nutui/src/utils/touchEmulator.js

/* eslint-disable */
/**
 * Emulate touch event
 * Source：https://github.com/hammerjs/touchemulator
 */

var eventTarget;
var supportTouch = 'ontouchstart' in window;

// polyfills
if (!document.createTouch) {
  document.createTouch = function(
    view,
    target,
    identifier,
    pageX,
    pageY,
    screenX,
    screenY
  ) {
    // auto set
    return new Touch(
      target,
      identifier,
      {
        pageX: pageX,
        pageY: pageY,
        screenX: screenX,
        screenY: screenY,
        clientX: pageX - window.pageXOffset,
        clientY: pageY - window.pageYOffset
      },
      0,
      0
    );
  };
}

if (!document.createTouchList) {
  document.createTouchList = function() {
    var touchList = TouchList();
    for (var i = 0; i < arguments.length; i++) {
      touchList[i] = arguments[i];
    }
    touchList.length = arguments.length;
    return touchList;
  };
}

/**
 * create an touch point
 * @constructor
 * @param target
 * @param identifier
 * @param pos
 * @param deltaX
 * @param deltaY
 * @returns {Object} touchPoint
 */

var Touch = function Touch(target, identifier, pos, deltaX, deltaY) {
  deltaX = deltaX || 0;
  deltaY = deltaY || 0;

  this.identifier = identifier;
  this.target = target;
  this.clientX = pos.clientX + deltaX;
  this.clientY = pos.clientY + deltaY;
  this.screenX = pos.screenX + deltaX;
  this.screenY = pos.screenY + deltaY;
  this.pageX = pos.pageX + deltaX;
  this.pageY = pos.pageY + deltaY;
};

/**
 * create empty touchlist with the methods
 * @constructor
 * @returns touchList
 */
function TouchList() {
  var touchList = [];

  touchList['item'] = function(index) {
    return this[index] || null;
  };

  // specified by Mozilla
  touchList['identifiedTouch'] = function(id) {
    return this[id + 1] || null;
  };

  return touchList;
}

/**
 * only trigger touches when the left mousebutton has been pressed
 * @param touchType
 * @returns {Function}
 */

var initiated = false;
function onMouse(touchType) {
  return function(ev) {
    // prevent mouse events

    if (ev.type === 'mousedown') {
      initiated = true;
    }

    if (ev.type === 'mouseup') {
      initiated = false;
    }

    if (ev.type === 'mousemove' && !initiated) {
      return;
    }

    // The EventTarget on which the touch point started when it was first placed on the surface,
    // even if the touch point has since moved outside the interactive area of that element.
    // also, when the target doesnt exist anymore, we update it
    if (
      ev.type === 'mousedown' ||
      !eventTarget ||
      (eventTarget && !eventTarget.dispatchEvent)
    ) {
      eventTarget = ev.target;
    }

    triggerTouch(touchType, ev);

    // reset
    if (ev.type === 'mouseup') {
      eventTarget = null;
    }
  };
}

/**
 * trigger a touch event
 * @param eventName
 * @param mouseEv
 */
function triggerTouch(eventName, mouseEv) {
  var touchEvent = document.createEvent('Event');
  touchEvent.initEvent(eventName, true, true);

  touchEvent.altKey = mouseEv.altKey;
  touchEvent.ctrlKey = mouseEv.ctrlKey;
  touchEvent.metaKey = mouseEv.metaKey;
  touchEvent.shiftKey = mouseEv.shiftKey;

  touchEvent.touches = getActiveTouches(mouseEv);
  touchEvent.targetTouches = getActiveTouches(mouseEv);
  touchEvent.changedTouches = createTouchList(mouseEv);

  eventTarget.dispatchEvent(touchEvent);
}

/**
 * create a touchList based on the mouse event
 * @param mouseEv
 * @returns {TouchList}
 */
function createTouchList(mouseEv) {
  var touchList = TouchList();
  touchList.push(new Touch(eventTarget, 1, mouseEv, 0, 0));
  return touchList;
}

/**
 * receive all active touches
 * @param mouseEv
 * @returns {TouchList}
 */
function getActiveTouches(mouseEv) {
  // empty list
  if (mouseEv.type === 'mouseup') {
    return TouchList();
  }
  return createTouchList(mouseEv);
}

/**
 * TouchEmulator initializer
 */
function TouchEmulator() {
  window.addEventListener('mousedown', onMouse('touchstart'), true);
  window.addEventListener('mousemove', onMouse('touchmove'), true);
  window.addEventListener('mouseup', onMouse('touchend'), true);
}

// start distance when entering the multitouch mode
TouchEmulator['multiTouchOffset'] = 75;

if (!supportTouch) {
  new TouchEmulator();
}