Method updateCellHeader

handsontable/src/tableView.ts:1597–1622

* Updates header cell content. * * @private * @param {HTMLElement} element Element to update. * @param {number} index Row index or column index. * @param {Function} content Function which should be returns content for this cell. * @param {number} [headerLevel=0] The index of header

(
    element: HTMLElement, index: number, content: (index: number, headerLevel?: number) => unknown, headerLevel = 0
  )

   *                                 values counting from 0 to N).
   */
  updateCellHeader(
    element: HTMLElement, index: number, content: (index: number, headerLevel?: number) => unknown, headerLevel = 0
  ) {
    let renderedIndex = index;
    const parentOverlay = this._wt.wtOverlays.getParentOverlay(element) || this._wt;

    // prevent wrong calculations from SampleGenerator
    if (element.parentNode) {
      if (hasClass(element, 'colHeader')) {
        renderedIndex = parentOverlay.wtTable.columnFilter!.sourceToRendered(index);

      } else if (hasClass(element, 'rowHeader')) {
        renderedIndex = parentOverlay.wtTable.rowFilter!.sourceToRendered(index);
      }
    }

    if (renderedIndex > -1) {
      fastInnerHTML(element, String(content(index, headerLevel)), this.hot.getSettings().sanitizer ?? true,
        'header', this.hot.rootGridElement ?? undefined);

    } else {
      // workaround for https://github.com/handsontable/handsontable/issues/1946
      fastInnerText(element, String.fromCharCode(160));
      addClass(element, 'cornerHeader');
    }
  }

  /**
   * Given a element's left (or right in RTL mode) position relative to the viewport, returns maximum