code: public int getSortColRenderIndex() {
          final ValueExpression veSortBy = getValueExpression(PropertyKeys.sortBy.name());
          if (veSortBy == null) {
              return -1;
          }
  
          final String sortByExp = veSortBy.getExpressionString();
          int colIdx = 0;
          for (final SheetColumn column : getColumns()) {
              if (!column.isRendered()) {
                  continue;
              }
  
              final ValueExpression veCol = column.getValueExpression(PropertyKeys.sortBy.name());
              if (veCol != null) {
                  if (veCol.getExpressionString().equals(sortByExp)) {
                      return colIdx;
                  }
              }
              colIdx++;
          }
          return -1;
      }
docs: Gets the rendered col index of the column corresponding to the current sortBy. This is used to keep track of the current sort column in the page.
  
  @return