Source: recognizers/swipe.js

/**
 * Swipe
 * Recognized when the pointer is moving fast (velocity), with enough distance in the allowed direction.
 * @constructor
 * @extends AttrRecognizer
 */
function SwipeRecognizer() {
    AttrRecognizer.apply(this, arguments);
}

inherit(SwipeRecognizer, AttrRecognizer, {
    /**
     * @namespace
     * @memberof SwipeRecognizer
     */
    defaults: {
        event: 'swipe',
        threshold: 10,
        velocity: 0.3,
        direction: DIRECTION_HORIZONTAL | DIRECTION_VERTICAL,
        pointers: 1
    },

    getTouchAction: function() {
        return PanRecognizer.prototype.getTouchAction.call(this);
    },

    attrTest: function(input) {
        var direction = this.options.direction;
        var velocity;

        if (direction & (DIRECTION_HORIZONTAL | DIRECTION_VERTICAL)) {
            velocity = input.overallVelocity;
        } else if (direction & DIRECTION_HORIZONTAL) {
            velocity = input.overallVelocityX;
        } else if (direction & DIRECTION_VERTICAL) {
            velocity = input.overallVelocityY;
        }

        return this._super.attrTest.call(this, input) &&
            direction & input.offsetDirection &&
            input.distance > this.options.threshold &&
            input.maxPointers == this.options.pointers &&
            abs(velocity) > this.options.velocity && input.eventType & INPUT_END;
    },

    emit: function(input) {
        var direction = directionStr(input.offsetDirection);
        if (direction) {
            this.manager.emit(this.options.event + direction, input);
        }

        this.manager.emit(this.options.event, input);
    }
});