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Old 10-20-10, 03:51 PM   #1
rpug
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Default separate X screen causes my twinview screen to maximize across both displays

Hi,

I have a JATON Video-558PCI-QDLP card, which is basically a card that has two GeForce 8400 GS chips on it.

I have three displays hooked up.

Two are set up as TwinView. The third is set up as a separate X screen.

When I have the third running as the separate X screen, the two that are set up as TwinView start acting weird. My gnome panels expand across both displays as do windows when I maximize them. When I only have the twinview X screen enabled, then it works fine.

I can't seem to figure out how to fix this.

I am running Ubuntu 10.10 (x86_64) with NVIDIA driver 260.19.06.

Xorg conf is attached.

Thanks in advance for any help..
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File Type: txt xorg.conf.txt (2.6 KB, 129 views)
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Old 10-21-10, 04:02 AM   #2
weltall
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Default Re: separate X screen causes my twinview screen to maximize across both displays

i've the same problem when using a displaylink device as separate x screen with the same setup for the nvidia managed screens.
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Old 10-21-10, 09:48 AM   #3
rpug
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Default Re: separate X screen causes my twinview screen to maximize across both displays

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Originally Posted by weltall View Post
i've the same problem when using a displaylink device as separate x screen with the same setup for the nvidia managed screens.
It seems that once you set up a separate X screen, twinview stops sending Xinerama info which is why this happens. I don't know a workaround unfortunately.
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Old 10-21-10, 09:56 AM   #4
AaronP
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Default Re: separate X screen causes my twinview screen to maximize across both displays

This is a limitation in the Xinerama extension protocol. It's only capable of describing a single logical X screen, so when you have two, it has to be turned off. This means that your window manager doesn't know where your physical displays are.
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Old 10-21-10, 11:50 AM   #5
rpug
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Default Re: separate X screen causes my twinview screen to maximize across both displays

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Originally Posted by AaronP View Post
This is a limitation in the Xinerama extension protocol. It's only capable of describing a single logical X screen, so when you have two, it has to be turned off. This means that your window manager doesn't know where your physical displays are.
That's frustrating.. I wish that it could describe the twinview X screen, and not bother with the separate X display which is only 1 monitor.
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Old 11-20-10, 05:02 AM   #6
pigeon
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Default Re: separate X screen causes my twinview screen to maximize across both displays

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Originally Posted by AaronP View Post
This is a limitation in the Xinerama extension protocol. It's only capable of describing a single logical X screen, so when you have two, it has to be turned off. This means that your window manager doesn't know where your physical displays are.
Thanks. Took me a while to find this answer.

Maybe that should be added to the README.txt?
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Old 11-20-10, 06:08 PM   #7
pigeon
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Default Re: separate X screen causes my twinview screen to maximize across both displays

Out of desperation and curiosity, I wrote a very simple shared library to override the XineramaQueryScreens() function to return the info I wanted (and XineramaIsActive() to always return true too). I then LD_PRELOAD it to see the effect.

My setup is 3 screens, 2 cards. The left 19" and center 20" screen are on card 1 with TwinView on. The right 19" screen is on card 2. The resolutions are respectively 1440x900, 1680x1050, 1440x900.

I have my "fake" XineramaQueryScreens() to always return 2 heads, 1440x900+0+0 and 1680x1050+1440+0.

xdpyinfo -ext XINERAMA now shows:

Code:
XINERAMA version 1.1 opcode: 150
  head #0: 1440x900 @ 0,0
  head #1: 1680x1050 @ 1440,0

I'm using Xfce. The desktop settings now thinks I have two screens, and each of them has 2 monitors. So, "Screen1 Monitor1", "Screen1 Monitor2", "Screen2 Monitor1", "Screen2 Monitor2".

Obviously, that is not true. However, as far as I can tell, everything seems to work the way it should. My left, center, right are S1M1, S1M2, S2M1. S2M2 is a dead screen, but I don't see any bad things with it being there so far. And I'm guessing since my S1M1 has the same resolution as S2M1, it works without any weird behavior.

Desktop wallpaper are shown correctly for the 3 "real" screens. Xfce panel also behaves properly. Maximized windows are also correct, not spanning across two monitors.

Now I'm thinking, would it make sense for the NVIDIA configuration to have something for the user to force it to do something like that? Kinda like a i-know-what-i-am-doing-just-let-me-do-it option? It might be something like the TwinViewXineramaInfoOverride option. Maybe a ForceXineramaInfoOverride?

Or am I totally wrong here?

Thanks.
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Geforce 6600 256MB RAM
Geforce Go 7400 256MB RAM
Geforce 9300M GS 256MB RAM (ASUS N10J)
ION 512MB RAM (Acer Revo)
GTX 460 1G RAM x 2
GeForce GT 335M (Alienware M11X R2)
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Old 11-20-10, 08:49 PM   #8
JaXXoN
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Default Re: separate X screen causes my twinview screen to maximize across both displays

Quote:
Originally Posted by pigeon View Post
Or am I totally wrong here?
Sort of.

Several "fakearama"-solutions have been around for a while, i.e.
http://www.nvnews.net/vbulletin/showthread.php?t=85604

I think this feature should be part of the Xserver itself, i.e. you could
then also sub-divide a single 30" LCD to i.e. four pseudo 15" LCDs if
that better matches your work habits. It would be even better if
the XineramaInfo could be changes during run-time on the fly
so that you can match the behaviour to whatever is currently
required (i.e. further sub-divide one of the 15" pseudo LCDs
mentioned in the example, above). Should be very easy to
implement that in Xorg.

regards

Bernhard
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Old 11-20-10, 09:54 PM   #9
pigeon
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Default Re: separate X screen causes my twinview screen to maximize across both displays

Quote:
Originally Posted by JaXXoN View Post
Sort of.

Several "fakearama"-solutions have been around for a while, i.e.
http://www.nvnews.net/vbulletin/showthread.php?t=85604

I think this feature should be part of the Xserver itself, i.e. you could
then also sub-divide a single 30" LCD to i.e. four pseudo 15" LCDs if
that better matches your work habits. It would be even better if
the XineramaInfo could be changes during run-time on the fly
so that you can match the behaviour to whatever is currently
required (i.e. further sub-divide one of the 15" pseudo LCDs
mentioned in the example, above). Should be very easy to
implement that in Xorg.
Ah, nice. And that was a long time ago too.

Being an X option would make more sense.

One thing though is, as far as I understand it, Xinerama could mean two different things. One is to allow windows to be moved across multiple X servers. The other is simply a kind of information that defines the dimension and offset of screens/monitors.

For instance, I have Xinerama turned off, so I cannot move a window across my two servers (cos I want performance and compositing), and yet, I need the Xinerama screen information so that the window manager and other things would know there are three monitors.
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Geforce 6600 256MB RAM
Geforce Go 7400 256MB RAM
Geforce 9300M GS 256MB RAM (ASUS N10J)
ION 512MB RAM (Acer Revo)
GTX 460 1G RAM x 2
GeForce GT 335M (Alienware M11X R2)
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