How to cancel drag and drop when it is in progress?

[David Bovill]

Is there a way for a script to cancel a drag and drop event while it is in
progress?

  set the dragdata to empty

Does not seem to work?

Am I right that if a mouseDown handler starts a drag-and-drop - then a
mouseUp event is not sent (a dragdrop may be sent instead) - but a
mouseDoubleUp is sent?