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Swift at Apple: Migrating the TrueType hinting interpreter

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11–20 of 139 posts

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#11

I'm surprised the code has visible LLM smells. Though, I shouldn't be surprised. I hope the important bits are still human-controlled (and the same for Apple's many operating systems that absolutely deserve to remain stable and understood).

From what I got Apple is using claude code A LOT internally

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#12

Interesting that this is published under the MIT, rather than Apple’s more favorite Apache 2, license

Why is it interesting?

Presumably because MIT is even more permissive and it’s a change in Apple’s behavior.

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#13
post #4
post #2

During the State of Platform keynote, on the subject of Swift adoption across macOS, several examples were given, not only TrueType engine. RIS is happening across all OS levels, if the keynote is to be believed.

Curious the direction of Webkit as there was a nebulous mention of select portions being rewritten from C++ to Swift. And yet, the new ECMAScript module (ESM) loader for Safari 27 is implemented in C++ ( https://webkit.org/blog/17967/news-from-wwdc26-webkit-in-saf... ).

No idea, maybe the private parts of the code, Safari isn't open source, or is coming later.

In any case I would have liked to have more info during the deep dive sessions.

As it is, Meet with Apple on security (a 5h long event) had much more information.

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#14
post #11

I'm surprised the code has visible LLM smells. Though, I shouldn't be surprised. I hope the important bits are still human-controlled (and the same for Apple's many operating systems that absolutely deserve to remain stable and understood).

From what I got Apple is using claude code A LOT internally

Yes they are using Claude Code - not the Xcode agents.

It worries me. I hope Codex adoption picks up there.

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#16

I'm surprised the code has visible LLM smells. Though, I shouldn't be surprised. I hope the important bits are still human-controlled (and the same for Apple's many operating systems that absolutely deserve to remain stable and understood).

I assure you, every inch of the interpreter code has been stared at by humans, a lot. TBH even the assembly generated by it has.

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#17

As much as I enjoyed Swift, one can only wonder what the world would look like if they had gone with Rust as their default language instead.

Modern Swift borrows a lot from Rust! And it also has its own benefits, both ergonomic and also supporting eg generic in dynamic libraries

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#18

Back in 2023 there was talks about Microsoft rewriting the font stuff in Rust for similar reasons Apple is now doing the Swift move. I'm not sure what became of it and if it ever shipped. If anyone knows I'd be curious.

Russinovitch (Azure's CTO/CISO) gave a speech at RustConf 2025 and mentions it(DirectWriteCore) took 2 engineers 6 months resulting in 154K LOC and 5-15 percent performance increase for font shaping. https://www.youtube.com/watch?v=uDtMuS7BExE&list=PL2b0df3jKK...

Re: Swift at Apple: Migrating the TrueType hinting interpreter

#20

As much as I enjoyed Swift, one can only wonder what the world would look like if they had gone with Rust as their default language instead.

Modern Swift borrows a lot from Rust! And it also has its own benefits, both ergonomic and also supporting eg generic in dynamic libraries

These days I mainly write Rust but I did write a semi complex iOS app and enjoyed Swift. I just didn't love how slow the type checker was and how it got lost. I recall having to break things into smaller bits to help the compiler, and there were some oddities about the language.

The gap between the two languages is quite small, it just makes me wish Apple was also all-in on Rust

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