Text shaping engines, which is probably the closest thing to what you mean by “Unicode rendering engine”, are incredibly complicated. For example, look how lon

Text shaping engines, which is probably the closest thing to what you mean by “Unicode rendering engine”, are incredibly complicated. For example, look how long the Microsoft text-shaping docs are for just one script, Tibetan: https://docs.microsoft.com/en-us/typography/script-development/tibetan https://docs.microsoft.com/en-us/typography/script-developme... . Then look at the table of contents and note that there are a bunch of other sections for various other complex scripts.