[laurmaedje]

On the shaping side, support should be quite good as rustybuzz replicates harfbuzz results 1-1. (I think, it passes the whole test suite.) Regarding higher-level text layout: We have implemented BiDi, shaping, line breaking, reshaping, and font fallback to the best of our knowledge. (And I have been in the Harfbuzz and Chromium sources and bug trackers more than I can count while implementing it.) However, it's difficult to test as we can't catch many mistakes in the output that would be obvious to native speakers. This is something where we will need input from the community. Finally, there are also many specifics that we don't support yet like Kashida for Arabic or dictionary-based line breaking for Thai.