@Override
	public synchronized void dragEnter(DropTargetDragEvent dtde) {
		
		initializeAutoscrolling(dtde.getLocation());
		DropTargetDragEventWrapper eventWrapper = new DropTargetDragEventWrapper(dtde);
		primaryDropTarget.dragEnter(eventWrapper);
		activeDropTarget = primaryDropTarget;
		if (!eventWrapper.isAccepted()) {
			activeDropTarget = secondaryDropTarget;
			secondaryDropTarget.dragEnter(eventWrapper);
		}
		if (!eventWrapper.isAccepted()) {
			activeDropTarget = null;
		}
		eventWrapper.flush();
	}
Combines two drop targets and sends events to them in priority order.  If the first drop target
accepts the event, then the second drop target is not accessed. 
<p>
Either of the given drop targets can be an instance of CascadedDropTarget, effectively creating 
a tree structure of drop targets.
Ghidra/Framework/Generic/src/main/java/ghidra/util/CascadedDropTarget.java