/**
* Wrapper for GS ( L, to calculate and send correct data length.
*
* @param string $m Modifier/variant for function. Usually '0'.
* @param string $fn Function number to use, as character.
* @param string $data Data to send.
* @throws InvalidArgumentException Where the input lengths are bad.
*/
private function wrapperSendGraphicsData($m, $fn, $data = '')
{
if (strlen($m) != 1 || strlen($fn) != 1) {
throw new InvalidArgumentException("wrapperSendGraphicsData: m and fn must be one character each.");
}
$header = $this->intLowHigh(strlen($data) + 2, 2);
$this->connector->write(self::GS . "(L" . $header . $m . $fn . $data);
}
