On Wednesday 15 April 2009 19:55:56 Greg Freemyer wrote:
> When I connect up to the projector, X / KDE is not auto-detecting the
> extra screen until I logout.
>
> Thus I would like to have a way to force X and/or KDE to detect the
> projector and reconfig itself.
>
> Is this possible:
>
> from KDM login screen?
>
> after being logged into KDE 4.2.2?
>
> As I said, currently it only autodetects on logout from KDE. So if
> I'm sitting at the KDM, I have to connect up the projector, login,
> then logout, and login a second time. At which point I have a dual
> screen capability.

Yes, it's definitely possible (even with 4.1.3 on 11.1). A KDED module (kephal) watches for XRANDR events indicating that a monitor or projector was hotplugged and pops up a dialog shortly after the cable was connected asking if your desktop should be extended onto the new screen.

The catch is that driver support for XRANDR events is patchy at best. nvidia binary is probably the worst since it only supports xrandr 1.1. I know it works nicely on intel 945GM on 11.1 because I presented in exactly this way with 11.1 at FOSDEM in February (satisfyingly, a GNOME colleague uttered a surprised "KDE can do /that/?!).

Does 'xrandr' show the projector after hotplug (but before logout)?

Does 'qdbus org.kde.kded /modules/kephal/Screens org.kde.Kephal.Screens.numScreens' reflect the number of connected displays?

HTH

Will