docs: public void arc(double centerX, double centerY,
  			double radiusX, double radiusY,
  			double startAngle, double length) {
  		this.gc.arc(
  				doc2fxX(centerX), doc2fxY(centerY),
  				doc2fxSize(radiusX), doc2fxSize(radiusY),
  				doc2fxAngle(Math.toDegrees(startAngle)), doc2fxSize(length));
  	}