Comment 5 for bug 1085841

As multiseat support in LightDM is enhanced, please consider the following:

1. There are currently two models of multiseat setup: one based on USB multiseat devices with DisplayLink (or similar) technology, like Plugable Docking Station, and another one based on multiple video cards, with keyboards/mice/audio devices plugged directly in the CPU or via ordinary USB hubs.

In the first model, input assignment to each seat is trivial: one only needs to pair the display and input connected to the same multiseat device, which is done automatically. On the other hand, the second model (most common in Brazil), display and input pairing is not trivial. The common solution, found in proprietary solutions like Userful Multiseat and Windows Multipoint Server, to do the right seat assignment for input devices is an interface of kind

"Please press F<x> key in the keyboard in front of this display",

where <x> is 1 for the first seat, 2 for the second seat, etc. If the keyboard is connected to a hub, all other devices connected to the same hub are automatically assigned to that seat. It would be nice if LightDM could implement such an interface for seat assignment.

2. Before systemd-logind, all multiseat settings were DISPLAY-oriented, but now IMHO it makes more sense to write these settings in a more "seat id"-oriented fashion. In lightdm.conf, instead of having

[Seat:1]
(...)
xserver-seat=seat-1
(...)

I propose something like

[seat-1]
(...)
xserver-display=:1
(...)

This approach is specially useful for autologin. It make more sense to assign autologin users to seat ids than DISPLAY values. I want, for example, user "bob" loggind automatically in seat-1, regardless of which is the value of DISPLAY environment variable on that seat.