chenglou/pretext

A fast, accurate, comprehensive text measurement and layout library — by Cheng Lou (Reason / ReScript core team).

What it is

A TypeScript library for low-level text measurement and layout — width, height, line-breaking, kerning, font fallback, mixed-script handling. Aimed at canvas / WebGL / non-DOM renderers that can't rely on browser text layout. Authored by Cheng Lou, who has shipped multiple high-quality OSS libraries in adjacent layout / rendering spaces.

Key features

Accurate text measurement matching browser layout where applicable.
Line-breaking, font fallback, mixed-script support.
TypeScript-first, framework-agnostic.
MIT-licensed.

Tech stack

TypeScript primary.
Pure library — no UI dependencies.

When to reach for it

You're building canvas / WebGL UIs that need accurate text layout outside the DOM.
You're implementing a custom renderer (PDF, native, embedded) where browser CSS isn't available.

When not to reach for it

You're using DOM-rendered text — browser layout is more capable and free.
You don't need accurate measurement — measureText is enough for simple cases.

Maturity signal

48k stars, 2.7k forks, MIT, actively maintained. Authored by Cheng Lou (known for ReasonReact and other layout work). The high star count for a niche library reflects the author's reputation in the JS/ReScript community.

Alternatives

harfbuzz/harfbuzz (via WASM) — use for the canonical text-shaping engine.
Browser measureText — use when you only need width.

Wiki: chenglou/pretext