multiseat (was: Re: Input Devices (was: Re: [Xgl/Xegl] Input Devices))

[Daniel Stone]

On Thu, Jul 28, 2005 at 01:45:49AM -0400, Jon Smirl wrote:
> On 7/28/05, Daniel Stone <daniel at fooishbar.org> wrote:
> > On Wed, Jul 27, 2005 at 04:22:42PM -0400, Jon Smirl wrote:
> > > Different users on each card is easy.
> > 
> > No, it really isn't.
> 
> Why?

Input is hard.  How do you associate a particular input device to a
particular user?  Now imagine the world of USB, where you have to deal
with hotplug input devices.  Oh, and don't forget real users, who will
want to do audio, and plug in USB thumbdrives.  If you plug in a
thumbdrive with your GPG key on it, you don't want someone else to get
their grubby mitts on it.

VGA routing is a bitch.  If you don't believe me, stick four utterly
random cards in one machine, start four X servers, and watch it quickly
collapse in a heap.

That and trying to deal with four separate heads when the VT system only
has the concept of one.  Anywhere from one to four heads can be present
on a four-user system, and you have to deal with that accordingly, and
DTRT with sharing VTs, and what to do when someone hits the console.

It's a surprisingly non-trival problem space, trust me.