anchor.diff:    }
   
     void _handleMarkerChange(workspace.MarkerChangeEvent event) {
  +    /*%TRACE3*/ print("(4> 2/1/14): _handleMarkerChange!"); // TRACE%
       if (event.hasChangesFor(currentFile)) {
         setMarkers(currentFile.getMarkers());
       }
  
positive.code: 
    ace.EditSession get currentSession => _aceEditor.session;
  
    void switchTo(ace.EditSession session, [workspace.File file]) {
      if (_foldListenerSubscription != null) {
        _foldListenerSubscription.cancel();
  
negative.code:       _aceEditor.session = ace.createEditSession('', new ace.Mode('ace/mode/text'));
        _aceEditor.readOnly = true;
      } else {
  
        if (!filenameBySession.containsKey(session)) {
          String filename = file == null ? 'no file' : file.name ;
          print("Haven't seen this session before.  I will call you '${filename}'");
          filenameBySession[session] = filename;
        } else {
          print("Ah, session ${filenameBySession[session]} again ...");
        }
  
        _aceEditor.session = session;
  
        if (_aceEditor.readOnly) {
  