Moving windows between monitors with different scaling causes isues

Bug #1983508 reported by Petr Doležal
This bug affects 1 person
Affects Status Importance Assigned to Milestone
mutter (Ubuntu)

Bug Description

When two displays are connected and one has a 200% scaling, moving apps between them results in several issues:

Apps that can actively scale (such as native Nautilus, Settings...):

 When dragging the window around, it automatically adjusts scaling based on on which of the monitors is the majority of the app (this is probably correct behaviour),

BUT when using keyboard shortcuts [Ctrl] + [Super] + ←/↑/↓/→, fullscreen windows jump around and scale correctly, but half-full screen apps (arranged by [Super] + ←/→) cannot go from the larger monitor to the smaller, they get stuck in the scaled-up version and don't fit on the smaller display.

Small non-maximized windows don't have this issue, possibly because when they first move in their scaled-up state, they do fit on the smaller monitor still, and only then are they scaled down.

Apps that don't support changes in scaling and only apply the new scaling on a relaunch (such as Chrome) don't have these issues, but they obviously have that other problem.

Description: Ubuntu 20.04.4 LTS
Release: 20.04
mutter 3.36.9

What I expect:
Windows covering half a full screen, when moved to a different display with different scaling (using a keyboard), stay covering half a full screen.

What happens instead:
When moved to a display with higher scaling, this happens correctly, but when moved to a monitor with lower scaling, they get "stuck" on both monitors in their inflated state.
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27.24
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2020-10-14 (658 days ago)
InstallationMedia: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
Package: mutter 3.36.9-0ubuntu0.20.04.2
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 5.15.0-43.46~20.04.1-generic 5.15.39
Tags: focal wayland-session
Uname: Linux 5.15.0-43-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin lxd plugdev sambashare sudo video
_MarkForUpload: True

Revision history for this message
Daniel van Vugt (vanvugt) wrote :

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 1983508

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

tags: added: focal
Changed in mutter (Ubuntu):
status: New → Incomplete
Revision history for this message
Petr Doležal (elkir) wrote : Dependencies.txt

apport information

tags: added: apport-collected wayland-session
description: updated
Revision history for this message
Petr Doležal (elkir) wrote : ProcCpuinfoMinimal.txt

apport information

Revision history for this message
Petr Doležal (elkir) wrote : ProcEnviron.txt

apport information

Revision history for this message
Daniel van Vugt (vanvugt) wrote :

Thanks. This sounds like a problem with mutter's window constraints logic.

I would recommend that you:

1. Confirm the bug is still present in GNOME 42 (Ubuntu 22.04); and then

2. Report it upstream at

3. Tell us the new issue ID.

Changed in mutter (Ubuntu):
status: Incomplete → New
tags: added: multimonitor scaling
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