docs: protected void finishGridRow() {
      GridBagConstraints constraints = new GridBagConstraints();
      constraints.gridwidth = GridBagConstraints.REMAINDER;
      constraints.weightx = 0;
      final JLabel icon;
      if(param.isOptional()) {
        if(param.isDefined() && param.tookDefaultValue() && !(param instanceof Flag)) {
          // TODO: better icon for default value?
          icon = new JLabel(StockIcon.getStockIcon(StockIcon.DIALOG_INFORMATION));
          icon.setToolTipText("Default value: "+param.getDefaultValueAsString());
        }
        else {
          icon = new JLabel();
          icon.setMinimumSize(new Dimension(16, 16));
        }
      }
      else {
        if(!param.isDefined()) {
          icon = new JLabel(StockIcon.getStockIcon(StockIcon.DIALOG_ERROR));
          icon.setToolTipText("Missing value.");
        }
        else {
          icon = new JLabel();
          icon.setMinimumSize(new Dimension(16, 16));
        }
      }
      parent.add(icon, constraints);
    }