public IDirectableViewer addViewer(IDirectableViewer viewer){
  if (viewer instanceof MainViewer)   this.viewer=(MainViewer)viewer;
  viewers.add(viewer);
  directorListeners.add(viewer);
  ProjectManager.projectWindowChanged(this,viewer,true);
  return viewer;
}

public IDirectableViewer addViewer ( IDirectableViewer viewer ) { if ( viewer instanceof MainViewer ) this . viewer = ( MainViewer ) viewer ; viewers . add ( viewer ) ; directorListeners . add ( viewer ) ; ProjectManager . projectWindowChanged ( this , viewer , true ) ; return viewer ; }
add a viewer to this doc
