Scale display doesn't work with an external monitor attached

[Carlos Perelló Marín]

I have a Dell XPS 13" (2018) connected to an LG 4K 32" display thru USB-C cable. both screens are supposed to have the same resolution, but the laptop one uses 200% of scale setting due to small size.

When the laptop is connected to the external display, the scale setting does nothing and almost everything looks pretty small and hard to read, only gnome-terminal content seems to follow the scaling setting but windows decorators and app menus are pretty small.

If I disconnect the external display everything works as expected (at least with the usual apps like GNOME apps, Firefox, Chrome, etc...).

I'm using Ubuntu 18.10 with latest updates installed.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: xorg 1:7.7+19ubuntu8
ProcVersionSignature: Ubuntu 4.18.0-13.14-generic 4.18.17
Uname: Linux 4.18.0-13-generic x86_64
ApportVersion: 2.20.10-0ubuntu13.1
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Tue Jan 29 13:08:45 2019
DistUpgraded: 2019-01-05 13:19:27,114 ERROR got error from PostInstallScript ./xorg_fix_proprietary.py ([Errno 2] No such file or directory: './xorg_fix_proprietary.py': './xorg_fix_proprietary.py')
DistroCodename: cosmic
DistroVariant: ubuntu
DkmsStatus: virtualbox, 5.2.18, 4.18.0-13-generic, x86_64: installed
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation UHD Graphics 620 [8086:5917] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Dell UHD Graphics 620 [1028:07e6]
InstallationDate: Installed on 2019-01-05 (24 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
MachineType: Dell Inc. XPS 13 9370
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.18.0-13-generic root=UUID=0331a22b-f276-4072-83bb-95f04eb8ba77 ro quiet splash vt.handoff=1
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to cosmic on 2019-01-05 (23 days ago)
dmi.bios.date: 11/04/2018
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.6.3
dmi.board.name: 0F6P3V
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.6.3:bd11/04/2018:svnDellInc.:pnXPS139370:pvr:rvnDellInc.:rn0F6P3V:rvrA00:cvnDellInc.:ct10:cvr:
dmi.product.family: XPS
dmi.product.name: XPS 13 9370
dmi.product.sku: 07E6
dmi.sys.vendor: Dell Inc.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.95-1
version.libgl1-mesa-dri: libgl1-mesa-dri 18.2.2-0ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 18.2.2-0ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.20.1-3ubuntu2.1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-3

[Sebastien Bacher (seb128)]

Thank you for your bug report, could you add your journalctl log after triggering the issue? What screen resolution do you use?

[Carlos Perelló Marín (carlos)]

You have the journalctl output first, when I disconnect the USB-C cable and then when I connect it back.

I have the external display set as the main desktop with all the bars (in case it helps to debug this)

Thanks.

[Carlos Perelló Marín (carlos)]

Forgot the screen resolution, both displays use 3840x2160

[Sebastien Bacher (seb128)]

the log has this warning which might have to do with it
'setup_framebuffers: assertion 'width > 0' failed'

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 18.10 (cosmic) reached end-of-life on July 18, 2019.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in and change the bug status to Confirmed.