Ubuntu 18.10 broke dual-screen dual-desktop configuration

[C. Jeffery Small]

I'm running Xubuntu. I finally reported this problem to the Xfce group and received this response:

"As arandr/xrandr does not detect correctly your 2nd screen, this seems that it is not related directly to Xfce, but a bug in Xubuntu stack. Can you please open a bug on Xubuntu project if the issue is still present for you?"

Thus this bug report.

I've been running Xubuntu for years with two monitors, each running an independent xfce4 desktop -- i.e., configured without Xinerama. This has worked fine for every upgrade through 18.04. When upgrading to 18.10, something significant changed and the the second monitor (display :0.1) was disabled. After much reading and work, I have only been able to restore some extremely hobbled functionality. I am unable to get a second xfce4-desktop, panel or window manager running on the second screen. I have assembled detailed screenshots and command output at the following link:

http://smallthoughts.com/xfce/xfce.html

I'm using an NVIDIA Quadro K-4000 graphics card and no hardware changes were made between 18.04 and 18.10.

The nvidia-settings tool reports both monitors active (as configured in /etc/X11/xorg.conf) but the xfce4-display-settings and aarandr tools each show only one display (although xrandr can be forced to report on the second display. See full documentation at the above link.)

What changed in the latest release, and what needs to be done to get the second monitor running a second desktop once again? I have been struggling with this for many months now and it has severely impacted the use of my system. As a new release of Ubuntu in coming, I would appreciate it if this could be prioritized and addressed as quickly as possible.

I will provide additional information upon request.

P.S.: There is really no documentation available on running multiple desktops on separate screens when Xinerama is not used to tie the screens together into a single desktop. This is a common configuration and I would like to request that as part of the solution to this problem, the setup steps be documented and this multi-desktop configuration be made a standard part of the development and testing process for each Ubuntu release.

13-> lsb_release -rd
Description: Ubuntu 18.10
Release: 18.10

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1822181/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

This is an automated message:

OK automated message, I'd be happy to list a specific source package if I knew what it might be. I really am not sure what might be responsible here any more than the people in the Xfce group were. If some humans on the team could review this issue and have a suggestion as to where to focus, I would be happy to add one or more packages or let others fill in that info. I'm not sure how the core Ubuntu system is broken down.

I'll tag it against xfwm4, but I'm not sure that the problem is more fundamental than at the window manager level.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Not sure that this is the correct package, but it's a starting point.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Any takers?

[Theo Linkspfeifer (lastonestanding)]

My suggestion would be to test with Xubuntu 19.04 Beta.

The window manager is not responsible for display configuration, xfce4-settings is (and it relies on RandR). Maybe Xorg and/or the nvidia driver is to blame for the changed behavior.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Is there anyone else in the Xubuntu world running a dual monitor dual desktop configuration?

[Steve Fatula (rs26)]

I have the exact same issue in the exact same way, been struggling to make it work and it simply does not. It did work in previous xubuntu versions, but not 18.10, something broke it.

Essentially, if you watch the machine boot up, you will see the second monitor initially shows some stuff, then, it eventually goes not blank but some light color, CJS called it light gray, lets go with that. It does not respond, I cannot send anything to that display. nvidia control panel shows both screens set up as shown by the OP. The control panel shows the second display as :0.1, and, if I for example DISPLAY=:0.1 thunar, it displays on display 0.0

If you shut the machine down, the formerly inactive second display comes to life and shows the shutdown process.

If you remove the double screen portion of xorg.conf and use a single screen, it works fine. But that's not what is desired here.

If there is any info I can provide, please let me know. Like CJS, this is very bad for me.

[Theo Linkspfeifer (lastonestanding)]

As mentioned before, please test with Xubuntu 19.04.

[Steve Fatula (rs26)]

I will test with 19.04, but if it does not work, then, I am going to format and load 18.04.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Steve, glad to see that there is someone else with this problem, but sorry that you are also experiencing the difficulties.

Like Steve, I tried using Xinerama and was able to get the single desktop to span the two monitors, but starting a second desktop, as desired, does not work. This is why I identified the window manager as a possible locus of the problem. If someone thinks it relates to a different package, please make the necessary change.

I have upgraded Xubuntu many times up through 18.04 and had no problem. There is definitely something significant that changed in 18.10 that caused this problem. From the outside it is difficult to determine where to point the finger as to what may be the source of the problem. That is why I was hoping that a variety of people working on the core components affecting this could look into it. I tried to provide as much configuration and diagnostics information as I could in order to allow someone with a test setup to add a second monitor and configure it for dual independent desktops and see what results you get. As I said before, this configuration should be part of the standard testing before any release, and well documented.

BTW, I've also been (long ago) in discussions with the Nvidia people and they/I don't think it has anything to do with their driver. I tried a number of different Nvidia driver packages as well as the Xorg version, and nothing made any difference.

I will upgrade and test with 19.04 when released (what have I got to lose) but this machine is my live work system and I really cannot screw with it too much as a test bed.

And like Steve, I'll happily provide any additional info I can, upon request.

[Steve Fatula (rs26)]

19.04 is released as of yesterday I think, that's why I shall test it hopefully today or tomorrow. Save yourself some time, I will do so.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Thanks Steve.

[Steve Fatula (rs26)]

So, I Loaded up 19.04, didn't take too long, and, the result was identical, still doesn't work, still the same symptoms. For me, this is with nvidia 418 driver, my card doesn't work with 415 driver since it's an RTX2060. For me, xrandr -q shows all devices except the second monitor, it doesn't show at all, in my case, this is DP-2, not even listed. It's MIA from xrandr. However, it shows in nvidia-settings. Just like CJS says though, I can xrandr -display :0.1 and it does show and even says connected.

Is it for sure this is not an nvidia driver issue?

I don't know what else to do other than install xubuntu 18.04 and hope it still works.

[Steve Fatula (rs26)]

I wonder if it has to do with this change:

https://bugzilla.xfce.org/show_bug.cgi?id=7502

Maybe it can't start that second screen due to this?

[Steve Fatula (rs26)]

Wish I could delete that post! I saw the latest posts as 2019, but the bug was 2011. This worked long after that.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Steve, thanks for looking into this with 19.04. I wasn't expecting that it would improve things, but I decided that if I was going to pour more effort into this, U would wait for the next OS release.

Yes, the other post may not be directly relevant to our problem, but it's still interesting. I've thought that some underlying change may have been made to disallow a second session manager to run, so this might be a clue as to where to look. I get the same xrandr results as you.

% xrandr -q
Screen 0: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DVI-I-0 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
   1600x1200 60.00*+
   1280x1024 85.02 75.02 60.02
   1024x768 85.00 75.03 70.07 60.00
   800x600 85.06 75.00 72.19 60.32 56.25
   640x480 85.01 75.00 72.81 59.94
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)

% xrandr -display :0.1
Screen 1: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DP-3 connected primary 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
   1600x1200 60.00*+
   1280x1024 85.02 75.02 60.02
   1024x768 85.00 75.03 70.07 60.00
   800x600 85.06 75.00 72.19 60.32 56.25
   640x480 85.01 75.00 72.81 59.94

Now, can we get developers responsible for different parts of the OS related to display recognition and the launching of xfce4 to please coordinate on this problem and track down the source. It definitely happened due to a change from 18.04 to 18.10, so diffs between those two versions is the place to look.

[Steve Fatula (rs26)]

Definitely works with 18.04 xubuntu, got it working immediately with the same config, same nvidia driver, etc. Wanted to make sure nothing real recent, like within months, may have broken it. So, I agree that there was a change made that breaks it in 18.10+.

And I totally agree that updated doc for multi screen doc should be updated or created as needed.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

Steve, I also made an earlier report to Nvidia regarding this. You might consider adding a comment at the following link in order to prod more discussion and involvement there as well. Regards.

https://devtalk.nvidia.com/default/topic/1046553/linux/quadro-k4000-second-monitor-problem-on-xubuntu-18-04/

[Simon Steinbeiß (ochosi)]

I can't imagine that this bug has anything to do with xfwm4 or Xfce in general.

If you're not seeing a screen / display exposed through RandR but you see it through Nvidia's settings UI then it sounds like the driver or the combination of driver and kernel are at fault.
Xfce builds on top of RandR and can therefore only react to what it gets from there, so I'm afraid there's nothing much that can be done on the Xfce side.

I would suggest you try different versions of the Nvidia driver (maybe you can get the same one you used for 18.04 just to exclude that) or even the open source nouveau driver.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

As previously reported, I've tried a number of different Nvidia and the X.Org drivers with no better results.

And as previously reported:
--------------------------------------------------
54-> xrandr
Screen 0: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DVI-I-0 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
   1600x1200 60.00*+
   1280x1024 85.02 75.02 60.02
   1024x768 85.00 75.03 70.07 60.00
   800x600 85.06 75.00 72.19 60.32 56.25
   640x480 85.01 75.00 72.81 59.94
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis

Note: No DP-3? RandR must be numbering the display ports differently from NVIDIA.

The above output is identical to what you get with the command: xrandr -display :0.0

However, you can probe the second screen with the command: xrandr -display :0.1

55-> xrandr -display :0.1
Screen 1: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DP-3 connected primary 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
   1600x1200 60.00*+
   1280x1024 85.02 75.02 60.02
   1024x768 85.00 75.03 70.07 60.00
   800x600 85.06 75.00 72.19 60.32 56.25
   640x480 85.01 75.00 72.81 59.94
--------------------------------------------------

So, as you can see, RandR DOES know about the second display, but it does not properly integrate it into the system.

Since you say that Xfce is built upon RandR, I'd say that that may be the place to start.

I don't know what is going on down at this level, but if someone in the developer community thinks this is actually a RandR problem, please change the target package from my guess of xfwm4 to libxrandr2 or whatever you think appropriate.

Still, this is a lot of theorizing when someone in the developer group could be testing this out on a dual screen configuration and see what actually happens!

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 18.10 (cosmic) reached end-of-life on July 18, 2019.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in and change the bug status to Confirmed.

[C. Jeffery Small (loyhz2ay-jeff-h670zbts)]

I am VERY interested in continuing work on this. I'm now running 19.04 and the problem persists. I cannot change the status so please update it.

There has been a long running discussion on the Xfce buglist which you can review here:

https://bugzilla.xfce.org/show_bug.cgi?id=15116

The problem seems to be that the move to gtk3 is the source of the condition as it has dropped support for multiple monitors. Olivier Fourdan is maintaining xfwm4 and he has apparently done something internally that allows X11-aware applications to be launched on a separate display (:0.1) in addition to the native display (:0.0), but none of the other Xfce components such as the panel, desktop, etc have the ability to run more than one instance on the main display.

In this forum discussion:

https://forum.xfce.org/viewtopic.php?pid=50336#p50336

member gert pointed to this patch in the gtk3 repository that seems to indicate that multi-screen support has been added back into the toolkit.

https://github.com/xfce-mirror/xfwm4/commit/b52c2f5b740434803342c471d4dcb5dd62eb99a1

However, this patched version of gtk has not yet made it into a Ubuntu distribution.

Losing multi-headed independent desktop support has been a terrible step backwards for Ubuntu. Please look into this more closely and make sure that the 19.10 release gets the tools required to get this capability restored.

I'll provide additional info if necessary. However, as an end0user in this arena, I don't have more insights into the interactions of the display components making up the various desktop environments.

On a couple of other forums, I asked whether there was another flavor of Ubuntu that was properly supporting multiple screens. I received zero replies. Multiple independent desktops is critical (as opposed to Xinerama mode) so that material can be displayed statically on one display while changing workspaces on the other screen.