[nvidia] fractional monitor scaling fails due to overlapping monitors

[Ian Johnson]

After an upgrade with focal-proposed this morning, I am unable to set any scaling for any of my monitors without the monitor turning blank for 15 seconds and reverting to 100% scaling.

I am using X11 with gnome and proprietary nvidia drivers on Focal. I have 3 monitors attached, all 4K, and my usual setup is to enable fractional scaling, and set all 3 monitors to 150% scaling.

Now however, I cannot change the monitors to use any scaling, and even if I disconnect 2 of the monitors to only have a single monitor I still cannot use scaling.

Finally note I am just using the Settings window, I haven't fiddled with xrandr at all manually.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: mutter 3.36.0-2ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-20.24-generic 5.4.27
Uname: Linux 5.4.0-20-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu21
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Wed Mar 25 11:24:05 2020
InstallationDate: Installed on 2019-07-05 (264 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: mutter
UpgradeStatus: No upgrade log present (probably fresh install)

[Ian Johnson (anonymouse67)]

Attaching monitors.xml since it doesn't seem that apport picked it up

[Ian Johnson (anonymouse67)]

Oddly enough I was able to get 200% scaling to work randomly by not quite lining up all the monitors and offsetting them from each other in the settings window.

Is there anything I could try manually to unbreak the situation or is there a debian package I could downgrade to in order to get scaling to work again on my system?

[Ian Johnson (anonymouse67)]

FWIW, if I switch to using the noveau driver and then login via Wayland, I can enable fractional scaling through Settings and that is successful, but unfortunately then all the text in some apps becomes rather blurry.

[Ian Johnson (anonymouse67)]

Actually after testing this out, I was able to use fractional scaling with X11 again by using the nouveau driver instead of the proprietary nvidia driver, which on my machine is at nvidia-440. This is a sufficient work-around for me, it's unfortunate I can't use the proprietary nvidia driver with fractional scaling but nouveau is okay for now.

[Marco Trevisan (Treviño) (3v1n0)]

Alberto, do you know what could trigger this?

[Ian Johnson (anonymouse67)]

Is this perhaps a duplicate of https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1869750 ?

[Daniel van Vugt (vanvugt)]

That depends on whether you find this bug is now fixed after the latest updates...?

[Ian Johnson (anonymouse67)]

It is still unfortunately happening to me, but I also have a new permutation of this, my machine also happens to suffer from https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1292398, so when I boot up my machine the incorrect monitor layout is present, and I find that if I first set the main monitor correctly (because it always uses the wrong one for the main monitor), then set scaling to 200% it does work. But if I do the inverse, and first set scaling to 200% then change the main monitor, it does not work and I have to reboot and then first set the main monitor.

[Ian Johnson (anonymouse67)]

I should point out that the behavior in comment #9 happens when I am using the nvidia 440 drivers.

I still cannot use fractional scaling with the nvidia drivers successfully under any ordering, but I can at least use 200% scaling if I set it first, then set the main monitor it works.

[Daniel van Vugt (vanvugt)]

^^^
I had heard hints of that elsewhere but nobody has opened a bug for it. Please open a new bug for that.

[Ian Johnson (anonymouse67)]

Daniel, I filed that issue as https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1873266

[Ian Johnson (anonymouse67)]

Okay, so now looking back at this bug, I see that when I have Focal with X11 and the 440 nvidia drivers enabled, I can set scaling to integer multiples without problems, but enabling fractional scaling and then using a fractional scaling results in the black screen problem mentioned in this bug as well as this in the system journal:

gnome-control-c[6913]: Config not applicable: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Logical monitors overlap

[Daniel van Vugt (vanvugt)]

The black screen issue should stay in bug 1873403.

[Ian Johnson (anonymouse67)]

Daniel, it sounds then like you are saying this is a duplicate of 1873403?

[Ian Johnson (anonymouse67)]

(the issues here originally were that the screens go black and that I couldn't set the main monitor after changing scaling, for which I filed 1873266, as per your request)

[Daniel van Vugt (vanvugt)]

Kind of. I think this bug should stay separate because it seems to have a clear cause:

gnome-control-c[6913]: Config not applicable: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Logical monitors overlap

that's not the same as bug 1873403 which happens even on single monitor systems.

Although we should ideally fix the simpler case (bug 1873403) first, and then we might find that also fixes this bug. It's complicated and I am still confused. It will probably take a few weeks to sort out. This bug can stay open in the mean time.

[Daniel van Vugt (vanvugt)]

Worth noting that the Settings GUI doesn't let you make overlapping monitors. It can happen via bugs though, like bug 1874217. So maybe that needs fixing first.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.