When switching from fractional scaling back to integer scaling, only part of the screen is used

[Pierre Equoy]

Steps
=====

- In Settings > Display, activate Fractional Scaling, and set it to 175%.
- Deactivate fractional scaling and press Apply

Expected results
================

The screen goes back to 200% integer scaling

Actual results
==============

Only the upper left quarter of the screen is being used.

Workaround
==========

After pressing Apply, a popup asks if we want to keep changes or revert them.

Pressing "Revert" does not revert anything, but actually updates the screen to use the full screen instead of just the upper left section, while remaining in 200% integer scaling!

Information
===========

Version: Ubuntu Jammy Jellyfish (development branch) [Beta image]
Release: 22.04

Device: Dell Precision 7760 with Nvidia GPU
CID: 202103-28858

Third party software installed during installation

Wayland in use.

ii linux-generic-hwe-20.04 5.15.0.23.25 amd64 Complete Generic Linux kernel and headers
ii linux-headers-5.15.0-23 5.15.0-23.23 all Header files related to Linux kernel version 5.15.0
ii linux-headers-5.15.0-23-generic 5.15.0-23.23 amd64 Linux kernel headers for version 5.15.0 on 64 bit x86 SMP
ii linux-headers-generic-hwe-20.04 5.15.0.23.25 amd64 Generic Linux kernel headers
ii linux-image-5.15.0-23-generic 5.15.0-23.23 amd64 Signed kernel image generic
ii linux-image-generic-hwe-20.04 5.15.0.23.25 amd64 Generic Linux kernel image
ii linux-modules-5.15.0-23-generic 5.15.0-23.23 amd64 Linux kernel extra modules for version 5.15.0 on 64 bit x86 SMP
ii linux-modules-extra-5.15.0-23-generic 5.15.0-23.23 amd64 Linux kernel extra modules for version 5.15.0 on 64 bit x86 SMP
ii linux-modules-nvidia-510-5.15.0-23-generic 5.15.0-23.23+1 amd64 Linux kernel nvidia modules for version 5.15.0-23
ii linux-modules-nvidia-510-generic-hwe-20.04 5.15.0-23.23+1 amd64 Extra drivers for nvidia-510 for the generic-hwe-20.04 flavour
ii linux-objects-nvidia-510-5.15.0-23-generic 5.15.0-23.23+1 amd64 Linux kernel nvidia modules for version 5.15.0-23 (objects)
ii linux-signatures-nvidia-5.15.0-23-generic 5.15.0-23.23+1 amd64 Linux kernel signatures for nvidia modules for version 5.15.0-23-generic

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: gnome-shell 42~beta-1ubuntu3
ProcVersionSignature: Ubuntu 5.15.0-23.23-generic 5.15.27
Uname: Linux 5.15.0-23-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu79
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Apr 1 10:51:09 2022
DisplayManager: gdm3
GsettingsChanges:
 b'org.gnome.shell' b'welcome-dialog-last-shown-version' b"'42.beta'"
 b'org.gnome.desktop.input-sources' b'sources' b"[('xkb', 'us')]"
 b'org.gnome.desktop.interface' b'gtk-im-module' b"'gtk-im-context-simple'"
 b'org.gnome.desktop.privacy' b'report-technical-problems' b'true'
 b'org.gnome.mutter' b'experimental-features' b"['scale-monitor-framebuffer']"
InstallationDate: Installed on 2022-04-01 (0 days ago)
InstallationMedia: Ubuntu 22.04 LTS "Jammy Jellyfish" - Beta amd64 (20220329.1)
RelatedPackageVersions: mutter-common 42~beta-1ubuntu2
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Pierre Equoy (pieq)]

The video shows what happens when user is using 175% fractional scaling and then deactivate Fractional Scaling:

- only the upper left part of the screen is used
- a popup asks if user wants to keep or revert the changes
- if user clicks Revert, it doesn't actually revert back to Fractional Scaling, but it remains in integer scaling, and the whole screen is being used.

[Daniel van Vugt (vanvugt)]

I've been seeing this issue (on rare occasions) for years. So it's not new but also not common enough to be a big concern. Once a user has settled on a choice of resolution and rebooted, they will never see it again.

[Launchpad Janitor (janitor)]

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

[Seth Arnold (seth-arnold)]

But who would keep that resolution when it sure *looks* broken? I can understand the "it's not new and we don't know how to fix it" :) but probably users won't know that they'll be fine after a reboot.

Thanks

[Daniel van Vugt (vanvugt)]

Good point. I haven't done a duplicate check yet but I expect other people have reported this somewhere

[jeremyszu (os369510)]

The related issue reported when using Xorg:
https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1966050

[Daniel van Vugt (vanvugt)]

The Xorg implementation of fractional scaling isn't really related to the Wayland one so we shouldn't link the bugs together.

Xorg fractional scaling is an Ubuntu patch.
https://bugs.launchpad.net/ubuntu/+bugs?field.tag=xrandr-scaling

Wayland fractional scaling is an upstream feature.
https://bugs.launchpad.net/ubuntu/+bugs?field.tag=wayland-fractional-scaling