Vendor things

third-party/vendor/ab_glyph/README.md

@@ -0,0 +1,42 @@
+ab_glyph
+[![crates.io](https://img.shields.io/crates/v/ab_glyph.svg)](https://crates.io/crates/ab_glyph)
+[![Documentation](https://docs.rs/ab_glyph/badge.svg)](https://docs.rs/ab_glyph)
+========
+Fast API for loading, scaling, positioning and rasterizing OpenType font glyphs.
+
+```rust
+use ab_glyph::{FontRef, Font, Glyph, point};
+
+let font = FontRef::try_from_slice(include_bytes!("../../dev/fonts/Exo2-Light.otf"))?;
+
+// Get a glyph for 'q' with a scale & position.
+let q_glyph: Glyph = font.glyph_id('q').with_scale_and_position(24.0, point(100.0, 0.0));
+
+// Draw it.
+if let Some(q) = font.outline_glyph(q_glyph) {
+    q.draw(|x, y, c| { /* draw pixel `(x, y)` with coverage: `c` */ });
+}
+```
+
+## no_std
+no_std environments are supported using `alloc` & [`libm`](https://github.com/rust-lang/libm).
+```toml
+ab_glyph = { default-features = false, features = ["libm"] }
+```
+
+## Comparison with [`rusttype`](https://gitlab.redox-os.org/redox-os/rusttype)
+ab_glyph is a rewrite of rusttype made after I added .otf support for the latter and saw some performance issue's
+with the rusttype API.
+
+ab_glyph is a more focussed API concentrating on high performance for both .ttf & .otf fonts.
+
+When laying out glyphs into paragraph, ab_glyph is faster than rusttype using .ttf fonts &
+**much** faster for .otf fonts.
+
+```
+group                               ab-glyph                    rusttype 0.9
+-----                               --------                    ------------
+layout_a_sentence (exo2-ttf)        1.00     11.1±0.08µs        1.56     17.3±0.14µs
+layout_a_sentence (exo2-otf)        1.00     11.1±0.12µs        8.85     98.1±1.17µs
+```
+_Note: Numbers from May-2020 benchmarks, ab-glyph performance is also expected to have improved since then_.