/* nodes with non-valid data are not included */
 private static Navigatable[] getNavigatablesForNodes(Node[] nodes) {
   if (nodes == null) {
     return null;
   }
   final List<Navigatable> result = new ArrayList<Navigatable>();
   for (final Node node : nodes) {
     /*
     if (!node.isDataValid()) {
       continue;
     }
     */
     Object userObject = node.getUserObject();
     if (userObject instanceof Navigatable) {
       result.add((Navigatable) userObject);
     }
   }
   return result.toArray(new Navigatable[result.size()]);
 }
    @Override
    public void calcData(final DataKey key, final DataSink sink) {
      Node node = getSelectedNode();

      if (key == PlatformDataKeys.PROJECT) {
        sink.put(PlatformDataKeys.PROJECT, myProject);
      } else if (key == USAGE_VIEW_KEY) {
        sink.put(USAGE_VIEW_KEY, UsageViewImpl.this);
      } else if (key == PlatformDataKeys.NAVIGATABLE_ARRAY) {
        sink.put(PlatformDataKeys.NAVIGATABLE_ARRAY, getNavigatablesForNodes(getSelectedNodes()));
      } else if (key == PlatformDataKeys.EXPORTER_TO_TEXT_FILE) {
        sink.put(PlatformDataKeys.EXPORTER_TO_TEXT_FILE, myTextFileExporter);
      } else if (key == USAGES_KEY) {
        final Set<Usage> selectedUsages = getSelectedUsages();
        sink.put(
            USAGES_KEY,
            selectedUsages != null
                ? selectedUsages.toArray(new Usage[selectedUsages.size()])
                : null);
      } else if (key == USAGE_TARGETS_KEY) {
        sink.put(USAGE_TARGETS_KEY, getSelectedUsageTargets());
      } else if (key == PlatformDataKeys.VIRTUAL_FILE_ARRAY) {
        final Set<Usage> usages = getSelectedUsages();
        Usage[] ua = usages != null ? usages.toArray(new Usage[usages.size()]) : null;
        VirtualFile[] data = UsageDataUtil.provideVirtualFileArray(ua, getSelectedUsageTargets());
        sink.put(PlatformDataKeys.VIRTUAL_FILE_ARRAY, data);
      } else if (key == PlatformDataKeys.HELP_ID) {
        sink.put(PlatformDataKeys.HELP_ID, HELP_ID);
      } else if (key == PlatformDataKeys.COPY_PROVIDER) {
        sink.put(PlatformDataKeys.COPY_PROVIDER, this);
      } else if (node != null) {
        Object userObject = node.getUserObject();
        if (userObject instanceof TypeSafeDataProvider) {
          ((TypeSafeDataProvider) userObject).calcData(key, sink);
        } else if (userObject instanceof DataProvider) {
          DataProvider dataProvider = (DataProvider) userObject;
          Object data = dataProvider.getData(key.getName());
          if (data != null) {
            sink.put(key, data);
          }
        }
      }
    }