Firefox UI font changed after upgrade from Kubuntu 16.04 to Kubuntu 18.04

Question

I recently updated my computer from Kubuntu 16.04 to Kubuntu 18.04. Before upgrading, I backed up my home directory elsewhere, erased the boot drive, and re-installed the new OS. Afterwards, I copied my home directory back to the drive.

Everything is going fine except for the UI font on Firefox. The UI font looks vertically stretched compared to other fonts. I also noticed that when I make a new user account on the computer, the fonts look normal again.

Here is an image showing what my fonts look like after upgrading (ugly):

And here is what the fonts look like on a new user profile:

Notice on the top image, the characters appear to be stretched vertically. From what I can tell, it is the same font, just stretched vertically for some reason.

Things I've tried so far (with no success):

• Removing my ~/.mozilla directory (where the Firefox profile is kept)
• Removing my ~/.config directory

Is there somewhere else where configurations like this one are stored? I'm not sure what else to try here.

Answer 1

Apparently, I had custom settings for Font hinting and antialiasing in the KDE system settings. Removing the ~/.fonts.conf configuration file and restarting firefox seems to have solved this issue.