins are invited to copy to /etc/X11/sessions and customize
if they want that. This is the approach I would personally recommend
for lightdm too.
If the maintainers of lightdm do not want to remove this option, then
I think lightdm should behave like older versions of gdm3: it should
list a "Default Xsession" option *in lightdm only*, without providing
that option in other display managers. To achieve that, please install
/debian/lightdm-xsession.desktop into /usr/share/lightdm/sessions/
(which is already searched by lightdm, as far as I can see) instead of
into /usr/share/xsessions/ (which is searched by all display managers).
Thanks,
smcv