claude-code / ink / measure-text.ts

import { lineWidth } from './line-width-cache.js'

type Output = {
  width: number
  height: number
}

// Single-pass measurement: computes both width and height in one
// iteration instead of two (widestLine + countVisualLines).
// Uses indexOf to avoid array allocation from split('\n').
function measureText(text: string, maxWidth: number): Output {
  if (text.length === 0) {
    return {
      width: 0,
      height: 0,
    }
  }

  // Infinite or non-positive width means no wrapping — each line is one visual line.
  // Must check before the loop since Math.ceil(w / Infinity) = 0.
  const noWrap = maxWidth <= 0 || !Number.isFinite(maxWidth)

  let height = 0
  let width = 0
  let start = 0

  while (start <= text.length) {
    const end = text.indexOf('\n', start)
    const line = end === -1 ? text.substring(start) : text.substring(start, end)

    const w = lineWidth(line)
    width = Math.max(width, w)

    if (noWrap) {
      height++
    } else {
      height += w === 0 ? 1 : Math.ceil(w / maxWidth)
    }

    if (end === -1) break
    start = end + 1
  }

  return { width, height }
}

export default measureText