Setting up for dual screens

optiluca · Posted: Wed Jul 20, 2011 9:24 pm Post subject: Setting up for dual screens

Hi all. Firstly, apologies if this has already been covered before, but the topic is proving quite hard to search around for, given the rapidly evolving nature of Xorg which renders half the info out there wrong/obsolete..

I am trying to set up dual monitors on my laptop, running an nvidia card with proprietary drivers. Twinview works just fine, but it has a few perks that I find quite annoying, so I wanted to give a "true" dual monitor setup a try. As the second monitor will only be rarely plugged in, I would like to be able to hotplug it with the X server already started. This is done using xrandr I believe. However, from what I understand Xorg.conf needs to have a few sections added for everything to function correctly. Namely, a "Virtual" line needs to be added, in order to tell Xorg how big the "Virtual screen" which contains the 2 physical displays should be.

With this modification, my Xorg.conf reads as follows

BradN · Posted: Sat Jul 23, 2011 7:35 pm Post subject:

First idea, make sure everything's compiled with the xinerama use flag, it might help. I think what's happening on your setup is that this section...

Section "Screen"
Identifier "Default Screen Section"
Subsection "Display"
Virtual 3840 2160
EndSubSection
EndSection

is making it want to do a larger virtual screen. Unfortunately I haven't set up multiple monitors in a long time so I haven't kept up with what needs to be done in xorg.conf for that type of stuff. I thought this stuff has become a lot more automated and might not even need xorg.conf settings if your desktop environment has good monitor configuration capability.

Be careful to check the dates on howtos and forum posts with regard to this stuff because I think a lot of it's changed lately.

geki · Posted: Sun Jul 24, 2011 9:13 am Post subject:

I switched from nvidia propietary to intel i915 these days with monitor and TV setup.
I guess this will work for any good gfx card and monitor/TV these days?!
well, maybe the device with nvidia driver needs to be set. does not need to be for intel here.

this is my xorg.conf:
http://geki.ath.cx/hacks/xorg.conf

my xrandr line to setup: ( i.e. put in ~/.xinitrc or ~/.xsession )

Gusar · Posted: Sun Jul 24, 2011 12:29 pm Post subject:

Look into Twinview, in particular TwinviewXineramaInfoOrder. And as has been said, compile everything with the xinerama USE flag, if it isn't already.

optiluca · Posted: Sun Jul 24, 2011 10:24 pm Post subject:

As I said in my original post, twinview does work, but it has a few weird perks that I don't particularly like.

Also, xinerama is indeed enabled globally. I don't have my secondary screen to try at the moment, but when I last tried connecting it and running xrandr -q, nothing was found other than my laptop screen. Also, the xorg.conf you posted only contains unrelated information as far as I can make out, eg paths/modules/inputs, nothing related to displays. I'll try the xrandr command you posted, but considering xrandr -q finds nothing I am not too confident...

BTW, the external monitor is attached via an HDMI cable, thru a Displayport/HDMI adaptor. As I said, it works just fine using twinview, via the nvidia-settings program, but I'd like to use xrandr instead

_________________
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Gusar · Posted: Sun Jul 24, 2011 10:46 pm Post subject:

BradN · Posted: Mon Jul 25, 2011 2:01 am Post subject:

It could be related to 3d acceleration spanning the displays or even more exotic stuff like stereo displays - nvidia actually supports some unusual stuff in their linux drivers.

lyallp · Posted: Mon Jul 25, 2011 6:20 am Post subject:

Before I start, if there is a better way to do this, I am all ears.

I guess I could merge both xorg config files into one and have the xdm-setup simply set the X startup parameter, indicating which serverLayout to use, however, this works for me and if it isn't broken, I probably won't get around to fixing it.

Anyway, on to what I have....

I have a HP EliteBook 8540w working with two different sized monitors, with the large, external, monitor plugged into the docking bay in addition to the built in panel.
I use nvidia proprietary drivers.
So, my screen real estate varies depending upon if I am docked or undocked.
I assume that docking state will only change whilst powered down and not under hibernation.
A hot dock/undock will result in the no change in my monitor configuration, possibly causing issues if I undock and being unable to access windows. I am ok with this.

Given all this, I have approached it in such a way that X will setup, depending upon what it's configuration is at X startup time.
A little extra effort, I guess I could make it 'switch' as I hot dock/undock.

I use Fluxbox, so a lot of the 'KDE/Gnome' functionality is not available to me.

I use an init script /etc/init.d/xdm-setup, on which my /etc/init.d/xdm depends.

I have tweaked this script to check to see if I am docked or not, on the assumption that the second monitor is available whilst docked.
My external monitor is a 24" widescreen which is positioned on the LEFT of the laptop.
Additionally, the bottom of the two screens line up physically, so I wanted the bottom of the 'screens' to line up.

The /etc/init.d/xdm-setup script

optiluca · Posted: Mon Aug 01, 2011 10:21 pm Post subject:

lyallp · Posted: Tue Aug 02, 2011 3:41 am Post subject:

In my attempts to have acpi events cause the display readjustment, I have come up with a script that uses disper.
My acpi events invoke it but it doesn't affect my logged in session.
As a workaround, I have assigned the script to a key, which I can press when I dock/undock.
I also set this to run in my .Xsession
This works with my HP EliteBook 8540w with the hp_wmi module configured.