title: JqueryUI draggable/droppable - Identify the drop target when the drop is invalid
body: <p>I am using the draggable/droppable plugins of jquery-ui and i have the following scenario.</p>
  
  <p>Three droppable targets (<em>each one accepts a single type of elements, based on class</em>) and multiple elements (<em>one of the three types that are accepted by the droppables</em>).</p>
  
  <p>I am using the <code>revert</code> option on the draggables and the <code>accept</code> on the droppables. </p>
  
  <p>Everything works normally in terms of functionality. </p>
  
  <p><strong>What I need</strong>: to identify the drop target when the drop is invalid (<em>dropped on a droppable that does not accept the dragged element</em>)</p>
  
  <p><strong>What is the actual problem</strong>: All events of droppable fire only when the dragged element is acceptable by it.</p>
  
  <p>I need that information so that i can display error messages customized for the specific wrong drop-target.</p>
  
  <p>I really cannot wrap my head around this problem (<em>besides using another drag/drop system..</em>), so any pointers/ideas are welcome..</p>