QList<PlotItem*> PlotItemManager::plotsForView(View *view) {
  QList<QGraphicsItem*> graphics_items = view->scene()->items();
  QList<PlotItem *> plot_items;

  foreach(QGraphicsItem* graphics_item, graphics_items) {
    PlotItem *item = dynamic_cast<PlotItem*>(graphics_item);
    if (item && item->isVisible()) {
      plot_items.append(item);
    }
  }