Pretext Does What CSS Can't — Measuring Text Before the DOM Even Exists

Pretext is a new JS/TS library from Cheng Lou (React core, react-motion, Midjourney) that calculates multiline text height without DOM reflow. It splits work into a one-time prepare() pass via off-screen canvas, then a pure-arithmetic layout() hot path that runs in ~0.09ms. The result: accurate pre-render height prediction for virtualized lists, chat UIs, and canvas renderers — plus layout primitives CSS literally doesn't have, like finding the minimum width for a block of text at a fixed line count. Solid i18n, rigorous accuracy testing, 7k+ GitHub stars in days. Still early: no SSR, system-ui is broken on macOS, and the 500x benchmark is the author's own caveat.