Save button missing in screen config for multi monitors with different scaling values

[Simon Riget]

When using two screens, changes in screen resolution, placement etc. doesn't result in a [save] button appearing at the top bar, as expected.

This is rendering two screen mode useless, unless the default setting is usable.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: gnome-control-center 1:3.26.1-0ubuntu5
ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
Uname: Linux 4.13.0-16-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.1
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Nov 4 00:05:39 2017
ExecutablePath: /usr/bin/gnome-control-center
InstallationDate: Installed on 2015-07-29 (828 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
SourcePackage: gnome-control-center
UpgradeStatus: Upgraded to artful on 2017-11-01 (2 days ago)

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. The issue you are reporting is an upstream one and it would be nice if somebody having it could send the bug to the developers of the software by following the instructions at https://wiki.ubuntu.com/Bugs/Upstream/GNOME. If you have done so, please tell us the number of the upstream bug (or the link), so we can add a bugwatch that will inform us about its status. Thanks in advance.

[Sebastien Bacher (seb128)]

The log has this warning

"Config not applicable: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Logical monitor scales must be identical"

Do you scaling for the monitors? Which values?

[Simon Riget (simoi)]

Yes.

Screen 1: 3840 x 2160 scaling 200%
Screen 2: 1680 x 1050 scaling 100%

Had to go back to xorg
It worked (for the most part) in 17.04.

[Sebastien Bacher (seb128)]

The issue seems to have been reported upstream as well, see e.g https://gitlab.gnome.org/GNOME/gnome-control-center/issues/18