swiper/src/components/mousewheel/mousewheel.js

Most modern mobile touch slider and framework with hardware accelerated transitions

import { window, document } from 'ssr-window';
import $ from '../../utils/dom';
import Utils from '../../utils/utils';

function isEventSupported() {
  const eventName = 'onwheel';
  let isSupported = eventName in document;

  if (!isSupported) {
    const element = document.createElement('div');
    element.setAttribute(eventName, 'return;');
    isSupported = typeof element[eventName] === 'function';
  }

  if (!isSupported
    && document.implementation
    && document.implementation.hasFeature
    // always returns true in newer browsers as per the standard.
    // @see http://dom.spec.whatwg.org/#dom-domimplementation-hasfeature
    && document.implementation.hasFeature('', '') !== true
  ) {
    // This is the only way to test support for the `wheel` event in IE9+.
    isSupported = document.implementation.hasFeature('Events.wheel', '3.0');
  }

  return isSupported;
}
const Mousewheel = {
  lastScrollTime: Utils.now(),
  lastEventBeforeSnap: undefined,
  recentWheelEvents: [],
  event() {
    if (window.navigator.userAgent.indexOf('firefox') > -1) return 'DOMMouseScroll';
    return isEventSupported() ? 'wheel' : 'mousewheel';
  },
  normalize(e) {
    // Reasonable defaults
    const PIXEL_STEP = 10;
    const LINE_HEIGHT = 40;
    const PAGE_HEIGHT = 800;

    let sX = 0;
    let sY = 0; // spinX, spinY
    let pX = 0;
    let pY = 0; // pixelX, pixelY

    // Legacy
    if ('detail' in e) {
      sY = e.detail;
    }
    if ('wheelDelta' in e) {
      sY = -e.wheelDelta / 120;
    }
    if ('wheelDeltaY' in e) {
      sY = -e.wheelDeltaY / 120;
    }
    if ('wheelDeltaX' in e) {
      sX = -e.wheelDeltaX / 120;
    }

    // side scrolling on FF with DOMMouseScroll
    if ('axis' in e && e.axis === e.HORIZONTAL_AXIS) {
      sX = sY;
      sY = 0;
    }

    pX = sX * PIXEL_STEP;
    pY = sY * PIXEL_STEP;

    if ('deltaY' in e) {
      pY = e.deltaY;
    }
    if ('deltaX' in e) {
      pX = e.deltaX;
    }

    if (e.shiftKey && !pX) { // if user scrolls with shift he wants horizontal scroll
      pX = pY;
      pY = 0;
    }

    if ((pX || pY) && e.deltaMode) {
      if (e.deltaMode === 1) { // delta in LINE units
        pX *= LINE_HEIGHT;
        pY *= LINE_HEIGHT;
      } else { // delta in PAGE units
        pX *= PAGE_HEIGHT;
        pY *= PAGE_HEIGHT;
      }
    }

    // Fall-back if spin cannot be determined
    if (pX && !sX) {
      sX = (pX < 1) ? -1 : 1;
    }
    if (pY && !sY) {
      sY = (pY < 1) ? -1 : 1;
    }

    return {
      spinX: sX,
      spinY: sY,
      pixelX: pX,
      pixelY: pY,
    };
  },
  handleMouseEnter() {
    const swiper = this;
    swiper.mouseEntered = true;
  },
  handleMouseLeave() {
    const swiper = this;
    swiper.mouseEntered = false;
  },
  handle(event) {
    let e = event;
    const swiper = this;
    const params = swiper.params.mousewheel;

    if (swiper.params.cssMode) {
      e.preventDefault();
    }

    let target = swiper.$el;
    if (swiper.params.mousewheel.eventsTarged !== 'container') {
      target = $(swiper.params.mousewheel.eventsTarged);
    }
    if (!swiper.mouseEntered && !target[0].contains(e.target) && !params.releaseOnEdges) return true;

    if (e.originalEvent) e = e.originalEvent; // jquery fix
    let delta = 0;
    const rtlFactor = swiper.rtlTranslate ? -1 : 1;

    const data = Mousewheel.normalize(e);

    if (params.forceToAxis) {
      if (swiper.isHorizontal()) {
        if (Math.abs(data.pixelX) > Math.abs(data.pixelY)) delta = -data.pixelX * rtlFactor;
        else return true;
      } else if (Math.abs(data.pixelY) > Math.abs(data.pixelX)) delta = -data.pixelY;
      else return true;
    } else {
      delta = Math.abs(data.pixelX) > Math.abs(data.pixelY) ? -data.pixelX * rtlFactor : -data.pixelY;
    }

    if (delta === 0) return true;

    if (params.invert) delta = -delta;

    if (!swiper.params.freeMode) {
      // Register the new event in a variable which stores the relevant data
      const newEvent = {
        time: Utils.now(),
        delta: Math.abs(delta),
        direction: Math.sign(delta),
        raw: event,
      };

      // Keep the most recent events
      const recentWheelEvents = swiper.mousewheel.recentWheelEvents;
      if (recentWheelEvents.length >= 2) {
        recentWheelEvents.shift(); // only store the last N events
      }
      const prevEvent = recentWheelEvents.length ? recentWheelEvents[recentWheelEvents.length - 1] : undefined;
      recentWheelEvents.push(newEvent);

      // If there is at least one previous recorded event:
      //   If direction has changed or
      //   if the scroll is quicker than the previous one:
      //     Animate the slider.
      // Else (this is the first time the wheel is moved):
      //     Animate the slider.
      if (prevEvent) {
        if (newEvent.direction !== prevEvent.direction || newEvent.delta > prevEvent.delta || newEvent.time > prevEvent.time + 150) {
          swiper.mousewheel.animateSlider(newEvent);
        }
      } else {
        swiper.mousewheel.animateSlider(newEvent);
      }

      // If it's time to release the scroll:
      //   Return now so you don't hit the preventDefault.
      if (swiper.mousewheel.releaseScroll(newEvent)) {
        return true;
      }
    } else {
      // Freemode or scrollContainer:

      // If we recently snapped after a momentum scroll, then ignore wheel events
      // to give time for the deceleration to finish. Stop ignoring after 500 msecs
      // or if it's a new scroll (larger delta or inverse sign as last event before
      // an end-of-momentum snap).
      const newEvent = { time: Utils.now(), delta: Math.abs(delta), direction: Math.sign(delta) };
      const { lastEventBeforeSnap } = swiper.mousewheel;
      const ignoreWheelEvents = lastEventBeforeSnap
        && newEvent.time < lastEventBeforeSnap.time + 500
        && newEvent.delta <= lastEventBeforeSnap.delta
        && newEvent.direction === lastEventBeforeSnap.direction;
      if (!ignoreWheelEvents) {
        swiper.mousewheel.lastEventBeforeSnap = undefined;

        if (swiper.params.loop) {
          swiper.loopFix();
        }
        let position = swiper.getTranslate() + (delta * params.sensitivity);
        const wasBeginning = swiper.isBeginning;
        const wasEnd = swiper.isEnd;

        if (position >= swiper.minTranslate()) position = swiper.minTranslate();
        if (position <= swiper.maxTranslate()) position = swiper.maxTranslate();

        swiper.setTransition(0);
        swiper.setTranslate(position);
        swiper.updateProgress();
        swiper.updateActiveIndex();
        swiper.updateSlidesClasses();

        if ((!wasBeginning && swiper.isBeginning) || (!wasEnd && swiper.isEnd)) {
          swiper.updateSlidesClasses();
        }

        if (swiper.params.freeModeSticky) {
          // When wheel scrolling starts with sticky (aka snap) enabled, then detect
          // the end of a momentum scroll by storing recent (N=15?) wheel events.
          // 1. do all N events have decreasing or same (absolute value) delta?
          // 2. did all N events arrive in the last M (M=500?) msecs?
          // 3. does the earliest event have an (absolute value) delta that's
          //    at least P (P=1?) larger than the most recent event's delta?
          // 4. does the latest event have a delta that's smaller than Q (Q=6?) pixels?
          // If 1-4 are "yes" then we're near the end of a momuntum scroll deceleration.
          // Snap immediately and ignore remaining wheel events in this scroll.
          // See comment above for "remaining wheel events in this scroll" determination.
          // If 1-4 aren't satisfied, then wait to snap until 500ms after the last event.
          clearTimeout(swiper.mousewheel.timeout);
          swiper.mousewheel.timeout = undefined;
          const recentWheelEvents = swiper.mousewheel.recentWheelEvents;
          if (recentWheelEvents.length >= 15) {
            recentWheelEvents.shift(); // only store the last N events
          }
          const prevEvent = recentWheelEvents.length ? recentWheelEvents[recentWheelEvents.length - 1] : undefined;
          const firstEvent = recentWheelEvents[0];
          recentWheelEvents.push(newEvent);
          if (prevEvent && (newEvent.delta > prevEvent.delta || newEvent.direction !== prevEvent.direction)) {
            // Increasing or reverse-sign delta means the user started scrolling again. Clear the wheel event log.
            recentWheelEvents.splice(0);
          } else if (recentWheelEvents.length >= 15
              && newEvent.time - firstEvent.time < 500
              && firstEvent.delta - newEvent.delta >= 1
              && newEvent.delta <= 6
          ) {
            // We're at the end of the deceleration of a momentum scroll, so there's no need
            // to wait for more events. Snap ASAP on the next tick.
            // Also, because there's some remaining momentum we'll bias the snap in the
            // direction of the ongoing scroll because it's better UX for the scroll to snap
            // in the same direction as the scroll instead of reversing to snap.  Therefore,
            // if it's already scrolled more than 20% in the current direction, keep going.
            const snapToThreshold = delta > 0 ? 0.8 : 0.2;
            swiper.mousewheel.lastEventBeforeSnap = newEvent;
            recentWheelEvents.splice(0);
            swiper.mousewheel.timeout = Utils.nextTick(() => {
              swiper.slideToClosest(swiper.params.speed, true, undefined, snapToThreshold);
            }, 0); // no delay; move on next tick
          }
          if (!swiper.mousewheel.timeout) {
            // if we get here, then we haven't detected the end of a momentum scroll, so
            // we'll consider a scroll "complete" when there haven't been any wheel events
            // for 500ms.
            swiper.mousewheel.timeout = Utils.nextTick(() => {
              const snapToThreshold = 0.5;
              swiper.mousewheel.lastEventBeforeSnap = newEvent;
              recentWheelEvents.splice(0);
              swiper.slideToClosest(swiper.params.speed, true, undefined, snapToThreshold);
            }, 500);
          }
        }

        // Emit event
        if (!ignoreWheelEvents) swiper.emit('scroll', e);

        // Stop autoplay
        if (swiper.params.autoplay && swiper.params.autoplayDisableOnInteraction) swiper.autoplay.stop();
        // Return page scroll on edge positions
        if (position === swiper.minTranslate() || position === swiper.maxTranslate()) return true;
      }
    }

    if (e.preventDefault) e.preventDefault();
    else e.returnValue = false;
    return false;
  },
  animateSlider(newEvent) {
    const swiper = this;
    // If the movement is NOT big enough and
    // if the last time the user scrolled was too close to the current one (avoid continuously triggering the slider):
    //   Don't go any further (avoid insignificant scroll movement).
    if (newEvent.delta >= 6 && Utils.now() - swiper.mousewheel.lastScrollTime < 60) {
      // Return false as a default
      return true;
    }
    // If user is scrolling towards the end:
    //   If the slider hasn't hit the latest slide or
    //   if the slider is a loop and
    //   if the slider isn't moving right now:
    //     Go to next slide and
    //     emit a scroll event.
    // Else (the user is scrolling towards the beginning) and
    // if the slider hasn't hit the first slide or
    // if the slider is a loop and
    // if the slider isn't moving right now:
    //   Go to prev slide and
    //   emit a scroll event.
    if (newEvent.direction < 0) {
      if ((!swiper.isEnd || swiper.params.loop) && !swiper.animating) {
        swiper.slideNext();
        swiper.emit('scroll', newEvent.raw);
      }
    } else if ((!swiper.isBeginning || swiper.params.loop) && !swiper.animating) {
      swiper.slidePrev();
      swiper.emit('scroll', newEvent.raw);
    }
    // If you got here is because an animation has been triggered so store the current time
    swiper.mousewheel.lastScrollTime = (new window.Date()).getTime();
    // Return false as a default
    return false;
  },
  releaseScroll(newEvent) {
    const swiper = this;
    const params = swiper.params.mousewheel;
    if (newEvent.direction < 0) {
      if (swiper.isEnd && !swiper.params.loop && params.releaseOnEdges) {
        // Return true to animate scroll on edges
        return true;
      }
    } else if (swiper.isBeginning && !swiper.params.loop && params.releaseOnEdges) {
      // Return true to animate scroll on edges
      return true;
    }
    return false;
  },
  enable() {
    const swiper = this;
    const event = Mousewheel.event();
    if (swiper.params.cssMode) {
      swiper.wrapperEl.removeEventListener(event, swiper.mousewheel.handle);
      return true;
    }
    if (!event) return false;
    if (swiper.mousewheel.enabled) return false;
    let target = swiper.$el;
    if (swiper.params.mousewheel.eventsTarged !== 'container') {
      target = $(swiper.params.mousewheel.eventsTarged);
    }
    target.on('mouseenter', swiper.mousewheel.handleMouseEnter);
    target.on('mouseleave', swiper.mousewheel.handleMouseLeave);
    target.on(event, swiper.mousewheel.handle);
    swiper.mousewheel.enabled = true;
    return true;
  },
  disable() {
    const swiper = this;
    const event = Mousewheel.event();
    if (swiper.params.cssMode) {
      swiper.wrapperEl.addEventListener(event, swiper.mousewheel.handle);
      return true;
    }
    if (!event) return false;
    if (!swiper.mousewheel.enabled) return false;
    let target = swiper.$el;
    if (swiper.params.mousewheel.eventsTarged !== 'container') {
      target = $(swiper.params.mousewheel.eventsTarged);
    }
    target.off(event, swiper.mousewheel.handle);
    swiper.mousewheel.enabled = false;
    return true;
  },
};

export default {
  name: 'mousewheel',
  params: {
    mousewheel: {
      enabled: false,
      releaseOnEdges: false,
      invert: false,
      forceToAxis: false,
      sensitivity: 1,
      eventsTarged: 'container',
    },
  },
  create() {
    const swiper = this;
    Utils.extend(swiper, {
      mousewheel: {
        enabled: false,
        enable: Mousewheel.enable.bind(swiper),
        disable: Mousewheel.disable.bind(swiper),
        handle: Mousewheel.handle.bind(swiper),
        handleMouseEnter: Mousewheel.handleMouseEnter.bind(swiper),
        handleMouseLeave: Mousewheel.handleMouseLeave.bind(swiper),
        animateSlider: Mousewheel.animateSlider.bind(swiper),
        releaseScroll: Mousewheel.releaseScroll.bind(swiper),
        lastScrollTime: Utils.now(),
        lastEventBeforeSnap: undefined,
        recentWheelEvents: [],
      },
    });
  },
  on: {
    init() {
      const swiper = this;
      if (!swiper.params.mousewheel.enabled && swiper.params.cssMode) {
        swiper.mousewheel.disable();
      }
      if (swiper.params.mousewheel.enabled) swiper.mousewheel.enable();
    },
    destroy() {
      const swiper = this;
      if (swiper.params.cssMode) {
        swiper.mousewheel.enable();
      }
      if (swiper.mousewheel.enabled) swiper.mousewheel.disable();
    },
  },
};