There are many ways to affect the glyphs that are used to show text on screen. Since macOS 10.11 El Capitan (released in 2015), possibly the simplest override points are in
NSLayoutManagerDelegate. Another, arguably more ancient way to replace glyphs on-the-fly is to override and customize
NSGlyphGenerator. This predates the existence of
NSLayoutManagerDelegate, and it’s not even available on iOS, so that’s how arcane the approach outlines here will be.
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