fontcull

A Rust port of the parts of glyphhanger I use regularly.

Why?

glyphhanger is amazing, but it's 5+ years old and requires a specific old version of Chrome/Puppeteer that's become painful to maintain. With the help of Claude, I ported the core functionality to Rust.

What it does

Opens URLs in a headless browser (via chromiumoxide)
Extracts all glyphs/characters used on the page (including ::before/::after pseudo-elements)
Optionally spiders the site to find more pages
Subsets font files to only include the characters actually used

Usage

# Just get the unicode range of characters used
fontcull https://example.com

# Subset fonts based on page content
fontcull https://example.com --subset=fonts/*.ttf

# Spider multiple pages
fontcull https://example.com --spider-limit=10 --subset=fonts/*.ttf

# Filter by font family
fontcull https://example.com --subset=fonts/*.ttf --family="My Font"

# Add extra characters to always include
fontcull https://example.com --subset=fonts/*.ttf --whitelist="0123456789"

Subsetting backends

klippa (default): Pure Rust subsetting via fontations, woff2 compression via vendored Google woff2
pyftsubset (--pyftsubset): Falls back to Python's fonttools (requires pip install fonttools brotli)

Install

cargo install --git https://github.com/bearcove/fontcull

Requires Chrome/Chromium installed (uses your system browser, no specific version needed).

Library usage

fontcull can also be used as a library for font subsetting:

use fontcull::{subset_font_to_woff2, analyze_fonts, extract_css_from_html};
use std::collections::HashSet;

// Direct subsetting with known characters
let font_data = std::fs::read("font.ttf").unwrap();
let chars: HashSet<char> = "Hello World".chars().collect();
let woff2 = subset_font_to_woff2(&font_data, &chars).unwrap();

// Or analyze HTML/CSS to find which characters are used (requires `static-analysis` feature)
let html = r#"<html><style>body { font-family: "MyFont"; }</style><body>Hello</body></html>"#;
let css = extract_css_from_html(html);
let analysis = analyze_fonts(html, &css);

Features

klippa (default): Pure Rust font subsetting
static-analysis: Static HTML/CSS parsing for font usage detection
browser (default): Browser-based glyph extraction for CLI

fontcull 1.0.5