_dragMoveUpdate(e) {
      let clientX = e.targetTouches[0].clientX;
      let currentScrollTop = this.isOpen ? this.el.scrollTop : M.getDocumentScrollTop();
      this.deltaX = Math.abs(this._xPos - clientX);
      this._xPos = clientX;
      this.velocityX = this.deltaX / (Date.now() - this._time);
      this._time = Date.now();
      if (this._initialScrollTop !== currentScrollTop) {
        this._verticallyScrolling = true;
      }
    }
Set variables needed at each drag move update tick
@param {Event} e