docs: function onDrag(evt) {
      const
          rect = this._rect,
          x = valueToX.call(this, this._value),
          min = -x,
          max = rect.width - x,
          tx = clamp(evt.x - evt.x0, min, max),
          value = xToValue.call(this, x + tx);
      Dom.css(this.$elements.button, { transform: `translateX(${tx}px)` });
      this.displayedValue = valueToDisplayedValue.call(this, value);
      if (this.smooth) {
          this._dragging = true;
          this.value = value;
      }
  }