gFontFile is too broad in application, leads to 'general instability' #7
Description
To elaborate, since gFontFile hijacks the drawing of every font in the system, this causes fonts set by the user natively in macOS apps like Mail, TextEdit, etc (anything using NSFontPanel really) to be overriden. This can especially causes issues in Terminal, for example, which becomes unreadable if gFontFile isn't monospaced with no recourse but to disable font replacement system wide.
Some apps also crash when using font replacement, such as Passwords (from console logs, this may be caused by monogram drawing) and WhatsApp for Mac.
The best solution here appears to be to only hijack the drawing of the main Apple System UI Fonts only (i.e. San Francisco) as a baseline as these can't ever be user-selected anyways and are likely the primary fonts people want replaced.