Font Render Service

A client-server tool for comparing font rendering with the Windows DirectWrite rasterizer. The server runs on Windows, renders fonts (TTF, OTF, WOFF, WOFF2) in headless Chromium and returns PNG screenshots, optionally with per-glyph geometry. Clients run on any machine on the network.

┌────────────────────────┐        HTTP + Bearer token       ┌──────────────────────────────┐
│  Clients (any OS)      │  ── POST /fonts, /render ──────▶ │  Windows (server)            │
│  font-render (CLI)     │  ◀─ PNG / JSON (+geometry) ───── │  FastAPI + Playwright        │
│  hintbench             │                                  │  pool of headless Chromium   │
│  font-render-bot       │                                  │  DirectWrite rasterization   │
│  (Telegram, own repo)  │                                  │  NSSM service                │
│                        │                                  │                              │
│  Admin: font-render,   │  ── POST /update (admin token) ▶ │  signed release from GitHub  │
│  web admin /admin/     │  ◀─ verify, install, restart ─── │                              │
└────────────────────────┘                                  └──────────────────────────────┘

The Telegram bot lives in its own repository (font-render-bot) and runs on the server host as a separate service with its own updates; for the server it is just another render client with its own token. Admin calls (/update, /admin/*) come from font-render and the web admin with an admin token.

Quick start

Server (Windows) — one command in PowerShell (see docs/deployment.md, which also covers the git checkout install for development):

irm https://github.com/typedev/font-render-server/releases/latest/download/install.ps1 | iex

It prints the web admin address and the admin token. Repair or update: run it again. Remove: Apps & features → Font Render Service. Lost token: Start → Font Render → Reset admin token.

Client (any OS) — the font-render-client package (client/README.md):

uv tool install font-render-client           # from PyPI (or: pipx install font-render-client)
font-render login http://SERVER:41800          # asks for the token you got from the server's admin
font-render font_a.ttf font_b.otf             # comparison waterfall -> ./renders/
font-render font.ttf --plain --zoom 4         # text only, 4x nearest-neighbor
font-render --info                            # server info + which client you are

From a checkout of this repository (development; tokens in .env instead of login):

uv sync
cp .env.example .env   # FONT_RENDER_SERVER, FONT_RENDER_CLIENT_TOKEN (and FONT_RENDER_ADMIN_TOKEN for admin)
uv run font-render --info
# web admin: http://SERVER:41800/admin/ (log in with an admin token)

Commands

Installed with the client package the commands run as they are; in a checkout prefix them with uv run.

Common options: --server URL / -s (default FONT_RENDER_SERVER), --token (legacy admin form token of old checkout servers).

Render options of font-render:

Documentation

• docs/api.md — HTTP API: /render, /fonts, geometry mode, errors, Server-Timing
• docs/auth.md — client tokens: issuing, rotating, closing anonymous access
• docs/admin.md — web admin: status, clients, requests, logs, maintenance
• docs/deployment.md — Windows server setup, service, updates, logs, configuration
• docs/development.md — code layout, tests, pixel identity, benchmarks
• docs/releasing.md — release signing key, making a release
• docs/embedded.md — embedded mode: a private server for a desktop app (hintbench on Windows)
• docs/distribution.md — how install, release updates, uninstall and developer mode work (design)
• CHANGELOG.md — releases
• TODO.md — planned work

Project layout

src/font_render/         server package (FastAPI app, auth, browser pool, font cache, page builder)
client/                  font-render-client package (font-render, -batch, -clients, login)
src/font_render_tools/   pixel-check (needs the server package)
tests/                   pytest suite
install.ps1              one-command installer (published with each release)
deploy/windows/          launcher.py, font-render-server.cmd, reset-admin.cmd, uninstall.cmd
                         (installed layout); setup_service.bat, start_server.bat (checkout)
scripts/                 build_release.py, smoke_test.ps1 (CI), release_key.py (signing key)
.github/workflows/       release.yml: tests, build, Windows smoke test, sign, publish
docs/                    documentation