Make macvim set to do non-native fullscreen (NNFS) mode. Then do `mvim -u NONE -U NONE -N` then do: ``` :set co=80 :set fuopt-=maxhorz :set fu ``` What should happen is that MacVim enters NNFS, but `&co` is still 80. What actually happens is that MacVim acts as if the `-=maxhorz` didn't happen. It might be related to one of the additional difficulties from #488.