Method updateStickyHeaderRowStyles

src/cdk/table/table.ts:829–848

* Updates the header sticky styles. First resets all applied styles with respect to the cells * sticking to the top. Then, evaluating which cells need to be stuck to the top. This is * automatically called when the header row changes its displayed set of columns, or if its * sticky input ch

()

   * of these events.
   */
  updateStickyHeaderRowStyles(): void {
    const headerRows = this._getRenderedRows(this._headerRowOutlet);

    // Hide the thead element if there are no header rows. This is necessary to satisfy
    // overzealous a11y checkers that fail because the `rowgroup` element does not contain
    // required child `row`.
    if (this._isNativeHtmlTable) {
      const thead = closestTableSection(this._headerRowOutlet, 'thead');
      if (thead) {
        thead.style.display = headerRows.length ? '' : 'none';
      }
    }

    const stickyStates = this._headerRowDefs.map(def => def.sticky);
    this._stickyStyler.clearStickyPositioning(headerRows, ['top']);
    this._stickyStyler.stickRows(headerRows, stickyStates, 'top');

    // Reset the dirty state of the sticky input change since it has been used.
    this._headerRowDefs.forEach(def => def.resetStickyChanged());
  }

  /**
   * Updates the footer sticky styles. First resets all applied styles with respect to the cells