Windows not painted completely since 18.04

[Captain Chaos]

Since upgrading to Xubuntu 18.04, the graphics on my desktop are broken. It seems to affect all windows and menus, which are painted incompletely, or with the wrong colours. It seems to get progressively worse, to the point of making programs unusable because entire sections of the user interface are missing, so this should have high priority IMHO. I will attach a few screenshots as examples.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xfwm4 4.12.4-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-22.24-generic 4.15.17
Uname: Linux 4.15.0-22-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.1
Architecture: amd64
CurrentDesktop: XFCE
Date: Tue Jun 5 17:29:02 2018
InstallationDate: Installed on 2017-03-23 (439 days ago)
InstallationMedia: Xubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215)
SourcePackage: xfwm4
UpgradeStatus: Upgraded to bionic on 2018-05-14 (22 days ago)

[Captain Chaos (launchpad-chaos)]

The problem appears to go away after selecting the proprietary Nvidia driver instead of the Nouveau driver. So it is at least an interaction with the Nouveau driver, or possible the bug is in that driver. Should I report it there?

[Theo Linkspfeifer (lastonestanding)]

I suggest that you download the Xubuntu 18.10 daily ISO, then boot into live mode and check if the issue with the open source driver is present too.

Another thing to test is to see if disabling the builtin compositor (Settings > Windows Manager Tweaks > Compositor) eliminates the glitch.

[Launchpad Janitor (janitor)]

[Expired for xserver-xorg-video-nouveau (Ubuntu) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for xfwm4 (Ubuntu) because there has been no activity for 60 days.]