title: Connect draggable to sortable only if visible?
body: <p>In the jquery ui docs for draggable, we can specify a sortable to connect to:</p>
  
  <pre><code>$( ".selector" ).draggable({ connectToSortable: 'ul#myList' });
  </code></pre>
  
  <p>is it possible to connect to a sortable only when its visibility is set to 'visible'? Something like:</p>
  
  <pre><code>$( ".selector" ).draggable({ connectToSortable: 'ul#myList:visibility=visible' });
  </code></pre>
  
  <p>I don't want to let the user drop elements on my sortable target unless it is visible,</p>
  
  <p>Thanks</p>