> How do I tell lightdm to set the screen resolution when it shows the
> login screen?
>
> I would prefer to have lightdm set it directly instead of relying on
> xrandr.
LightDM doesn't control the resolution, so you have two choices. You
can either run xrandr as part of the display-setup or similar command
in lightdm.conf, or you can create your own xorg.conf and set your
preferred monitor layout/resolution in there.
The xrandr method is much simpler and more modern, but the xorg.conf one
is pretty much mandatory if you want to do more complicated things like
use multiple video cards from different vendors.
Cheers,
Adam.