@docen/pretext

Vendored fork of @chenglou/pretext 0.0.8 (commit a79a6a5) — fast, deterministic text measurement and line breaking — maintained in-tree so docen can carry Word/CJK layout fixes upstream won't.

The upstream project measures and breaks text through the canvas 2d API with pure arithmetic on top; the rich-inline entry adds multi-font inline runs, collapsed spaces, and extra-width atoms. This fork exists because docen's editor needs edit == render at Word-level CJK fidelity, which requires deep changes to the measurement internals — beyond what a patch file can sanely carry.

Vendored changes

• CJK canvas→DOM advance correction (measurement.ts) — canvas measureText rounds fullwidth CJK advances up to whole pixels; at fractional font sizes (11pt = 14.67px) every glyph over-measures by ~0.33px, flipping wrapped line counts versus the DOM render. A per-font hidden-span probe measures the delta and getCorrectedSegmentWidth subtracts it per CJK grapheme.
• Empty-text atom retention (rich-inline.ts) — an inline item whose text is pure whitespace but carries extraWidth (an inline image's padding/border chrome) survives prepareRichInline as a zero-text unbreakable atom instead of being collapsed away.
• The . entry keeps the full upstream surface (prepare / layout / layoutWithLines …); docen consumes ./rich-inline from @docen/layout (line breaking) and @docen/editor (paginator measurement).

Installation

# Install with pnpm
$ pnpm add @docen/pretext

# Install with npm
$ npm install @docen/pretext

Quick Start

import { prepareRichInline, layoutNextRichInlineLineRange } from "@docen/pretext/rich-inline";

const prepared = prepareRichInline([{ text: "甲乙丙丁", font: "16px serif" }]);
const range = layoutNextRichInlineLineRange(prepared, 64);

License

• MIT © Demo Macro — includes vendored code © Pretext contributors, MIT.