Swift at Apple: Migrating the TrueType Hinting Interpreter

Apple rewrote the TrueType font hinting interpreter from C to memory-safe Swift for its Fall 2025 releases to address security vulnerabilities in this critical attack surface that processes untrusted font data from the internet. The Swift implementation not only eliminates memory safety risks but also achieves 13% better performance than the original C version while maintaining pixel-identical rendering compatibility through rigorous testing against millions of real-world PDF files and fonts.