Comment 30 for bug 1760818

I'm able to reproduce the faulty on bionic (not upgraded from xenial), with GTK_IM_MODULE=xim and an empty .xinputrc.

Can also confirm the workaround suggested by Heiko L seems to fix this issue, by changing /usr/share/themes/Ambiance/gtk-3.20/gtk.css to this:

> textview text {
> background-color: white;
> }
> scrollbar {
> background-color: white;
> }
> @import url("gtk-main.css");

This worked immediately after restarting gnome-calculator (installed from deb, not snap) and gedit, no other system changes were required.