Function _itemsResized

src/material/tabs/paginated-tab-header.ts:272–298

Sends any changes that could affect the layout of the items.

()

  /** Sends any changes that could affect the layout of the items. */
  private _itemsResized(): Observable<ResizeObserverEntry[]> {
    if (typeof ResizeObserver !== 'function') {
      return EMPTY;
    }

    return this._items.changes.pipe(
      startWith(this._items),
      switchMap(
        (tabItems: QueryList<MatPaginatedTabHeaderItem>) =>
          new Observable((observer: Observer<ResizeObserverEntry[]>) =>
            this._ngZone.runOutsideAngular(() => {
              const resizeObserver = new ResizeObserver(entries => observer.next(entries));
              tabItems.forEach(item => resizeObserver.observe(item.elementRef.nativeElement));
              return () => {
                resizeObserver.disconnect();
              };
            }),
          ),
      ),
      // Skip the first emit since the resize observer emits when an item
      // is observed for new items when the tab is already inserted
      skip(1),
      // Skip emissions where all the elements are invisible since we don't want
      // the header to try and re-render with invalid measurements. See #25574.
      filter(entries => entries.some(e => e.contentRect.width > 0 && e.contentRect.height > 0)),
    );
  }

  ngAfterContentChecked(): void {
    // If the number of tab labels have changed, check if scrolling should be enabled