Wallet/src/js/services/swipe.js

'use strict';

/*  
 * This is a modification from https://github.com/angular/angular.js/blob/master/src/ngTouch/swipe.js
 */


angular.module('copayApp.services')
  .factory('$swipe', [
  function() {
    // The total distance in any direction before we make the call on swipe vs. scroll.
    var MOVE_BUFFER_RADIUS = 10;

    var POINTER_EVENTS = {
      'touch': {
        start: 'touchstart',
        move: 'touchmove',
        end: 'touchend',
        cancel: 'touchcancel'
      }
    };

    function getCoordinates(event) {
      var originalEvent = event.originalEvent || event;
      var touches = originalEvent.touches && originalEvent.touches.length ? originalEvent.touches : [originalEvent];
      var e = (originalEvent.changedTouches && originalEvent.changedTouches[0]) || touches[0];

      return {
        x: e.clientX,
        y: e.clientY
      };
    }

    function getEvents(pointerTypes, eventType) {
      var res = [];
      angular.forEach(pointerTypes, function(pointerType) {
        var eventName = POINTER_EVENTS[pointerType][eventType];
        if (eventName) {
          res.push(eventName);
        }
      });
      return res.join(' ');
    }

    return {
      /**
       * @ngdoc method
       * @name $swipe#bind
       *
       * @description
       * The main method of `$swipe`. It takes an element to be watched for swipe motions, and an
       * object containing event handlers.
       * The pointer types that should be used can be specified via the optional
       * third argument, which is an array of strings `'mouse'` and `'touch'`. By default,
       * `$swipe` will listen for `mouse` and `touch` events.
       *
       * The four events are `start`, `move`, `end`, and `cancel`. `start`, `move`, and `end`
       * receive as a parameter a coordinates object of the form `{ x: 150, y: 310 }`.
       *
       * `start` is called on either `mousedown` or `touchstart`. After this event, `$swipe` is
       * watching for `touchmove` or `mousemove` events. These events are ignored until the total
       * distance moved in either dimension exceeds a small threshold.
       *
       * Once this threshold is exceeded, either the horizontal or vertical delta is greater.
       * - If the horizontal distance is greater, this is a swipe and `move` and `end` events follow.
       * - If the vertical distance is greater, this is a scroll, and we let the browser take over.
       *   A `cancel` event is sent.
       *
       * `move` is called on `mousemove` and `touchmove` after the above logic has determined that
       * a swipe is in progress.
       *
       * `end` is called when a swipe is successfully completed with a `touchend` or `mouseup`.
       *
       * `cancel` is called either on a `touchcancel` from the browser, or when we begin scrolling
       * as described above.
       *
       */
      bind: function(element, eventHandlers, pointerTypes) {
        // Absolute total movement, used to control swipe vs. scroll.
        var totalX, totalY;
        // Coordinates of the start position.
        var startCoords;
        // Last event's position.
        var lastPos;
        // Whether a swipe is active.
        var active = false;

        pointerTypes = pointerTypes || ['touch'];
        element.on(getEvents(pointerTypes, 'start'), function(event) {
          startCoords = getCoordinates(event);
          active = true;
          totalX = 0;
          totalY = 0;
          lastPos = startCoords;
          eventHandlers['start'] && eventHandlers['start'](startCoords, event);
        });
        var events = getEvents(pointerTypes, 'cancel');
        if (events) {
          element.on(events, function(event) {
            active = false;
            eventHandlers['cancel'] && eventHandlers['cancel'](event);
          });
        }

        element.on(getEvents(pointerTypes, 'move'), function(event) {
          if (!active) return;

          // Android will send a touchcancel if it thinks we're starting to scroll.
          // So when the total distance (+ or - or both) exceeds 10px in either direction,
          // we either:
          // - On totalX > totalY, we send preventDefault() and treat this as a swipe.
          // - On totalY > totalX, we let the browser handle it as a scroll.

          if (!startCoords) return;
          var coords = getCoordinates(event);

          totalX += Math.abs(coords.x - lastPos.x);
          totalY += Math.abs(coords.y - lastPos.y);

          lastPos = coords;

          if (totalX < MOVE_BUFFER_RADIUS && totalY < MOVE_BUFFER_RADIUS) {
            return;
          }

          // One of totalX or totalY has exceeded the buffer, so decide on swipe vs. scroll.
          if (totalY > totalX) {
            // Allow native scrolling to take over.
            active = false;
            eventHandlers['cancel'] && eventHandlers['cancel'](event);
            return;
          } else {

            // Prevent the browser from scrolling.
            event.preventDefault();
            eventHandlers['move'] && eventHandlers['move'](coords, event);
          }
        });

        element.on(getEvents(pointerTypes, 'end'), function(event) {
          if (!active) return;
          active = false;
          eventHandlers['end'] && eventHandlers['end'](getCoordinates(event), event);
        });
      }
    };
  }
]);