Forgive my ignorance, but what front end is that? (assuming it's a front end, that is...)
MewUI, the built-in MAME front-end. You see it when you launch MAME without a system name on the command line. Specifically, this commit
fixes a bunch of text rendering issues in MAME's internal UI on OSX. I was trying to update the Japanese translation, and it was so bad I had to do something about it. It's bad enough in English, but Japanese was unusably bad.
Here's Japanese in 0.188:
Note how the characters are jammed up against the colons and Japanese comma, half-width space is far too big, the digit 1 is jammed up against whatever comes after it, small kana don't get a whole character space like they should, full-width spaces aren't rendered at all, lowercase i is jammed up against whatever comes after it, etc.
Here's Japanese in latest head:
It doesn't make you want to puke the moment you see it, and it's all legible.