code: protected void stroke(ZoomableGraphicsContext gc, T element) {
  		final double radius = element.getRadius();
  		final double diameter = radius * radius;
  		final double minx = element.getX() - radius;
  		final double miny = element.getY() - radius;
  		gc.strokeOval(minx, miny, diameter, diameter);
  	}
docs: Stroke the circle.
  
  @param gc the graphics context that must be used for drawing.
  @param element the map element.