title: How to know if raphael object is hidden?
body: <p>I am creating a diagram application in which I hide and show few elements e.g.</p>
  
  <pre><code>var c = paper.circle(10, 10, 10);
  c.hide()
  
  var c2 = paper.circle(10, 10, 10);
  c2.show()
  </code></pre>
  
  <p>Now I want to act upon such shapes e.g. calculate bounding box etc but I am not able to find how to get if shape is hidden or not? Is there something like this shape.is_visible() or shape.attr('visible')</p>