{"id":52246,"date":"2026-06-12T15:34:17","date_gmt":"2026-06-12T19:34:17","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=52246"},"modified":"2026-06-12T16:43:14","modified_gmt":"2026-06-12T20:43:14","slug":"rewriting-apples-truetype-hinting-interpreter-in-swift","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2026\/06\/12\/rewriting-apples-truetype-hinting-interpreter-in-swift\/","title":{"rendered":"Rewriting Apple’s TrueType Hinting Interpreter in Swift"},"content":{"rendered":"

Scott Perry<\/a>:<\/p>\n

\n

My team rewrote Apple's TrueType hinting interpreter in Swift, ask me anything.<\/p>\n

[…]<\/p>\n

I feel like naming just one would be a disservices to all of the features that made this effort possible (C interop, generics, noncopyable\/nonescapable types) but at the end of the day I think the star of the show was the optimizer; despite being faster than the code it replaced, the new code is super readable and that was only possible because the optimizer was able to completely eliminate all of our abstractions.<\/p>\n<\/blockquote>\n\n

The new version is faster, but the main motivation was security concerns.<\/p>\n\n

Dmitrii Kalianov<\/a>:<\/p>\n

\n

Is hinting useful\/being used in the days of hi-dpi displays? I was under impression that Apple switched to grayscale anti-aliasing and ditched hinting.<\/p>\n<\/blockquote>\n\n

Scott Perry<\/a>:<\/p>\n

\n

For the most part hinting isn’t really necessary anymore, but thanks to being Turing-complete it has been Hyrum’s law-ed by at least one CJK font that uses hinting to lay out strokes in its characters.<\/p>\n<\/blockquote>\n\n

Alex Rosenberg<\/a>:<\/p>\n

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There were three major TrueType implementations at Apple IIRC:<\/p>\n