Full-screen window flickers once when switching to it

[Torsten Bronger]

When using *some* applications (I observed it with Emacs and gnome-terminal) in full-screen mode, they flicker once shortly after switching to them with e.g. Alt-Tab. To reproduce it:

1. Open Emacs in full-screen mode and one other application (e.g. Chromium).
2. Switch to the other app with Alt-Tab.
3. Switch back to Emacs.

Then I observe:

1. Emacs becomes visible.
2. After a fraction of a second, the Emacs windows is transparent for a very very short time (flicker).
3. Then, the windows is stable and usable.

Usually, I do not observe this behaviour right from the start. I have to work with the computer for a couple of minutes to see it. I have been unable to find out whether a certain action triggers the problem. However, when it occurs, it does not go away again until the next restart of the X server.

This is regression that I observe since Ubuntu 19.10.

Changes of the graphics driver does not change anything, however, switching to Wayland solves the problem.
---
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
DistroRelease: Ubuntu 19.10
InstallationDate: Installed on 2019-11-16 (75 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
Package: mutter 3.34.1+git20191107-1ubuntu1~19.10.1
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 5.3.0-29.31-generic 5.3.13
Tags: eoan
Uname: Linux 5.3.0-29-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip docker lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1861391/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Torsten Bronger (bronger)]

I am not sure whether it is really the gnome-shell that it responsible. However, it happens with more than one application (Emacs and the terminal window), and I can exclude the graphics driver.

[Daniel van Vugt (vanvugt)]

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 1861391

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 https://wiki.ubuntu.com/ReportingBugs.

[Torsten Bronger (bronger)]

apport information

[Torsten Bronger (bronger)]

apport information

[Torsten Bronger (bronger)]

apport information

[Daniel van Vugt (vanvugt)]

Hmm, that didn't collect what I expected. Please try running the command again now.

[Daniel van Vugt (vanvugt)]

Or run:

  lspci -k > lspcik.txt
  dmesg > dmesg.txt
  journalctl -b0 > journal.txt
  dpkg -l > dpkgs.txt

and then attach all four text files.

[Daniel van Vugt (vanvugt)]

Thanks and sorry for the trouble...

I think this is either a bug in Mutter's fullscreen unredirect feature (which exists for Xorg sessions only), or it could be another instance of bug 561370 which is very intermittent.

To prove the issue is NOT bug 561370 we would probably need to see the same flickering in a non-GTK app.

[Torsten Bronger (bronger)]

I cannot reproduce this problem anymore with Ubuntu 20.04 Beta.