How can I test if there are any changes in the Drag/Drop Field Layout Designer?
As of Craft 2.2, all you need to do is add a data-confirm-unload attribute to the &lt;form&gt; element that wraps your Field Layout Designer:

&lt;form method="post" accept-charset="UTF-8" data-confirm-unload&gt;


Craft will then automatically check to see if there were any changes in the form on page unload, and give the user a chance to stay on the page (same way the Edit Entry page works).