Setting fractional scaling beyond 125% causes segfault

[Nick Nemeth]

Setting fractional scaling between 125% and 175% yields improper behavior. When set to 125%, display will be scaled to 200%. Attempting to use either 150% or 175% scaling causes gnome-control-center to segfault. Selecting 200% scaling exhibits proper behavior.

Steps to reproduce the issue:

1. Enable the Fractional Scaling toggle under Displays in gnome-control-center.
2a. Select 125% beside Scale, and press "Apply" at the top right. Display should scale to 200% and the selected scale should also change to 200%.
2b. Select either 150% or 175% beside Scale and press "Apply" at the top right. Monitor may possibly turn off for a few seconds, and gnome-control-center will have segfaulted with scaling remaining at 100% when it turns back on.

Release: Ubuntu 20.04 LTS
Package version: 1:3.36.1-1ubuntu5
Expected behavior: Display scaling set properly to fractional values
Exhibited behavior: Improper scaling with scale set to 125% and segmentation faults with 150% and 175% scale

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-control-center 1:3.36.1-1ubuntu5
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Thu Apr 23 21:17:22 2020
InstallationDate: Installed on 2020-04-23 (0 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-control-center
UpgradeStatus: No upgrade log present (probably fresh install)

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It sounds like some part of the system has crashed. To help us find the cause of the crash please follow these steps:

1. Look in /var/crash for crash files and if found run:
    ubuntu-bug YOURFILE.crash
Then tell us the ID of the newly-created bug.

2. If step 1 failed then look at https://errors.ubuntu.com/user/ID where ID is the content of file /var/lib/whoopsie/whoopsie-id on the machine. Do you find any links to recent problems on that page? If so then please send the links to us.

3. If step 2 also failed then apply the workaround from bug 994921, reboot, reproduce the crash, and retry step 1.

Please take care to avoid attaching .crash files to bugs as we are unable to process them as file attachments. It would also be a security risk for yourself.

[Daniel van Vugt (vanvugt)]

It's probably bug 1874197, please still please follow the instructions in comment #2 to be sure...

[Launchpad Janitor (janitor)]

[Expired for gnome-control-center (Ubuntu) because there has been no activity for 60 days.]