My configuration is the following:

  • computer is a Dell M3800 (a beefy laptop); its internal display is 15 inch, 1920x1080 resolution;
  • there is also an external display, which is a 24 inch display, same resolution, connected via HDMI.

There is something really strange since the upgrade, and I'm not sure why that is...

The configuration of the displays is so that the laptop is on the left (which it is, physically) and the large screen on the right. I have windows on both screens.

When I leave the computer alone and screens enter "power saving", if I wake the screens up, all windows are "back" to the laptop screen...

Since the initial question, I have noticed that in fact this has nothing to do with my locking the screen at all; it is systematic as long as the screens enter power saving mode (note: the screens, not the computer).

For this I have tried another configuration: only activate the Asus monitor via HDMI and deactivate the laptop's internal display... On wake up, the laptop screen highlights briefly before X "remembers" that "uh no, the guy wants the external display only" and switches back to the wanted configuration again.

Also, this laptop has an nVidia chipset, and it doesn't matter whether I use the nouveau driver or nVidia proprietary driver: the effects are the same.

I have opened a bug (link), but in the meanwhile, is there a workaround for this apart from, in settings, never let the screens "fall asleep", which is a waste?

  • there have been a few complaints of nvidia drivers misbehaving in 16.04. See if this answer helps. – astrob0t Apr 25 '16 at 10:29
  • @astrob0t I did most of the steps here except the purge; done this, rebooted. As I explained too, I also modified the settings so that the screens never "turn off" and right now the problem is fixed... I'll try and reactivate it just to see. Oh and, in case it matters but I don't believe it does, I use Unity. – fge Apr 25 '16 at 10:38
  • Yes, please try all the steps of the answer and let us know if it works. purge is like the most important step where all the buggy nvidia drivers are removed and then the next steps install the proper ones. – astrob0t Apr 25 '16 at 10:59
  • @astrob0t well, unrelated but I confirm that my multiscreen bug is just as I reported. I do also have graphics artifacts with nouveau, kind of like the questions you linked to describe (items not displaying correctly), but this multiscreen bug is, at a first glance, independent from this one. If you want me to do some more tests, just ask. – fge Apr 25 '16 at 12:33
  • I can confirm this too. Nvidia 950 desktop system with no Intel GPU backing it. It behaves the same if you pull a cable on the monitor and re-attach it. I also saw variations of this with 15.10 - so it isn't exactly a new problem. – RoundSparrow hilltx Jun 21 '16 at 11:22

I have the same laptop but with a 4k screen and i don't have this issue although my external screen is connected via displayport/thunderbolt.

I found that the HDMI socket was not as reliable for external screens and would struggle with my 4k external screen, that said your resolutions shouldn't be a problem.

There might be some issues with HDMI-CEC which can be used to control screens via HDMI - http://hdmicec.blogspot.co.uk/2012/05/how-to-find-out-if-your-device-is-hdmi.html

I found it was much more reliable on my setup if i used the graphics drivers ppa https://launchpad.net/~graphics-drivers/+archive/ubuntu/ppa

I use nvidia-367 and it seems to be much faster at initialising screens, previous versions often timed out getting 4k sync so would take ages to start and give me errors.

  • i still get issues where the windows all end up on the desktop occasionally if they monitors take too long to sync. This is likely a bug in the intel driver rather than nivdia, even though nvidia updates do help its the intel driver that does the hardware control. This is less of an issue if you force nvidia mode in nvidia-settings prime configuration as it syncs faster, you get less resolution options betweeen hd and 4k this way though. – Amias Sep 5 '16 at 13:33

I see this problem with Dell Precision 5510. 1 monitor is hdmi, other is VGA plugged into a thonderbolt adapter. Nvidia 1000m and intel graphics.

The Intel graphic display is nicer, nvidia has lots of tearing. However Intel has horrible resume from screen lock problem described here. Awake from suspend is ok if machine is not unplugged and used elsewhere. The hdmi monitor almost always stays black after wake from screenlock and will not wake up without logging out.

If using nvidia driver then there is a 50% chance monitor will wake up if I try with arandr.

If you did not try arandr yet, you should. It is nice gui view of xrandr and you can turn monitors off and on. It can save configs.

When arandr does not 'wake up' the monitor, fix requires log out, after which it is fine, until I go to bathroom and screen lock kicks in. Have considered getting bucket to avoid trip away from desk :)

When one monitor goes black, the desktop / window manager does not squeeze everything onto the surviving monitor. Some apps are on the dark side, but xfce4 workspace switcher shows both in panel.

I have no luck with optimus/bumblebee. nvidia-settings has nice chooser to switch display driver, requires log out to change over.

I will go find more, different types of monitors. Am suspecting aged monitors are part of explanation. These are 24" Dell monitors that must be 4 or 5 year old. To others with trouble, do you have same?

Please think on this. If I reboot, both displays are found instantly and all is well. Doesn't that mean the video driver itself is ok? In ubuntu 16.04, I did have the "my cursor is invisible after suspend" problem, but only in the Intel display case (https://bugs.launchpad.net/ubuntu/+bug/1573454, https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1568604). Nvidia did not show same. Then we got word the light-locker should be removed to fix. Xscreensaver to the rescue. Maybe display driver had defect, but locker contributed. We were blaming display driver entirely.

Hmm. Makes me wonder if Xscreensaver may link to black screen trouble. Will test. If you have the black screen trouble, have you made other desktop/locker changes?

  • I am using a Dell 22" monitor alongside a 720p tv,on ubuntu 16.04 and everything works fine.No drivers were needed besides whatever installed with Ubuntu.My Dell monitor is an older one I bought used. – Bob Jan 30 '17 at 23:47

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