RustType Fonts

OpenType fonts loaded with rusttype are rendered with the embedded_ttf crate, providing high-quality text rendering with support for variable sizing and antialiasing.

// MDBook does not appear to support include_bytes!, so this example is marked ignore.
// If you find this example broken, please open an issue :)
extern crate buoyant;
extern crate embedded_graphics;
extern crate embedded_graphics_simulator;
extern crate rusttype;
use embedded_graphics::{pixelcolor::Rgb888, prelude::*};
use embedded_graphics_simulator::{OutputSettings, SimulatorDisplay, Window};

const BACKGROUND_COLOR: Rgb888 = Rgb888::CSS_DARK_SLATE_GRAY;
const DEFAULT_COLOR: Rgb888 = Rgb888::WHITE;

fn main() {
    let mut window = Window::new("Example", &OutputSettings::default());
    let mut display: SimulatorDisplay<Rgb888> = SimulatorDisplay::new(Size::new(480, 320));

    display.clear(BACKGROUND_COLOR).unwrap();

    view()
        .as_drawable(display.size(), DEFAULT_COLOR, &mut ())
        .draw(&mut display)
        .unwrap();

    window.show_static(&display);
}

use buoyant::view::prelude::*;
use std::sync::LazyLock;

static SF_ROUNDED: LazyLock<rusttype::Font<'static>> = LazyLock::new(|| {
    let bytes = include_bytes!("fonts/SF-Pro-Rounded-Regular.otf");
    rusttype::Font::try_from_bytes(bytes).unwrap()
});

static COMIC_SANS: LazyLock<rusttype::Font<'static>> = LazyLock::new(|| {
    let bytes = include_bytes!("fonts/Comic Sans MS.ttf");
    rusttype::Font::try_from_bytes(bytes).unwrap()
});

fn view() -> impl View<Rgb888, ()> {
    VStack::new((
        Text::new("Small caption text", &*SF_ROUNDED).with_font_size(20),
        Text::new("Bigger body text", &*SF_ROUNDED).with_font_size(40),
        Text::new("Excessively large heading", &*SF_ROUNDED)
            .with_font_size(60)
            .multiline_text_alignment(HorizontalTextAlignment::Center),
        Text::new("Even this awful font works", &*COMIC_SANS).with_font_size(40),
    ))
    .with_spacing(10)
    .with_alignment(HorizontalAlignment::Center)
    .foreground_color(Rgb888::CSS_BLANCHED_ALMOND)
    .flex_infinite_width(HorizontalAlignment::Center)
    .padding(Edges::All, 20)
    .hint_background_color(BACKGROUND_COLOR)
}

Loading RustType Fonts

rusttype::Font::try_from_bytes(bytes) is not a const fn, so fonts must be initialized at runtime.

Depending on the features available and desired functionality, different static initialization methods can be used. std::sync::LazyLock is a convenient choice for std environments, while core::cell::OnceCell or core::cell::LazyCell may be preferable for static font initialization in no_std contexts. Dynamic font loading is possible, but left as an exercise for the reader.