Dual Monitor setup

finarfin · n00b Joined: 20 Sep 2011 Posts: 62

Hi all,

i just followed the wiki guide on how to setup a dual monitor environment for my laptop (so i followed the Intermittent Dual-Monitors), then i installed xrandr and tried to update the xorg.conf, when i plug the second monitor and i launch

Gusar · Posted: Mon Feb 13, 2012 8:09 pm Post subject:

Sound like you need to recompile your entire machine with the xinerama USE flag.

Also, your xorg.conf as such does absolutely nothing, you can get rid of it. If you want to permanently have a dual-head setup, see here.

gorkypl · Guru Joined: 04 Oct 2010 Posts: 444 Location: Kraków, PL

To me it looks rather like an issue with window manager/desktop environment. What WM do you use?

Also two important things:
1) In my opinion USE="xinerama" has absolutely nothing to do with the issue, I recommend not to enable it as it is deprecated.
2) Your entire xorg.conf is not needed, either use xrandr with '--right-of' part, or set your xorg.conf similar to the straight example given by Gusar.

Gusar · Posted: Wed Feb 15, 2012 3:06 pm Post subject:

gorkypl · Guru Joined: 04 Oct 2010 Posts: 444 Location: Kraków, PL

Gusar · Posted: Thu Feb 16, 2012 12:30 pm Post subject:

What you need to differentiate is "xinerama the extention" and "xinerama the protocol". xrandr and twinview use the protocol, but not the extension.

It seems to me you're using the extension with your setup. Which will work for apps because they see DISPLAY=:0.0 and DISPLAY=:0.1 and so on. But if you use xrandr, there's just DISPLAY=:0 and nothing else. So that apps can then know where the separate displays are, they need to speak the xinerama protocol.

gorkypl · Guru Joined: 04 Oct 2010 Posts: 444 Location: Kraków, PL

Do you have any links to papers that can help me understand this? It's not so important and I know that X is rather messy, but I'd just like to know the things a bit more.

Especially I'm not sure if I understand the extension/protocol difference.
Protocol defines the communication between server and clients and is used also by RandR, while extension simple enables several screens, yes?

Gusar · Posted: Thu Feb 16, 2012 3:08 pm Post subject:

The extension stitches multiple independent screens together, so that you can move the mouse (and the apps themselves, I think) from one to another. But with xrandr, there's no independent screens, it's one big screen. "Merged framebuffer" being the technical term. One framebuffer spanning all displays.

gorkypl · Guru Joined: 04 Oct 2010 Posts: 444 Location: Kraków, PL

finarfin · n00b Joined: 20 Sep 2011 Posts: 62

Sorry for the delay of my answer!

So:
1. I have fluxbox installed as wm
2. Looking at the log i found that line:

Gusar · Posted: Fri Feb 17, 2012 8:51 pm Post subject:

Err, I don't get it. Why are you checking for the x11 flag?? Check for the xinerama flag. Fluxbox has it. And I'm quite sure you don't have it activated.

Activate the flag globally then do an "emerge --newuse world". These are the basics of using Gentoo, I can't believe I need to be explaining them.

finarfin · n00b Joined: 20 Sep 2011 Posts: 62

finarfin · n00b Joined: 20 Sep 2011 Posts: 62

Ok i added the use flag for xinerama on my system.

It updated also fluxbox package. Now the windows are opened in only one window automatically, and the bar is not stretched between two monitors. This is a good step forward.

But the background image is still stretched. Then i try to
But now if i try to set two different background using:

Gusar · Posted: Sat Feb 18, 2012 10:06 am Post subject:

Read what I wrote above - xrandr doesn't have separate DISPLAYs anymore. I think Fluxbox has a different, more proper way to set wallpapers for multiple displays, but it's been many many years since I used it, so I wouldn't know how. So you'll have to RTFM.