VizChitra Fonts

Typography lab and font pipeline for VizChitra Sans — a Cairo derivative with a custom RETA axis for the per-character slant effect we call Retalics.

github.com/vizchitra/fonts, deployed to fonts.vizchitra.com as the fonts Worker on the vizchitra Cloudflare account. See docs/plan.md for the three-phase plan and docs/spec.md for the original brief.

pnpm install
pnpm dev          # the Retalics Lab at /

Five commands are the whole web interface: dev, build, check, test, deploy. pnpm check and pnpm test must pass before committing.

pnpm test runs two projects: fast node unit tests, and real-browser tests in Chromium, WebKit and Firefox via Playwright (*.browser.test.ts). The browser ones screenshot type specimens and measure rendered shear, because the font questions this project cares about cannot be answered any other way — see docs/compat.md. First run needs pnpm exec playwright install chromium webkit firefox.

Deploying

Work goes through a PR. Merging to main runs CI and deploys to fonts.vizchitra.com as the fonts Worker on the vizchitra Cloudflare account.

Nothing account-specific is committed — this repo is public. wrangler.jsonc carries no account_id; CI supplies CLOUDFLARE_ACCOUNT_ID and CLOUDFLARE_API_TOKEN from the production environment secrets. A one-off local deploy therefore needs the account passed explicitly:

CLOUDFLARE_ACCOUNT_ID=<vizchitra account id> pnpm deploy

Font files are served from versioned, immutable paths with _headers supplying Access-Control-Allow-Origin. Without that header a cross-origin @font-face silently fails, so nothing else could use these fonts. A font revision ships as /v2/; bytes under an existing version never change.

Fonts

Font work runs on Python via uv (managed by mise — see .mise.toml). Never conda, never system Python.

uv run font-src/fetch.py     # download upstream originals, verify hashes
uv run font-src/subset.py    # build the unicode-range split woff2 subsets
uv run font-src/css.py       # regenerate src/lib/styles/fonts.css

Sources are pinned in fonts.lock.json. Each family comes from a different upstream, for reasons worth not rediscovering:

Family	Source	Version
Cairo	google/fonts	3.130 — upstream Gue3bara's last release is v3.116 (2020)
IBM Plex Sans	google/fonts	3.201 — IBM's own npm package ships no variable font
Fira Code	tonsky/FiraCode release ZIP	6.2 — Google's build is stale at 5.002

Only Cairo is ever modified. Plex and Fira Code are redistributed as-is; the subsets served to browsers are a derived delivery artifact, built alongside the untouched originals.

Three things that look like bugs and are not:

• Cairo's italic @font-face uses the bare oblique keyword with no angle range. Adding a range breaks it in two of three engines — Chromium stacks a synthetic skew on the real axis, WebKit drops the axis entirely. Measured, and pinned by src/lib/fonts/slant.browser.test.ts.

• Fira Code's family name really is Fira Code Light and its wght axis defaults to 300. That is upstream's naming — anything using it sets an explicit font-weight (see app.css), rather than patching the font.

• --layout-features='*' in font-src/subset.py is load-bearing: fontTools' default drops all 42 cvXX/ssXX stylistic sets. Ligatures survive either way, via GSUB closure.