This gives me javascript in PDF vibes, but its probably very useful for highly complex writing systems. Also goes to show what an incredibly complex subject this is, Harfbuzz is pretty much the only open source text shaping library that does it properly as far as i can tell. Behdad Esfahbod [1] is probably one of the most important developers on the planet considering how omnipresent his work has been to this day. Harfbuzz is used in Firefox, Chrome and Safari for example.