API Reference — @hexdrinker/pretext-native-core

The core layout engine is a platform-independent package that handles tokenization, line breaking, and layout calculation. It has no React Native dependency and can be used in any JavaScript environment.

computeLayout(input, measureFunc, cache?)

Compute text layout given an input, a measurement function, and an optional cache.

Parameters

Parameter	Type	Description
input	TextMeasureInput	Text and style parameters
measureFunc	MeasureFunc	Function that measures word width
cache	LayoutCache	Optional cache instance

Returns TextMeasureResult

import { computeLayout } from '@hexdrinker/pretext-native-core';

const result = computeLayout(
  { text: 'Hello, world!', width: 300, fontSize: 14 },
  measureFunc
);

---

LayoutCache

Two-tier LRU cache for word measurements and layout results.

Constructor

const cache = new LayoutCache(maxWordEntries?, maxLayoutEntries?);

Parameter	Type	Default	Description
maxWordEntries	number	2000	Max word-level cache entries
maxLayoutEntries	number	500	Max layout-level cache entries

Methods

getStats()

const stats = cache.getStats();
// { hits: number, misses: number, wordEntries: number, layoutEntries: number }

clear()

cache.clear();

---

tokenize(text)

Split text into tokens (words, whitespace, CJK characters, emoji).

import { tokenize } from '@hexdrinker/pretext-native-core';

const tokens = tokenize('Hello 안녕하세요 🎉');
// ['Hello', ' ', '안', '녕', '하', '세', '요', ' ', '🎉']

---

breakLines(tokens, widths, maxWidth)

Given tokens and their measured widths, determine line breaks.

import { breakLines } from '@hexdrinker/pretext-native-core';

const lines = breakLines(tokens, measuredWidths, 300);

---

Types

MeasureFunc

type MeasureFunc = (text: string, fontSize: number) => number;

A function that returns the pixel width of a given string at a given font size. On device, this is backed by CoreText/StaticLayout. In tests, you can provide a mock or the JS heuristic adapter.

TextMeasureInput

interface TextMeasureInput {
  text: string;
  width: number;
  fontSize: number;
  fontFamily?: string;
  fontWeight?: string;
  lineHeight?: number;
  letterSpacing?: number;
  maxLines?: number;
  allowFontScaling?: boolean;
}

TextMeasureResult

interface TextMeasureResult {
  height: number;
  lineCount: number;
  lines: LineInfo[];
  truncated: boolean;
}