# denise-text
[](https://crates.io/crates/denise-text)
[](https://docs.rs/denise-text)
[](https://github.com/bisand/denise/blob/main/LICENSE)
Fonts, a bounded glyph cache, line layout and word wrapping for **[Denise]**, a
direct-rendering UI toolkit in Rust for embedded Linux and systems without a
desktop environment.
One `TextEngine` holds every font an application uses and one `GlyphAtlas` that
caches what has been rasterised. Measurement and drawing both go through it, so a
label measured during layout and drawn a moment later rasterises its glyphs
exactly once.
```rust
use denise::{Color, Point};
use denise_render::Pen;
use denise_text::{TextEngine, TextStyle};
# fn demo(canvas: &mut Pen<'_>) {
let mut text = TextEngine::new();
let style = TextStyle::built_in(16);
let extent = text.measure(style, "Kjærlighet på Øy");
text.draw(canvas, style, Point::new(20, 20), "Kjærlighet på Øy", Color::WHITE);
// And the lines a paragraph becomes at a given width, borrowing the input.
let lines: Vec<&str> = text.wrap(style, "en to tre fire fem seks", 80);
# let _ = (extent, lines);
# }
```
## Three tiers, and what each costs
Measured as the increase in a stripped, statically linked
`aarch64-unknown-linux-musl` binary:
| Built-in bitmap | *none* | 0 | Latin plus `æøå`, whole-number scales |
| TrueType | `truetype` | +270 KB | Real fonts, proportional metrics, anti-aliasing |
| Baked | none; `bake` in a build script | the tables | A real face at the sizes it was baked at, no parser on the panel |
| Shaped | `shaping` | +3.1 MB | Ligatures, bidi, complex scripts, font fallback |
A style that names no font carries `FontId::DEFAULT`, which is a redirection
rather than a face. `TextEngine::set_default_font` points it at a registered
source, and everything drawn from an unnamed style follows — so an application
registers a face and says one more line, rather than threading a `TextStyle`
through every widget it builds.
`FontId::DEFAULT` is the built-in bitmap until something says otherwise, which is
what a board with no fonts installed gets and why the bitmap face is always
registered first.
For scale: the whole of Denise, DRM, evdev and the widgets is about **840 KB**, so
the shaping tier is four times the rest of the toolkit put together. It is there
because some panels genuinely need it, and off by default because most do not — a
temperature readout and a Norwegian name do not need a shaper.
## Wrapping
Greedy, returning slices that borrow the input, and explicit `\n` always breaks. A
word wider than the line overflows on a line of its own rather than being cut
between characters: breaking mid-word means knowing where a grapheme ends, and half
of an `æ` is nothing.
## Where this sits
Depends on [`denise`](https://crates.io/crates/denise) and
[`denise-render`](https://crates.io/crates/denise-render).
[`denise-ui`](https://crates.io/crates/denise-ui) re-exports `TextStyle` and passes
the tier features through, so an application picks its text tier once.
`#![forbid(unsafe_code)]`.
## Status
**M5 complete, M6 in progress.** The glyph cache is benchmarked in CI. Part of
[Denise][Denise] — see the [repository README][Denise] and [docs/design.md] for
the whole picture.
MIT licensed.
[Denise]: https://github.com/bisand/denise
[docs/design.md]: https://github.com/bisand/denise/blob/main/docs/design.md