private void showOrHideProblemView() {
    boolean showProblems =
        PreferenceStoreHelper.getInstancePreferenceStore()
            .getBoolean(IPreferenceConstants.I_PARSER_POPUP_ERRORS);
    if (showProblems) {
      if (TLAMarkerHelper.currentSpecHasProblems()) {
        // This used to be in Activator. However,
        // at startup there might not be an
        // activePage which results in a
        // NullPointerException. Thus, have the
        // ProblemView check the parse status when
        // UI startup complete.
        ProblemView view = (ProblemView) UIHelper.getActivePage().findView(ProblemView.ID);
        // show
        if (view != null) {
          // already shown, hide
          UIHelper.hideView(ProblemView.ID);
        }

        // not shown, show
        UIHelper.openViewNoFocus(ProblemView.ID);
      } else {
        // hide
        UIHelper.hideView(ProblemView.ID);
      }
    }
  }
 public void resourceChanged(IResourceChangeEvent event) {
   // no marker update
   if (!hasMarkerDelta(event)) {
     return;
   } else {
     UIHelper.runUIAsync(
         new Runnable() {
           public void run() {
             showOrHideProblemView();
           }
         });
   }
 }
  /**
   * @see
   *     org.eclipse.core.commands.AbstractHandler#execute(org.eclipse.core.commands.ExecutionEvent)
   */
  public Object execute(ExecutionEvent event) throws ExecutionException {
    IWorkbenchWindow window = HandlerUtil.getActiveWorkbenchWindowChecked(event);

    Spec spec = Activator.getSpecManager().getSpecLoaded();

    FileDialog openFileDialog = UIHelper.getFileDialog(window.getShell());
    openFileDialog.setText("Add TLA+ module to the spec");
    openFileDialog.setFilterPath(ResourceHelper.getParentDirName(spec.getRootFile()));

    openFileDialog.setFilterExtensions(ACCEPTED_EXTENSIONS);
    String moduleFileName = openFileDialog.open();
    if (moduleFileName != null) {
      IFile module = ResourceHelper.getLinkedFile(spec.getProject(), moduleFileName, false);

      // add .tla extension is the file does not have any extension
      if (module != null && module.getFileExtension() == null) {
        moduleFileName = ResourceHelper.getModuleFileName(moduleFileName);
        module = ResourceHelper.getLinkedFile(spec.getProject(), moduleFileName, false);
      }

      // check if it a TLA file
      if (!ResourceHelper.isModule(module)) {
        // selected non-TLA file
        // module exists and is already registered in the spec
        MessageDialog.openInformation(
            window.getShell(),
            "The selected file is not a TLA+ file",
            "The provided file "
                + module.getName()
                + " is not a TLA+ file.\n Please select a file with .tla extension.");
        return null;

      } else {
        if (module.isLinked()) {
          // module exists and is already registered in the spec
          MessageDialog.openInformation(
              window.getShell(),
              "TLA+ Module is part of the spec",
              "The provided module "
                  + module.getName()
                  + " has already been added to the specification previously.");
        } else {
          IPath modulePath = new Path(moduleFileName);
          // check the folder we are in
          if (!ResourceHelper.isProjectParent(
              modulePath.removeLastSegments(1), spec.getProject())) {
            // the selected resource is not in the same directory as
            // the root file
            MessageDialog.openInformation(
                window.getShell(),
                "TLA+ Module is not part of the current spec.",
                "The provided module "
                    + module.getName()
                    + " is not part of the spec which is currently open. It will therefore be opened in read-only mode.\n"
                    + "If you want to make changes to this file, you will have to open the corresponding spec first.");

            // Open TLA's read-only editor on a .tla file that does
            // *not* belong to the current spec. It is opened
            // read-only, because we want to allow any changes,
            // because we couldn't parse the spec anyway. The reason
            // why this functionality is offered, is to allow users
            // to look at .tla files of closed spec.
            // http://wiki.eclipse.org/FAQ_How_do_I_open_an_editor_on_a_file_outside_the_workspace%3F
            final IFileStore fileStore =
                EFS.getLocalFileSystem().getStore(new Path(moduleFileName));
            if (!fileStore.fetchInfo().isDirectory() && fileStore.fetchInfo().exists()) {
              UIHelper.openEditor(
                  "org.lamport.tla.toolbox.editor.basic.TLAEditorReadOnly",
                  new FileStoreEditorInput(fileStore));
            } else {
              throw new ExecutionException(
                  moduleFileName
                      + " cannot be opened in read-only mode because its file content could not be obtained.");
            }
            return null;
          }

          // !module.exists()
          if (!modulePath.toFile().exists()) {
            // the provided file does not exist
            boolean createNew =
                MessageDialog.openQuestion(
                    window.getShell(),
                    "TLA+ Module is not found",
                    "The provided module "
                        + module.getName()
                        + " does not exist. Should the new file be created?");
            if (createNew) {
              // the module point to a virtual path /WS_ROOT/SPEC_NAME/module_name.tla
              // assuming the fact that the root file is located in directory
              // /ROOT_DIR/SPEC_NAME.tla
              // and the Spec's project name is /ROOT_DIR/SPEC_NAME.project
              // the file should be created in /ROOT_DIR/module_name.tla and linked to the virtual
              // path.

              try {
                ResourcesPlugin.getWorkspace()
                    .run(ResourceHelper.createTLAModuleCreationOperation(modulePath), null);
              } catch (CoreException e) {
                e.printStackTrace();
                // exception, no chance to recover
                return null;
              }
            } else {
              return null;
            }
          }
          // adding the file to the spec
          module = createModuleFile(spec, moduleFileName, modulePath);
        }

        // create parameters for the handler
        Map<String, String> parameters = new HashMap<String, String>();
        parameters.put(
            OpenModuleHandler.PARAM_MODULE,
            ResourceHelper.getModuleNameChecked(module.getName(), false));

        // runs the command and opens the module in the editor
        UIHelper.runCommand(OpenModuleHandler.COMMAND_ID, parameters);
      }
    }

    return null;
  }