swaitsandClaude Opus 4.7
784658e5c6
Faithful Rust port of Maurycy's mcufont.h — a 5x5 monospace pixel font (~350 bytes of bitmap data) covering A-Z, a-z, 0-9, and the punctuation set - + . , ? ! : = '. - no_std, forbid(unsafe_code), zero deps with default features. - Public glyph tables (UPPER / LOWER / DIGITS / SYMBOLS), SYM_* index constants, and a glyph(c: char) lookup. - Each glyph row is packed in bits 7..=3 MSB-first so the bytes are byte-for-byte compatible with embedded_graphics::ImageRaw. - Optional `embedded-graphics` feature exposes MCU_FONT (MonoFont<'static>), FONT_DATA, and McuGlyphMapping for drop-in use with MonoTextStyle / Text on any DrawTarget (SSD1306 over I²C, ST7735, etc.). - Per-category feature flags (upper / lower / numbers / symbols, all on by default) so users can drop unused glyphs from flash. Licensed CC BY-NC-SA 4.0, inherited from the upstream font data. An email is out to the upstream author asking for a permissive software license (MIT / Apache-2.0); if granted, the crate will be relicensed and a new version published. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
97 lines
4.4 KiB
Markdown
97 lines
4.4 KiB
Markdown
# mcufont
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Tiny 5×5 monospace pixel font for microcontrollers. `no_std`, zero dependencies (with default features), ~350 bytes of font data.
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Faithful Rust port of [Maurycy's `mcufont`](https://maurycyz.com/projects/mcufont/) C header. Covers `A–Z`, `a–z`, `0–9`, and the punctuation set `- + . , ? ! : = '`.
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## Usage — raw
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```rust
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use mcufont::{glyph, GLYPH_WIDTH, GLYPH_HEIGHT};
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if let Some(g) = glyph('A') {
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for row in g {
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// bit 7 = leftmost pixel, bit 3 = rightmost; bits 2..=0 are zero.
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for x in 0..GLYPH_WIDTH {
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let on = (row >> (7 - x)) & 1 == 1;
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// ... blit to your framebuffer
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}
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}
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}
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```
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The static tables `UPPER`, `LOWER`, `DIGITS`, `SYMBOLS` are also public — index them directly if you don't need the lookup function.
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## Usage — `embedded-graphics`
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Enable the `embedded-graphics` feature in `Cargo.toml`:
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```toml
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mcufont = { version = "0.1", features = ["embedded-graphics"] }
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```
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Then drop `MCU_FONT` into a `MonoTextStyle`:
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```rust
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use embedded_graphics::{
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mono_font::MonoTextStyle, pixelcolor::BinaryColor,
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prelude::*, text::Text,
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};
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use mcufont::eg::MCU_FONT;
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let style = MonoTextStyle::new(&MCU_FONT, BinaryColor::On);
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Text::new("Hello", Point::new(0, 5), style).draw(&mut display)?;
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```
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Works with any `embedded-graphics` `DrawTarget` — SSD1306 over I²C, SH1106, ST7735, fbink, etc.
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## Features
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| Feature | Default | What it adds |
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| ------------------- | ------- | ---------------------------------------------------------------- |
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| `upper` | yes | `A–Z` (130 bytes) |
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| `lower` | yes | `a–z` (130 bytes) |
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| `numbers` | yes | `0–9` (50 bytes) |
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| `symbols` | yes | `- + . , ? ! : = '` (45 bytes) |
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| `embedded-graphics` | no | `MonoFont` integration + concatenated strip (~2× the flash cost) |
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Disable any category you don't need to save flash. With all four enabled the raw tables sum to ~355 bytes.
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## Glyph format
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Each glyph is `[u8; 5]` — one byte per row. Pixels are packed in **bits 7..=3 MSB-first** (bit 7 = leftmost pixel); bits 2..=0 are always zero. This layout matches `embedded_graphics::image::ImageRaw` byte ordering for a 5-pixel-wide row, so the same bytes drive both the raw API and the `embedded-graphics` integration with no transformation.
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```text
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byte = 0b A B C D E _ _ _ → row pixels = A B C D E
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```
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## Embedded targets
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Plain `static` arrays land in `.rodata`, which is mapped to flash on the common embedded Rust targets — Cortex-M, RISC-V, ESP32, etc. The crate is `no_std` and uses no allocator. AVR's Harvard architecture (`PROGMEM`) is **not** addressed; AVR Rust support is nightly-only and out of scope for this crate.
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## License — read this
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This crate is currently licensed **CC BY-NC-SA 4.0** — the only license offered for the upstream font data on the source page. That means:
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- **Non-commercial use only.** You cannot ship this crate (or work derived from its font data) in a product you sell.
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- **ShareAlike.** Any derivative work that incorporates the font data must also be licensed under CC BY-NC-SA 4.0.
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- This is **not** an OSI-approved open-source license. It is incompatible with most permissive and copyleft software licenses.
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If those terms don't fit your project, this crate is not for you.
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Full license text: [`LICENSE`](./LICENSE) — see also <https://creativecommons.org/licenses/by-nc-sa/4.0/>.
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### Pending relicense
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We've reached out to the upstream author asking for a permissive software license (MIT or Apache-2.0) on the original C source. If granted, this crate will be relicensed accordingly and a new version published. Until then the inherited CC BY-NC-SA 4.0 license stands.
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Watch the [CHANGELOG](./CHANGELOG.md) for the relicense, if and when it lands.
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## Attribution
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- 5×5 font data and original C implementation: <https://maurycyz.com/projects/mcufont/>
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- Original 5×6 `font-inline.h` it was based on: lcamtuf, <https://lcamtuf.coredump.cx/soft/embedded/font-inline.h>
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- Lineage further traces to the ZX Spectrum 8×8 system font.
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This Rust crate (scaffolding, `embedded-graphics` integration, tests) is itself a derivative work and is therefore also CC BY-NC-SA 4.0.
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