[news.eclipse.platform] Question about Common Navigator and drop adapter

[Eric Rizzo <eclipse-news@xxxxxxxxxxxx>]

I've got a common navigator viewer for which I need to do some 
specialized drag-and-drop handling. I'm trying to define a 
CommonDropAdapterAssistant to be used for certain file types. So in my 
plugin.xml I have something like this:

<dropAssistant
         class="org.skyway.core.ui.navigator.SkywayDropAssistant"
         id="org.skyway.core.ui.navigator.dropAssistant">
      <possibleDropTargets>
         <adapt type="org.skyway.core.model.Container"></adapt>
      </possibleDropTargets>
</dropAssistant>

The problem is, even when the drop target can not be adapted to a 
org.skyway.core.model.Container, the drop operation is allowed to proceed.
I think this is because there is always a 
org.eclipse.ui.navigator.resources.ResourceDropAdapterAssistant included 
(it is declared by the plugin org.eclipse.ui.navigator.resources) and 
it's possibleDropTargets expression includes any target that can be 
adapted to an IFile, IFolder, or IProject.

So can I have a drop assistant that controls the validation of drops on 
particular files and folders? In other words, can I override this 
behavior of ResourceDropAdapterAssistant for certain resources, while 
keeping it in place for everything else?

Eric