getSite().registerContextMenu(contextMenu, new UnwrappingSelectionProvider(viewer));
int dndOperations = DND.DROP_COPY | DND.DROP_MOVE | DND.DROP_LINK;
Transfer[] transfers = new Transfer[] { LocalTransfer.getInstance() };
viewer.addDragSupport(dndOperations, transfers, new ViewerDragAdapter(viewer));
viewer.addDropSupport(dndOperations, transfers, new EditingDomainViewerDropAdapter(editingDomain, viewer));
}