code: function gestureContinue(element, clientX, clientY) {
  
    // Calculate and save the velocity since the last event. If this is the last
    // movement of the gesture, this velocity will be used to determine whether
    // the user is trying to flick.
    const deltaX = clientX - element[previousXKey];
    const deltaY = clientY - element[previousYKey];
    const now = Date.now();
    const deltaTime = now - element[previousTimeKey];
    const velocity = deltaX / deltaTime * 1000;
  
    element[previousXKey] = clientX;
    element[previousYKey] = clientY;
    element[previousTimeKey] = now;
    element[previousVelocityKey] = velocity;
  
    const verticalSwipe = Math.abs(deltaY) > Math.abs(deltaX);
    const vertical = element.state.swipeAxis === 'vertical';
    const swipeAlongAxis = vertical === verticalSwipe;
  
    if (!swipeAlongAxis) {
      // Move was mostly along the other axis.
      return false;
    }
  
    // Move was mostly along desired axis.
  
    if (vertical && isAnyAncestorScrolled(element[symbols.swipeTarget])) {
      // Don't interfere with scrolling.
      return false;
    }
  
    const swipeFraction = getSwipeFraction(element, clientX, clientY);
  
    if (swipeFraction < 0 && !element.state.enableNegativeSwipe ||
        swipeFraction > 0 && !element.state.enablePositiveSwipe) {
      // Swipe was in a direction that's not explicitly enabled.
      return false;
    }
  
    element.setState({ swipeFraction });
    
    // Indicate that the event was handled. It'd be nicer if we didn't have
    // to do this so that, e.g., a user could be swiping left and right
    // while simultaneously scrolling up and down. (Native touch apps can do
    // that.) However, Mobile Safari wants to handle swipe events near the
    // page and interpret them as navigations. To avoid having a horiziontal
    // swipe misintepreted as a navigation, we indicate that we've handled
    // the event, and prevent default behavior.
    return true;
  }
docs: /*
  Invoked when the user has moved during a touch operation.