drawText method
Draw a text at position (x,y).
Implementation
@override
void drawText(String text, num x, num y, PFont font, PStyle style) {
  x = transform.x(x);
  y = transform.y(y);
  var clip = _clip;
  if (clip != null) {
    var m = measureText(text, font);
    var box = PRectangle(x, y, m.actualWidth, m.actualHeight);
    var r = clip.intersection(box);
    if (r.isZeroDimension) return;
    _callClipped(clip, box, () => _drawTextImpl(style, font, x, y, text));
  } else {
    _drawTextImpl(style, font, x, y, text);
  }
}