Method update

src/track/thumb.ts:43–57

(
    scrollOffset: number,
    containerSize: number,
    pageSize: number,
  )

  }

  update(
    scrollOffset: number,
    containerSize: number,
    pageSize: number,
  ) {
    // calculate thumb size
    // pageSize > containerSize -> scrollable
    this.realSize = Math.min(containerSize / pageSize, 1) * containerSize;
    this.displaySize = Math.max(this.realSize, this._minSize);

    // calculate thumb offset
    this.offset = scrollOffset / pageSize * (containerSize + (this.realSize - this.displaySize));

    setStyle(this.element, this._getStyle());
  }

  private _getStyle() {
    switch (this._direction) {