Function _scrollToLabel

src/material/tabs/paginated-tab-header.ts:510–547

* Moves the tab list such that the desired tab label (marked by index) is moved into view. * * This is an expensive call that forces a layout reflow to compute box and scroll metrics and * should be called sparingly.

(labelIndex: number)

   * should be called sparingly.
   */
  _scrollToLabel(labelIndex: number) {
    if (this.disablePagination) {
      return;
    }

    const selectedLabel = this._items ? this._items.toArray()[labelIndex] : null;

    if (!selectedLabel) {
      return;
    }

    // The view length is the visible width of the tab labels.
    const viewLength = this._tabListContainer.nativeElement.offsetWidth;
    const {offsetLeft, offsetWidth} = selectedLabel.elementRef.nativeElement;

    let labelBeforePos: number, labelAfterPos: number;
    if (this._getLayoutDirection() == 'ltr') {
      labelBeforePos = offsetLeft;
      labelAfterPos = labelBeforePos + offsetWidth;
    } else {
      labelAfterPos = this._tabListInner.nativeElement.offsetWidth - offsetLeft;
      labelBeforePos = labelAfterPos - offsetWidth;
    }

    const beforeVisiblePos = this.scrollDistance;
    const afterVisiblePos = this.scrollDistance + viewLength;

    if (labelBeforePos < beforeVisiblePos) {
      // Scroll header to move label to the before direction
      this.scrollDistance -= beforeVisiblePos - labelBeforePos;
    } else if (labelAfterPos > afterVisiblePos) {
      // Scroll header to move label to the after direction
      this.scrollDistance += Math.min(
        labelAfterPos - afterVisiblePos,
        labelBeforePos - beforeVisiblePos,
      );
    }
  }

  /**
   * Evaluate whether the pagination controls should be displayed. If the scroll width of the