spleen-font — tiny no_std PSF-2 bitmap‐font reader

This crate ships the six Spleen fixed-width fonts and gives you a panic-free, heap-free API to render them on any framebuffer.

              glyph lookup        row iterator         bit iterator
            ┌──────────────┐   ┌────────────────┐   ┌────────────────┐
UTF-8 ──► `PSF2Font` ──────► `Glyph<'_>` ───────►  `GlyphRow<'_>` ────► bool
            │    (cache)   │   |  one scan-line │   |    one pixel   │
            └──────────────┘   └────────────────┘   └────────────────┘

Features

• no_std, zero allocations – suitable for kernels and bootloaders.
• Constant-time glyph lookup for ASCII and cached Unicode.
• < 2 KiB RAM: 64-entry ring cache + iterator state.
• Exposes only data; pixel drawing/framebuffer manipulation is left to the user.

Quick start

This example assumes that you have a framebuffer and a function to set pixels, and that you have enabled the s8x16 feature in your Cargo.toml.

// Pick a bundled font (8×16 is a good default) from the feature list (below)
use spleen_font::{PSF2Font, FONT_8X16};
fn set_pixel(_: &mut [u8], _: usize, _: usize, _: bool) {}

let mut font  = PSF2Font::new(FONT_8X16).unwrap();

// Look up a glyph (cached) and blit it.
if let Some(glyph) = font.glyph_for_utf8("é".as_bytes()) {
    for (row_y, row) in glyph.enumerate() {
        for (col_x, on) in row.enumerate() {
            set_pixel(framebuffer, col_x, row_y, on);
        }
    }
}

Features

To reduce the overall footprint, each of the six fonts is gated behind a feature. Note that while this does not reduce the size of the crate on crates.io, it does reduce the size of the compiled binary - only the blob for the selected font you enable will be included in the final binary.

Each entry is a raw byte slice &[u8] where the slice is the raw PSF-2 file embedded via include_bytes!.

By default, no font is enabled. Enabling a font in your Cargo.toml should look like this:

[dependencies]
spleen-font = { version = "0.1", features = ["s8x16"] }

Re-exports

• PSF2Font — loader + glyph/Unicode lookup.
• Glyph / GlyphRow — iterators over rows and pixels.

Spleen font Copyright (c) 2018-2024, Frederic Cambus, BSD2 License

*.psfu files obtained from https://github.com/fcambus/spleen

Contributions

Contributions are welcome! Please open an issue or submit a pull request.