private void installPositionMarkers(IModelParser parser, IDocument document) {
    PositionMarker marker = new PositionMarker();
    marker.setBase(_editor.getBase());
    marker.setDocument(document);

    IPreferenceStore prefs = UIPlugin.getDefault().getPreferenceStore();

    if (prefs.getBoolean(UIPreferences.ENABLE_ASSIST_PREF)) {
      IPositionMarkerParticipant participant = new CodeAssistMarkerParticipant();
      marker.addParticipant(participant);
    }

    if (prefs.getBoolean(UIPreferences.ENABLE_FOLDING_PREF)) {
      IPositionMarkerParticipant participant = new FoldingMarkerParticipant(_editor);
      marker.addParticipant(participant);
    }

    parser.addTreeTracker(marker);
  }