There is probably only a handful of things that are probably less understood at the SDK level as to how just exactly the Drag-Drop event sequence is generated, captured, and handled. First off, the UIComponent is the one where events can be registered but does absolutely nothing about dispatching or even ‘psuedo-dispatching’ through an intermediary.


Not In Here:

Case is point – we all know about the DragManager, and how you have to enable certain targets to allow the capture sequence to generate events for the final drop event, however it’s really the SystemManager that handles a bunch of marshalling for you – since it sits at the near root level it knows about MouseEvents for just about every object.

It’s this ferrying back and forth between the InterManagerRequest.DRAG_MANAGER_REQUEST event between the DragManager and ultimately passed through the Implementor (ie DragManagerImpl), and the SystemManager, is what creates the DragEvent to eventually be fired via the DragProxy. This is why the documentation says it is important to trigger the allowDragDrop method from within the DragEvent.ENTER event – because the target is then assigned directly to the proxy instance.