[nvidia] with x11 fractional scaling enabled, cannot change main monitor after setting scaling for monitors

[Ian Johnson]

After booting with nvidia drivers, if I change which monitor is the main one first, then change the scaling from 100% to 200%, it works. But doing this in the inverse direction, by first setting the scaling and then changing the main monitor, it fails and the screens go black. Oddly enough, it also fails to revert this setting and I have to hard-reboot (though I could probably try switching ttys, etc).

This is with focal and focal-proposed enabled. I also have the proprietary 440 nvidia drivers enabled, and I'm using default gnome with x11.
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ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2019-07-05 (287 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair nvidia_modeset nvidia
Package: nvidia-graphics-drivers-440
PackageArchitecture: amd64
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 5.4.0-24.28-generic 5.4.30
Tags: focal package-from-proposed
Uname: Linux 5.4.0-24-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip docker kvm libvirt lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True

[Daniel van Vugt (vanvugt)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please execute the following command only once, as it will automatically gather debugging information, in a terminal:

apport-collect 1873266

When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.

[Ian Johnson (anonymouse67)]

apport information

[Ian Johnson (anonymouse67)]

apport information

[Daniel van Vugt (vanvugt)]

"screens go black" reminds me of bug 1873403 which might be somehow related.

[Daniel van Vugt (vanvugt)]

Can you please look in Settings > Screen Display and tell us if 'Fractional Scaling' is enabled?

[Ian Johnson (anonymouse67)]

Yes, 'Fractional Scaling' is enabled, sorry I should have specified. I am unable to actually use fractional scaling however due to https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1869042

[Ian Johnson (anonymouse67)]

Also, if I disable Fractional Scaling, it now works to use/apply these settings in any order

[Daniel van Vugt (vanvugt)]

The screen going black with Nvidia is mostly being tracked in bug 1873403. Let's wait till that's fixed and then if this problem reoccurs we can reopen it.