Fontdue

Fontdue is a simple, no_std (does not use the standard library for portability), pure Rust, TrueType (.ttf/.ttc) & OpenType (.otf) font rasterizer and layout tool. It strives to make interacting with fonts as fast as possible, and currently has the lowest end to end latency for a font rasterizer.

Roadmap

Current goal (milestone 1): fontdue is designed to be a replacement for rusttype (link), ab_glyph (link), parts of glyph_brush (link), and glyph_brush_layout (link). This is a class of font libraries that don't tackle shaping.

Future goals: Shaping - the complex layout of text such as Arabic and Devanagari - will be added. There are two potential pure Rust libraries (allsorts or rustybuzz) that are candidates for providing a shaping backend to Fontdue, but are relatively immature right now.

A non-goal of this library is to be allocation free and have a fast, "zero cost" initial load. This library does make allocations and depends on the alloc crate. Fonts are fully parsed on creation and relevant information is stored in a more convenient to access format. Unlike other font libraries, the font structures have no lifetime dependencies since it allocates its own space.

Example

Rasterization

The rasterization API is done for milestone 1 and should not see major changes.

// Read the font data.
let font = include_bytes!("../resources/Roboto-Regular.ttf") as &[u8];
// Parse it into the font type.
let font = fontdue::Font::from_bytes(font, fontdue::FontSettings::default()).unwrap();
// Rasterize and get the layout metrics for the letter 'g' at 17px.
let (metrics, bitmap) = font.rasterize('g', 17.0);

Layout

The layout API is immature and may see many more major breaking changes before milestone 1.

// Read the font data.
let font = include_bytes!("../resources/fonts/Roboto-Regular.ttf") as &[u8];
// Parse it into the font type.
let roboto_regular = Font::from_bytes(font, fontdue::FontSettings::default()).unwrap();
// The list of fonts that will be used during layout.
let fonts = &[roboto_regular];
// Create a layout context. Laying out text needs some heap allocations; reusing this context
// reduces the need to reallocate space. We inform layout of which way the Y axis points here.
let mut layout = Layout::new(CoordinateSystem::PositiveYUp);
// By default, layout is initialized with the default layout settings. This call is redundant, but
// demonstrates setting the value with your custom settings.
layout.reset(&LayoutSettings {
    ..LayoutSettings::default()
});
// The text that will be laid out, its size, and the index of the font in the font list to use for
// that section of text.
layout.append(fonts, &TextStyle::new("Hello ", 35.0, 0));
layout.append(fonts, &TextStyle::new("world!", 40.0, 0));
// Prints the layout for "Hello world!"
println!("{:?}", layout.glyphs());

// If you wanted to attached metadata based on the TextStyle to the glyphs returned in the
// glyphs() function, you can use the TextStyle::with_metadata function. In this example, the
// Layout type is now parameterized with u8 (Layout<u8>). All styles need to share the same
// metadata type.
let mut layout = Layout::new(CoordinateSystem::PositiveYUp);
layout.append(fonts, &TextStyle::with_user_data("Hello ", 35.0, 0, 10u8));
layout.append(fonts, &TextStyle::with_user_data("world!", 40.0, 0, 20u8));
println!("{:?}", layout.glyphs());

Performance

Rasterization

These benchmarks measure the time it takes to generate the glyph metrics and bitmap for the text "Sphinx of black quartz, judge my vow." over a range of sizes. The lower the line in the graph the better.

Layout

This benchmark measures the time it takes to layout latin characters of sample text with wrapping on word boundaries.

Notices

Maintenance

Please bear with me on new features or quirks that you find. I will definitely get to issues you open (also thank you for opening them), but I don't have as much time as I would like to work on fontdue so please be patient, this is a mostly solo project <3.

TrueType & OpenType Table Support

Fontdue depends on ttf-parser (link) for parsing fonts, which supports a wide range of TrueType and OpenType features.

Attribution

Fontdue started as a slightly more production ready wrapper around font-rs (link) because of how fast it made rasterization look, and how simple the wonderful rusttype (link) crate made font parsing look. Since then, I've rewritten fontdue from the ground up, but I feel like it still deservers some attribution.