When the user clicks the Source button, I need to do a test and based on the results either permit or cancel the mode change.  I had code to capture the mode change event that was working fine in version 3 of CKEditor but does not after an upgrade to 4.2.1  I have tried capturing the beforeSetMode, beforeModeUnload and mode events.  I can capture them but calling evt.cancel() and evt.stop() seem to have no effect as does returning false.  I printed out the contents of those methods and found function (){e=1} and function (){a=1} respectively (not exactly robust code).

Can anyone offer a means to cancel a mode change event?