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rustybuzz

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rustybuzz is a complete harfbuzz's shaping algorithm port to Rust.

Matches harfbuzz v10.0.1, commit c7ef6a2e (one commit after v10.0.1)

Why?

Because you can add rustybuzz = "*" to your project and it just works. No need for a C++ compiler. No need to configure anything. No need to link to system libraries.

Conformance

rustybuzz passes nearly all of harfbuzz shaping tests (2221 out of 2252 to be more precise). So it's mostly identical, but there are still some tiny edge-cases which are not implemented yet or cannot be implemented at all.

Major changes

Performance

At the moment, performance isn't that great. We're 1.5-2x slower than harfbuzz.

See benches/README.md for details.

Notes about the port

rustybuzz is not a faithful port.

harfbuzz can roughly be split into 6 parts: shaping, subsetting, TrueType parsing, Unicode routines, custom containers and utilities (harfbuzz doesn't use C++ std) and glue for system/3rd party libraries. In the mean time, rustybuzz contains only shaping. All of the TrueType parsing was moved to the ttf-parser. Subsetting was removed. Unicode code was mostly moved to external crates. We don't need custom containers because Rust's std is good enough. And we do not use any non Rust libraries, so no glue code either.

In the end, we still have around 23 KLOC. While harfbuzz is around 80 KLOC.

Lines of code

As mentioned above, rustybuzz has around 23 KLOC. But this is not strictly true, because there are a lot of auto-generated data tables.

You can find the "real" code size using:

tokei --exclude hb/unicode_norm.rs --exclude hb/ot_shaper_vowel_constraints.rs \
      --exclude '*_machine.rs' --exclude '*_table.rs' src

Which gives us around 17 KLOC, which is still a lot.

Future work

Since the port is finished, there is not much to do other than syncing it with a new harfbuzz releases. However, there is still lots of potential areas of improvement:

All of this is a lot of work, so contributions are more than welcome.

Safety

The library is completely safe.

We do have one unsafe to cast between two POD structures, which is perfectly safe. But except that, there are no unsafe in this library and in most of its dependencies (excluding bytemuck).

Alternatives

License

rustybuzz is licensed under the MIT.

harfbuzz is licensed under the Old MIT