code: protected List<AbstractColumn> getVisibleColumns() {
  		List<AbstractColumn> visibleColums = new ArrayList<AbstractColumn>(getReport().getColumns());
  		for (DJGroup group : getReport().getColumnsGroups()) {
  			if (group.getLayout().isHideColumn()) {
  				visibleColums.remove(group.getColumnToGroupBy());
  			}
  		}
  		return visibleColums;
  	}
docs: Returns a list with the columns that are visible.
  Invisible column are the one whose group is configured with hideColumn = true (in the GroupLayout)
  @return