Allsorts
Font parser, shaping engine, and subsetter for OpenType, WOFF, and WOFF2 implemented in Rust
Allsorts is a font parser, shaping engine, and subsetter for OpenType, WOFF, and WOFF2
written entirely in Rust. It was extracted from
[Prince](https://www.princexml.com/), a tool that typesets and lays out HTML
and CSS documents into PDF.
The Allsorts shaping engine was developed in conjunction with [a specification
for OpenType shaping](https://github.com/n8willis/opentype-shaping-documents/),
which aims to specify OpenType font shaping behaviour.
## Features
* **Parse** TrueType/OpenType (`glyf`, `CFF`, `CFF2`), WOFF, and WOFF2 files.
* **Shape** Arabic, Cyrillic, Greek, Hebrew, [Indic
scripts](https://en.wikipedia.org/wiki/Languages_of_India) (Bengali,
Devanagari, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya, Sinhala, Tamil,
Telugu), Khmer, Lao, Latin, Syriac, Thai, and other scripts.
* **Subset** from TrueType, OpenType, WOFF, and WOFF2 files into OpenType.
* **Instance** variable fonts into non-variable fonts.
## What is font shaping?
Font shaping is the process of taking text in the form of Unicode codepoints
and a font, and laying out glyphs from the font according to the text. This
involves honouring kerning, ligatures, and substitutions specified by the font.
For some languages this is relatively straightforward. For others, such as
Indic scripts it is quite complex. After shaping, another library such as
[Pathfinder](https://github.com/servo/pathfinder) or
[FreeType](https://www.freetype.org/) is responsible for rendering the glyphs.
To learn more about text rendering, Andrea Cognolato has a good [overview of
modern font rending on
Linux](https://mrandri19.github.io/2019/07/24/modern-text-rendering-linux-overview.html).
The concepts remain similar on other platforms.
## Examples
Refer to the [Allsorts Tools repository](https://github.com/yeslogic/allsorts-tools) for
a set of tools that exercise Allsorts font parsing, shaping, and subsetting.
## Unimplemented Features / Known Issues
We don't currently support:
* Shaping Mongolian, and Tibetan.
* Apple's [morx table](https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6morx.html).
* Unicode normalisation.
Known limitations:
* The crate is not extensively documented yet ([#5](https://github.com/yeslogic/allsorts/issues/5)).
* Allsorts does not do font lookup/matching. For this something like
[font-kit](https://github.com/pcwalton/font-kit) is recommended.
## Development Status
Allsorts is still under active development but reached its first release
milestone with its inclusion in Prince 13 in 2019. In Prince it is responsible
for all font loading, and font shaping.
Currently, the font parsing code is handwritten. It is planned for this to
eventually be replaced by machine generated code via our [declarative data
definition language project](https://github.com/yeslogic/fathom).
## Platform Support
Allsorts CI runs tests on Linux, macOS, and Windows. Via Prince it is also
built for FreeBSD.
## Building and Testing
**Minimum Supported Rust Version:** 1.66.0
To build the crate ensure you have [Rust 1.66.0 or newer installed](https://www.rust-lang.org/tools/install).
Build with `cargo build` and run the tests with `cargo test`.
### Cargo Features
| Feature | Description | Default Enabled | Extra Dependencies |
|---------------|--------------------------------------------------|:---------------:|--------------------------|
| `outline` | Enable code for accessing glyph outlines | ✅ | |
| `flate2_zlib` | Use the zlib backend to flate2 | ✅ | `zlib` |
| `flate2_rust` | Use the Rust backend to flate2 | ❌ | `miniz_oxide` |
| `prince` | Enable Prince specific tests and code | ❌ | |
| `specimen` | Enable module for generating HTML font specimens | ❌ | `upon`, `unicode-blocks` |
**Note:** In our testing the `zlib` `flate2` backend was faster but you may
prefer the Rust backend for a pure Rust solution when compiling to WASM or
similar.
## Contributing
Contributions are welcome, please refer to the
[contributing document](https://github.com/yeslogic/allsorts/blob/master/CONTRIBUTING.md)
for more details.
## Code of Conduct
We aim to uphold the Rust community standards:
> We are committed to providing a friendly, safe and welcoming environment for
> all, regardless of gender, sexual orientation, disability, ethnicity,
> religion, or similar personal characteristic.
We follow the [Rust code of conduct](https://www.rust-lang.org/policies/code-of-conduct).
## Acknowledgements
* [OpenType shaping documents](https://github.com/n8willis/opentype-shaping-documents/)
forms the specification from which the shaping engine is implemented.
* [HarfBuzz](https://github.com/harfbuzz/harfbuzz) the widely used open source
font shaping engine was used as reference for test output.
* The [Adobe Annotated OpenType Specification](https://github.com/adobe-type-tools/aots)
test suite is used as part of the Allsorts test suite.
* [ttf-parser](https://github.com/RazrFalcon/ttf-parser) for CFF CharString parsing code.
## License
Allsorts is distributed under the terms of the Apache License (Version 2.0).
See [LICENSE](https://github.com/yeslogic/allsorts/blob/master/LICENSE) for details.
