Function isZeroWidth

src/ink/stringWidth.ts:129–203

(codePoint: number)

}

function isZeroWidth(codePoint: number): boolean {
  // Fast path for common printable range
  if (codePoint >= 0x20 && codePoint < 0x7f) return false
  if (codePoint >= 0xa0 && codePoint < 0x0300) return codePoint === 0x00ad

  // Control characters
  if (codePoint <= 0x1f || (codePoint >= 0x7f && codePoint <= 0x9f)) return true

  // Zero-width and invisible characters
  if (
    (codePoint >= 0x200b && codePoint <= 0x200d) || // ZW space/joiner
    codePoint === 0xfeff || // BOM
    (codePoint >= 0x2060 && codePoint <= 0x2064) // Word joiner etc.
  ) {
    return true
  }

  // Variation selectors
  if (
    (codePoint >= 0xfe00 && codePoint <= 0xfe0f) ||
    (codePoint >= 0xe0100 && codePoint <= 0xe01ef)
  ) {
    return true
  }

  // Combining diacritical marks
  if (
    (codePoint >= 0x0300 && codePoint <= 0x036f) ||
    (codePoint >= 0x1ab0 && codePoint <= 0x1aff) ||
    (codePoint >= 0x1dc0 && codePoint <= 0x1dff) ||
    (codePoint >= 0x20d0 && codePoint <= 0x20ff) ||
    (codePoint >= 0xfe20 && codePoint <= 0xfe2f)
  ) {
    return true
  }

  // Indic script combining marks (covers Devanagari through Malayalam)
  if (codePoint >= 0x0900 && codePoint <= 0x0d4f) {
    // Signs and vowel marks at start of each script block
    const offset = codePoint & 0x7f
    if (offset <= 0x03) return true // Signs at block start
    if (offset >= 0x3a && offset <= 0x4f) return true // Vowel signs, virama
    if (offset >= 0x51 && offset <= 0x57) return true // Stress signs
    if (offset >= 0x62 && offset <= 0x63) return true // Vowel signs
  }

  // Thai/Lao combining marks
  // Note: U+0E32 (SARA AA), U+0E33 (SARA AM), U+0EB2, U+0EB3 are spacing vowels (width 1), not combining marks
  if (
    codePoint === 0x0e31 || // Thai MAI HAN-AKAT
    (codePoint >= 0x0e34 && codePoint <= 0x0e3a) || // Thai vowel signs (skip U+0E32, U+0E33)
    (codePoint >= 0x0e47 && codePoint <= 0x0e4e) || // Thai vowel signs and marks
    codePoint === 0x0eb1 || // Lao MAI KAN
    (codePoint >= 0x0eb4 && codePoint <= 0x0ebc) || // Lao vowel signs (skip U+0EB2, U+0EB3)
    (codePoint >= 0x0ec8 && codePoint <= 0x0ecd) // Lao tone marks
  ) {
    return true
  }