https://github.com/harfbuzz/harfrust
Port of RustyBuzz to use Fontations
https://github.com/harfbuzz/harfrust
Last synced: 4 days ago
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Port of RustyBuzz to use Fontations
- Host: GitHub
- URL: https://github.com/harfbuzz/harfrust
- Owner: harfbuzz
- License: mit
- Created: 2024-07-15T16:04:15.000Z (12 months ago)
- Default Branch: main
- Last Pushed: 2025-06-14T11:24:06.000Z (16 days ago)
- Last Synced: 2025-06-19T01:40:44.210Z (11 days ago)
- Language: Rust
- Homepage:
- Size: 8.03 MB
- Stars: 76
- Watchers: 18
- Forks: 8
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
[](https://github.com/harfbuzz/harfrust/actions/workflows/main.yml)
[](https://crates.io/crates/harfrust)
[](https://docs.rs/harfrust)
# HarfRust
HarfRust is a Rust port of [HarfBuzz](https://github.com/harfbuzz/harfbuzz) text shaping engine.
See [Major changes](#major-changes) below for major differences between HarfRust and HarfBuzz.
HarfRust started as a fork of [RustyBuzz](https://docs.rs/rustybuzz) to explore porting from `ttf-parser` to
[`read-fonts`](https://docs.rs/read-fonts) to avoid shipping (and maintaining)
multiple implementations of core font parsing for [`skrifa`](https://docs.rs/skrifa) consumers.
Further context in https://github.com/googlefonts/fontations/issues/956.
Matches HarfBuzz [v11.2.1](https://github.com/harfbuzz/harfbuzz/releases/tag/11.2.1).
## Why?
https://github.com/googlefonts/oxidize outlines Google Fonts motivations to try to migrate font
production and consumption to Rust.
## Major changes
- No font size property. Shaping is always using UnitsPerEm. You should scale the result manually.
- Most of the font loading and parsing is done using [`read-fonts`](https://docs.rs/read-fonts).
- HarfRust doesn't provide any integration with external libraries, so no FreeType, CoreText, or Uniscribe/DirectWrite font-loading integration, and no ICU, or GLib Unicode-functions integration, as well as no `graphite2` library support.
- `mort` table is not supported, since it's deprecated by Apple.
- No `graphite` library support.
## Conformance
The following conformance issues need to be fixed:
- HarfRust does not yet fully pass the HarfBuzz shaping or fuzzing tests
- Malformed fonts will cause an error. HarfBuzz uses fallback/dummy shaper in this case.
- No Arabic fallback shaper. This requires the ability to build lookups on the fly. In HarfBuzz (C++) this requires serialization code that is associated with subsetting.
- `avar2` as well as other parts of the boring-expansion-spec are not supported yet.
## Performance
At the moment, performance isn't that great. HarfRust can be 3x slower than HarfBuzz.
See [benches/README.md](./benches/README.md) for details.
## Notes about the port
HarfRust is not a full port of HarfBuzz. HarfBuzz (C++ edition) can roughly be split into 6 parts:
1. shaping, ported to HarfRust
2. Unicode routines, ported to HarfRust
3. font parsing, handled by [`read-fonts`](https://docs.rs/read-fonts)
4. subsetting, handled by [`klippa`](https://github.com/googlefonts/fontations/tree/main/klippa)
5. custom containers and utilities (HarfBuzz doesn't use C++ standard library), reimplemented in [`fontations`](https://github.com/googlefonts/fontations) where appropriate (e.g. int set)
6. glue for system/3rd party libraries, not ported
## Safety
The library is completely safe.
There are no `unsafe` in this library and in most of its dependencies (excluding `bytemuck`).
## Developer documents
For notes on the backporting process of HarfBuzz code, see [docs/backporting.md](docs/backporting.md).
For notes on generating state machine using `ragel`, see [docs/ragel.md](docs/ragel.md).
The following HarfBuzz _studies_ are relevant to HarfRust development:
- 2025 - [Introducing HarfRust][2]
- 2025 – [Caching][1]
## License
HarfRust is licensed under the **MIT** license.
HarfBuzz is [licensed](https://github.com/harfbuzz/harfbuzz/blob/main/COPYING) under the **Old MIT**
[2]: https://docs.google.com/document/d/1aH_waagdEM5UhslQxCeFEb82ECBhPlZjy5_MwLNLBYo/preview
[1]: https://docs.google.com/document/d/1_VgObf6Je0J8byMLsi7HCQHnKo2emGnx_ib_sHo-bt4/preview