isGraphic function
IsGraphic reports whether the rune is defined as a Graphic by Unicode.
Such characters include letters, marks, numbers, punctuation, symbols, and spaces, from categories L, M, N, P, S, Zs.
Implementation
bool isGraphic(int rune) {
if (isPrintable(rune)) return true;
if (rune > 0xFFFF) return false;
final i = _bsearch(_isGraphic, rune);
return i < _isGraphic.length && rune == _isGraphic[i];
}