Is it possible to force a monitor to stay in the server layout?

[Sven Berkvens-Matthijsse]

Hello Aaron, Alex,

Alex Deucher schreef op 2012-12-21 17:10:
> On Fri, Dec 21, 2012 at 10:52 AM, Aaron Plattner <aplattner at nvidia.com> wrote:
>> On 12/21/12 06:29, Sven Berkvens-Matthijsse wrote:
>>>
>>> Hello,
>>>
>>> I can't seem to find an answer to my question anywhere on the web.
>>> Either my use case is weird, or I'm not searching correctly :-)
>>>
>>> I have X.org server 1.11.3 running on Ubuntu. I'm using the radeon
>>> driver with a Radeon HD6450. I have three monitors connected to the card
>>> (all three monitors have a DVI input), and I've set up the server to
>>> have all three monitors in one large desktop. This works brilliantly!
>>>
>>> Sometimes, I need to connect one of the monitors to another PC or other
>>> equipment with a HDMI or DVI output. My problem is that if I pull out
>>> one of the cables that is connected to the HD6450, that the card (and
>>> the X server) will detect that the monitor has been disconnected from
>>> the card. Consequently, the desktop size is modified and all my Gnome
>>> panels will be jumbled. If I reconnect the monitor, it comes back
>>> online, but the positioning of the windows and panels is not restored to
>>> what it used to be.
>>
>>
>> It's the X clients' job to effect that sort of policy.  In your case, it's
>> probably gnome-settings-daemon.  You could try killing it as an experiment
>> to see if the behavior goes away, or logging into a simpler desktop
>> environment like Fluxbox that doesn't have a monitor policy daemon.

I tried stopping the gnome-settings-daemon, and that indeed stopped the
unwanted behavior. I thought it was the X server that actually took the
display out of the server layout, but that is not the case, as I can see
now. I also checked with xrandr: the disconnected display is marked as
such, but the total configured resolution does not change.

>> I don't know offhand if gnome-settings-daemon has an option to turn off
>> automatic reconfiguration of the screens.

I have not been able to find such a setting. But I will look further now
that I know the behavior results from Gnome itself.

>>> What I would like is to be able to tell the X server that I don't care
>>> whether monitors are disconnected or not, and that it should keep the
>>> desktop size fixed, no matter which monitors are connected. My X
>>> configuration file includes a full server layout section, and also
>>> contains the resolutions of the monitors. Therefor, it should be
>>> possible, I guess, I just don't know how. Perhaps the current software
>>> is not able to handle this specific situation. I can live with it if the
>>> monitors need to be connected at the time that the X server starts. As
>>> long as I can disconnect them later on without the server layout and
>>> desktop size changing.
>>
>>
>> The nvidia driver has a "UseHotplugEvents" option you can use to suppress
>> the RandR events that clients like gnome-settings-daemon listen for, to work
>> around this sort of problem.  Maybe the radeon driver has something similar?
> 
> There's no runtime option, but you can disable udev support in the
> build with the --disable-udev configure option for xf86-video-ati.  As
> Aaron said, it's preferable to disable that behavior in your desktop
> environment however.

Agreed. I'll try to find out how to stop Gnome from reconfiguring my
screen layout.

> Alex

Thank you for your kind and swift responses,
Sven