ISelection selection = event.getSelection();
if (selection instanceof IStructuredSelection && ((IStructuredSelection)selection).size() == 1) {
Object object = ((IStructuredSelection)selection).getFirstElement();
EditingDomain domain = ((IEditingDomainProvider)activeEditorPart).getEditingDomain();
newChildDescriptors = domain.getNewChildDescriptors(object, null);
newSiblingDescriptors = domain.getNewChildDescriptors(null, object);
}
// Generate actions for selection; populate and redraw the menus.
//
createChildActions = generateCreateChildActions(newChildDescriptors, selection);