## ttf-parser
[](https://travis-ci.org/RazrFalcon/ttf-parser)
[](https://crates.io/crates/ttf-parser)
[](https://docs.rs/ttf-parser)
[](https://www.rust-lang.org)
A high-level, safe, zero-allocation TrueType font parser.
Can be used as Rust and as C library.
### Features
- A high-level API, for people who doesn't know how TrueType works internally.
Basically, no direct access to font tables.
- A [C API](./c-api).
- Zero heap allocations.
- Zero unsafe.
- Zero dependencies.
- `no_std`/WASM compatible.
- Fast. See the *Performance* section.
- Stateless. No mutable parsing methods.
- Simple and maintainable code (no magic numbers).
### Safety
- The library must not panic. Any panic considered as a critical bug and should be reported.
- The library forbids the unsafe code.
- No heap allocations, so crash due to OOM is not possible.
- All recursive methods have a depth limit.
- Technically, should use less than 64KiB of stack in worst case scenario.
- Most of arithmetic operations are checked.
- Most of numeric casts are checked.
### Alternatives
It's very hard to compare different libraries, so we are using table-based comparison.
There are roughly three types of TrueType tables:
- A table with a list of properties (like `head`, `OS/2`, etc.).<br/>
If a library tries to parse it at all then we mark it as supported.
- A table that contains a single type of data (`glyf`, `CFF` (kinda), `hmtx`, etc.).<br/>
Can only be supported or not.
- A table that contains multiple subtables (`cmap`, `kern`, `GPOS`, etc.).<br/>
Can be partially supported and we note which subtables are actually supported.
| Memory safe | ✓ | | |
| Thread safe | ✓ | | ~<sup>1</sup> |
| Zero allocation | ✓ | | |
| Variable fonts | ✓ | ✓ | |
| Rendering | | ✓ | ~<sup>2</sup> |
| `avar` table | ✓ | ✓ | |
| `bdat` table | | ✓ | |
| `bloc` table | | ✓ | |
| `CBDT` table | ✓ | ✓ | |
| `CBLC` table | ✓ | ✓ | |
| `CFF ` table | ~<sup>3</sup> | ✓ | ~<sup>3</sup> |
| `CFF2` table | ✓ | ✓ | |
| `cmap` table | ~ (no 8; Unicode-only) | ✓ | ~ (no 2,8,10,14; Unicode-only) |
| `EBDT` table | | ✓ | |
| `EBLC` table | | ✓ | |
| `fvar` table | ✓ | ✓ | |
| `gasp` table | | ✓ | |
| `GDEF` table | ~ | | |
| `glyf` table | ~<sup>4</sup> | ✓ | ~<sup>4</sup> |
| `GPOS` table | | | ~ (only 2) |
| `GSUB` table | | | |
| `gvar` table | ✓ | ✓ | |
| `head` table | ✓ | ✓ | ✓ |
| `hhea` table | ✓ | ✓ | ✓ |
| `hmtx` table | ✓ | ✓ | ✓ |
| `HVAR` table | ✓ | ✓ | |
| `kern` table | ✓ | ~ (only 0) | ~ (only 0) |
| `maxp` table | ✓ | ✓ | ✓ |
| `MVAR` table | ✓ | ✓ | |
| `name` table | ✓ | ✓ | |
| `OS/2` table | ✓ | ✓ | |
| `post` table | ✓ | ✓ | |
| `sbix` table | ~ (PNG only) | ~ (PNG only) | |
| `SVG ` table | ✓ | | ✓ |
| `vhea` table | ✓ | ✓ | |
| `vmtx` table | ✓ | ✓ | |
| `VORG` table | ✓ | ✓ | |
| `VVAR` table | ✓ | ✓ | |
| Language | Rust + C API | C | C |
| Dynamic lib size | ~300KiB | ~760KiB<sup>5</sup> | ? (header-only) |
| Tested version | 0.6.0 | 2.9.1 | 1.24 |
| License | MIT / Apache-2.0 | FTL / GPLv2 | public domain |
Legend:
- ✓ - supported
- ~ - partial
- *nothing* - not supported
Notes:
1. `stb_truetype` outline parsing method is reentrant.
2. Very primitive.
3. Matching points are not supported.
4. `type2` only. `seac` is not supported.
5. Depends on build flags.
### Performance
TrueType fonts designed for fast querying, so most of the methods are very fast.
The main exception is glyph outlining. Glyphs can be stored using two different methods:
using [Glyph Data](https://docs.microsoft.com/en-us/typography/opentype/spec/glyf) format
and [Compact Font Format](http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/font/pdfs/5176.CFF.pdf) (pdf).
The first one is fairly simple which makes it faster to process.
The second one is basically a tiny language with a stack-based VM, which makes it way harder to process.
The [benchmark](./benches/outline/) tests how long it takes to outline all glyphs in the font.
| `glyf` | `0.827 ms` | `1.194 ms` | **`0.695 ms`** |
| `gvar` | **`3.252 ms`** | `3.594 ms` | - |
| `CFF` | **`1.209 ms`** | `5.946 ms` | `2.862 ms` |
| `CFF2` | **`1.921 ms`** | `7.001 ms` | - |
**Note:** FreeType is surprisingly slow, so I'm worried that I've messed something up.
And here are some methods benchmarks:
```text
test from_data_otf_cff2 ... bench: 775 ns/iter (+/- 75)
test outline_glyph_276_from_cff2 ... bench: 763 ns/iter (+/- 59)
test outline_glyph_276_from_cff ... bench: 754 ns/iter (+/- 69)
test from_data_otf_cff ... bench: 618 ns/iter (+/- 8)
test outline_glyph_276_from_glyf ... bench: 581 ns/iter (+/- 14)
test outline_glyph_8_from_cff2 ... bench: 451 ns/iter (+/- 27)
test from_data_ttf ... bench: 400 ns/iter (+/- 9)
test family_name ... bench: 392 ns/iter (+/- 7)
test outline_glyph_8_from_cff ... bench: 285 ns/iter (+/- 10)
test outline_glyph_8_from_glyf ... bench: 252 ns/iter (+/- 8)
test glyph_name_276 ... bench: 220 ns/iter (+/- 2)
test glyph_index_u41 ... bench: 13 ns/iter (+/- 0)
test subscript_metrics ... bench: 2 ns/iter (+/- 0)
test glyph_advance ... bench: 2 ns/iter (+/- 0)
test glyph_side_bearing ... bench: 2 ns/iter (+/- 0)
test glyph_name_8 ... bench: 1 ns/iter (+/- 0)
test ascender ... bench: 1 ns/iter (+/- 0)
test underline_metrics ... bench: 1 ns/iter (+/- 0)
test strikeout_metrics ... bench: 1 ns/iter (+/- 0)
test x_height ... bench: 1 ns/iter (+/- 0)
test units_per_em ... bench: 0.5 ns/iter (+/- 0)
test width ... bench: 0.2 ns/iter (+/- 0)
```
`family_name` is expensive, because it allocates a `String` and the original data
is stored as UTF-16 BE.
`glyph_name_8` is faster than `glyph_name_276`, because for glyph indexes lower than 258
we are using predefined names, so no parsing is involved.
### Error handling
`ttf-parser` is designed to parse well-formed fonts, so it does not have an `Error` enum.
It doesn't mean that it will crash or panic on malformed fonts, only that the
error handling will boil down to `Option::None`. So you will not get a detailed cause of an error.
By doing so we can simplify an API quite a lot since otherwise, we will have to use
`Result<Option<T>, Error>`.
### License
Licensed under either of
- Apache License, Version 2.0
([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license
([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.