Messed up (?GTK) graphics in Tumbleweed KDE

Some time in the recent past this has happened:

This is the main screen of xsane. Some other apps have been similarly affected (Iscan, guayadeque (a music player)), but most have not. I suspect it has something to do with GTK support, as I have found that in the “Application Style” unit of KDE System Settings, clicking on “Preview” in the Gnome/GTK Application Style theme selectors produces the same kind of image, regardless of which GTK2 or GTK3 theme I select.

I thought that it might have been because of a messed up update, but this current image is from a fresh install of the newest (20191203) Tumbleweed image.

Has anyone else seen this?

Update—I created a new user as a test, and when logged in under the new user the gtk graphics error disappears.

So something is corrupted in my user settings.

Does anyone have any idea where to look?

Possibly you have a corrupted cache. Log out of KDE, login on a vtty (Ctrl-Alt-F3), delete content of ~/.cache/, then log into KDE to check if it helped.

Additionally, check what font you have set for GTK applications to use…

(KDE) System Settings -> Application Style -> GNOME/GTK Application Style - Font

That was the issue.

Changing the GTK font fixed it. Some of the fonts work, some don’t. I was using “Utopia” for my system font. Changing the GTK font to “Noto Sans” cleared it up.

As noted though, many other fonts besides Utopia cause garbled text.