Strange graphics issue after upgrading to 18.04 that affects only one user account

I decided to clean up a bit some abandoned "dot-files" in my home folder (the home directory of the affected account) and managed to resolve the problem.

The problem was caused by my .xinputrc file that contained a single line of code:

run_im xim

In comments it was saying that it was created by im-config. (I do not remember why I executed im-config.) After I removed this file, the glitches were gone.

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Update. It seems that the file got automatically regenerated with the following content:

# im-config(8) generated on Sun, 29 Jul 2018 09:11:43 +0200
run_im ibus
# im-config signature: 1badc17f2a2c24108e97cd2fd412e476  -

There is currently no problems with this new content. (I am not sure if the file was regenerated by Ubuntu.)

I had the same graphical issues in Ubuntu 18.04 LTS (after upgrading from version 16.04.5 to 18.04.1), only the following command solved the problems:

$ dconf reset -f /org/gnome/

Reinstall the Drivers

Per this answerr try reinstalling intel drivers:

sudo apt-get update
sudo apt-get install --reinstall xserver-xorg-video-intel xserver-xorg-core
sudo dpkg-reconfigure xserver-xorg

If this doesn't work, you might be able to fix it by tweaking settings with intel goodies:

sudo apt install intel-microcode inteltool intel-gpu-tools

But I don't know how to use them so you are on your own. Here is a reference manual for intel-gpu-tools and you can always read the manpages. eg

man intel-gpu-tools