For most applications, the default settings are acceptable. This section describes the minimum requirements for an application to enable drag and drop.
At a minimum, the application must create the source and target adapters on the appropriate widgets. On the source adapter it does not need to hook the dragStartCallback unless it intends to change the vote, images, or offsets to values other than the defaults or unless it wants to deny drag and drop in certain cases by setting the doit flag to false. An application must hook the dragCompleteCallback to perform the operation. The dragChangeCallback does not need to be hooked, nor does the dragCancelCallback.
On the target adapters, the application only needs to hook the dragOverCallback if it needs to check the kind of items being dragged to ensure that the target widget can receive them or if it does not want the default target vote. It should hook the dropCallback to perform the operation. It does not need to hook the dragLeaveCallback or dragCancelCallback.