embedded-text-font

#![no_std] bitmap font engine for MCUs: compile TTF/OTF/BDF into a compact .etf format, load from ROM or external flash, lay out text, and draw pixels—optionally through embedded-graphics.

Note: This repo have NOT published yet (publish = false).

Features

• .etf fonts with optional PackBits RLE
• etfc: subset / Unicode ranges / variable-font axes
• ReadStorage + ExternalEtfFont for SPI NOR (and friends)
• Stack LRU GlyphCache (no heap)
• Layout: multiline, character/word wrap, line spacing
• Built-in AsciiFont8x16, GB2312/GBK decoder
• embedded-graphics 0.8 TextRenderer adapter

Crates

Crate	Role
embedded-text-font-core	Traits (Font, ReadStorage, …), GBK
embedded-text-font	.etf parse, external storage, cache
embedded-text-font-font	Static fonts
embedded-text-font-renderer	Layout + draw
embedded-text-font-eg	EG adapter
etfc	Font compiler CLI

TTF/OTF/BDF ──etfc──► .etf ──► EtfFont / ExternalEtfFont ──► layout ──► pixels
                                         ▲ ReadStorage / GlyphCache (optional)

Usage

[dependencies]
embedded-text-font = { path = "crates/embedded-text-font" }
embedded-text-font-renderer = { path = "crates/embedded-text-font-renderer" }
# optional:
embedded-text-font-eg = { path = "crates/embedded-text-font-eg" }
embedded-graphics = "0.8"

use embedded_text_font_core::Point;
use embedded_text_font::EtfFont;
use embedded_text_font_renderer::{LayoutConfig, draw_multiline_text};

let font = EtfFont::parse(include_bytes!("ui.etf")).unwrap();
let cfg = LayoutConfig::new().with_max_width(128);
let origin = Point::new(0, font.ascent() as i32);

draw_multiline_text("Hello", origin, &font, cfg, |x, y, on| {
    if on { /* plot (x, y) */ }
    Ok::<(), core::convert::Infallible>(())
})
.unwrap();

External flash + cache:

use embedded_text_font::{ExternalEtfFont, GlyphCache};

let font = GlyphCache::<_, 32, 256>::new(ExternalEtfFont::new(&flash).unwrap());

embedded-graphics:

use embedded_graphics::{pixelcolor::BinaryColor, prelude::*, text::{Baseline, Text}};
use embedded_text_font_eg::EmbeddedEtfRenderer;
use embedded_text_font::EtfFont;

let font = EtfFont::parse(include_bytes!("ui.etf")).unwrap();
let style = EmbeddedEtfRenderer::new(&font, BinaryColor::On);
Text::with_baseline("Hello", Point::zero(), style, Baseline::Top).draw(&mut display)?;

etfc

cargo run -p etfc -- compile \
  --font Font.ttf --output ui.etf \
  --size 16 --ranges 0020-007E,4E00-9FFF --compress

Flag	Meaning
-f / -o	Input font / output .etf
-s / -r	Subset file / Unicode ranges
-c	PackBits RLE
--size	Em size in px (default 16)
--encoding	BDF encoding (utf8, gbk, …)
--variation	e.g. wght=400

cargo run -p etfc -- inspect --font Font.ttf --size 16 --compress

Examples

ASCII-art preview in the terminal:

cargo run --bin example-latin          # compressed Latin ETF
cargo run --bin example-builtin-ascii  # AsciiFont8x16
cargo run --bin example-chinese
cargo run --bin example-spi-flash      # ExternalEtfFont + GlyphCache
cargo run --bin example-eg
cargo run --bin example-layout
cargo run --bin example-gbk            # GBK decode → same CJK string as chinese

Also: example-japanese, example-variable-width, example-italic.

License

Apache-2.0