Can't use second monitor from xfce4

[Olivier Fourdan]

On Wed, Nov 17, 2010 at 3:28 PM, Mike McNally <emmecinque at gmail.com> wrote:
> I've got Ubuntu (not Xubuntu) 10.10 installed on a Lenovo U460 laptop. The
> laptop has a dual-GPU architecture. I find that in no circumstances (from
> Linux) can I access a second monitor plugged into the DVI port when I've got
> the laptop "forced" (via BIOS setting) into using the NVidia GPU. With the
> BIOS set to use the Intel GPU, however, I can use the secondary monitor, but
> only when I log in with a Gnome or Openbox session. From XFCE, I can't get
> the second monitor to do anything at all.
> One of my points of confusion is that I can find no tool in the xfce4 suite
> that allows monitor configuration like the Gnome "Monitors" tool in the
> Gnome control center. When I use that to set things up within a Gnome
> session, it all works  just fine - the second monitor is correctly detected,
> gets the right resolution, is positioned correctly for mouse movement, etc.
> Same goes for Openbox.  From xfce4, however, the second monitor remains
> dark. Even if I run the gnome-control-center from the xfce session, nothing
> happens, though the Gnome tool does "see" the second monitor; it just
> doesn't actually work.
> So, what *is* the "normal" xfce4 way of setting up monitors?  Any clue as to
> why I'd be seeing this behavior?

Did you try with xrandr directly, from the command line in X?

Cheers,
Olivier