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Old 06-22-06, 01:07 PM   #1
dododge
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Default No Xinerama data from TwinView when using two cards

I've got three monitors and two 7900GTs. The left monitor is attached to one card. The center and right monitors are attached to the other card, and are configured for TwinView.

I've made sure that Xorg is not loading its own Xinerama extension, so that TwinView can provide the correct data. What I find is that if I enable only the card with two monitors, this works fine. But when I enable both cards and all three monitors, TwinView no longer provides any Xinerama data at all and I end up with two distinct X screens (one per card). I've tried various things, such as using ConnectedMonitor to force the card with only one monitor to set up TwinView of its own, but no change.

In the log file, when only one card is used I see a line where the NVIDIA driver is enabling Xinerama. When both cards are used, that line is missing.

To test the Xinerama data and make sure it's not just a window manager issue, I use a little C program to call XineramaQueryScreens directly. When using just the one card with two monitors, I get back two Xinerama screens from TwinView as expected. When both cards are enabled, I just get an Xlib error indicating that the Xinerama extension is not present in the server.

For the time being I've re-enabled Xorg's Xinerama support, which at least gives a unified desktop across all three monitors but of course thinks the two TwinView displays are a single screen so window placement is a mess.

I've previously had Xinerama working for all three screens by disabling TwinView entirely, using a distinct Device section for each monitor, and using Xorg's own Xinerama support. But I've had issues with getting OpenGL completely covering all three heads at once in that configuration, and things seem to at least be better (but still not perfect) with TwinView.
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Old 06-22-06, 01:12 PM   #2
netllama
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Default Re: No Xinerama data from TwinView when using two cards

Please generate and post an nvidia-bug-report.log along with information on the problem you're trying to solve. Its not clear to me why you believe there is no Xinerama information provided by the nvidia X driver, outside of your test app.

Thanks,
Lonni
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Old 07-25-06, 12:08 PM   #3
JTorrance
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Default Re: No Xinerama data from TwinView when using two cards

Hi!

I'm having the same problem: 2 NVidia cards (I call them A and B)
A has 2 CRTs.
B has 1 TV.

When TwinView is active on A, and card B is DISabled, The XineramaInfo works and the gnome-panel for instance covers one monitor.

When TwinView is active on A and card B is ENabled, The XineramaInfo for A seems to disappear and the gnome-panel covers both monitors. Dialogs are displayed in the middle of the two monitors etc.

What I want is:
card A: XDisplay :0.0, Two monitors and XineramaInfo
card B: XDisplay :0.1, One TV

Is there any solution for this problem?

Thanks
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Old 07-25-06, 12:14 PM   #4
netllama
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Default Re: No Xinerama data from TwinView when using two cards

JTorrance, this is a Gnome issue, not an nvidia driver bug. If you have evidence that suggests otherwise, please provide an nvidia-bug-report.log.

Thnks,
Lonni
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Old 07-25-06, 12:49 PM   #5
JTorrance
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Default Re: No Xinerama data from TwinView when using two cards

Hi!

When only card A is active, the gnome-panel looks fine. When card B is active as well, the panel spans both monitors. This looks like the xinerama information is somehow broken/lost. However many apps maximize to only one monitor. So I think the xinerama info ist not completely lost.

Is there a program to extract all the available xinerama information? It would help a lot to compare its output when used with one card and with two cards.

However, I attached the log. The xorg.conf is a mess, sorry.

Thanks
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Old 07-25-06, 12:52 PM   #6
JTorrance
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Default Re: No Xinerama data from TwinView when using two cards

Hi!

Sorry, somehow the attachement disapperaed.

Thanks
Attached Files
File Type: zip log.zip (22.0 KB, 118 views)
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Old 07-25-06, 01:39 PM   #7
netllama
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Default Re: No Xinerama data from TwinView when using two cards

I see that you've set "NoTwinViewXineramaInfo" to false. Does that change the behavior? If so, then you're hitting a Gnome bug/limitation.

Thanks,
Lonni
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Old 07-25-06, 02:28 PM   #8
JTorrance
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Default Re: No Xinerama data from TwinView when using two cards

Hi!

Thanks for the quick replies.
OK, I enabled the "NoTwinViewXineramaInfo" option.

It really makes a difference.

Both cards enabled:
If the option is DISabled gnome-panel spans both screens but windows are maximized to one screen.

If the option is ENabled gnome-panel spans both screens and windows are maximized to both screens.


Only one card enabled:
If the option is DISabled, all windows (including the gnome-panel) use only one screen. This is the ideal behavior.

If the option is ENabled, all windows (including the gnome-panel) span both screens. This is the not-so-ideal but expected behavior.


So the problem is the following:

Twinview+2cards+Gnome => Gnome somehow misinterprets the xinerama data and/or incorporates some other information which leads to this misconfiguration of the desktop.
The question: Is it really a Gnome-issue or does the nvidia driver provide some information that is unexpected/wrong?

Thanks
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Old 07-25-06, 03:15 PM   #9
JTorrance
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Default Re: No Xinerama data from TwinView when using two cards

Hi!

The initiator of this thread:
http://www.nvnews.net/vbulletin/show...maQueryScreens
wrote a small testprogram to query xinerama-data. He used it on a similar setup as the one I described.

This is a quote from the thread:
"Now this is a bit more interesting, seems XineramaIsActive returns false, but returns valid data."

Could it be, that my WM (sawfish) only queries "XineramaQueryScreens" while gnome first verifies if xinerama is really active (XineramaIsActive) and then because of the negative response ignores the valid data from "XineramaQueryScreens"? Could it be that the TwinView xinerama interface gives a wrong response to "XineramaIsActive" queries when two cards are installed?

Thanks
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