@Override
public void createPartControl(Composite parent) {

	(...)
	
	this.hookContextMenu();
	
	(...)
}
	
	
private void hookContextMenu() {
	MenuManager menuMgr = new MenuManager("#PopupMenu"); //$NON-NLS-1$
	
	menuMgr.setRemoveAllWhenShown(true);
	menuMgr.addMenuListener(new IMenuListener() {
		
		public void menuAboutToShow(IMenuManager manager) {
			TreeNavigator.this.fillContextMenu(manager);
		}
	});
	Menu menu = menuMgr.createContextMenu(viewer.getControl());
	viewer.getControl().setMenu(menu);
	getSite().registerContextMenu(menuMgr, viewer);
}


@SuppressWarnings("unchecked")
private void fillContextMenu(IMenuManager manager) {
	
	(contribute with the "old school" actions")
    
}