[Spice-devel] spice-vdagent and X Display Managers on Ubuntu 16.04

[Sergio L. Pascual]

Hi,

I've just spent some time tuning an Ubuntu 16.04 (I know Fedora is
preferred around here, but a lot of clients seem to prefer Ubuntu and
its derivatives) desktop for VDI usage, and I had a hard time finding a
X Display Manager which plays nice with spice-vdagent (in the sense of
adapting properly to resolution changes, something critical for mobile
clients). I'd like to share my findings:

 - lightdm, slim, kdm: there's no way to specify a program to be
executed while running the greeter, must be worked around with a
wrapper. Changing resolution results in the greeter crashing and/or
hanging.

 - gdm: applications to be run alongside with greeter can be specified
in "/usr/share/gdm/greeter/autostart" (which spice-vdagent already
uses). Sadly, gdm > 3.14 tries to run Xorg as gdm (on greeter) or
logged in user (after log in), which is not supported by QXL driver, as
it needs direct PCI access.

 - sddm: needs a wrapper too, but deals nicely with resolution changes
*IF* not using the "breeze" theme (this drove me crazy for a while,
diving into its source code).

So sddm looks like the best option for recent distros, with the only
downside being the amount of QT dependencies it brings with it. I'm
going to ask if sddm has a way I haven't found for running a script
with the greeter, or if such a feature would be accepted. 

-- 
Sergio L. Pascual