Re: Interaction between g-s-d RandR component and VirtualBox Guest Additions

[Bastien Nocera <hadess hadess net>]

On Tue, 2011-01-11 at 00:27 +0100, Michael Thayer wrote:
> Hello Frederico,
> 
> Sorry for the delayed response (due to the holiday season and a major
> product release!)
> 
> Le mardi 28 décembre 2010 à 20:01 -0600, Federico Mena Quintero a
> écrit :
> > On Wed, 2010-12-22 at 17:09 +0100, Michael Thayer wrote:
> > > Under the hood this is done by a tool running on the guest system which
> > > is notified of the change and pokes the guest video driver.  The guest
> > > video driver then changes its RandR mode list so that its preferred
> > > resolution is the new host window size and the tool switches to that
> > > resolution.
> > > 
> > > This works well until the user uses gnome-display-properties to select a
> > > resolution.  After this it seems that g-s-d tries to take over
> > > responsibility for screen resolutions, and the result is not very
> > > pretty.
> I have investigated this a bit, as I was mainly going on user reports
> before, and it seems I misunderstood the issue slightly.  It turns out
> that this only happens immediately after the user logs into X/gdm, and
> that on start up, g-s-d is setting the resolution to the last one that
> the user set using gnome-display-properties.  Actually some versions of
> g-d-p had a tick box to say whether you wanted this behaviour or not,
> but it seems to have gone away again.  Since g-s-d is started after our
> tool it doesn't see and take into account the monitor hotplug event, and
> it also ignores the monitor's preferred resolution.
> 
> If I read [http://live.gnome.org/RandR#Storage_of_RANDR_configurations]
> and the resources it points to right, one way of getting round this
> would be to fake EDID data with, say, a random changing serial number.

Rather than trying to guess what might be happening, I would suggest you
test this under a recent version of gnome-settings-daemon (2.32, or the
upcoming 3.x releases), and enable debugging on startup:
http://git.gnome.org/browse/gnome-settings-daemon/commit/?h=gnome-2-32&id=c763d6d860b2c1b01344e6514eb486e8bc453b69

This will show you what the xrandr plugin is doing. If there are older
versions that cannot work reliably with VirtualBox, you could disable
the xrandr plugin on those systems using GConf.

Cheers