randr 1.2: Primary Output for Laptop + external Screen

Marius Gedminas mgedmin at b4net.lt
Mon Aug 27 13:54:15 PDT 2007

On Mon, Aug 27, 2007 at 12:49:21PM -0700, Keith Packard wrote:
> On Mon, 2007-08-27 at 21:31 +0200, Andreas Schildbach wrote:
> > I'd like to hear your opinion on the desired behavior of the video 
> > drivers in typical laptop situations with an internal display and an 
> > external screen attached (extending the desktop).
> > 
> > Currently for example the intel driver uses the external screen as the 
> > primary output. It is listed first with xrandr. I'm not sure if this is 
> > intentional or just coincidence.
> It's coincidence -- the laptop hardware has two crtcs, and the LVDS can
> only be driven by the second.
> Note that RandR doesn't really want the order to be significant; it
> would be better if the desktop environment knew about outputs and could
> refer to a specific output as 'primary' or 'holds toolbar' or whatever.

I think most desktop environments assume Xinerama screen #0 is the
primary one.

The old radeon driver had an option "MergedXineramaCRT2IsScreen0" for this.
It would be nice if xrandr 1.2 had something like this, e.g.

    xrandr --output VGA --primary

to move my GNOME panels/gdm to the external screen, then

    xrandr --output LVDS --primary

to move them back.

I'd prefer LVDS to be primary by default, for the same reason --
connecting and disconnecting an external display makes the primary
screen jump back and forth, which is a bit unexpected.

Marius Gedminas
If nothing else helps, read the documentation.
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