As all the Apple faithful know by now, Apple released the latest version of macOS on Monday. I was literally minutes away from starting the upgrade when I stumbled upon a tweet that indicated a problem with Emacs and Mojave:
Anyone running #emacs on #mojave? It seems the text is not rendered.
— Davide Restivo (@gutt3r) September 26, 2018
I did a bit of research and the problem appears to be real. Perry Metzger, who knows a thing or two about Emacs, posted a report to the Emacs-Devel list with the same complaint. The problem is that Emacs is using a now deprecated method of drawing the screen and with Mojave it no longer works. According to the thread, there’s a not-altogether-satisfactory patch available but more work needs to be done by the people who understand that particular low-level area of Emacs.
If you’re using Emacs on a Mac, you should probably hold off upgrading to Mojave until things get sorted out. Terminal Emacs is unaffected so if you restrict your Emacs use to the terminal, you’ll probably be Okay.