for left button activation
      return button === 0;
    }
  }

  function isSyntheticClick(ev) {
    if (ev.type === 'click') {
      // ev.detail is 0 for HTMLElement.click in most browsers
      if (ev.detail === 0) {
        return true;
      }
      // in the worst case, check that the x/y position of the click is within
      // the bounding box of the target of the event
      // Thanks IE 10 >:(
      let t = Gestures._findOriginalTarget(ev);
      // make sure the target of the event is an elemen