mayContainTerminalGraphics function

bool mayContainTerminalGraphics(String value)

Whether value can contain one of the graphics protocols handled here.

This is intentionally a cheap prefilter for hot renderer paths. It may return true for malformed payloads, but it must not return false for any sequence recognized by the parsing helpers in this library.

Implementation

bool mayContainTerminalGraphics(String value) {
  if (value.length <= 3) {
    // Short strings (most common cell content).  Terminal graphics introducers
    // are 0x1B (ESC), 0x90 (DCS), or 0x9F (APC) — none are printable ASCII.
    var hasControlOrHigh = false;
    for (var i = 0; i < value.length; i++) {
      final cu = value.codeUnitAt(i);
      if (cu < 0x20 || cu >= 0x80) {
        hasControlOrHigh = true;
        break;
      }
    }
    if (!hasControlOrHigh) return false;
  }

  var escIndex = value.indexOf('\x1b');
  while (escIndex != -1) {
    if (escIndex + 2 < value.length) {
      final next = value.codeUnitAt(escIndex + 1);
      final third = value.codeUnitAt(escIndex + 2);
      if ((next == 0x5F && third == 0x47) || (next == 0x50 && third == 0x71)) {
        return true;
      }
    }
    escIndex = value.indexOf('\x1b', escIndex + 1);
  }

  return value.contains('\x9fG') || value.contains('\x90q');
}