_onTouchStart(evt) {
      this._cancelTouchOut = false;
      if (this.disabled || this._mouseOrTouchDown) {
        return;
      }
      const x = evt.type === "touchstart" ? evt.touches[0].pageX : evt.pageX;
      const y = evt.type === "touchstart" ? evt.touches[0].pageY : evt.pageY;
      this._movSelectedValue = this.selectedValue;
      this._calculateDimensions();
      this._calculatePosition(x, y);
      this._mouseOrTouchDown = true;
    }
TouchStart/MouseDown event handler.

@param {event} evt Event object