interact.js

/**
 * interact.js v1.2.4
 *
 * Copyright (c) 2012-2015 Taye Adeyemi <dev@taye.me>
 * Open source under the MIT License.
 * https://raw.github.com/taye/interact.js/master/LICENSE
 */
(function (realWindow) {
    'use strict';

    var // get wrapped window if using Shadow DOM polyfill
        window = (function () {
            // create a TextNode
            var el = realWindow.document.createTextNode('');

            // check if it's wrapped by a polyfill
            if (el.ownerDocument !== realWindow.document
                && typeof realWindow.wrap === 'function'
                && realWindow.wrap(el) === el) {
                // return wrapped window
                return realWindow.wrap(realWindow);
            }

            // no Shadow DOM polyfil or native implementation
            return realWindow;
        }()),

        document           = window.document,
        DocumentFragment   = window.DocumentFragment   || blank,
        SVGElement         = window.SVGElement         || blank,
        SVGSVGElement      = window.SVGSVGElement      || blank,
        SVGElementInstance = window.SVGElementInstance || blank,
        HTMLElement        = window.HTMLElement        || window.Element,

        PointerEvent = (window.PointerEvent || window.MSPointerEvent),
        pEventTypes,

        hypot = Math.hypot || function (x, y) { return Math.sqrt(x * x + y * y); },

        tmpXY = {},     // reduce object creation in getXY()

        documents       = [],   // all documents being listened to

        interactables   = [],   // all set interactables
        interactions    = [],   // all interactions

        dynamicDrop     = false,

        // {
        //      type: {
        //          selectors: ['selector', ...],
        //          contexts : [document, ...],
        //          listeners: [[listener, useCapture], ...]
        //      }
        //  }
        delegatedEvents = {},

        defaultOptions = {
            base: {
                accept        : null,
                actionChecker : null,
                styleCursor   : true,
                preventDefault: 'auto',
                origin        : { x: 0, y: 0 },
                deltaSource   : 'page',
                allowFrom     : null,
                ignoreFrom    : null,
                _context      : document,
                dropChecker   : null
            },

            drag: {
                enabled: false,
                manualStart: true,
                max: Infinity,
                maxPerElement: 1,

                snap: null,
                restrict: null,
                inertia: null,
                autoScroll: null,

                axis: 'xy',
            },

            drop: {
                enabled: false,
                accept: null,
                overlap: 'pointer'
            },

            resize: {
                enabled: false,
                manualStart: false,
                max: Infinity,
                maxPerElement: 1,

                snap: null,
                restrict: null,
                inertia: null,
                autoScroll: null,

                square: false,
                axis: 'xy',

                // object with props left, right, top, bottom which are
                // true/false values to resize when the pointer is over that edge,
                // CSS selectors to match the handles for each direction
                // or the Elements for each handle
                edges: null,

                // a value of 'none' will limit the resize rect to a minimum of 0x0
                // 'negate' will alow the rect to have negative width/height
                // 'reposition' will keep the width/height positive by swapping
                // the top and bottom edges and/or swapping the left and right edges
                invert: 'none'
            },

            gesture: {
                manualStart: false,
                enabled: false,
                max: Infinity,
                maxPerElement: 1,

                restrict: null
            },

            perAction: {
                manualStart: false,
                max: Infinity,
                maxPerElement: 1,

                snap: {
                    enabled     : false,
                    endOnly     : false,
                    range       : Infinity,
                    targets     : null,
                    offsets     : null,

                    relativePoints: null
                },

                restrict: {
                    enabled: false,
                    endOnly: false
                },

                autoScroll: {
                    enabled     : false,
                    container   : null,     // the item that is scrolled (Window or HTMLElement)
                    margin      : 60,
                    speed       : 300       // the scroll speed in pixels per second
                },

                inertia: {
                    enabled          : false,
                    resistance       : 10,    // the lambda in exponential decay
                    minSpeed         : 100,   // target speed must be above this for inertia to start
                    endSpeed         : 10,    // the speed at which inertia is slow enough to stop
                    allowResume      : true,  // allow resuming an action in inertia phase
                    zeroResumeDelta  : true,  // if an action is resumed after launch, set dx/dy to 0
                    smoothEndDuration: 300    // animate to snap/restrict endOnly if there's no inertia
                }
            },

            _holdDuration: 600
        },

        // Things related to autoScroll
        autoScroll = {
            interaction: null,
            i: null,    // the handle returned by window.setInterval
            x: 0, y: 0, // Direction each pulse is to scroll in

            // scroll the window by the values in scroll.x/y
            scroll: function () {
                var options = autoScroll.interaction.target.options[autoScroll.interaction.prepared.name].autoScroll,
                    container = options.container || getWindow(autoScroll.interaction.element),
                    now = new Date().getTime(),
                    // change in time in seconds
                    dt = (now - autoScroll.prevTime) / 1000,
                    // displacement
                    s = options.speed * dt;

                if (s >= 1) {
                    if (isWindow(container)) {
                        container.scrollBy(autoScroll.x * s, autoScroll.y * s);
                    }
                    else if (container) {
                        container.scrollLeft += autoScroll.x * s;
                        container.scrollTop  += autoScroll.y * s;
                    }

                    autoScroll.prevTime = now;
                }

                if (autoScroll.isScrolling) {
                    cancelFrame(autoScroll.i);
                    autoScroll.i = reqFrame(autoScroll.scroll);
                }
            },

            edgeMove: function (event) {
                var interaction,
                    target,
                    doAutoscroll = false;

                for (var i = 0; i < interactions.length; i++) {
                    interaction = interactions[i];

                    if (interaction.interacting()
                        && checkAutoScroll(interaction.target, interaction.prepared.name)) {

                        target = interaction.target;
                        doAutoscroll = true;
                        break;
                    }
                }

                if (!doAutoscroll) { return; }

                var top,
                    right,
                    bottom,
                    left,
                    options = target.options[interaction.prepared.name].autoScroll,
                    container = options.container || getWindow(interaction.element);

                if (isWindow(container)) {
                    left   = event.clientX < autoScroll.margin;
                    top    = event.clientY < autoScroll.margin;
                    right  = event.clientX > container.innerWidth  - autoScroll.margin;
                    bottom = event.clientY > container.innerHeight - autoScroll.margin;
                }
                else {
                    var rect = getElementRect(container);

                    left   = event.clientX < rect.left   + autoScroll.margin;
                    top    = event.clientY < rect.top    + autoScroll.margin;
                    right  = event.clientX > rect.right  - autoScroll.margin;
                    bottom = event.clientY > rect.bottom - autoScroll.margin;
                }

                autoScroll.x = (right ? 1: left? -1: 0);
                autoScroll.y = (bottom? 1:  top? -1: 0);

                if (!autoScroll.isScrolling) {
                    // set the autoScroll properties to those of the target
                    autoScroll.margin = options.margin;
                    autoScroll.speed  = options.speed;

                    autoScroll.start(interaction);
                }
            },

            isScrolling: false,
            prevTime: 0,

            start: function (interaction) {
                autoScroll.isScrolling = true;
                cancelFrame(autoScroll.i);

                autoScroll.interaction = interaction;
                autoScroll.prevTime = new Date().getTime();
                autoScroll.i = reqFrame(autoScroll.scroll);
            },

            stop: function () {
                autoScroll.isScrolling = false;
                cancelFrame(autoScroll.i);
            }
        },

        // Does the browser support touch input?
        supportsTouch = (('ontouchstart' in window) || window.DocumentTouch && document instanceof window.DocumentTouch),

        // Does the browser support PointerEvents
        supportsPointerEvent = !!PointerEvent,

        // Less Precision with touch input
        margin = supportsTouch || supportsPointerEvent? 20: 10,

        pointerMoveTolerance = 1,

        // for ignoring browser's simulated mouse events
        prevTouchTime = 0,

        // Allow this many interactions to happen simultaneously
        maxInteractions = Infinity,

        // Check if is IE9 or older
        actionCursors = (document.all && !window.atob) ? {
            drag    : 'move',
            resizex : 'e-resize',
            resizey : 's-resize',
            resizexy: 'se-resize',

            resizetop        : 'n-resize',
            resizeleft       : 'w-resize',
            resizebottom     : 's-resize',
            resizeright      : 'e-resize',
            resizetopleft    : 'se-resize',
            resizebottomright: 'se-resize',
            resizetopright   : 'ne-resize',
            resizebottomleft : 'ne-resize',

            gesture : ''
        } : {
            drag    : 'move',
            resizex : 'ew-resize',
            resizey : 'ns-resize',
            resizexy: 'nwse-resize',

            resizetop        : 'ns-resize',
            resizeleft       : 'ew-resize',
            resizebottom     : 'ns-resize',
            resizeright      : 'ew-resize',
            resizetopleft    : 'nwse-resize',
            resizebottomright: 'nwse-resize',
            resizetopright   : 'nesw-resize',
            resizebottomleft : 'nesw-resize',

            gesture : ''
        },

        actionIsEnabled = {
            drag   : true,
            resize : true,
            gesture: true
        },

        // because Webkit and Opera still use 'mousewheel' event type
        wheelEvent = 'onmousewheel' in document? 'mousewheel': 'wheel',

        eventTypes = [
            'dragstart',
            'dragmove',
            'draginertiastart',
            'dragend',
            'dragenter',
            'dragleave',
            'dropactivate',
            'dropdeactivate',
            'dropmove',
            'drop',
            'resizestart',
            'resizemove',
            'resizeinertiastart',
            'resizeend',
            'gesturestart',
            'gesturemove',
            'gestureinertiastart',
            'gestureend',

            'down',
            'move',
            'up',
            'cancel',
            'tap',
            'doubletap',
            'hold'
        ],

        globalEvents = {},

        // Opera Mobile must be handled differently
        isOperaMobile = navigator.appName == 'Opera' &&
            supportsTouch &&
            navigator.userAgent.match('Presto'),

        // scrolling doesn't change the result of
        // getBoundingClientRect/getClientRects on iOS <=7 but it does on iOS 8
        isIOS7orLower = (/iP(hone|od|ad)/.test(navigator.platform)
                            && /OS [1-7][^\d]/.test(navigator.appVersion)),

        // prefix matchesSelector
        prefixedMatchesSelector = 'matches' in Element.prototype?
                'matches': 'webkitMatchesSelector' in Element.prototype?
                    'webkitMatchesSelector': 'mozMatchesSelector' in Element.prototype?
                        'mozMatchesSelector': 'oMatchesSelector' in Element.prototype?
                            'oMatchesSelector': 'msMatchesSelector',

        // will be polyfill function if browser is IE8
        ie8MatchesSelector,

        // native requestAnimationFrame or polyfill
        reqFrame = realWindow.requestAnimationFrame,
        cancelFrame = realWindow.cancelAnimationFrame,

        // Events wrapper
        events = (function () {
            var useAttachEvent = ('attachEvent' in window) && !('addEventListener' in window),
                addEvent       = useAttachEvent?  'attachEvent': 'addEventListener',
                removeEvent    = useAttachEvent?  'detachEvent': 'removeEventListener',
                on             = useAttachEvent? 'on': '',

                elements          = [],
                targets           = [],
                attachedListeners = [];

            function add (element, type, listener, useCapture) {
                var elementIndex = indexOf(elements, element),
                    target = targets[elementIndex];

                if (!target) {
                    target = {
                        events: {},
                        typeCount: 0
                    };

                    elementIndex = elements.push(element) - 1;
                    targets.push(target);

                    attachedListeners.push((useAttachEvent ? {
                            supplied: [],
                            wrapped : [],
                            useCount: []
                        } : null));
                }

                if (!target.events[type]) {
                    target.events[type] = [];
                    target.typeCount++;
                }

                if (!contains(target.events[type], listener)) {
                    var ret;

                    if (useAttachEvent) {
                        var listeners = attachedListeners[elementIndex],
                            listenerIndex = indexOf(listeners.supplied, listener);

                        var wrapped = listeners.wrapped[listenerIndex] || function (event) {
                            if (!event.immediatePropagationStopped) {
                                event.target = event.srcElement;
                                event.currentTarget = element;

                                event.preventDefault = event.preventDefault || preventDef;
                                event.stopPropagation = event.stopPropagation || stopProp;
                                event.stopImmediatePropagation = event.stopImmediatePropagation || stopImmProp;

                                if (/mouse|click/.test(event.type)) {
                                    event.pageX = event.clientX + getWindow(element).document.documentElement.scrollLeft;
                                    event.pageY = event.clientY + getWindow(element).document.documentElement.scrollTop;
                                }

                                listener(event);
                            }
                        };

                        ret = element[addEvent](on + type, wrapped, Boolean(useCapture));

                        if (listenerIndex === -1) {
                            listeners.supplied.push(listener);
                            listeners.wrapped.push(wrapped);
                            listeners.useCount.push(1);
                        }
                        else {
                            listeners.useCount[listenerIndex]++;
                        }
                    }
                    else {
                        ret = element[addEvent](type, listener, useCapture || false);
                    }
                    target.events[type].push(listener);

                    return ret;
                }
            }

            function remove (element, type, listener, useCapture) {
                var i,
                    elementIndex = indexOf(elements, element),
                    target = targets[elementIndex],
                    listeners,
                    listenerIndex,
                    wrapped = listener;

                if (!target || !target.events) {
                    return;
                }

                if (useAttachEvent) {
                    listeners = attachedListeners[elementIndex];
                    listenerIndex = indexOf(listeners.supplied, listener);
                    wrapped = listeners.wrapped[listenerIndex];
                }

                if (type === 'all') {
                    for (type in target.events) {
                        if (target.events.hasOwnProperty(type)) {
                            remove(element, type, 'all');
                        }
                    }
                    return;
                }

                if (target.events[type]) {
                    var len = target.events[type].length;

                    if (listener === 'all') {
                        for (i = 0; i < len; i++) {
                            remove(element, type, target.events[type][i], Boolean(useCapture));
                        }
                    } else {
                        for (i = 0; i < len; i++) {
                            if (target.events[type][i] === listener) {
                                element[removeEvent](on + type, wrapped, useCapture || false);
                                target.events[type].splice(i, 1);

                                if (useAttachEvent && listeners) {
                                    listeners.useCount[listenerIndex]--;
                                    if (listeners.useCount[listenerIndex] === 0) {
                                        listeners.supplied.splice(listenerIndex, 1);
                                        listeners.wrapped.splice(listenerIndex, 1);
                                        listeners.useCount.splice(listenerIndex, 1);
                                    }
                                }

                                break;
                            }
                        }
                    }

                    if (target.events[type] && target.events[type].length === 0) {
                        target.events[type] = null;
                        target.typeCount--;
                    }
                }

                if (!target.typeCount) {
                    targets.splice(elementIndex);
                    elements.splice(elementIndex);
                    attachedListeners.splice(elementIndex);
                }
            }

            function preventDef () {
                this.returnValue = false;
            }

            function stopProp () {
                this.cancelBubble = true;
            }

            function stopImmProp () {
                this.cancelBubble = true;
                this.immediatePropagationStopped = true;
            }

            return {
                add: add,
                remove: remove,
                useAttachEvent: useAttachEvent,

                _elements: elements,
                _targets: targets,
                _attachedListeners: attachedListeners
            };
        }());

    function blank () {}

    function isElement (o) {
        if (!o || (typeof o !== 'object')) { return false; }

        var _window = getWindow(o) || window;

        return (/object|function/.test(typeof _window.Element)
            ? o instanceof _window.Element //DOM2
            : o.nodeType === 1 && typeof o.nodeName === "string");
    }
    function isWindow (thing) { return !!(thing && thing.Window) && (thing instanceof thing.Window); }
    function isDocFrag (thing) { return !!thing && thing instanceof DocumentFragment; }
    function isArray (thing) {
        return isObject(thing)
                && (typeof thing.length !== undefined)
                && isFunction(thing.splice);
    }
    function isObject   (thing) { return !!thing && (typeof thing === 'object'); }
    function isFunction (thing) { return typeof thing === 'function'; }
    function isNumber   (thing) { return typeof thing === 'number'  ; }
    function isBool     (thing) { return typeof thing === 'boolean' ; }
    function isString   (thing) { return typeof thing === 'string'  ; }

    function trySelector (value) {
        if (!isString(value)) { return false; }

        // an exception will be raised if it is invalid
        document.querySelector(value);
        return true;
    }

    function extend (dest, source) {
        for (var prop in source) {
            dest[prop] = source[prop];
        }
        return dest;
    }

    function copyCoords (dest, src) {
        dest.page = dest.page || {};
        dest.page.x = src.page.x;
        dest.page.y = src.page.y;

        dest.client = dest.client || {};
        dest.client.x = src.client.x;
        dest.client.y = src.client.y;

        dest.timeStamp = src.timeStamp;
    }

    function setEventXY (targetObj, pointer, interaction) {
        if (!pointer) {
            if (interaction.pointerIds.length > 1) {
                pointer = touchAverage(interaction.pointers);
            }
            else {
                pointer = interaction.pointers[0];
            }
        }

        getPageXY(pointer, tmpXY, interaction);
        targetObj.page.x = tmpXY.x;
        targetObj.page.y = tmpXY.y;

        getClientXY(pointer, tmpXY, interaction);
        targetObj.client.x = tmpXY.x;
        targetObj.client.y = tmpXY.y;

        targetObj.timeStamp = new Date().getTime();
    }

    function setEventDeltas (targetObj, prev, cur) {
        targetObj.page.x     = cur.page.x      - prev.page.x;
        targetObj.page.y     = cur.page.y      - prev.page.y;
        targetObj.client.x   = cur.client.x    - prev.client.x;
        targetObj.client.y   = cur.client.y    - prev.client.y;
        targetObj.timeStamp = new Date().getTime() - prev.timeStamp;

        // set pointer velocity
        var dt = Math.max(targetObj.timeStamp / 1000, 0.001);
        targetObj.page.speed   = hypot(targetObj.page.x, targetObj.page.y) / dt;
        targetObj.page.vx      = targetObj.page.x / dt;
        targetObj.page.vy      = targetObj.page.y / dt;

        targetObj.client.speed = hypot(targetObj.client.x, targetObj.page.y) / dt;
        targetObj.client.vx    = targetObj.client.x / dt;
        targetObj.client.vy    = targetObj.client.y / dt;
    }

    // Get specified X/Y coords for mouse or event.touches[0]
    function getXY (type, pointer, xy) {
        xy = xy || {};
        type = type || 'page';

        xy.x = pointer[type + 'X'];
        xy.y = pointer[type + 'Y'];

        return xy;
    }

    function getPageXY (pointer, page, interaction) {
        page = page || {};

        if (pointer instanceof InteractEvent) {
            if (/inertiastart/.test(pointer.type)) {
                interaction = interaction || pointer.interaction;

                extend(page, interaction.inertiaStatus.upCoords.page);

                page.x += interaction.inertiaStatus.sx;
                page.y += interaction.inertiaStatus.sy;
            }
            else {
                page.x = pointer.pageX;
                page.y = pointer.pageY;
            }
        }
        // Opera Mobile handles the viewport and scrolling oddly
        else if (isOperaMobile) {
            getXY('screen', pointer, page);

            page.x += window.scrollX;
            page.y += window.scrollY;
        }
        else {
            getXY('page', pointer, page);
        }

        return page;
    }

    function getClientXY (pointer, client, interaction) {
        client = client || {};

        if (pointer instanceof InteractEvent) {
            if (/inertiastart/.test(pointer.type)) {
                extend(client, interaction.inertiaStatus.upCoords.client);

                client.x += interaction.inertiaStatus.sx;
                client.y += interaction.inertiaStatus.sy;
            }
            else {
                client.x = pointer.clientX;
                client.y = pointer.clientY;
            }
        }
        else {
            // Opera Mobile handles the viewport and scrolling oddly
            getXY(isOperaMobile? 'screen': 'client', pointer, client);
        }

        return client;
    }

    function getScrollXY (win) {
        win = win || window;
        return {
            x: win.scrollX || win.document.documentElement.scrollLeft,
            y: win.scrollY || win.document.documentElement.scrollTop
        };
    }

    function getPointerId (pointer) {
        return isNumber(pointer.pointerId)? pointer.pointerId : pointer.identifier;
    }

    function getActualElement (element) {
        return (element instanceof SVGElementInstance
            ? element.correspondingUseElement
            : element);
    }

    function getWindow (node) {
        if (isWindow(node)) {
            return node;
        }

        var rootNode = (node.ownerDocument || node);

        return rootNode.defaultView || rootNode.parentWindow || window;
    }

    function getElementRect (element) {
        var scroll = isIOS7orLower
                ? { x: 0, y: 0 }
                : getScrollXY(getWindow(element)),
            clientRect = (element instanceof SVGElement)?
                element.getBoundingClientRect():
                element.getClientRects()[0];

        return clientRect && {
            left  : clientRect.left   + scroll.x,
            right : clientRect.right  + scroll.x,
            top   : clientRect.top    + scroll.y,
            bottom: clientRect.bottom + scroll.y,
            width : clientRect.width || clientRect.right - clientRect.left,
            height: clientRect.heigh || clientRect.bottom - clientRect.top
        };
    }

    function getTouchPair (event) {
        var touches = [];

        // array of touches is supplied
        if (isArray(event)) {
            touches[0] = event[0];
            touches[1] = event[1];
        }
        // an event
        else {
            if (event.type === 'touchend') {
                if (event.touches.length === 1) {
                    touches[0] = event.touches[0];
                    touches[1] = event.changedTouches[0];
                }
                else if (event.touches.length === 0) {
                    touches[0] = event.changedTouches[0];
                    touches[1] = event.changedTouches[1];
                }
            }
            else {
                touches[0] = event.touches[0];
                touches[1] = event.touches[1];
            }
        }

        return touches;
    }

    function touchAverage (event) {
        var touches = getTouchPair(event);

        return {
            pageX: (touches[0].pageX + touches[1].pageX) / 2,
            pageY: (touches[0].pageY + touches[1].pageY) / 2,
            clientX: (touches[0].clientX + touches[1].clientX) / 2,
            clientY: (touches[0].clientY + touches[1].clientY) / 2
        };
    }

    function touchBBox (event) {
        if (!event.length && !(event.touches && event.touches.length > 1)) {
            return;
        }

        var touches = getTouchPair(event),
            minX = Math.min(touches[0].pageX, touches[1].pageX),
            minY = Math.min(touches[0].pageY, touches[1].pageY),
            maxX = Math.max(touches[0].pageX, touches[1].pageX),
            maxY = Math.max(touches[0].pageY, touches[1].pageY);

        return {
            x: minX,
            y: minY,
            left: minX,
            top: minY,
            width: maxX - minX,
            height: maxY - minY
        };
    }

    function touchDistance (event, deltaSource) {
        deltaSource = deltaSource || defaultOptions.deltaSource;

        var sourceX = deltaSource + 'X',
            sourceY = deltaSource + 'Y',
            touches = getTouchPair(event);


        var dx = touches[0][sourceX] - touches[1][sourceX],
            dy = touches[0][sourceY] - touches[1][sourceY];

        return hypot(dx, dy);
    }

    function touchAngle (event, prevAngle, deltaSource) {
        deltaSource = deltaSource || defaultOptions.deltaSource;

        var sourceX = deltaSource + 'X',
            sourceY = deltaSource + 'Y',
            touches = getTouchPair(event),
            dx = touches[0][sourceX] - touches[1][sourceX],
            dy = touches[0][sourceY] - touches[1][sourceY],
            angle = 180 * Math.atan(dy / dx) / Math.PI;

        if (isNumber(prevAngle)) {
            var dr = angle - prevAngle,
                drClamped = dr % 360;

            if (drClamped > 315) {
                angle -= 360 + (angle / 360)|0 * 360;
            }
            else if (drClamped > 135) {
                angle -= 180 + (angle / 360)|0 * 360;
            }
            else if (drClamped < -315) {
                angle += 360 + (angle / 360)|0 * 360;
            }
            else if (drClamped < -135) {
                angle += 180 + (angle / 360)|0 * 360;
            }
        }

        return  angle;
    }

    function getOriginXY (interactable, element) {
        var origin = interactable
                ? interactable.options.origin
                : defaultOptions.origin;

        if (origin === 'parent') {
            origin = parentElement(element);
        }
        else if (origin === 'self') {
            origin = interactable.getRect(element);
        }
        else if (trySelector(origin)) {
            origin = closest(element, origin) || { x: 0, y: 0 };
        }

        if (isFunction(origin)) {
            origin = origin(interactable && element);
        }

        if (isElement(origin))  {
            origin = getElementRect(origin);
        }

        origin.x = ('x' in origin)? origin.x : origin.left;
        origin.y = ('y' in origin)? origin.y : origin.top;

        return origin;
    }

    // http://stackoverflow.com/a/5634528/2280888
    function _getQBezierValue(t, p1, p2, p3) {
        var iT = 1 - t;
        return iT * iT * p1 + 2 * iT * t * p2 + t * t * p3;
    }

    function getQuadraticCurvePoint(startX, startY, cpX, cpY, endX, endY, position) {
        return {
            x:  _getQBezierValue(position, startX, cpX, endX),
            y:  _getQBezierValue(position, startY, cpY, endY)
        };
    }

    // http://gizma.com/easing/
    function easeOutQuad (t, b, c, d) {
        t /= d;
        return -c * t*(t-2) + b;
    }

    function nodeContains (parent, child) {
        while (child) {
            if (child === parent) {
                return true;
            }

            child = child.parentNode;
        }

        return false;
    }

    function closest (child, selector) {
        var parent = parentElement(child);

        while (isElement(parent)) {
            if (matchesSelector(parent, selector)) { return parent; }

            parent = parentElement(parent);
        }

        return null;
    }

    function parentElement (node) {
        var parent = node.parentNode;

        if (isDocFrag(parent)) {
            // skip past #shado-root fragments
            while ((parent = parent.host) && isDocFrag(parent)) {}

            return parent;
        }

        return parent;
    }

    function inContext (interactable, element) {
        return interactable._context === element.ownerDocument
                || nodeContains(interactable._context, element);
    }

    function testIgnore (interactable, interactableElement, element) {
        var ignoreFrom = interactable.options.ignoreFrom;

        if (!ignoreFrom || !isElement(element)) { return false; }

        if (isString(ignoreFrom)) {
            return matchesUpTo(element, ignoreFrom, interactableElement);
        }
        else if (isElement(ignoreFrom)) {
            return nodeContains(ignoreFrom, element);
        }

        return false;
    }

    function testAllow (interactable, interactableElement, element) {
        var allowFrom = interactable.options.allowFrom;

        if (!allowFrom) { return true; }

        if (!isElement(element)) { return false; }

        if (isString(allowFrom)) {
            return matchesUpTo(element, allowFrom, interactableElement);
        }
        else if (isElement(allowFrom)) {
            return nodeContains(allowFrom, element);
        }

        return false;
    }

    function checkAxis (axis, interactable) {
        if (!interactable) { return false; }

        var thisAxis = interactable.options.drag.axis;

        return (axis === 'xy' || thisAxis === 'xy' || thisAxis === axis);
    }

    function checkSnap (interactable, action) {
        var options = interactable.options;

        if (/^resize/.test(action)) {
            action = 'resize';
        }

        return options[action].snap && options[action].snap.enabled;
    }

    function checkRestrict (interactable, action) {
        var options = interactable.options;

        if (/^resize/.test(action)) {
            action = 'resize';
        }

        return  options[action].restrict && options[action].restrict.enabled;
    }

    function checkAutoScroll (interactable, action) {
        var options = interactable.options;

        if (/^resize/.test(action)) {
            action = 'resize';
        }

        return  options[action].autoScroll && options[action].autoScroll.enabled;
    }

    function withinInteractionLimit (interactable, element, action) {
        var options = interactable.options,
            maxActions = options[action.name].max,
            maxPerElement = options[action.name].maxPerElement,
            activeInteractions = 0,
            targetCount = 0,
            targetElementCount = 0;

        for (var i = 0, len = interactions.length; i < len; i++) {
            var interaction = interactions[i],
                otherAction = interaction.prepared.name,
                active = interaction.interacting();

            if (!active) { continue; }

            activeInteractions++;

            if (activeInteractions >= maxInteractions) {
                return false;
            }

            if (interaction.target !== interactable) { continue; }

            targetCount += (otherAction === action.name)|0;

            if (targetCount >= maxActions) {
                return false;
            }

            if (interaction.element === element) {
                targetElementCount++;

                if (otherAction !== action.name || targetElementCount >= maxPerElement) {
                    return false;
                }
            }
        }

        return maxInteractions > 0;
    }

    // Test for the element that's "above" all other qualifiers
    function indexOfDeepestElement (elements) {
        var dropzone,
            deepestZone = elements[0],
            index = deepestZone? 0: -1,
            parent,
            deepestZoneParents = [],
            dropzoneParents = [],
            child,
            i,
            n;

        for (i = 1; i < elements.length; i++) {
            dropzone = elements[i];

            // an element might belong to multiple selector dropzones
            if (!dropzone || dropzone === deepestZone) {
                continue;
            }

            if (!deepestZone) {
                deepestZone = dropzone;
                index = i;
                continue;
            }

            // check if the deepest or current are document.documentElement or document.rootElement
            // - if the current dropzone is, do nothing and continue
            if (dropzone.parentNode === dropzone.ownerDocument) {
                continue;
            }
            // - if deepest is, update with the current dropzone and continue to next
            else if (deepestZone.parentNode === dropzone.ownerDocument) {
                deepestZone = dropzone;
                index = i;
                continue;
            }

            if (!deepestZoneParents.length) {
                parent = deepestZone;
                while (parent.parentNode && parent.parentNode !== parent.ownerDocument) {
                    deepestZoneParents.unshift(parent);
                    parent = parent.parentNode;
                }
            }

            // if this element is an svg element and the current deepest is
            // an HTMLElement
            if (deepestZone instanceof HTMLElement
                && dropzone instanceof SVGElement
                && !(dropzone instanceof SVGSVGElement)) {

                if (dropzone === deepestZone.parentNode) {
                    continue;
                }

                parent = dropzone.ownerSVGElement;
            }
            else {
                parent = dropzone;
            }

            dropzoneParents = [];

            while (parent.parentNode !== parent.ownerDocument) {
                dropzoneParents.unshift(parent);
                parent = parent.parentNode;
            }

            n = 0;

            // get (position of last common ancestor) + 1
            while (dropzoneParents[n] && dropzoneParents[n] === deepestZoneParents[n]) {
                n++;
            }

            var parents = [
                dropzoneParents[n - 1],
                dropzoneParents[n],
                deepestZoneParents[n]
            ];

            child = parents[0].lastChild;

            while (child) {
                if (child === parents[1]) {
                    deepestZone = dropzone;
                    index = i;
                    deepestZoneParents = [];

                    break;
                }
                else if (child === parents[2]) {
                    break;
                }

                child = child.previousSibling;
            }
        }

        return index;
    }

    function Interaction () {
        this.target          = null; // current interactable being interacted with
        this.element         = null; // the target element of the interactable
        this.dropTarget      = null; // the dropzone a drag target might be dropped into
        this.dropElement     = null; // the element at the time of checking
        this.prevDropTarget  = null; // the dropzone that was recently dragged away from
        this.prevDropElement = null; // the element at the time of checking

        this.prepared        = {     // action that's ready to be fired on next move event
            name : null,
            axis : null,
            edges: null
        };

        this.matches         = [];   // all selectors that are matched by target element
        this.matchElements   = [];   // corresponding elements

        this.inertiaStatus = {
            active       : false,
            smoothEnd    : false,

            startEvent: null,
            upCoords: {},

            xe: 0, ye: 0,
            sx: 0, sy: 0,

            t0: 0,
            vx0: 0, vys: 0,
            duration: 0,

            resumeDx: 0,
            resumeDy: 0,

            lambda_v0: 0,
            one_ve_v0: 0,
            i  : null
        };

        if (isFunction(Function.prototype.bind)) {
            this.boundInertiaFrame = this.inertiaFrame.bind(this);
            this.boundSmoothEndFrame = this.smoothEndFrame.bind(this);
        }
        else {
            var that = this;

            this.boundInertiaFrame = function () { return that.inertiaFrame(); };
            this.boundSmoothEndFrame = function () { return that.smoothEndFrame(); };
        }

        this.activeDrops = {
            dropzones: [],      // the dropzones that are mentioned below
            elements : [],      // elements of dropzones that accept the target draggable
            rects    : []       // the rects of the elements mentioned above
        };

        // keep track of added pointers
        this.pointers    = [];
        this.pointerIds  = [];
        this.downTargets = [];
        this.downTimes   = [];
        this.holdTimers  = [];

        // Previous native pointer move event coordinates
        this.prevCoords = {
            page     : { x: 0, y: 0 },
            client   : { x: 0, y: 0 },
            timeStamp: 0
        };
        // current native pointer move event coordinates
        this.curCoords = {
            page     : { x: 0, y: 0 },
            client   : { x: 0, y: 0 },
            timeStamp: 0
        };

        // Starting InteractEvent pointer coordinates
        this.startCoords = {
            page     : { x: 0, y: 0 },
            client   : { x: 0, y: 0 },
            timeStamp: 0
        };

        // Change in coordinates and time of the pointer
        this.pointerDelta = {
            page     : { x: 0, y: 0, vx: 0, vy: 0, speed: 0 },
            client   : { x: 0, y: 0, vx: 0, vy: 0, speed: 0 },
            timeStamp: 0
        };

        this.downEvent   = null;    // pointerdown/mousedown/touchstart event
        this.downPointer = {};

        this._eventTarget    = null;
        this._curEventTarget = null;

        this.prevEvent = null;      // previous action event
        this.tapTime   = 0;         // time of the most recent tap event
        this.prevTap   = null;

        this.startOffset    = { left: 0, right: 0, top: 0, bottom: 0 };
        this.restrictOffset = { left: 0, right: 0, top: 0, bottom: 0 };
        this.snapOffsets    = [];

        this.gesture = {
            start: { x: 0, y: 0 },

            startDistance: 0,   // distance between two touches of touchStart
            prevDistance : 0,
            distance     : 0,

            scale: 1,           // gesture.distance / gesture.startDistance

            startAngle: 0,      // angle of line joining two touches
            prevAngle : 0       // angle of the previous gesture event
        };

        this.snapStatus = {
            x       : 0, y       : 0,
            dx      : 0, dy      : 0,
            realX   : 0, realY   : 0,
            snappedX: 0, snappedY: 0,
            targets : [],
            locked  : false,
            changed : false
        };

        this.restrictStatus = {
            dx         : 0, dy         : 0,
            restrictedX: 0, restrictedY: 0,
            snap       : null,
            restricted : false,
            changed    : false
        };

        this.restrictStatus.snap = this.snapStatus;

        this.pointerIsDown   = false;
        this.pointerWasMoved = false;
        this.gesturing       = false;
        this.dragging        = false;
        this.resizing        = false;
        this.resizeAxes      = 'xy';

        this.mouse = false;

        interactions.push(this);
    }

    Interaction.prototype = {
        getPageXY  : function (pointer, xy) { return   getPageXY(pointer, xy, this); },
        getClientXY: function (pointer, xy) { return getClientXY(pointer, xy, this); },
        setEventXY : function (target, ptr) { return  setEventXY(target, ptr, this); },

        pointerOver: function (pointer, event, eventTarget) {
            if (this.prepared.name || !this.mouse) { return; }

            var curMatches = [],
                curMatchElements = [],
                prevTargetElement = this.element;

            this.addPointer(pointer);

            if (this.target
                && (testIgnore(this.target, this.element, eventTarget)
                    || !testAllow(this.target, this.element, eventTarget))) {
                // if the eventTarget should be ignored or shouldn't be allowed
                // clear the previous target
                this.target = null;
                this.element = null;
                this.matches = [];
                this.matchElements = [];
            }

            var elementInteractable = interactables.get(eventTarget),
                elementAction = (elementInteractable
                                 && !testIgnore(elementInteractable, eventTarget, eventTarget)
                                 && testAllow(elementInteractable, eventTarget, eventTarget)
                                 && validateAction(
                                     elementInteractable.getAction(pointer, this, eventTarget),
                                     elementInteractable));

            if (elementAction && !withinInteractionLimit(elementInteractable, eventTarget, elementAction)) {
                 elementAction = null;
            }

            function pushCurMatches (interactable, selector) {
                if (interactable
                    && inContext(interactable, eventTarget)
                    && !testIgnore(interactable, eventTarget, eventTarget)
                    && testAllow(interactable, eventTarget, eventTarget)
                    && matchesSelector(eventTarget, selector)) {

                    curMatches.push(interactable);
                    curMatchElements.push(eventTarget);
                }
            }

            if (elementAction) {
                this.target = elementInteractable;
                this.element = eventTarget;
                this.matches = [];
                this.matchElements = [];
            }
            else {
                interactables.forEachSelector(pushCurMatches);

                if (this.validateSelector(pointer, curMatches, curMatchElements)) {
                    this.matches = curMatches;
                    this.matchElements = curMatchElements;

                    this.pointerHover(pointer, event, this.matches, this.matchElements);
                    events.add(eventTarget,
                                        PointerEvent? pEventTypes.move : 'mousemove',
                                        listeners.pointerHover);
                }
                else if (this.target) {
                    if (nodeContains(prevTargetElement, eventTarget)) {
                        this.pointerHover(pointer, event, this.matches, this.matchElements);
                        events.add(this.element,
                                            PointerEvent? pEventTypes.move : 'mousemove',
                                            listeners.pointerHover);
                    }
                    else {
                        this.target = null;
                        this.element = null;
                        this.matches = [];
                        this.matchElements = [];
                    }
                }
            }
        },

        // Check what action would be performed on pointerMove target if a mouse
        // button were pressed and change the cursor accordingly
        pointerHover: function (pointer, event, eventTarget, curEventTarget, matches, matchElements) {
            var target = this.target;

            if (!this.prepared.name && this.mouse) {

                var action;

                // update pointer coords for defaultActionChecker to use
                this.setEventXY(this.curCoords, pointer);

                if (matches) {
                    action = this.validateSelector(pointer, matches, matchElements);
                }
                else if (target) {
                    action = validateAction(target.getAction(this.pointers[0], this, this.element), this.target);
                }

                if (target && target.options.styleCursor) {
                    if (action) {
                        target._doc.documentElement.style.cursor = getActionCursor(action);
                    }
                    else {
                        target._doc.documentElement.style.cursor = '';
                    }
                }
            }
            else if (this.prepared.name) {
                this.checkAndPreventDefault(event, target, this.element);
            }
        },

        pointerOut: function (pointer, event, eventTarget) {
            if (this.prepared.name) { return; }

            // Remove temporary event listeners for selector Interactables
            if (!interactables.get(eventTarget)) {
                events.remove(eventTarget,
                                       PointerEvent? pEventTypes.move : 'mousemove',
                                       listeners.pointerHover);
            }

            if (this.target && this.target.options.styleCursor && !this.interacting()) {
                this.target._doc.documentElement.style.cursor = '';
            }
        },

        selectorDown: function (pointer, event, eventTarget, curEventTarget) {
            var that = this,
                // copy event to be used in timeout for IE8
                eventCopy = events.useAttachEvent? extend({}, event) : event,
                element = eventTarget,
                pointerIndex = this.addPointer(pointer),
                action;

            this.holdTimers[pointerIndex] = setTimeout(function () {
                that.pointerHold(events.useAttachEvent? eventCopy : pointer, eventCopy, eventTarget, curEventTarget);
            }, defaultOptions._holdDuration);

            this.pointerIsDown = true;

            // Check if the down event hits the current inertia target
            if (this.inertiaStatus.active && this.target.selector) {
                // climb up the DOM tree from the event target
                while (isElement(element)) {

                    // if this element is the current inertia target element
                    if (element === this.element
                        // and the prospective action is the same as the ongoing one
                        && validateAction(this.target.getAction(pointer, this, this.element), this.target).name === this.prepared.name) {

                        // stop inertia so that the next move will be a normal one
                        cancelFrame(this.inertiaStatus.i);
                        this.inertiaStatus.active = false;

                        this.collectEventTargets(pointer, event, eventTarget, 'down');
                        return;
                    }
                    element = parentElement(element);
                }
            }

            // do nothing if interacting
            if (this.interacting()) {
                this.collectEventTargets(pointer, event, eventTarget, 'down');
                return;
            }

            function pushMatches (interactable, selector, context) {
                var elements = ie8MatchesSelector
                    ? context.querySelectorAll(selector)
                    : undefined;

                if (inContext(interactable, element)
                    && !testIgnore(interactable, element, eventTarget)
                    && testAllow(interactable, element, eventTarget)
                    && matchesSelector(element, selector, elements)) {

                    that.matches.push(interactable);
                    that.matchElements.push(element);
                }
            }

            // update pointer coords for defaultActionChecker to use
            this.setEventXY(this.curCoords, pointer);

            while (isElement(element) && !action) {
                this.matches = [];
                this.matchElements = [];

                interactables.forEachSelector(pushMatches);

                action = this.validateSelector(pointer, this.matches, this.matchElements);
                element = parentElement(element);
            }

            if (action) {
                this.prepared.name  = action.name;
                this.prepared.axis  = action.axis;
                this.prepared.edges = action.edges;

                this.collectEventTargets(pointer, event, eventTarget, 'down');

                return this.pointerDown(pointer, event, eventTarget, curEventTarget, action);
            }
            else {
                // do these now since pointerDown isn't being called from here
                this.downTimes[pointerIndex] = new Date().getTime();
                this.downTargets[pointerIndex] = eventTarget;
                this.downEvent = event;
                extend(this.downPointer, pointer);

                copyCoords(this.prevCoords, this.curCoords);
                this.pointerWasMoved = false;
            }

            this.collectEventTargets(pointer, event, eventTarget, 'down');
        },

        // Determine action to be performed on next pointerMove and add appropriate
        // style and event Listeners
        pointerDown: function (pointer, event, eventTarget, curEventTarget, forceAction) {
            if (!forceAction && !this.inertiaStatus.active && this.pointerWasMoved && this.prepared.name) {
                this.checkAndPreventDefault(event, this.target, this.element);

                return;
            }

            this.pointerIsDown = true;

            var pointerIndex = this.addPointer(pointer),
                action;

            // If it is the second touch of a multi-touch gesture, keep the target
            // the same if a target was set by the first touch
            // Otherwise, set the target if there is no action prepared
            if ((this.pointerIds.length < 2 && !this.target) || !this.prepared.name) {

                var interactable = interactables.get(curEventTarget);

                if (interactable
                    && !testIgnore(interactable, curEventTarget, eventTarget)
                    && testAllow(interactable, curEventTarget, eventTarget)
                    && (action = validateAction(forceAction || interactable.getAction(pointer, this, curEventTarget), interactable, eventTarget))
                    && withinInteractionLimit(interactable, curEventTarget, action)) {
                    this.target = interactable;
                    this.element = curEventTarget;
                }
            }

            var target = this.target,
                options = target && target.options;

            if (target && !this.interacting()) {
                action = action || validateAction(forceAction || target.getAction(pointer, this, curEventTarget), target, this.element);

                this.setEventXY(this.startCoords);

                if (!action) { return; }

                if (options.styleCursor) {
                    target._doc.documentElement.style.cursor = getActionCursor(action);
                }

                this.resizeAxes = action.name === 'resize'? action.axis : null;

                if (action === 'gesture' && this.pointerIds.length < 2) {
                    action = null;
                }

                this.prepared.name  = action.name;
                this.prepared.axis  = action.axis;
                this.prepared.edges = action.edges;

                this.snapStatus.snappedX = this.snapStatus.snappedY =
                    this.restrictStatus.restrictedX = this.restrictStatus.restrictedY = NaN;

                this.downTimes[pointerIndex] = new Date().getTime();
                this.downTargets[pointerIndex] = eventTarget;
                this.downEvent = event;
                extend(this.downPointer, pointer);

                this.setEventXY(this.prevCoords);
                this.pointerWasMoved = false;

                this.checkAndPreventDefault(event, target, this.element);
            }
            // if inertia is active try to resume action
            else if (this.inertiaStatus.active
                && curEventTarget === this.element
                && validateAction(target.getAction(pointer, this, this.element), target).name === this.prepared.name) {

                cancelFrame(this.inertiaStatus.i);
                this.inertiaStatus.active = false;

                this.checkAndPreventDefault(event, target, this.element);
            }
        },

        setModifications: function (coords, preEnd) {
            var target         = this.target,
                shouldMove     = true,
                shouldSnap     = checkSnap(target, this.prepared.name)     && (!target.options[this.prepared.name].snap.endOnly     || preEnd),
                shouldRestrict = checkRestrict(target, this.prepared.name) && (!target.options[this.prepared.name].restrict.endOnly || preEnd);

            if (shouldSnap    ) { this.setSnapping   (coords); } else { this.snapStatus    .locked     = false; }
            if (shouldRestrict) { this.setRestriction(coords); } else { this.restrictStatus.restricted = false; }

            if (shouldSnap && this.snapStatus.locked && !this.snapStatus.changed) {
                shouldMove = shouldRestrict && this.restrictStatus.restricted && this.restrictStatus.changed;
            }
            else if (shouldRestrict && this.restrictStatus.restricted && !this.restrictStatus.changed) {
                shouldMove = false;
            }

            return shouldMove;
        },

        setStartOffsets: function (action, interactable, element) {
            var rect = interactable.getRect(element),
                origin = getOriginXY(interactable, element),
                snap = interactable.options[this.prepared.name].snap,
                restrict = interactable.options[this.prepared.name].restrict,
                width, height;

            if (rect) {
                this.startOffset.left = this.startCoords.page.x - rect.left;
                this.startOffset.top  = this.startCoords.page.y - rect.top;

                this.startOffset.right  = rect.right  - this.startCoords.page.x;
                this.startOffset.bottom = rect.bottom - this.startCoords.page.y;

                if ('width' in rect) { width = rect.width; }
                else { width = rect.right - rect.left; }
                if ('height' in rect) { height = rect.height; }
                else { height = rect.bottom - rect.top; }
            }
            else {
                this.startOffset.left = this.startOffset.top = this.startOffset.right = this.startOffset.bottom = 0;
            }

            this.snapOffsets.splice(0);

            var snapOffset = snap && snap.offset === 'startCoords'
                                ? {
                                    x: this.startCoords.page.x - origin.x,
                                    y: this.startCoords.page.y - origin.y
                                }
                                : snap && snap.offset || { x: 0, y: 0 };

            if (rect && snap && snap.relativePoints && snap.relativePoints.length) {
                for (var i = 0; i < snap.relativePoints.length; i++) {
                    this.snapOffsets.push({
                        x: this.startOffset.left - (width  * snap.relativePoints[i].x) + snapOffset.x,
                        y: this.startOffset.top  - (height * snap.relativePoints[i].y) + snapOffset.y
                    });
                }
            }
            else {
                this.snapOffsets.push(snapOffset);
            }

            if (rect && restrict.elementRect) {
                this.restrictOffset.left = this.startOffset.left - (width  * restrict.elementRect.left);
                this.restrictOffset.top  = this.startOffset.top  - (height * restrict.elementRect.top);

                this.restrictOffset.right  = this.startOffset.right  - (width  * (1 - restrict.elementRect.right));
                this.restrictOffset.bottom = this.startOffset.bottom - (height * (1 - restrict.elementRect.bottom));
            }
            else {
                this.restrictOffset.left = this.restrictOffset.top = this.restrictOffset.right = this.restrictOffset.bottom = 0;
            }
        },

        /*\
         * Interaction.start
         [ method ]
         *
         * Start an action with the given Interactable and Element as tartgets. The
         * action must be enabled for the target Interactable and an appropriate number
         * of pointers must be held down 鈥� 1 for drag/resize, 2 for gesture.
         *
         * Use it with `interactable.<action>able({ manualStart: false })` to always
         * [start actions manually](https://github.com/taye/interact.js/issues/114)
         *
         - action       (object)  The action to be performed - drag, resize, etc.
         - interactable (Interactable) The Interactable to target
         - element      (Element) The DOM Element to target
         = (object) interact
         **
         | interact(target)
         |   .draggable({
         |     // disable the default drag start by down->move
         |     manualStart: true
         |   })
         |   // start dragging after the user holds the pointer down
         |   .on('hold', function (event) {
         |     var interaction = event.interaction;
         |
         |     if (!interaction.interacting()) {
         |       interaction.start({ name: 'drag' },
         |                         event.interactable,
         |                         event.currentTarget);
         |     }
         | });
        \*/
        start: function (action, interactable, element) {
            if (this.interacting()
                || !this.pointerIsDown
                || this.pointerIds.length < (action.name === 'gesture'? 2 : 1)) {
                return;
            }

            // if this interaction had been removed after stopping
            // add it back
            if (indexOf(interactions, this) === -1) {
                interactions.push(this);
            }

            this.prepared.name  = action.name;
            this.prepared.axis  = action.axis;
            this.prepared.edges = action.edges;
            this.target         = interactable;
            this.element        = element;

            this.setStartOffsets(action.name, interactable, element);
            this.setModifications(this.startCoords.page);

            this.prevEvent = this[this.prepared.name + 'Start'](this.downEvent);
        },

        pointerMove: function (pointer, event, eventTarget, curEventTarget, preEnd) {
            this.recordPointer(pointer);

            this.setEventXY(this.curCoords, (pointer instanceof InteractEvent)
                                                ? this.inertiaStatus.startEvent
                                                : undefined);

            var duplicateMove = (this.curCoords.page.x === this.prevCoords.page.x
                                 && this.curCoords.page.y === this.prevCoords.page.y
                                 && this.curCoords.client.x === this.prevCoords.client.x
                                 && this.curCoords.client.y === this.prevCoords.client.y);

            var dx, dy,
                pointerIndex = this.mouse? 0 : indexOf(this.pointerIds, getPointerId(pointer));

            // register movement greater than pointerMoveTolerance
            if (this.pointerIsDown && !this.pointerWasMoved) {
                dx = this.curCoords.client.x - this.startCoords.client.x;
                dy = this.curCoords.client.y - this.startCoords.client.y;

                this.pointerWasMoved = hypot(dx, dy) > pointerMoveTolerance;
            }

            if (!duplicateMove && (!this.pointerIsDown || this.pointerWasMoved)) {
                if (this.pointerIsDown) {
                    clearTimeout(this.holdTimers[pointerIndex]);
                }

                this.collectEventTargets(pointer, event, eventTarget, 'move');
            }

            if (!this.pointerIsDown) { return; }

            if (duplicateMove && this.pointerWasMoved && !preEnd) {
                this.checkAndPreventDefault(event, this.target, this.element);
                return;
            }

            // set pointer coordinate, time changes and speeds
            setEventDeltas(this.pointerDelta, this.prevCoords, this.curCoords);

            if (!this.prepared.name) { return; }

            if (this.pointerWasMoved
                // ignore movement while inertia is active
                && (!this.inertiaStatus.active || (pointer instanceof InteractEvent && /inertiastart/.test(pointer.type)))) {

                // if just starting an action, calculate the pointer speed now
                if (!this.interacting()) {
                    setEventDeltas(this.pointerDelta, this.prevCoords, this.curCoords);

                    // check if a drag is in the correct axis
                    if (this.prepared.name === 'drag') {
                        var absX = Math.abs(dx),
                            absY = Math.abs(dy),
                            targetAxis = this.target.options.drag.axis,
                            axis = (absX > absY ? 'x' : absX < absY ? 'y' : 'xy');

                        // if the movement isn't in the axis of the interactable
                        if (axis !== 'xy' && targetAxis !== 'xy' && targetAxis !== axis) {
                            // cancel the prepared action
                            this.prepared.name = null;

                            // then try to get a drag from another ineractable

                            var element = eventTarget;

                            // check element interactables
                            while (isElement(element)) {
                                var elementInteractable = interactables.get(element);

                                if (elementInteractable
                                    && elementInteractable !== this.target
                                    && !elementInteractable.options.drag.manualStart
                                    && elementInteractable.getAction(this.downPointer, this, element).name === 'drag'
                                    && checkAxis(axis, elementInteractable)) {

                                    this.prepared.name = 'drag';
                                    this.target = elementInteractable;
                                    this.element = element;
                                    break;
                                }

                                element = parentElement(element);
                            }

                            // if there's no drag from element interactables,
                            // check the selector interactables
                            if (!this.prepared.name) {
                                var getDraggable = function (interactable, selector, context) {
                                    var elements = ie8MatchesSelector
                                        ? context.querySelectorAll(selector)
                                        : undefined;

                                    if (interactable === this.target) { return; }

                                    if (inContext(interactable, eventTarget)
                                        && !interactable.options.drag.manualStart
                                        && !testIgnore(interactable, element, eventTarget)
                                        && testAllow(interactable, element, eventTarget)
                                        && matchesSelector(element, selector, elements)
                                        && interactable.getAction(this.downPointer, this, element).name === 'drag'
                                        && checkAxis(axis, interactable)
                                        && withinInteractionLimit(interactable, element, 'drag')) {

                                        return interactable;
                                    }
                                };

                                element = eventTarget;

                                while (isElement(element)) {
                                    var selectorInteractable = interactables.forEachSelector(getDraggable);

                                    if (selectorInteractable) {
                                        this.prepared.name = 'drag';
                                        this.target = selectorInteractable;
                                        this.element = element;
                                        break;
                                    }

                                    element = parentElement(element);
                                }
                            }
                        }
                    }
                }

                var starting = !!this.prepared.name && !this.interacting();

                if (starting
                    && (this.target.options[this.prepared.name].manualStart
                        || !withinInteractionLimit(this.target, this.element, this.prepared))) {
                    this.stop();
                    return;
                }

                if (this.prepared.name && this.target) {
                    if (starting) {
                        this.start(this.prepared, this.target, this.element);
                    }

                    var shouldMove = this.setModifications(this.curCoords.page, preEnd);

                    // move if snapping or restriction doesn't prevent it
                    if (shouldMove || starting) {
                        this.prevEvent = this[this.prepared.name + 'Move'](event);
                    }

                    this.checkAndPreventDefault(event, this.target, this.element);
                }
            }

            copyCoords(this.prevCoords, this.curCoords);

            if (this.dragging || this.resizing) {
                autoScroll.edgeMove(event);
            }
        },

        dragStart: function (event) {
            var dragEvent = new InteractEvent(this, event, 'drag', 'start', this.element);

            this.dragging = true;
            this.target.fire(dragEvent);

            // reset active dropzones
            this.activeDrops.dropzones = [];
            this.activeDrops.elements  = [];
            this.activeDrops.rects     = [];

            if (!this.dynamicDrop) {
                this.setActiveDrops(this.element);
            }

            var dropEvents = this.getDropEvents(event, dragEvent);

            if (dropEvents.activate) {
                this.fireActiveDrops(dropEvents.activate);
            }

            return dragEvent;
        },

        dragMove: function (event) {
            var target = this.target,
                dragEvent  = new InteractEvent(this, event, 'drag', 'move', this.element),
                draggableElement = this.element,
                drop = this.getDrop(dragEvent, draggableElement);

            this.dropTarget = drop.dropzone;
            this.dropElement = drop.element;

            var dropEvents = this.getDropEvents(event, dragEvent);

            target.fire(dragEvent);

            if (dropEvents.leave) { this.prevDropTarget.fire(dropEvents.leave); }
            if (dropEvents.enter) {     this.dropTarget.fire(dropEvents.enter); }
            if (dropEvents.move ) {     this.dropTarget.fire(dropEvents.move ); }

            this.prevDropTarget  = this.dropTarget;
            this.prevDropElement = this.dropElement;

            return dragEvent;
        },

        resizeStart: function (event) {
            var resizeEvent = new InteractEvent(this, event, 'resize', 'start', this.element);

            if (this.prepared.edges) {
                var startRect = this.target.getRect(this.element);

                if (this.target.options.resize.square) {
                    var squareEdges = extend({}, this.prepared.edges);

                    squareEdges.top    = squareEdges.top    || (squareEdges.left   && !squareEdges.bottom);
                    squareEdges.left   = squareEdges.left   || (squareEdges.top    && !squareEdges.right );
                    squareEdges.bottom = squareEdges.bottom || (squareEdges.right  && !squareEdges.top   );
                    squareEdges.right  = squareEdges.right  || (squareEdges.bottom && !squareEdges.left  );

                    this.prepared._squareEdges = squareEdges;
                }
                else {
                    this.prepared._squareEdges = null;
                }

                this.resizeRects = {
                    start     : startRect,
                    current   : extend({}, startRect),
                    restricted: extend({}, startRect),
                    previous  : extend({}, startRect),
                    delta     : {
                        left: 0, right : 0, width : 0,
                        top : 0, bottom: 0, height: 0
                    }
                };

                resizeEvent.rect = this.resizeRects.restricted;
                resizeEvent.deltaRect = this.resizeRects.delta;
            }

            this.target.fire(resizeEvent);

            this.resizing = true;

            return resizeEvent;
        },

        resizeMove: function (event) {
            var resizeEvent = new InteractEvent(this, event, 'resize', 'move', this.element);

            var edges = this.prepared.edges,
                invert = this.target.options.resize.invert,
                invertible = invert === 'reposition' || invert === 'negate';

            if (edges) {
                var dx = resizeEvent.dx,
                    dy = resizeEvent.dy,

                    start      = this.resizeRects.start,
                    current    = this.resizeRects.current,
                    restricted = this.resizeRects.restricted,
                    delta      = this.resizeRects.delta,
                    previous   = extend(this.resizeRects.previous, restricted);

                if (this.target.options.resize.square) {
                    var originalEdges = edges;

                    edges = this.prepared._squareEdges;

                    if ((originalEdges.left && originalEdges.bottom)
                        || (originalEdges.right && originalEdges.top)) {
                        dy = -dx;
                    }
                    else if (originalEdges.left || originalEdges.right) { dy = dx; }
                    else if (originalEdges.top || originalEdges.bottom) { dx = dy; }
                }

                // update the 'current' rect without modifications
                if (edges.top   ) { current.top    += dy; }
                if (edges.bottom) { current.bottom += dy; }
                if (edges.left  ) { current.left   += dx; }
                if (edges.right ) { current.right  += dx; }

                if (invertible) {
                    // if invertible, copy the current rect
                    extend(restricted, current);

                    if (invert === 'reposition') {
                        // swap edge values if necessary to keep width/height positive
                        var swap;

                        if (restricted.top > restricted.bottom) {
                            swap = restricted.top;

                            restricted.top = restricted.bottom;
                            restricted.bottom = swap;
                        }
                        if (restricted.left > restricted.right) {
                            swap = restricted.left;

                            restricted.left = restricted.right;
                            restricted.right = swap;
                        }
                    }
                }
                else {
                    // if not invertible, restrict to minimum of 0x0 rect
                    restricted.top    = Math.min(current.top, start.bottom);
                    restricted.bottom = Math.max(current.bottom, start.top);
                    restricted.left   = Math.min(current.left, start.right);
                    restricted.right  = Math.max(current.right, start.left);
                }

                restricted.width  = restricted.right  - restricted.left;
                restricted.height = restricted.bottom - restricted.top ;

                for (var edge in restricted) {
                    delta[edge] = restricted[edge] - previous[edge];
                }

                resizeEvent.edges = this.prepared.edges;
                resizeEvent.rect = restricted;
                resizeEvent.deltaRect = delta;
            }

            this.target.fire(resizeEvent);

            return resizeEvent;
        },

        gestureStart: function (event) {
            var gestureEvent = new InteractEvent(this, event, 'gesture', 'start', this.element);

            gestureEvent.ds = 0;

            this.gesture.startDistance = this.gesture.prevDistance = gestureEvent.distance;
            this.gesture.startAngle = this.gesture.prevAngle = gestureEvent.angle;
            this.gesture.scale = 1;

            this.gesturing = true;

            this.target.fire(gestureEvent);

            return gestureEvent;
        },

        gestureMove: function (event) {
            if (!this.pointerIds.length) {
                return this.prevEvent;
            }

            var gestureEvent;

            gestureEvent = new InteractEvent(this, event, 'gesture', 'move', this.element);
            gestureEvent.ds = gestureEvent.scale - this.gesture.scale;

            this.target.fire(gestureEvent);

            this.gesture.prevAngle = gestureEvent.angle;
            this.gesture.prevDistance = gestureEvent.distance;

            if (gestureEvent.scale !== Infinity &&
                gestureEvent.scale !== null &&
                gestureEvent.scale !== undefined  &&
                !isNaN(gestureEvent.scale)) {

                this.gesture.scale = gestureEvent.scale;
            }

            return gestureEvent;
        },

        pointerHold: function (pointer, event, eventTarget) {
            this.collectEventTargets(pointer, event, eventTarget, 'hold');
        },

        pointerUp: function (pointer, event, eventTarget, curEventTarget) {
            var pointerIndex = this.mouse? 0 : indexOf(this.pointerIds, getPointerId(pointer));

            clearTimeout(this.holdTimers[pointerIndex]);

            this.collectEventTargets(pointer, event, eventTarget, 'up' );
            this.collectEventTargets(pointer, event, eventTarget, 'tap');

            this.pointerEnd(pointer, event, eventTarget, curEventTarget);

            this.removePointer(pointer);
        },

        pointerCancel: function (pointer, event, eventTarget, curEventTarget) {
            var pointerIndex = this.mouse? 0 : indexOf(this.pointerIds, getPointerId(pointer));

            clearTimeout(this.holdTimers[pointerIndex]);

            this.collectEventTargets(pointer, event, eventTarget, 'cancel');
            this.pointerEnd(pointer, event, eventTarget, curEventTarget);

            this.removePointer(pointer);
        },

        // http://www.quirksmode.org/dom/events/click.html
        // >Events leading to dblclick
        //
        // IE8 doesn't fire down event before dblclick.
        // This workaround tries to fire a tap and doubletap after dblclick
        ie8Dblclick: function (pointer, event, eventTarget) {
            if (this.prevTap
                && event.clientX === this.prevTap.clientX
                && event.clientY === this.prevTap.clientY
                && eventTarget   === this.prevTap.target) {

                this.downTargets[0] = eventTarget;
                this.downTimes[0] = new Date().getTime();
                this.collectEventTargets(pointer, event, eventTarget, 'tap');
            }
        },

        // End interact move events and stop auto-scroll unless inertia is enabled
        pointerEnd: function (pointer, event, eventTarget, curEventTarget) {
            var endEvent,
                target = this.target,
                options = target && target.options,
                inertiaOptions = options && this.prepared.name && options[this.prepared.name].inertia,
                inertiaStatus = this.inertiaStatus;

            if (this.interacting()) {

                if (inertiaStatus.active) { return; }

                var pointerSpeed,
                    now = new Date().getTime(),
                    inertiaPossible = false,
                    inertia = false,
                    smoothEnd = false,
                    endSnap = checkSnap(target, this.prepared.name) && options[this.prepared.name].snap.endOnly,
                    endRestrict = checkRestrict(target, this.prepared.name) && options[this.prepared.name].restrict.endOnly,
                    dx = 0,
                    dy = 0,
                    startEvent;

                if (this.dragging) {
                    if      (options.drag.axis === 'x' ) { pointerSpeed = Math.abs(this.pointerDelta.client.vx); }
                    else if (options.drag.axis === 'y' ) { pointerSpeed = Math.abs(this.pointerDelta.client.vy); }
                    else   /*options.drag.axis === 'xy'*/{ pointerSpeed = this.pointerDelta.client.speed; }
                }
                else {
                    pointerSpeed = this.pointerDelta.client.speed;
                }

                // check if inertia should be started
                inertiaPossible = (inertiaOptions && inertiaOptions.enabled
                                   && this.prepared.name !== 'gesture'
                                   && event !== inertiaStatus.startEvent);

                inertia = (inertiaPossible
                           && (now - this.curCoords.timeStamp) < 50
                           && pointerSpeed > inertiaOptions.minSpeed
                           && pointerSpeed > inertiaOptions.endSpeed);

                if (inertiaPossible && !inertia && (endSnap || endRestrict)) {

                    var snapRestrict = {};

                    snapRestrict.snap = snapRestrict.restrict = snapRestrict;

                    if (endSnap) {
                        this.setSnapping(this.curCoords.page, snapRestrict);
                        if (snapRestrict.locked) {
                            dx += snapRestrict.dx;
                            dy += snapRestrict.dy;
                        }
                    }

                    if (endRestrict) {
                        this.setRestriction(this.curCoords.page, snapRestrict);
                        if (snapRestrict.restricted) {
                            dx += snapRestrict.dx;
                            dy += snapRestrict.dy;
                        }
                    }

                    if (dx || dy) {
                        smoothEnd = true;
                    }
                }

                if (inertia || smoothEnd) {
                    copyCoords(inertiaStatus.upCoords, this.curCoords);

                    this.pointers[0] = inertiaStatus.startEvent = startEvent =
                        new InteractEvent(this, event, this.prepared.name, 'inertiastart', this.element);

                    inertiaStatus.t0 = now;

                    target.fire(inertiaStatus.startEvent);

                    if (inertia) {
                        inertiaStatus.vx0 = this.pointerDelta.client.vx;
                        inertiaStatus.vy0 = this.pointerDelta.client.vy;
                        inertiaStatus.v0 = pointerSpeed;

                        this.calcInertia(inertiaStatus);

                        var page = extend({}, this.curCoords.page),
                            origin = getOriginXY(target, this.element),
                            statusObject;

                        page.x = page.x + inertiaStatus.xe - origin.x;
                        page.y = page.y + inertiaStatus.ye - origin.y;

                        statusObject = {
                            useStatusXY: true,
                            x: page.x,
                            y: page.y,
                            dx: 0,
                            dy: 0,
                            snap: null
                        };

                        statusObject.snap = statusObject;

                        dx = dy = 0;

                        if (endSnap) {
                            var snap = this.setSnapping(this.curCoords.page, statusObject);

                            if (snap.locked) {
                                dx += snap.dx;
                                dy += snap.dy;
                            }
                        }

                        if (endRestrict) {
                            var restrict = this.setRestriction(this.curCoords.page, statusObject);

                            if (restrict.restricted) {
                                dx += restrict.dx;
                                dy += restrict.dy;
                            }
                        }

                        inertiaStatus.modifiedXe += dx;
                        inertiaStatus.modifiedYe += dy;

                        inertiaStatus.i = reqFrame(this.boundInertiaFrame);
                    }
                    else {
                        inertiaStatus.smoothEnd = true;
                        inertiaStatus.xe = dx;
                        inertiaStatus.ye = dy;

                        inertiaStatus.sx = inertiaStatus.sy = 0;

                        inertiaStatus.i = reqFrame(this.boundSmoothEndFrame);
                    }

                    inertiaStatus.active = true;
                    return;
                }

                if (endSnap || endRestrict) {
                    // fire a move event at the snapped coordinates
                    this.pointerMove(pointer, event, eventTarget, curEventTarget, true);
                }
            }

            if (this.dragging) {
                endEvent = new InteractEvent(this, event, 'drag', 'end', this.element);

                var draggableElement = this.element,
                    drop = this.getDrop(endEvent, draggableElement);

                this.dropTarget = drop.dropzone;
                this.dropElement = drop.element;

                var dropEvents = this.getDropEvents(event, endEvent);

                if (dropEvents.leave) { this.prevDropTarget.fire(dropEvents.leave); }
                if (dropEvents.enter) {     this.dropTarget.fire(dropEvents.enter); }
                if (dropEvents.drop ) {     this.dropTarget.fire(dropEvents.drop ); }
                if (dropEvents.deactivate) {
                    this.fireActiveDrops(dropEvents.deactivate);
                }

                target.fire(endEvent);
            }
            else if (this.resizing) {
                endEvent = new InteractEvent(this, event, 'resize', 'end', this.element);
                target.fire(endEvent);
            }
            else if (this.gesturing) {
                endEvent = new InteractEvent(this, event, 'gesture', 'end', this.element);
                target.fire(endEvent);
            }

            this.stop(event);
        },

        collectDrops: function (element) {
            var drops = [],
                elements = [],
                i;

            element = element || this.element;

            // collect all dropzones and their elements which qualify for a drop
            for (i = 0; i < interactables.length; i++) {
                if (!interactables[i].options.drop.enabled) { continue; }

                var current = interactables[i],
                    accept = current.options.drop.accept;

                // test the draggable element against the dropzone's accept setting
                if ((isElement(accept) && accept !== element)
                    || (isString(accept)
                        && !matchesSelector(element, accept))) {

                    continue;
                }

                // query for new elements if necessary
                var dropElements = current.selector? current._context.querySelectorAll(current.selector) : [current._element];

                for (var j = 0, len = dropElements.length; j < len; j++) {
                    var currentElement = dropElements[j];

                    if (currentElement === element) {
                        continue;
                    }

                    drops.push(current);
                    elements.push(currentElement);
                }
            }

            return {
                dropzones: drops,
                elements: elements
            };
        },

        fireActiveDrops: function (event) {
            var i,
                current,
                currentElement,
                prevElement;

            // loop through all active dropzones and trigger event
            for (i = 0; i < this.activeDrops.dropzones.length; i++) {
                current = this.activeDrops.dropzones[i];
                currentElement = this.activeDrops.elements [i];

                // prevent trigger of duplicate events on same element
                if (currentElement !== prevElement) {
                    // set current element as event target
                    event.target = currentElement;
                    current.fire(event);
                }
                prevElement = currentElement;
            }
        },

        // Collect a new set of possible drops and save them in activeDrops.
        // setActiveDrops should always be called when a drag has just started or a
        // drag event happens while dynamicDrop is true
        setActiveDrops: function (dragElement) {
            // get dropzones and their elements that could receive the draggable
            var possibleDrops = this.collectDrops(dragElement, true);

            this.activeDrops.dropzones = possibleDrops.dropzones;
            this.activeDrops.elements  = possibleDrops.elements;
            this.activeDrops.rects     = [];

            for (var i = 0; i < this.activeDrops.dropzones.length; i++) {
                this.activeDrops.rects[i] = this.activeDrops.dropzones[i].getRect(this.activeDrops.elements[i]);
            }
        },

        getDrop: function (event, dragElement) {
            var validDrops = [];

            if (dynamicDrop) {
                this.setActiveDrops(dragElement);
            }

            // collect all dropzones and their elements which qualify for a drop
            for (var j = 0; j < this.activeDrops.dropzones.length; j++) {
                var current        = this.activeDrops.dropzones[j],
                    currentElement = this.activeDrops.elements [j],
                    rect           = this.activeDrops.rects    [j];

                validDrops.push(current.dropCheck(this.pointers[0], this.target, dragElement, currentElement, rect)
                                ? currentElement
                                : null);
            }

            // get the most appropriate dropzone based on DOM depth and order
            var dropIndex = indexOfDeepestElement(validDrops),
                dropzone  = this.activeDrops.dropzones[dropIndex] || null,
                element   = this.activeDrops.elements [dropIndex] || null;

            return {
                dropzone: dropzone,
                element: element
            };
        },

        getDropEvents: function (pointerEvent, dragEvent) {
            var dropEvents = {
                enter     : null,
                leave     : null,
                activate  : null,
                deactivate: null,
                move      : null,
                drop      : null
            };

            if (this.dropElement !== this.prevDropElement) {
                // if there was a prevDropTarget, create a dragleave event
                if (this.prevDropTarget) {
                    dropEvents.leave = {
                        target       : this.prevDropElement,
                        dropzone     : this.prevDropTarget,
                        relatedTarget: dragEvent.target,
                        draggable    : dragEvent.interactable,
                        dragEvent    : dragEvent,
                        interaction  : this,
                        timeStamp    : dragEvent.timeStamp,
                        type         : 'dragleave'
                    };

                    dragEvent.dragLeave = this.prevDropElement;
                    dragEvent.prevDropzone = this.prevDropTarget;
                }
                // if the dropTarget is not null, create a dragenter event
                if (this.dropTarget) {
                    dropEvents.enter = {
                        target       : this.dropElement,
                        dropzone     : this.dropTarget,
                        relatedTarget: dragEvent.target,
                        draggable    : dragEvent.interactable,
                        dragEvent    : dragEvent,
                        interaction  : this,
                        timeStamp    : dragEvent.timeStamp,
                        type         : 'dragenter'
                    };

                    dragEvent.dragEnter = this.dropElement;
                    dragEvent.dropzone = this.dropTarget;
                }
            }

            if (dragEvent.type === 'dragend' && this.dropTarget) {
                dropEvents.drop = {
                    target       : this.dropElement,
                    dropzone     : this.dropTarget,
                    relatedTarget: dragEvent.target,
                    draggable    : dragEvent.interactable,
                    dragEvent    : dragEvent,
                    interaction  : this,
                    timeStamp    : dragEvent.timeStamp,
                    type         : 'drop'
                };
            }
            if (dragEvent.type === 'dragstart') {
                dropEvents.activate = {
                    target       : null,
                    dropzone     : null,
                    relatedTarget: dragEvent.target,
                    draggable    : dragEvent.interactable,
                    dragEvent    : dragEvent,
                    interaction  : this,
                    timeStamp    : dragEvent.timeStamp,
                    type         : 'dropactivate'
                };
            }
            if (dragEvent.type === 'dragend') {
                dropEvents.deactivate = {
                    target       : null,
                    dropzone     : null,
                    relatedTarget: dragEvent.target,
                    draggable    : dragEvent.interactable,
                    dragEvent    : dragEvent,
                    interaction  : this,
                    timeStamp    : dragEvent.timeStamp,
                    type         : 'dropdeactivate'
                };
            }
            if (dragEvent.type === 'dragmove' && this.dropTarget) {
                dropEvents.move = {
                    target       : this.dropElement,
                    dropzone     : this.dropTarget,
                    relatedTarget: dragEvent.target,
                    draggable    : dragEvent.interactable,
                    dragEvent    : dragEvent,
                    interaction  : this,
                    dragmove     : dragEvent,
                    timeStamp    : dragEvent.timeStamp,
                    type         : 'dropmove'
                };
                dragEvent.dropzone = this.dropTarget;
            }

            return dropEvents;
        },

        currentAction: function () {
            return (this.dragging && 'drag') || (this.resizing && 'resize') || (this.gesturing && 'gesture') || null;
        },

        interacting: function () {
            return this.dragging || this.resizing || this.gesturing;
        },

        clearTargets: function () {
            if (this.target && !this.target.selector) {
                this.target = this.element = null;
            }

            this.dropTarget = this.dropElement = this.prevDropTarget = this.prevDropElement = null;
        },

        stop: function (event) {
            if (this.interacting()) {
                autoScroll.stop();
                this.matches = [];
                this.matchElements = [];

                var target = this.target;

                if (target.options.styleCursor) {
                    target._doc.documentElement.style.cursor = '';
                }

                // prevent Default only if were previously interacting
                if (event && isFunction(event.preventDefault)) {
                    this.checkAndPreventDefault(event, target, this.element);
                }

                if (this.dragging) {
                    this.activeDrops.dropzones = this.activeDrops.elements = this.activeDrops.rects = null;
                }

                this.clearTargets();
            }

            this.pointerIsDown = this.snapStatus.locked = this.dragging = this.resizing = this.gesturing = false;
            this.prepared.name = this.prevEvent = null;
            this.inertiaStatus.resumeDx = this.inertiaStatus.resumeDy = 0;

            // remove pointers if their ID isn't in this.pointerIds
            for (var i = 0; i < this.pointers.length; i++) {
                if (indexOf(this.pointerIds, getPointerId(this.pointers[i])) === -1) {
                    this.pointers.splice(i, 1);
                }
            }

            // delete interaction if it's not the only one
            if (interactions.length > 1) {
                interactions.splice(indexOf(interactions, this), 1);
            }
        },

        inertiaFrame: function () {
            var inertiaStatus = this.inertiaStatus,
                options = this.target.options[this.prepared.name].inertia,
                lambda = options.resistance,
                t = new Date().getTime() / 1000 - inertiaStatus.t0;

            if (t < inertiaStatus.te) {

                var progress =  1 - (Math.exp(-lambda * t) - inertiaStatus.lambda_v0) / inertiaStatus.one_ve_v0;

                if (inertiaStatus.modifiedXe === inertiaStatus.xe && inertiaStatus.modifiedYe === inertiaStatus.ye) {
                    inertiaStatus.sx = inertiaStatus.xe * progress;
                    inertiaStatus.sy = inertiaStatus.ye * progress;
                }
                else {
                    var quadPoint = getQuadraticCurvePoint(
                            0, 0,
                            inertiaStatus.xe, inertiaStatus.ye,
                            inertiaStatus.modifiedXe, inertiaStatus.modifiedYe,
                            progress);

                    inertiaStatus.sx = quadPoint.x;
                    inertiaStatus.sy = quadPoint.y;
                }

                this.pointerMove(inertiaStatus.startEvent, inertiaStatus.startEvent);

                inertiaStatus.i = reqFrame(this.boundInertiaFrame);
            }
            else {
                inertiaStatus.sx = inertiaStatus.modifiedXe;
                inertiaStatus.sy = inertiaStatus.modifiedYe;

                this.pointerMove(inertiaStatus.startEvent, inertiaStatus.startEvent);

                inertiaStatus.active = false;
                this.pointerEnd(inertiaStatus.startEvent, inertiaStatus.startEvent);
            }
        },

        smoothEndFrame: function () {
            var inertiaStatus = this.inertiaStatus,
                t = new Date().getTime() - inertiaStatus.t0,
                duration = this.target.options[this.prepared.name].inertia.smoothEndDuration;

            if (t < duration) {
                inertiaStatus.sx = easeOutQuad(t, 0, inertiaStatus.xe, duration);
                inertiaStatus.sy = easeOutQuad(t, 0, inertiaStatus.ye, duration);

                this.pointerMove(inertiaStatus.startEvent, inertiaStatus.startEvent);

                inertiaStatus.i = reqFrame(this.boundSmoothEndFrame);
            }
            else {
                inertiaStatus.sx = inertiaStatus.xe;
                inertiaStatus.sy = inertiaStatus.ye;

                this.pointerMove(inertiaStatus.startEvent, inertiaStatus.startEvent);

                inertiaStatus.active = false;
                inertiaStatus.smoothEnd = false;

                this.pointerEnd(inertiaStatus.startEvent, inertiaStatus.startEvent);
            }
        },

        addPointer: function (pointer) {
            var id = getPointerId(pointer),
                index = this.mouse? 0 : indexOf(this.pointerIds, id);

            if (index === -1) {
                index = this.pointerIds.length;
            }

            this.pointerIds[index] = id;
            this.pointers[index] = pointer;

            return index;
        },

        removePointer: function (pointer) {
            var id = getPointerId(pointer),
                index = this.mouse? 0 : indexOf(this.pointerIds, id);

            if (index === -1) { return; }

            if (!this.interacting()) {
                this.pointers.splice(index, 1);
            }

            this.pointerIds .splice(index, 1);
            this.downTargets.splice(index, 1);
            this.downTimes  .splice(index, 1);
            this.holdTimers .splice(index, 1);
        },

        recordPointer: function (pointer) {
            // Do not update pointers while inertia is active.
            // The inertia start event should be this.pointers[0]
            if (this.inertiaStatus.active) { return; }

            var index = this.mouse? 0: indexOf(this.pointerIds, getPointerId(pointer));

            if (index === -1) { return; }

            this.pointers[index] = pointer;
        },

        collectEventTargets: function (pointer, event, eventTarget, eventType) {
            var pointerIndex = this.mouse? 0 : indexOf(this.pointerIds, getPointerId(pointer));

            // do not fire a tap event if the pointer was moved before being lifted
            if (eventType === 'tap' && (this.pointerWasMoved
                // or if the pointerup target is different to the pointerdown target
                || !(this.downTargets[pointerIndex] && this.downTargets[pointerIndex] === eventTarget))) {
                return;
            }

            var targets = [],
                elements = [],
                element = eventTarget;

            function collectSelectors (interactable, selector, context) {
                var els = ie8MatchesSelector
                        ? context.querySelectorAll(selector)
                        : undefined;

                if (interactable._iEvents[eventType]
                    && isElement(element)
                    && inContext(interactable, element)
                    && !testIgnore(interactable, element, eventTarget)
                    && testAllow(interactable, element, eventTarget)
                    && matchesSelector(element, selector, els)) {

                    targets.push(interactable);
                    elements.push(element);
                }
            }

            while (element) {
                if (interact.isSet(element) && interact(element)._iEvents[eventType]) {
                    targets.push(interact(element));
                    elements.push(element);
                }

                interactables.forEachSelector(collectSelectors);

                element = parentElement(element);
            }

            // create the tap event even if there are no listeners so that
            // doubletap can still be created and fired
            if (targets.length || eventType === 'tap') {
                this.firePointers(pointer, event, eventTarget, targets, elements, eventType);
            }
        },

        firePointers: function (pointer, event, eventTarget, targets, elements, eventType) {
            var pointerIndex = this.mouse? 0 : indexOf(getPointerId(pointer)),
                pointerEvent = {},
                i,
                // for tap events
                interval, createNewDoubleTap;

            // if it's a doubletap then the event properties would have been
            // copied from the tap event and provided as the pointer argument
            if (eventType === 'doubletap') {
                pointerEvent = pointer;
            }
            else {
                extend(pointerEvent, event);
                if (event !== pointer) {
                    extend(pointerEvent, pointer);
                }

                pointerEvent.preventDefault           = preventOriginalDefault;
                pointerEvent.stopPropagation          = InteractEvent.prototype.stopPropagation;
                pointerEvent.stopImmediatePropagation = InteractEvent.prototype.stopImmediatePropagation;
                pointerEvent.interaction              = this;

                pointerEvent.timeStamp     = new Date().getTime();
                pointerEvent.originalEvent = event;
                pointerEvent.type          = eventType;
                pointerEvent.pointerId     = getPointerId(pointer);
                pointerEvent.pointerType   = this.mouse? 'mouse' : !supportsPointerEvent? 'touch'
                                                    : isString(pointer.pointerType)
                                                        ? pointer.pointerType
                                                        : [,,'touch', 'pen', 'mouse'][pointer.pointerType];
            }

            if (eventType === 'tap') {
                pointerEvent.dt = pointerEvent.timeStamp - this.downTimes[pointerIndex];

                interval = pointerEvent.timeStamp - this.tapTime;
                createNewDoubleTap = !!(this.prevTap && this.prevTap.type !== 'doubletap'
                       && this.prevTap.target === pointerEvent.target
                       && interval < 500);

                pointerEvent.double = createNewDoubleTap;

                this.tapTime = pointerEvent.timeStamp;
            }

            for (i = 0; i < targets.length; i++) {
                pointerEvent.currentTarget = elements[i];
                pointerEvent.interactable = targets[i];
                targets[i].fire(pointerEvent);

                if (pointerEvent.immediatePropagationStopped
                    ||(pointerEvent.propagationStopped && elements[i + 1] !== pointerEvent.currentTarget)) {
                    break;
                }
            }

            if (createNewDoubleTap) {
                var doubleTap = {};

                extend(doubleTap, pointerEvent);

                doubleTap.dt   = interval;
                doubleTap.type = 'doubletap';

                this.collectEventTargets(doubleTap, event, eventTarget, 'doubletap');

                this.prevTap = doubleTap;
            }
            else if (eventType === 'tap') {
                this.prevTap = pointerEvent;
            }
        },

        validateSelector: function (pointer, matches, matchElements) {
            for (var i = 0, len = matches.length; i < len; i++) {
                var match = matches[i],
                    matchElement = matchElements[i],
                    action = validateAction(match.getAction(pointer, this, matchElement), match);

                if (action && withinInteractionLimit(match, matchElement, action)) {
                    this.target = match;
                    this.element = matchElement;

                    return action;
                }
            }
        },

        setSnapping: function (pageCoords, status) {
            var snap = this.target.options[this.prepared.name].snap,
                targets = [],
                target,
                page,
                i;

            status = status || this.snapStatus;

            if (status.useStatusXY) {
                page = { x: status.x, y: status.y };
            }
            else {
                var origin = getOriginXY(this.target, this.element);

                page = extend({}, pageCoords);

                page.x -= origin.x;
                page.y -= origin.y;
            }

            status.realX = page.x;
            status.realY = page.y;

            page.x = page.x - this.inertiaStatus.resumeDx;
            page.y = page.y - this.inertiaStatus.resumeDy;

            var len = snap.targets? snap.targets.length : 0;

            for (var relIndex = 0; relIndex < this.snapOffsets.length; relIndex++) {
                var relative = {
                    x: page.x - this.snapOffsets[relIndex].x,
                    y: page.y - this.snapOffsets[relIndex].y
                };

                for (i = 0; i < len; i++) {
                    if (isFunction(snap.targets[i])) {
                        target = snap.targets[i](relative.x, relative.y, this);
                    }
                    else {
                        target = snap.targets[i];
                    }

                    if (!target) { continue; }

                    targets.push({
                        x: isNumber(target.x) ? (target.x + this.snapOffsets[relIndex].x) : relative.x,
                        y: isNumber(target.y) ? (target.y + this.snapOffsets[relIndex].y) : relative.y,

                        range: isNumber(target.range)? target.range: snap.range
                    });
                }
            }

            var closest = {
                    target: null,
                    inRange: false,
                    distance: 0,
                    range: 0,
                    dx: 0,
                    dy: 0
                };

            for (i = 0, len = targets.length; i < len; i++) {
                target = targets[i];

                var range = target.range,
                    dx = target.x - page.x,
                    dy = target.y - page.y,
                    distance = hypot(dx, dy),
                    inRange = distance <= range;

                // Infinite targets count as being out of range
                // compared to non infinite ones that are in range
                if (range === Infinity && closest.inRange && closest.range !== Infinity) {
                    inRange = false;
                }

                if (!closest.target || (inRange
                    // is the closest target in range?
                    ? (closest.inRange && range !== Infinity
                        // the pointer is relatively deeper in this target
                        ? distance / range < closest.distance / closest.range
                        // this target has Infinite range and the closest doesn't
                        : (range === Infinity && closest.range !== Infinity)
                            // OR this target is closer that the previous closest
                            || distance < closest.distance)
                    // The other is not in range and the pointer is closer to this target
                    : (!closest.inRange && distance < closest.distance))) {

                    if (range === Infinity) {
                        inRange = true;
                    }

                    closest.target = target;
                    closest.distance = distance;
                    closest.range = range;
                    closest.inRange = inRange;
                    closest.dx = dx;
                    closest.dy = dy;

                    status.range = range;
                }
            }

            var snapChanged;

            if (closest.target) {
                snapChanged = (status.snappedX !== closest.target.x || status.snappedY !== closest.target.y);

                status.snappedX = closest.target.x;
                status.snappedY = closest.target.y;
            }
            else {
                snapChanged = true;

                status.snappedX = NaN;
                status.snappedY = NaN;
            }

            status.dx = closest.dx;
            status.dy = closest.dy;

            status.changed = (snapChanged || (closest.inRange && !status.locked));
            status.locked = closest.inRange;

            return status;
        },

        setRestriction: function (pageCoords, status) {
            var target = this.target,
                restrict = target && target.options[this.prepared.name].restrict,
                restriction = restrict && restrict.restriction,
                page;

            if (!restriction) {
                return status;
            }

            status = status || this.restrictStatus;

            page = status.useStatusXY
                    ? page = { x: status.x, y: status.y }
                    : page = extend({}, pageCoords);

            if (status.snap && status.snap.locked) {
                page.x += status.snap.dx || 0;
                page.y += status.snap.dy || 0;
            }

            page.x -= this.inertiaStatus.resumeDx;
            page.y -= this.inertiaStatus.resumeDy;

            status.dx = 0;
            status.dy = 0;
            status.restricted = false;

            var rect, restrictedX, restrictedY;

            if (isString(restriction)) {
                if (restriction === 'parent') {
                    restriction = parentElement(this.element);
                }
                else if (restriction === 'self') {
                    restriction = target.getRect(this.element);
                }
                else {
                    restriction = closest(this.element, restriction);
                }

                if (!restriction) { return status; }
            }

            if (isFunction(restriction)) {
                restriction = restriction(page.x, page.y, this.element);
            }

            if (isElement(restriction)) {
                restriction = getElementRect(restriction);
            }

            rect = restriction;

            if (!restriction) {
                restrictedX = page.x;
                restrictedY = page.y;
            }
            // object is assumed to have
            // x, y, width, height or
            // left, top, right, bottom
            else if ('x' in restriction && 'y' in restriction) {
                restrictedX = Math.max(Math.min(rect.x + rect.width  - this.restrictOffset.right , page.x), rect.x + this.restrictOffset.left);
                restrictedY = Math.max(Math.min(rect.y + rect.height - this.restrictOffset.bottom, page.y), rect.y + this.restrictOffset.top );
            }
            else {
                restrictedX = Math.max(Math.min(rect.right  - this.restrictOffset.right , page.x), rect.left + this.restrictOffset.left);
                restrictedY = Math.max(Math.min(rect.bottom - this.restrictOffset.bottom, page.y), rect.top  + this.restrictOffset.top );
            }

            status.dx = restrictedX - page.x;
            status.dy = restrictedY - page.y;

            status.changed = status.restrictedX !== restrictedX || status.restrictedY !== restrictedY;
            status.restricted = !!(status.dx || status.dy);

            status.restrictedX = restrictedX;
            status.restrictedY = restrictedY;

            return status;
        },

        checkAndPreventDefault: function (event, interactable, element) {
            if (!(interactable = interactable || this.target)) { return; }

            var options = interactable.options,
                prevent = options.preventDefault;

            if (prevent === 'auto' && element && !/^input$|^textarea$/i.test(element.nodeName)) {
                // do not preventDefault on pointerdown if the prepared action is a drag
                // and dragging can only start from a certain direction - this allows
                // a touch to pan the viewport if a drag isn't in the right direction
                if (/down|start/i.test(event.type)
                    && this.prepared.name === 'drag' && options.drag.axis !== 'xy') {

                    return;
                }

                // with manualStart, only preventDefault while interacting
                if (options[this.prepared.name] && options[this.prepared.name].manualStart
                    && !this.interacting()) {
                    return;
                }

                event.preventDefault();
                return;
            }

            if (prevent === 'always') {
                event.preventDefault();
                return;
            }
        },

        calcInertia: function (status) {
            var inertiaOptions = this.target.options[this.prepared.name].inertia,
                lambda = inertiaOptions.resistance,
                inertiaDur = -Math.log(inertiaOptions.endSpeed / status.v0) / lambda;

            status.x0 = this.prevEvent.pageX;
            status.y0 = this.prevEvent.pageY;
            status.t0 = status.startEvent.timeStamp / 1000;
            status.sx = status.sy = 0;

            status.modifiedXe = status.xe = (status.vx0 - inertiaDur) / lambda;
            status.modifiedYe = status.ye = (status.vy0 - inertiaDur) / lambda;
            status.te = inertiaDur;

            status.lambda_v0 = lambda / status.v0;
            status.one_ve_v0 = 1 - inertiaOptions.endSpeed / status.v0;
        },

        _updateEventTargets: function (target, currentTarget) {
            this._eventTarget    = target;
            this._curEventTarget = currentTarget;
        }

    };

    function getInteractionFromPointer (pointer, eventType, eventTarget) {
        var i = 0, len = interactions.length,
            mouseEvent = (/mouse/i.test(pointer.pointerType || eventType)
                          // MSPointerEvent.MSPOINTER_TYPE_MOUSE
                          || pointer.pointerType === 4),
            interaction;

        var id = getPointerId(pointer);

        // try to resume inertia with a new pointer
        if (/down|start/i.test(eventType)) {
            for (i = 0; i < len; i++) {
                interaction = interactions[i];

                var element = eventTarget;

                if (interaction.inertiaStatus.active && interaction.target.options[interaction.prepared.name].inertia.allowResume
                    && (interaction.mouse === mouseEvent)) {
                    while (element) {
                        // if the element is the interaction element
                        if (element === interaction.element) {
                            // update the interaction's pointer
                            if (interaction.pointers[0]) {
                                interaction.removePointer(interaction.pointers[0]);
                            }
                            interaction.addPointer(pointer);

                            return interaction;
                        }
                        element = parentElement(element);
                    }
                }
            }
        }

        // if it's a mouse interaction
        if (mouseEvent || !(supportsTouch || supportsPointerEvent)) {

            // find a mouse interaction that's not in inertia phase
            for (i = 0; i < len; i++) {
                if (interactions[i].mouse && !interactions[i].inertiaStatus.active) {
                    return interactions[i];
                }
            }

            // find any interaction specifically for mouse.
            // if the eventType is a mousedown, and inertia is active
            // ignore the interaction
            for (i = 0; i < len; i++) {
                if (interactions[i].mouse && !(/down/.test(eventType) && interactions[i].inertiaStatus.active)) {
                    return interaction;
                }
            }

            // create a new interaction for mouse
            interaction = new Interaction();
            interaction.mouse = true;

            return interaction;
        }

        // get interaction that has this pointer
        for (i = 0; i < len; i++) {
            if (contains(interactions[i].pointerIds, id)) {
                return interactions[i];
            }
        }

        // at this stage, a pointerUp should not return an interaction
        if (/up|end|out/i.test(eventType)) {
            return null;
        }

        // get first idle interaction
        for (i = 0; i < len; i++) {
            interaction = interactions[i];

            if ((!interaction.prepared.name || (interaction.target.options.gesture.enabled))
                && !interaction.interacting()
                && !(!mouseEvent && interaction.mouse)) {

                interaction.addPointer(pointer);

                return interaction;
            }
        }

        return new Interaction();
    }

    function doOnInteractions (method) {
        return (function (event) {
            var interaction,
                eventTarget = getActualElement(event.path
                                               ? event.path[0]
                                               : event.target),
                curEventTarget = getActualElement(event.currentTarget),
                i;

            if (supportsTouch && /touch/.test(event.type)) {
                prevTouchTime = new Date().getTime();

                for (i = 0; i < event.changedTouches.length; i++) {
                    var pointer = event.changedTouches[i];

                    interaction = getInteractionFromPointer(pointer, event.type, eventTarget);

                    if (!interaction) { continue; }

                    interaction._updateEventTargets(eventTarget, curEventTarget);

                    interaction[method](pointer, event, eventTarget, curEventTarget);
                }
            }
            else {
                if (!supportsPointerEvent && /mouse/.test(event.type)) {
                    // ignore mouse events while touch interactions are active
                    for (i = 0; i < interactions.length; i++) {
                        if (!interactions[i].mouse && interactions[i].pointerIsDown) {
                            return;
                        }
                    }

                    // try to ignore mouse events that are simulated by the browser
                    // after a touch event
                    if (new Date().getTime() - prevTouchTime < 500) {
                        return;
                    }
                }

                interaction = getInteractionFromPointer(event, event.type, eventTarget);

                if (!interaction) { return; }

                interaction._updateEventTargets(eventTarget, curEventTarget);

                interaction[method](event, event, eventTarget, curEventTarget);
            }
        });
    }

    function InteractEvent (interaction, event, action, phase, element, related) {
        var client,
            page,
            target      = interaction.target,
            snapStatus  = interaction.snapStatus,
            restrictStatus  = interaction.restrictStatus,
            pointers    = interaction.pointers,
            deltaSource = (target && target.options || defaultOptions).deltaSource,
            sourceX     = deltaSource + 'X',
            sourceY     = deltaSource + 'Y',
            options     = target? target.options: defaultOptions,
            origin      = getOriginXY(target, element),
            starting    = phase === 'start',
            ending      = phase === 'end',
            coords      = starting? interaction.startCoords : interaction.curCoords;

        element = element || interaction.element;

        page   = extend({}, coords.page);
        client = extend({}, coords.client);

        page.x -= origin.x;
        page.y -= origin.y;

        client.x -= origin.x;
        client.y -= origin.y;

        var relativePoints = options[action].snap && options[action].snap.relativePoints ;

        if (checkSnap(target, action) && !(starting && relativePoints && relativePoints.length)) {
            this.snap = {
                range  : snapStatus.range,
                locked : snapStatus.locked,
                x      : snapStatus.snappedX,
                y      : snapStatus.snappedY,
                realX  : snapStatus.realX,
                realY  : snapStatus.realY,
                dx     : snapStatus.dx,
                dy     : snapStatus.dy
            };

            if (snapStatus.locked) {
                page.x += snapStatus.dx;
                page.y += snapStatus.dy;
                client.x += snapStatus.dx;
                client.y += snapStatus.dy;
            }
        }

        if (checkRestrict(target, action) && !(starting && options[action].restrict.elementRect) && restrictStatus.restricted) {
            page.x += restrictStatus.dx;
            page.y += restrictStatus.dy;
            client.x += restrictStatus.dx;
            client.y += restrictStatus.dy;

            this.restrict = {
                dx: restrictStatus.dx,
                dy: restrictStatus.dy
            };
        }

        this.pageX     = page.x;
        this.pageY     = page.y;
        this.clientX   = client.x;
        this.clientY   = client.y;

        this.x0        = interaction.startCoords.page.x;
        this.y0        = interaction.startCoords.page.y;
        this.clientX0  = interaction.startCoords.client.x;
        this.clientY0  = interaction.startCoords.client.y;
        this.ctrlKey   = event.ctrlKey;
        this.altKey    = event.altKey;
        this.shiftKey  = event.shiftKey;
        this.metaKey   = event.metaKey;
        this.button    = event.button;
        this.target    = element;
        this.t0        = interaction.downTimes[0];
        this.type      = action + (phase || '');

        this.interaction = interaction;
        this.interactable = target;

        var inertiaStatus = interaction.inertiaStatus;

        if (inertiaStatus.active) {
            this.detail = 'inertia';
        }

        if (related) {
            this.relatedTarget = related;
        }

        // end event dx, dy is difference between start and end points
        if (ending) {
            if (deltaSource === 'client') {
                this.dx = client.x - interaction.startCoords.client.x;
                this.dy = client.y - interaction.startCoords.client.y;
            }
            else {
                this.dx = page.x - interaction.startCoords.page.x;
                this.dy = page.y - interaction.startCoords.page.y;
            }
        }
        else if (starting) {
            this.dx = 0;
            this.dy = 0;
        }
        // copy properties from previousmove if starting inertia
        else if (phase === 'inertiastart') {
            this.dx = interaction.prevEvent.dx;
            this.dy = interaction.prevEvent.dy;
        }
        else {
            if (deltaSource === 'client') {
                this.dx = client.x - interaction.prevEvent.clientX;
                this.dy = client.y - interaction.prevEvent.clientY;
            }
            else {
                this.dx = page.x - interaction.prevEvent.pageX;
                this.dy = page.y - interaction.prevEvent.pageY;
            }
        }
        if (interaction.prevEvent && interaction.prevEvent.detail === 'inertia'
            && !inertiaStatus.active
            && options[action].inertia && options[action].inertia.zeroResumeDelta) {

            inertiaStatus.resumeDx += this.dx;
            inertiaStatus.resumeDy += this.dy;

            this.dx = this.dy = 0;
        }

        if (action === 'resize' && interaction.resizeAxes) {
            if (options.resize.square) {
                if (interaction.resizeAxes === 'y') {
                    this.dx = this.dy;
                }
                else {
                    this.dy = this.dx;
                }
                this.axes = 'xy';
            }
            else {
                this.axes = interaction.resizeAxes;

                if (interaction.resizeAxes === 'x') {
                    this.dy = 0;
                }
                else if (interaction.resizeAxes === 'y') {
                    this.dx = 0;
                }
            }
        }
        else if (action === 'gesture') {
            this.touches = [pointers[0], pointers[1]];

            if (starting) {
                this.distance = touchDistance(pointers, deltaSource);
                this.box      = touchBBox(pointers);
                this.scale    = 1;
                this.ds       = 0;
                this.angle    = touchAngle(pointers, undefined, deltaSource);
                this.da       = 0;
            }
            else if (ending || event instanceof InteractEvent) {
                this.distance = interaction.prevEvent.distance;
                this.box      = interaction.prevEvent.box;
                this.scale    = interaction.prevEvent.scale;
                this.ds       = this.scale - 1;
                this.angle    = interaction.prevEvent.angle;
                this.da       = this.angle - interaction.gesture.startAngle;
            }
            else {
                this.distance = touchDistance(pointers, deltaSource);
                this.box      = touchBBox(pointers);
                this.scale    = this.distance / interaction.gesture.startDistance;
                this.angle    = touchAngle(pointers, interaction.gesture.prevAngle, deltaSource);

                this.ds = this.scale - interaction.gesture.prevScale;
                this.da = this.angle - interaction.gesture.prevAngle;
            }
        }

        if (starting) {
            this.timeStamp = interaction.downTimes[0];
            this.dt        = 0;
            this.duration  = 0;
            this.speed     = 0;
            this.velocityX = 0;
            this.velocityY = 0;
        }
        else if (phase === 'inertiastart') {
            this.timeStamp = interaction.prevEvent.timeStamp;
            this.dt        = interaction.prevEvent.dt;
            this.duration  = interaction.prevEvent.duration;
            this.speed     = interaction.prevEvent.speed;
            this.velocityX = interaction.prevEvent.velocityX;
            this.velocityY = interaction.prevEvent.velocityY;
        }
        else {
            this.timeStamp = new Date().getTime();
            this.dt        = this.timeStamp - interaction.prevEvent.timeStamp;
            this.duration  = this.timeStamp - interaction.downTimes[0];

            if (event instanceof InteractEvent) {
                var dx = this[sourceX] - interaction.prevEvent[sourceX],
                    dy = this[sourceY] - interaction.prevEvent[sourceY],
                    dt = this.dt / 1000;

                this.speed = hypot(dx, dy) / dt;
                this.velocityX = dx / dt;
                this.velocityY = dy / dt;
            }
            // if normal move or end event, use previous user event coords
            else {
                // speed and velocity in pixels per second
                this.speed = interaction.pointerDelta[deltaSource].speed;
                this.velocityX = interaction.pointerDelta[deltaSource].vx;
                this.velocityY = interaction.pointerDelta[deltaSource].vy;
            }
        }

        if ((ending || phase === 'inertiastart')
            && interaction.prevEvent.speed > 600 && this.timeStamp - interaction.prevEvent.timeStamp < 150) {

            var angle = 180 * Math.atan2(interaction.prevEvent.velocityY, interaction.prevEvent.velocityX) / Math.PI,
                overlap = 22.5;

            if (angle < 0) {
                angle += 360;
            }

            var left = 135 - overlap <= angle && angle < 225 + overlap,
                up   = 225 - overlap <= angle && angle < 315 + overlap,

                right = !left && (315 - overlap <= angle || angle <  45 + overlap),
                down  = !up   &&   45 - overlap <= angle && angle < 135 + overlap;

            this.swipe = {
                up   : up,
                down : down,
                left : left,
                right: right,
                angle: angle,
                speed: interaction.prevEvent.speed,
                velocity: {
                    x: interaction.prevEvent.velocityX,
                    y: interaction.prevEvent.velocityY
                }
            };
        }
    }

    InteractEvent.prototype = {
        preventDefault: blank,
        stopImmediatePropagation: function () {
            this.immediatePropagationStopped = this.propagationStopped = true;
        },
        stopPropagation: function () {
            this.propagationStopped = true;
        }
    };

    function preventOriginalDefault () {
        this.originalEvent.preventDefault();
    }

    function getActionCursor (action) {
        var cursor = '';

        if (action.name === 'drag') {
            cursor =  actionCursors.drag;
        }
        if (action.name === 'resize') {
            if (action.axis) {
                cursor =  actionCursors[action.name + action.axis];
            }
            else if (action.edges) {
                var cursorKey = 'resize',
                    edgeNames = ['top', 'bottom', 'left', 'right'];

                for (var i = 0; i < 4; i++) {
                    if (action.edges[edgeNames[i]]) {
                        cursorKey += edgeNames[i];
                    }
                }

                cursor = actionCursors[cursorKey];
            }
        }

        return cursor;
    }

    function checkResizeEdge (name, value, page, element, interactableElement, rect) {
        // false, '', undefined, null
        if (!value) { return false; }

        // true value, use pointer coords and element rect
        if (value === true) {
            // if dimensions are negative, "switch" edges
            var width = isNumber(rect.width)? rect.width : rect.right - rect.left,
                height = isNumber(rect.height)? rect.height : rect.bottom - rect.top;

            if (width < 0) {
                if      (name === 'left' ) { name = 'right'; }
                else if (name === 'right') { name = 'left' ; }
            }
            if (height < 0) {
                if      (name === 'top'   ) { name = 'bottom'; }
                else if (name === 'bottom') { name = 'top'   ; }
            }

            if (name === 'left'  ) { return page.x < ((width  >= 0? rect.left: rect.right ) + margin); }
            if (name === 'top'   ) { return page.y < ((height >= 0? rect.top : rect.bottom) + margin); }

            if (name === 'right' ) { return page.x > ((width  >= 0? rect.right : rect.left) - margin); }
            if (name === 'bottom') { return page.y > ((height >= 0? rect.bottom: rect.top ) - margin); }
        }

        // the remaining checks require an element
        if (!isElement(element)) { return false; }

        return isElement(value)
                    // the value is an element to use as a resize handle
                    ? value === element
                    // otherwise check if element matches value as selector
                    : matchesUpTo(element, value, interactableElement);
    }

    function defaultActionChecker (pointer, interaction, element) {
        var rect = this.getRect(element),
            shouldResize = false,
            action = null,
            resizeAxes = null,
            resizeEdges,
            page = extend({}, interaction.curCoords.page),
            options = this.options;

        if (!rect) { return null; }

        if (actionIsEnabled.resize && options.resize.enabled) {
            var resizeOptions = options.resize;

            resizeEdges = {
                left: false, right: false, top: false, bottom: false
            };

            // if using resize.edges
            if (isObject(resizeOptions.edges)) {
                for (var edge in resizeEdges) {
                    resizeEdges[edge] = checkResizeEdge(edge,
                                                        resizeOptions.edges[edge],
                                                        page,
                                                        interaction._eventTarget,
                                                        element,
                                                        rect);
                }

                resizeEdges.left = resizeEdges.left && !resizeEdges.right;
                resizeEdges.top  = resizeEdges.top  && !resizeEdges.bottom;

                shouldResize = resizeEdges.left || resizeEdges.right || resizeEdges.top || resizeEdges.bottom;
            }
            else {
                var right  = options.resize.axis !== 'y' && page.x > (rect.right  - margin),
                    bottom = options.resize.axis !== 'x' && page.y > (rect.bottom - margin);

                shouldResize = right || bottom;
                resizeAxes = (right? 'x' : '') + (bottom? 'y' : '');
            }
        }

        action = shouldResize
            ? 'resize'
            : actionIsEnabled.drag && options.drag.enabled
                ? 'drag'
                : null;

        if (actionIsEnabled.gesture
            && interaction.pointerIds.length >=2
            && !(interaction.dragging || interaction.resizing)) {
            action = 'gesture';
        }

        if (action) {
            return {
                name: action,
                axis: resizeAxes,
                edges: resizeEdges
            };
        }

        return null;
    }

    // Check if action is enabled globally and the current target supports it
    // If so, return the validated action. Otherwise, return null
    function validateAction (action, interactable) {
        if (!isObject(action)) { return null; }

        var actionName = action.name,
            options = interactable.options;

        if ((  (actionName  === 'resize'   && options.resize.enabled )
            || (actionName      === 'drag'     && options.drag.enabled  )
            || (actionName      === 'gesture'  && options.gesture.enabled))
            && actionIsEnabled[actionName]) {

            if (actionName === 'resize' || actionName === 'resizeyx') {
                actionName = 'resizexy';
            }

            return action;
        }
        return null;
    }

    var listeners = {},
        interactionListeners = [
            'dragStart', 'dragMove', 'resizeStart', 'resizeMove', 'gestureStart', 'gestureMove',
            'pointerOver', 'pointerOut', 'pointerHover', 'selectorDown',
            'pointerDown', 'pointerMove', 'pointerUp', 'pointerCancel', 'pointerEnd',
            'addPointer', 'removePointer', 'recordPointer',
        ];

    for (var i = 0, len = interactionListeners.length; i < len; i++) {
        var name = interactionListeners[i];

        listeners[name] = doOnInteractions(name);
    }

    // bound to the interactable context when a DOM event
    // listener is added to a selector interactable
    function delegateListener (event, useCapture) {
        var fakeEvent = {},
            delegated = delegatedEvents[event.type],
            eventTarget = getActualElement(event.path
                                           ? event.path[0]
                                           : event.target),
            element = eventTarget;

        useCapture = useCapture? true: false;

        // duplicate the event so that currentTarget can be changed
        for (var prop in event) {
            fakeEvent[prop] = event[prop];
        }

        fakeEvent.originalEvent = event;
        fakeEvent.preventDefault = preventOriginalDefault;

        // climb up document tree looking for selector matches
        while (isElement(element)) {
            for (var i = 0; i < delegated.selectors.length; i++) {
                var selector = delegated.selectors[i],
                    context = delegated.contexts[i];

                if (matchesSelector(element, selector)
                    && nodeContains(context, eventTarget)
                    && nodeContains(context, element)) {

                    var listeners = delegated.listeners[i];

                    fakeEvent.currentTarget = element;

                    for (var j = 0; j < listeners.length; j++) {
                        if (listeners[j][1] === useCapture) {
                            listeners[j][0](fakeEvent);
                        }
                    }
                }
            }

            element = parentElement(element);
        }
    }

    function delegateUseCapture (event) {
        return delegateListener.call(this, event, true);
    }

    interactables.indexOfElement = function indexOfElement (element, context) {
        context = context || document;

        for (var i = 0; i < this.length; i++) {
            var interactable = this[i];

            if ((interactable.selector === element
                && (interactable._context === context))
                || (!interactable.selector && interactable._element === element)) {

                return i;
            }
        }
        return -1;
    };

    interactables.get = function interactableGet (element, options) {
        return this[this.indexOfElement(element, options && options.context)];
    };

    interactables.forEachSelector = function (callback) {
        for (var i = 0; i < this.length; i++) {
            var interactable = this[i];

            if (!interactable.selector) {
                continue;
            }

            var ret = callback(interactable, interactable.selector, interactable._context, i, this);

            if (ret !== undefined) {
                return ret;
            }
        }
    };

    /*\
     * interact
     [ method ]
     *
     * The methods of this variable can be used to set elements as
     * interactables and also to change various default settings.
     *
     * Calling it as a function and passing an element or a valid CSS selector
     * string returns an Interactable object which has various methods to
     * configure it.
     *
     - element (Element | string) The HTML or SVG Element to interact with or CSS selector
     = (object) An @Interactable
     *
     > Usage
     | interact(document.getElementById('draggable')).draggable(true);
     |
     | var rectables = interact('rect');
     | rectables
     |     .gesturable(true)
     |     .on('gesturemove', function (event) {
     |         // something cool...
     |     })
     |     .autoScroll(true);
    \*/
    function interact (element, options) {
        return interactables.get(element, options) || new Interactable(element, options);
    }

    /*\
     * Interactable
     [ property ]
     **
     * Object type returned by @interact
    \*/
    function Interactable (element, options) {
        this._element = element;
        this._iEvents = this._iEvents || {};

        var _window;

        if (trySelector(element)) {
            this.selector = element;

            var context = options && options.context;

            _window = context? getWindow(context) : window;

            if (context && (_window.Node
                    ? context instanceof _window.Node
                    : (isElement(context) || context === _window.document))) {

                this._context = context;
            }
        }
        else {
            _window = getWindow(element);

            if (isElement(element, _window)) {

                if (PointerEvent) {
                    events.add(this._element, pEventTypes.down, listeners.pointerDown );
                    events.add(this._element, pEventTypes.move, listeners.pointerHover);
                }
                else {
                    events.add(this._element, 'mousedown' , listeners.pointerDown );
                    events.add(this._element, 'mousemove' , listeners.pointerHover);
                    events.add(this._element, 'touchstart', listeners.pointerDown );
                    events.add(this._element, 'touchmove' , listeners.pointerHover);
                }
            }
        }

        this._doc = _window.document;

        if (!contains(documents, this._doc)) {
            listenToDocument(this._doc);
        }

        interactables.push(this);

        this.set(options);
    }

    Interactable.prototype = {
        setOnEvents: function (action, phases) {
            if (action === 'drop') {
                if (isFunction(phases.ondrop)          ) { this.ondrop           = phases.ondrop          ; }
                if (isFunction(phases.ondropactivate)  ) { this.ondropactivate   = phases.ondropactivate  ; }
                if (isFunction(phases.ondropdeactivate)) { this.ondropdeactivate = phases.ondropdeactivate; }
                if (isFunction(phases.ondragenter)     ) { this.ondragenter      = phases.ondragenter     ; }
                if (isFunction(phases.ondragleave)     ) { this.ondragleave      = phases.ondragleave     ; }
                if (isFunction(phases.ondropmove)      ) { this.ondropmove       = phases.ondropmove      ; }
            }
            else {
                action = 'on' + action;

                if (isFunction(phases.onstart)       ) { this[action + 'start'         ] = phases.onstart         ; }
                if (isFunction(phases.onmove)        ) { this[action + 'move'          ] = phases.onmove          ; }
                if (isFunction(phases.onend)         ) { this[action + 'end'           ] = phases.onend           ; }
                if (isFunction(phases.oninertiastart)) { this[action + 'inertiastart'  ] = phases.oninertiastart  ; }
            }

            return this;
        },

        /*\
         * Interactable.draggable
         [ method ]
         *
         * Gets or sets whether drag actions can be performed on the
         * Interactable
         *
         = (boolean) Indicates if this can be the target of drag events
         | var isDraggable = interact('ul li').draggable();
         * or
         - options (boolean | object) #optional true/false or An object with event listeners to be fired on drag events (object makes the Interactable draggable)
         = (object) This Interactable
         | interact(element).draggable({
         |     onstart: function (event) {},
         |     onmove : function (event) {},
         |     onend  : function (event) {},
         |
         |     // the axis in which the first movement must be
         |     // for the drag sequence to start
         |     // 'xy' by default - any direction
         |     axis: 'x' || 'y' || 'xy',
         |
         |     // max number of drags that can happen concurrently
         |     // with elements of this Interactable. Infinity by default
         |     max: Infinity,
         |
         |     // max number of drags that can target the same element+Interactable
         |     // 1 by default
         |     maxPerElement: 2
         | });
        \*/
        draggable: function (options) {
            if (isObject(options)) {
                this.options.drag.enabled = options.enabled === false? false: true;
                this.setPerAction('drag', options);
                this.setOnEvents('drag', options);

                if (/^x$|^y$|^xy$/.test(options.axis)) {
                    this.options.drag.axis = options.axis;
                }
                else if (options.axis === null) {
                    delete this.options.drag.axis;
                }

                return this;
            }

            if (isBool(options)) {
                this.options.drag.enabled = options;

                return this;
            }

            return this.options.drag;
        },

        setPerAction: function (action, options) {
            // for all the default per-action options
            for (var option in options) {
                // if this option exists for this action
                if (option in defaultOptions[action]) {
                    // if the option in the options arg is an object value
                    if (isObject(options[option])) {
                        // duplicate the object
                        this.options[action][option] = extend(this.options[action][option] || {}, options[option]);

                        if (isObject(defaultOptions.perAction[option]) && 'enabled' in defaultOptions.perAction[option]) {
                            this.options[action][option].enabled = options[option].enabled === false? false : true;
                        }
                    }
                    else if (isBool(options[option]) && isObject(defaultOptions.perAction[option])) {
                        this.options[action][option].enabled = options[option];
                    }
                    else if (options[option] !== undefined) {
                        // or if it's not undefined, do a plain assignment
                        this.options[action][option] = options[option];
                    }
                }
            }
        },

        /*\
         * Interactable.dropzone
         [ method ]
         *
         * Returns or sets whether elements can be dropped onto this
         * Interactable to trigger drop events
         *
         * Dropzones can receive the following events:
         *  - `dropactivate` and `dropdeactivate` when an acceptable drag starts and ends
         *  - `dragenter` and `dragleave` when a draggable enters and leaves the dropzone
         *  - `dragmove` when a draggable that has entered the dropzone is moved
         *  - `drop` when a draggable is dropped into this dropzone
         *
         *  Use the `accept` option to allow only elements that match the given CSS selector or element.
         *
         *  Use the `overlap` option to set how drops are checked for. The allowed values are:
         *   - `'pointer'`, the pointer must be over the dropzone (default)
         *   - `'center'`, the draggable element's center must be over the dropzone
         *   - a number from 0-1 which is the `(intersection area) / (draggable area)`.
         *       e.g. `0.5` for drop to happen when half of the area of the
         *       draggable is over the dropzone
         *
         - options (boolean | object | null) #optional The new value to be set.
         | interact('.drop').dropzone({
         |   accept: '.can-drop' || document.getElementById('single-drop'),
         |   overlap: 'pointer' || 'center' || zeroToOne
         | }
         = (boolean | object) The current setting or this Interactable
        \*/
        dropzone: function (options) {
            if (isObject(options)) {
                this.options.drop.enabled = options.enabled === false? false: true;
                this.setOnEvents('drop', options);
                this.accept(options.accept);

                if (/^(pointer|center)$/.test(options.overlap)) {
                    this.options.drop.overlap = options.overlap;
                }
                else if (isNumber(options.overlap)) {
                    this.options.drop.overlap = Math.max(Math.min(1, options.overlap), 0);
                }

                return this;
            }

            if (isBool(options)) {
                this.options.drop.enabled = options;

                return this;
            }

            return this.options.drop;
        },

        dropCheck: function (pointer, draggable, draggableElement, dropElement, rect) {
            var dropped = false;

            // if the dropzone has no rect (eg. display: none)
            // call the custom dropChecker or just return false
            if (!(rect = rect || this.getRect(dropElement))) {
                return (this.options.dropChecker
                    ? this.options.dropChecker(pointer, dropped, this, dropElement, draggable, draggableElement)
                    : false);
            }

            var dropOverlap = this.options.drop.overlap;

            if (dropOverlap === 'pointer') {
                var page = getPageXY(pointer),
                    origin = getOriginXY(draggable, draggableElement),
                    horizontal,
                    vertical;

                page.x += origin.x;
                page.y += origin.y;

                horizontal = (page.x > rect.left) && (page.x < rect.right);
                vertical   = (page.y > rect.top ) && (page.y < rect.bottom);

                dropped = horizontal && vertical;
            }

            var dragRect = draggable.getRect(draggableElement);

            if (dropOverlap === 'center') {
                var cx = dragRect.left + dragRect.width  / 2,
                    cy = dragRect.top  + dragRect.height / 2;

                dropped = cx >= rect.left && cx <= rect.right && cy >= rect.top && cy <= rect.bottom;
            }

            if (isNumber(dropOverlap)) {
                var overlapArea  = (Math.max(0, Math.min(rect.right , dragRect.right ) - Math.max(rect.left, dragRect.left))
                                  * Math.max(0, Math.min(rect.bottom, dragRect.bottom) - Math.max(rect.top , dragRect.top ))),
                    overlapRatio = overlapArea / (dragRect.width * dragRect.height);

                dropped = overlapRatio >= dropOverlap;
            }

            if (this.options.dropChecker) {
                dropped = this.options.dropChecker(pointer, dropped, this, dropElement, draggable, draggableElement);
            }

            return dropped;
        },

        /*\
         * Interactable.dropChecker
         [ method ]
         *
         * Gets or sets the function used to check if a dragged element is
         * over this Interactable. See @Interactable.dropCheck.
         *
         - checker (function) #optional
         * The checker is a function which takes a mouseUp/touchEnd event as a
         * parameter and returns true or false to indicate if the the current
         * draggable can be dropped into this Interactable
         *
         - checker (function) The function that will be called when checking for a drop
         * The checker function takes the following arguments:
         *
         - pointer (MouseEvent | PointerEvent | Touch) The pointer/event that ends a drag
         - dropped (boolean) The value from the default drop check
         - dropzone (Interactable) The dropzone interactable
         - dropElement (Element) The dropzone element
         - draggable (Interactable) The Interactable being dragged
         - draggableElement (Element) The actual element that's being dragged
         *
         = (Function | Interactable) The checker function or this Interactable
        \*/
        dropChecker: function (checker) {
            if (isFunction(checker)) {
                this.options.dropChecker = checker;

                return this;
            }
            if (checker === null) {
                delete this.options.getRect;

                return this;
            }

            return this.options.dropChecker;
        },

        /*\
         * Interactable.accept
         [ method ]
         *
         * Deprecated. add an `accept` property to the options object passed to
         * @Interactable.dropzone instead.
         *
         * Gets or sets the Element or CSS selector match that this
         * Interactable accepts if it is a dropzone.
         *
         - newValue (Element | string | null) #optional
         * If it is an Element, then only that element can be dropped into this dropzone.
         * If it is a string, the element being dragged must match it as a selector.
         * If it is null, the accept options is cleared - it accepts any element.
         *
         = (string | Element | null | Interactable) The current accept option if given `undefined` or this Interactable
        \*/
        accept: function (newValue) {
            if (isElement(newValue)) {
                this.options.drop.accept = newValue;

                return this;
            }

            // test if it is a valid CSS selector
            if (trySelector(newValue)) {
                this.options.drop.accept = newValue;

                return this;
            }

            if (newValue === null) {
                delete this.options.drop.accept;

                return this;
            }

            return this.options.drop.accept;
        },

        /*\
         * Interactable.resizable
         [ method ]
         *
         * Gets or sets whether resize actions can be performed on the
         * Interactable
         *
         = (boolean) Indicates if this can be the target of resize elements
         | var isResizeable = interact('input[type=text]').resizable();
         * or
         - options (boolean | object) #optional true/false or An object with event listeners to be fired on resize events (object makes the Interactable resizable)
         = (object) This Interactable
         | interact(element).resizable({
         |     onstart: function (event) {},
         |     onmove : function (event) {},
         |     onend  : function (event) {},
         |
         |     edges: {
         |       top   : true,       // Use pointer coords to check for resize.
         |       left  : false,      // Disable resizing from left edge.
         |       bottom: '.resize-s',// Resize if pointer target matches selector
         |       right : handleEl    // Resize if pointer target is the given Element
         |     },
         |
         |     // a value of 'none' will limit the resize rect to a minimum of 0x0
         |     // 'negate' will allow the rect to have negative width/height
         |     // 'reposition' will keep the width/height positive by swapping
         |     // the top and bottom edges and/or swapping the left and right edges
         |     invert: 'none' || 'negate' || 'reposition'
         |
         |     // limit multiple resizes.
         |     // See the explanation in the @Interactable.draggable example
         |     max: Infinity,
         |     maxPerElement: 1,
         | });
        \*/
        resizable: function (options) {
            if (isObject(options)) {
                this.options.resize.enabled = options.enabled === false? false: true;
                this.setPerAction('resize', options);
                this.setOnEvents('resize', options);

                if (/^x$|^y$|^xy$/.test(options.axis)) {
                    this.options.resize.axis = options.axis;
                }
                else if (options.axis === null) {
                    this.options.resize.axis = defaultOptions.resize.axis;
                }

                if (isBool(options.square)) {
                    this.options.resize.square = options.square;
                }

                return this;
            }
            if (isBool(options)) {
                this.options.resize.enabled = options;

                return this;
            }
            return this.options.resize;
        },

        /*\
         * Interactable.squareResize
         [ method ]
         *
         * Deprecated. Add a `square: true || false` property to @Interactable.resizable instead
         *
         * Gets or sets whether resizing is forced 1:1 aspect
         *
         = (boolean) Current setting
         *
         * or
         *
         - newValue (boolean) #optional
         = (object) this Interactable
        \*/
        squareResize: function (newValue) {
            if (isBool(newValue)) {
                this.options.resize.square = newValue;

                return this;
            }

            if (newValue === null) {
                delete this.options.resize.square;

                return this;
            }

            return this.options.resize.square;
        },

        /*\
         * Interactable.gesturable
         [ method ]
         *
         * Gets or sets whether multitouch gestures can be performed on the
         * Interactable's element
         *
         = (boolean) Indicates if this can be the target of gesture events
         | var isGestureable = interact(element).gesturable();
         * or
         - options (boolean | object) #optional true/false or An object with event listeners to be fired on gesture events (makes the Interactable gesturable)
         = (object) this Interactable
         | interact(element).gesturable({
         |     onstart: function (event) {},
         |     onmove : function (event) {},
         |     onend  : function (event) {},
         |
         |     // limit multiple gestures.
         |     // See the explanation in @Interactable.draggable example
         |     max: Infinity,
         |     maxPerElement: 1,
         | });
        \*/
        gesturable: function (options) {
            if (isObject(options)) {
                this.options.gesture.enabled = options.enabled === false? false: true;
                this.setPerAction('gesture', options);
                this.setOnEvents('gesture', options);

                return this;
            }

            if (isBool(options)) {
                this.options.gesture.enabled = options;

                return this;
            }

            return this.options.gesture;
        },

        /*\
         * Interactable.autoScroll
         [ method ]
         **
         * Deprecated. Add an `autoscroll` property to the options object
         * passed to @Interactable.draggable or @Interactable.resizable instead.
         *
         * Returns or sets whether dragging and resizing near the edges of the
         * window/container trigger autoScroll for this Interactable
         *
         = (object) Object with autoScroll properties
         *
         * or
         *
         - options (object | boolean) #optional
         * options can be:
         * - an object with margin, distance and interval properties,
         * - true or false to enable or disable autoScroll or
         = (Interactable) this Interactable
        \*/
        autoScroll: function (options) {
            if (isObject(options)) {
                options = extend({ actions: ['drag', 'resize']}, options);
            }
            else if (isBool(options)) {
                options = { actions: ['drag', 'resize'], enabled: options };
            }

            return this.setOptions('autoScroll', options);
        },

        /*\
         * Interactable.snap
         [ method ]
         **
         * Deprecated. Add a `snap` property to the options object passed
         * to @Interactable.draggable or @Interactable.resizable instead.
         *
         * Returns or sets if and how action coordinates are snapped. By
         * default, snapping is relative to the pointer coordinates. You can
         * change this by setting the
         * [`elementOrigin`](https://github.com/taye/interact.js/pull/72).
         **
         = (boolean | object) `false` if snap is disabled; object with snap properties if snap is enabled
         **
         * or
         **
         - options (object | boolean | null) #optional
         = (Interactable) this Interactable
         > Usage
         | interact(document.querySelector('#thing')).snap({
         |     targets: [
         |         // snap to this specific point
         |         {
         |             x: 100,
         |             y: 100,
         |             range: 25
         |         },
         |         // give this function the x and y page coords and snap to the object returned
         |         function (x, y) {
         |             return {
         |                 x: x,
         |                 y: (75 + 50 * Math.sin(x * 0.04)),
         |                 range: 40
         |             };
         |         },
         |         // create a function that snaps to a grid
         |         interact.createSnapGrid({
         |             x: 50,
         |             y: 50,
         |             range: 10,              // optional
         |             offset: { x: 5, y: 10 } // optional
         |         })
         |     ],
         |     // do not snap during normal movement.
         |     // Instead, trigger only one snapped move event
         |     // immediately before the end event.
         |     endOnly: true,
         |
         |     relativePoints: [
         |         { x: 0, y: 0 },  // snap relative to the top left of the element
         |         { x: 1, y: 1 },  // and also to the bottom right
         |     ],  
         |
         |     // offset the snap target coordinates
         |     // can be an object with x/y or 'startCoords'
         |     offset: { x: 50, y: 50 }
         |   }
         | });
        \*/
        snap: function (options) {
            var ret = this.setOptions('snap', options);

            if (ret === this) { return this; }

            return ret.drag;
        },

        setOptions: function (option, options) {
            var actions = options && isArray(options.actions)
                    ? options.actions
                    : ['drag'];

            var i;

            if (isObject(options) || isBool(options)) {
                for (i = 0; i < actions.length; i++) {
                    var action = /resize/.test(actions[i])? 'resize' : actions[i];

                    if (!isObject(this.options[action])) { continue; }

                    var thisOption = this.options[action][option];

                    if (isObject(options)) {
                        extend(thisOption, options);
                        thisOption.enabled = options.enabled === false? false: true;

                        if (option === 'snap') {
                            if (thisOption.mode === 'grid') {
                                thisOption.targets = [
                                    interact.createSnapGrid(extend({
                                        offset: thisOption.gridOffset || { x: 0, y: 0 }
                                    }, thisOption.grid || {}))
                                ];
                            }
                            else if (thisOption.mode === 'anchor') {
                                thisOption.targets = thisOption.anchors;
                            }
                            else if (thisOption.mode === 'path') {
                                thisOption.targets = thisOption.paths;
                            }

                            if ('elementOrigin' in options) {
                                thisOption.relativePoints = [options.elementOrigin];
                            }
                        }
                    }
                    else if (isBool(options)) {
                        thisOption.enabled = options;
                    }
                }

                return this;
            }

            var ret = {},
                allActions = ['drag', 'resize', 'gesture'];

            for (i = 0; i < allActions.length; i++) {
                if (option in defaultOptions[allActions[i]]) {
                    ret[allActions[i]] = this.options[allActions[i]][option];
                }
            }

            return ret;
        },


        /*\
         * Interactable.inertia
         [ method ]
         **
         * Deprecated. Add an `inertia` property to the options object passed
         * to @Interactable.draggable or @Interactable.resizable instead.
         *
         * Returns or sets if and how events continue to run after the pointer is released
         **
         = (boolean | object) `false` if inertia is disabled; `object` with inertia properties if inertia is enabled
         **
         * or
         **
         - options (object | boolean | null) #optional
         = (Interactable) this Interactable
         > Usage
         | // enable and use default settings
         | interact(element).inertia(true);
         |
         | // enable and use custom settings
         | interact(element).inertia({
         |     // value greater than 0
         |     // high values slow the object down more quickly
         |     resistance     : 16,
         |
         |     // the minimum launch speed (pixels per second) that results in inertia start
         |     minSpeed       : 200,
         |
         |     // inertia will stop when the object slows down to this speed
         |     endSpeed       : 20,
         |
         |     // boolean; should actions be resumed when the pointer goes down during inertia
         |     allowResume    : true,
         |
         |     // boolean; should the jump when resuming from inertia be ignored in event.dx/dy
         |     zeroResumeDelta: false,
         |
         |     // if snap/restrict are set to be endOnly and inertia is enabled, releasing
         |     // the pointer without triggering inertia will animate from the release
         |     // point to the snaped/restricted point in the given amount of time (ms)
         |     smoothEndDuration: 300,
         |
         |     // an array of action types that can have inertia (no gesture)
         |     actions        : ['drag', 'resize']
         | });
         |
         | // reset custom settings and use all defaults
         | interact(element).inertia(null);
        \*/
        inertia: function (options) {
            var ret = this.setOptions('inertia', options);

            if (ret === this) { return this; }

            return ret.drag;
        },

        getAction: function (pointer, interaction, element) {
            var action = this.defaultActionChecker(pointer, interaction, element);

            if (this.options.actionChecker) {
                return this.options.actionChecker(pointer, action, this, element, interaction);
            }

            return action;
        },

        defaultActionChecker: defaultActionChecker,

        /*\
         * Interactable.actionChecker
         [ method ]
         *
         * Gets or sets the function used to check action to be performed on
         * pointerDown
         *
         - checker (function | null) #optional A function which takes a pointer event, defaultAction string, interactable, element and interaction as parameters and returns an object with name property 'drag' 'resize' or 'gesture' and optionally an `edges` object with boolean 'top', 'left', 'bottom' and right props.
         = (Function | Interactable) The checker function or this Interactable
         *
         | interact('.resize-horiz').actionChecker(function (defaultAction, interactable) {
         |   return {
         |     // resize from the top and right edges
         |     name: 'resize',
         |     edges: { top: true, right: true }
         |   };
         | });
        \*/
        actionChecker: function (checker) {
            if (isFunction(checker)) {
                this.options.actionChecker = checker;

                return this;
            }

            if (checker === null) {
                delete this.options.actionChecker;

                return this;
            }

            return this.options.actionChecker;
        },

        /*\
         * Interactable.getRect
         [ method ]
         *
         * The default function to get an Interactables bounding rect. Can be
         * overridden using @Interactable.rectChecker.
         *
         - element (Element) #optional The element to measure.
         = (object) The object's bounding rectangle.
         o {
         o     top   : 0,
         o     left  : 0,
         o     bottom: 0,
         o     right : 0,
         o     width : 0,
         o     height: 0
         o }
        \*/
        getRect: function rectCheck (element) {
            element = element || this._element;

            if (this.selector && !(isElement(element))) {
                element = this._context.querySelector(this.selector);
            }

            return getElementRect(element);
        },

        /*\
         * Interactable.rectChecker
         [ method ]
         *
         * Returns or sets the function used to calculate the interactable's
         * element's rectangle
         *
         - checker (function) #optional A function which returns this Interactable's bounding rectangle. See @Interactable.getRect
         = (function | object) The checker function or this Interactable
        \*/
        rectChecker: function (checker) {
            if (isFunction(checker)) {
                this.getRect = checker;

                return this;
            }

            if (checker === null) {
                delete this.options.getRect;

                return this;
            }

            return this.getRect;
        },

        /*\
         * Interactable.styleCursor
         [ method ]
         *
         * Returns or sets whether the action that would be performed when the
         * mouse on the element are checked on `mousemove` so that the cursor
         * may be styled appropriately
         *
         - newValue (boolean) #optional
         = (boolean | Interactable) The current setting or this Interactable
        \*/
        styleCursor: function (newValue) {
            if (isBool(newValue)) {
                this.options.styleCursor = newValue;

                return this;
            }

            if (newValue === null) {
                delete this.options.styleCursor;

                return this;
            }

            return this.options.styleCursor;
        },

        /*\
         * Interactable.preventDefault
         [ method ]
         *
         * Returns or sets whether to prevent the browser's default behaviour
         * in response to pointer events. Can be set to:
         *  - `'always'` to always prevent
         *  - `'never'` to never prevent
         *  - `'auto'` to let interact.js try to determine what would be best
         *
         - newValue (string) #optional `true`, `false` or `'auto'`
         = (string | Interactable) The current setting or this Interactable
        \*/
        preventDefault: function (newValue) {
            if (/^(always|never|auto)$/.test(newValue)) {
                this.options.preventDefault = newValue;
                return this;
            }

            if (isBool(newValue)) {
                this.options.preventDefault = newValue? 'always' : 'never';
                return this;
            }

            return this.options.preventDefault;
        },

        /*\
         * Interactable.origin
         [ method ]
         *
         * Gets or sets the origin of the Interactable's element.  The x and y
         * of the origin will be subtracted from action event coordinates.
         *
         - origin (object | string) #optional An object eg. { x: 0, y: 0 } or string 'parent', 'self' or any CSS selector
         * OR
         - origin (Element) #optional An HTML or SVG Element whose rect will be used
         **
         = (object) The current origin or this Interactable
        \*/
        origin: function (newValue) {
            if (trySelector(newValue)) {
                this.options.origin = newValue;
                return this;
            }
            else if (isObject(newValue)) {
                this.options.origin = newValue;
                return this;
            }

            return this.options.origin;
        },

        /*\
         * Interactable.deltaSource
         [ method ]
         *
         * Returns or sets the mouse coordinate types used to calculate the
         * movement of the pointer.
         *
         - newValue (string) #optional Use 'client' if you will be scrolling while interacting; Use 'page' if you want autoScroll to work
         = (string | object) The current deltaSource or this Interactable
        \*/
        deltaSource: function (newValue) {
            if (newValue === 'page' || newValue === 'client') {
                this.options.deltaSource = newValue;

                return this;
            }

            return this.options.deltaSource;
        },

        /*\
         * Interactable.restrict
         [ method ]
         **
         * Deprecated. Add a `restrict` property to the options object passed to
         * @Interactable.draggable, @Interactable.resizable or @Interactable.gesturable instead.
         *
         * Returns or sets the rectangles within which actions on this
         * interactable (after snap calculations) are restricted. By default,
         * restricting is relative to the pointer coordinates. You can change
         * this by setting the
         * [`elementRect`](https://github.com/taye/interact.js/pull/72).
         **
         - options (object) #optional an object with keys drag, resize, and/or gesture whose values are rects, Elements, CSS selectors, or 'parent' or 'self'
         = (object) The current restrictions object or this Interactable
         **
         | interact(element).restrict({
         |     // the rect will be `interact.getElementRect(element.parentNode)`
         |     drag: element.parentNode,
         |
         |     // x and y are relative to the the interactable's origin
         |     resize: { x: 100, y: 100, width: 200, height: 200 }
         | })
         |
         | interact('.draggable').restrict({
         |     // the rect will be the selected element's parent
         |     drag: 'parent',
         |
         |     // do not restrict during normal movement.
         |     // Instead, trigger only one restricted move event
         |     // immediately before the end event.
         |     endOnly: true,
         |
         |     // https://github.com/taye/interact.js/pull/72#issue-41813493
         |     elementRect: { top: 0, left: 0, bottom: 1, right: 1 }
         | });
        \*/
        restrict: function (options) {
            if (!isObject(options)) {
                return this.setOptions('restrict', options);
            }

            var actions = ['drag', 'resize', 'gesture'],
                ret;

            for (var i = 0; i < actions.length; i++) {
                var action = actions[i];

                if (action in options) {
                    var perAction = extend({
                            actions: [action],
                            restriction: options[action]
                        }, options);

                    ret = this.setOptions('restrict', perAction);
                }
            }

            return ret;
        },

        /*\
         * Interactable.context
         [ method ]
         *
         * Gets the selector context Node of the Interactable. The default is `window.document`.
         *
         = (Node) The context Node of this Interactable
         **
        \*/
        context: function () {
            return this._context;
        },

        _context: document,

        /*\
         * Interactable.ignoreFrom
         [ method ]
         *
         * If the target of the `mousedown`, `pointerdown` or `touchstart`
         * event or any of it's parents match the given CSS selector or
         * Element, no drag/resize/gesture is started.
         *
         - newValue (string | Element | null) #optional a CSS selector string, an Element or `null` to not ignore any elements
         = (string | Element | object) The current ignoreFrom value or this Interactable
         **
         | interact(element, { ignoreFrom: document.getElementById('no-action') });
         | // or
         | interact(element).ignoreFrom('input, textarea, a');
        \*/
        ignoreFrom: function (newValue) {
            if (trySelector(newValue)) {            // CSS selector to match event.target
                this.options.ignoreFrom = newValue;
                return this;
            }

            if (isElement(newValue)) {              // specific element
                this.options.ignoreFrom = newValue;
                return this;
            }

            return this.options.ignoreFrom;
        },

        /*\
         * Interactable.allowFrom
         [ method ]
         *
         * A drag/resize/gesture is started only If the target of the
         * `mousedown`, `pointerdown` or `touchstart` event or any of it's
         * parents match the given CSS selector or Element.
         *
         - newValue (string | Element | null) #optional a CSS selector string, an Element or `null` to allow from any element
         = (string | Element | object) The current allowFrom value or this Interactable
         **
         | interact(element, { allowFrom: document.getElementById('drag-handle') });
         | // or
         | interact(element).allowFrom('.handle');
        \*/
        allowFrom: function (newValue) {
            if (trySelector(newValue)) {            // CSS selector to match event.target
                this.options.allowFrom = newValue;
                return this;
            }

            if (isElement(newValue)) {              // specific element
                this.options.allowFrom = newValue;
                return this;
            }

            return this.options.allowFrom;
        },

        /*\
         * Interactable.element
         [ method ]
         *
         * If this is not a selector Interactable, it returns the element this
         * interactable represents
         *
         = (Element) HTML / SVG Element
        \*/
        element: function () {
            return this._element;
        },

        /*\
         * Interactable.fire
         [ method ]
         *
         * Calls listeners for the given InteractEvent type bound globally
         * and directly to this Interactable
         *
         - iEvent (InteractEvent) The InteractEvent object to be fired on this Interactable
         = (Interactable) this Interactable
        \*/
        fire: function (iEvent) {
            if (!(iEvent && iEvent.type) || !contains(eventTypes, iEvent.type)) {
                return this;
            }

            var listeners,
                i,
                len,
                onEvent = 'on' + iEvent.type,
                funcName = '';

            // Interactable#on() listeners
            if (iEvent.type in this._iEvents) {
                listeners = this._iEvents[iEvent.type];

                for (i = 0, len = listeners.length; i < len && !iEvent.immediatePropagationStopped; i++) {
                    funcName = listeners[i].name;
                    listeners[i](iEvent);
                }
            }

            // interactable.onevent listener
            if (isFunction(this[onEvent])) {
                funcName = this[onEvent].name;
                this[onEvent](iEvent);
            }

            // interact.on() listeners
            if (iEvent.type in globalEvents && (listeners = globalEvents[iEvent.type]))  {

                for (i = 0, len = listeners.length; i < len && !iEvent.immediatePropagationStopped; i++) {
                    funcName = listeners[i].name;
                    listeners[i](iEvent);
                }
            }

            return this;
        },

        /*\
         * Interactable.on
         [ method ]
         *
         * Binds a listener for an InteractEvent or DOM event.
         *
         - eventType  (string | array | object) The types of events to listen for
         - listener   (function) The function to be called on the given event(s)
         - useCapture (boolean) #optional useCapture flag for addEventListener
         = (object) This Interactable
        \*/
        on: function (eventType, listener, useCapture) {
            var i;

            if (isString(eventType) && eventType.search(' ') !== -1) {
                eventType = eventType.trim().split(/ +/);
            }

            if (isArray(eventType)) {
                for (i = 0; i < eventType.length; i++) {
                    this.on(eventType[i], listener, useCapture);
                }

                return this;
            }

            if (isObject(eventType)) {
                for (var prop in eventType) {
                    this.on(prop, eventType[prop], listener);
                }

                return this;
            }

            if (eventType === 'wheel') {
                eventType = wheelEvent;
            }

            // convert to boolean
            useCapture = useCapture? true: false;

            if (contains(eventTypes, eventType)) {
                // if this type of event was never bound to this Interactable
                if (!(eventType in this._iEvents)) {
                    this._iEvents[eventType] = [listener];
                }
                else {
                    this._iEvents[eventType].push(listener);
                }
            }
            // delegated event for selector
            else if (this.selector) {
                if (!delegatedEvents[eventType]) {
                    delegatedEvents[eventType] = {
                        selectors: [],
                        contexts : [],
                        listeners: []
                    };

                    // add delegate listener functions
                    for (i = 0; i < documents.length; i++) {
                        events.add(documents[i], eventType, delegateListener);
                        events.add(documents[i], eventType, delegateUseCapture, true);
                    }
                }

                var delegated = delegatedEvents[eventType],
                    index;

                for (index = delegated.selectors.length - 1; index >= 0; index--) {
                    if (delegated.selectors[index] === this.selector
                        && delegated.contexts[index] === this._context) {
                        break;
                    }
                }

                if (index === -1) {
                    index = delegated.selectors.length;

                    delegated.selectors.push(this.selector);
                    delegated.contexts .push(this._context);
                    delegated.listeners.push([]);
                }

                // keep listener and useCapture flag
                delegated.listeners[index].push([listener, useCapture]);
            }
            else {
                events.add(this._element, eventType, listener, useCapture);
            }

            return this;
        },

        /*\
         * Interactable.off
         [ method ]
         *
         * Removes an InteractEvent or DOM event listener
         *
         - eventType  (string | array | object) The types of events that were listened for
         - listener   (function) The listener function to be removed
         - useCapture (boolean) #optional useCapture flag for removeEventListener
         = (object) This Interactable
        \*/
        off: function (eventType, listener, useCapture) {
            var i;

            if (isString(eventType) && eventType.search(' ') !== -1) {
                eventType = eventType.trim().split(/ +/);
            }

            if (isArray(eventType)) {
                for (i = 0; i < eventType.length; i++) {
                    this.off(eventType[i], listener, useCapture);
                }

                return this;
            }

            if (isObject(eventType)) {
                for (var prop in eventType) {
                    this.off(prop, eventType[prop], listener);
                }

                return this;
            }

            var eventList,
                index = -1;

            // convert to boolean
            useCapture = useCapture? true: false;

            if (eventType === 'wheel') {
                eventType = wheelEvent;
            }

            // if it is an action event type
            if (contains(eventTypes, eventType)) {
                eventList = this._iEvents[eventType];

                if (eventList && (index = indexOf(eventList, listener)) !== -1) {
                    this._iEvents[eventType].splice(index, 1);
                }
            }
            // delegated event
            else if (this.selector) {
                var delegated = delegatedEvents[eventType],
                    matchFound = false;

                if (!delegated) { return this; }

                // count from last index of delegated to 0
                for (index = delegated.selectors.length - 1; index >= 0; index--) {
                    // look for matching selector and context Node
                    if (delegated.selectors[index] === this.selector
                        && delegated.contexts[index] === this._context) {

                        var listeners = delegated.listeners[index];

                        // each item of the listeners array is an array: [function, useCaptureFlag]
                        for (i = listeners.length - 1; i >= 0; i--) {
                            var fn = listeners[i][0],
                                useCap = listeners[i][1];

                            // check if the listener functions and useCapture flags match
                            if (fn === listener && useCap === useCapture) {
                                // remove the listener from the array of listeners
                                listeners.splice(i, 1);

                                // if all listeners for this interactable have been removed
                                // remove the interactable from the delegated arrays
                                if (!listeners.length) {
                                    delegated.selectors.splice(index, 1);
                                    delegated.contexts .splice(index, 1);
                                    delegated.listeners.splice(index, 1);

                                    // remove delegate function from context
                                    events.remove(this._context, eventType, delegateListener);
                                    events.remove(this._context, eventType, delegateUseCapture, true);

                                    // remove the arrays if they are empty
                                    if (!delegated.selectors.length) {
                                        delegatedEvents[eventType] = null;
                                    }
                                }

                                // only remove one listener
                                matchFound = true;
                                break;
                            }
                        }

                        if (matchFound) { break; }
                    }
                }
            }
            // remove listener from this Interatable's element
            else {
                events.remove(this._element, eventType, listener, useCapture);
            }

            return this;
        },

        /*\
         * Interactable.set
         [ method ]
         *
         * Reset the options of this Interactable
         - options (object) The new settings to apply
         = (object) This Interactablw
        \*/
        set: function (options) {
            if (!isObject(options)) {
                options = {};
            }

            this.options = extend({}, defaultOptions.base);

            var i,
                actions = ['drag', 'drop', 'resize', 'gesture'],
                methods = ['draggable', 'dropzone', 'resizable', 'gesturable'],
                perActions = extend(extend({}, defaultOptions.perAction), options[action] || {});

            for (i = 0; i < actions.length; i++) {
                var action = actions[i];

                this.options[action] = extend({}, defaultOptions[action]);

                this.setPerAction(action, perActions);

                this[methods[i]](options[action]);
            }

            var settings = [
                    'accept', 'actionChecker', 'allowFrom', 'deltaSource',
                    'dropChecker', 'ignoreFrom', 'origin', 'preventDefault',
                    'rectChecker'
                ];

            for (i = 0, len = settings.length; i < len; i++) {
                var setting = settings[i];

                this.options[setting] = defaultOptions.base[setting];

                if (setting in options) {
                    this[setting](options[setting]);
                }
            }

            return this;
        },

        /*\
         * Interactable.unset
         [ method ]
         *
         * Remove this interactable from the list of interactables and remove
         * it's drag, drop, resize and gesture capabilities
         *
         = (object) @interact
        \*/
        unset: function () {
            events.remove(this, 'all');

            if (!isString(this.selector)) {
                events.remove(this, 'all');
                if (this.options.styleCursor) {
                    this._element.style.cursor = '';
                }
            }
            else {
                // remove delegated events
                for (var type in delegatedEvents) {
                    var delegated = delegatedEvents[type];

                    for (var i = 0; i < delegated.selectors.length; i++) {
                        if (delegated.selectors[i] === this.selector
                            && delegated.contexts[i] === this._context) {

                            delegated.selectors.splice(i, 1);
                            delegated.contexts .splice(i, 1);
                            delegated.listeners.splice(i, 1);

                            // remove the arrays if they are empty
                            if (!delegated.selectors.length) {
                                delegatedEvents[type] = null;
                            }
                        }

                        events.remove(this._context, type, delegateListener);
                        events.remove(this._context, type, delegateUseCapture, true);

                        break;
                    }
                }
            }

            this.dropzone(false);

            interactables.splice(indexOf(interactables, this), 1);

            return interact;
        }
    };

    function warnOnce (method, message) {
        var warned = false;

        return function () {
            if (!warned) {
                window.console.warn(message);
                warned = true;
            }

            return method.apply(this, arguments);
        };
    }

    Interactable.prototype.snap = warnOnce(Interactable.prototype.snap,
         'Interactable#snap is deprecated. See the new documentation for snapping at http://interactjs.io/docs/snapping');
    Interactable.prototype.restrict = warnOnce(Interactable.prototype.restrict,
         'Interactable#restrict is deprecated. See the new documentation for resticting at http://interactjs.io/docs/restriction');
    Interactable.prototype.inertia = warnOnce(Interactable.prototype.inertia,
         'Interactable#inertia is deprecated. See the new documentation for inertia at http://interactjs.io/docs/inertia');
    Interactable.prototype.autoScroll = warnOnce(Interactable.prototype.autoScroll,
         'Interactable#autoScroll is deprecated. See the new documentation for autoScroll at http://interactjs.io/docs/#autoscroll');

    /*\
     * interact.isSet
     [ method ]
     *
     * Check if an element has been set
     - element (Element) The Element being searched for
     = (boolean) Indicates if the element or CSS selector was previously passed to interact
    \*/
    interact.isSet = function(element, options) {
        return interactables.indexOfElement(element, options && options.context) !== -1;
    };

    /*\
     * interact.on
     [ method ]
     *
     * Adds a global listener for an InteractEvent or adds a DOM event to
     * `document`
     *
     - type       (string | array | object) The types of events to listen for
     - listener   (function) The function to be called on the given event(s)
     - useCapture (boolean) #optional useCapture flag for addEventListener
     = (object) interact
    \*/
    interact.on = function (type, listener, useCapture) {
        if (isString(type) && type.search(' ') !== -1) {
            type = type.trim().split(/ +/);
        }

        if (isArray(type)) {
            for (var i = 0; i < type.length; i++) {
                interact.on(type[i], listener, useCapture);
            }

            return interact;
        }

        if (isObject(type)) {
            for (var prop in type) {
                interact.on(prop, type[prop], listener);
            }

            return interact;
        }

        // if it is an InteractEvent type, add listener to globalEvents
        if (contains(eventTypes, type)) {
            // if this type of event was never bound
            if (!globalEvents[type]) {
                globalEvents[type] = [listener];
            }
            else {
                globalEvents[type].push(listener);
            }
        }
        // If non InteractEvent type, addEventListener to document
        else {
            events.add(document, type, listener, useCapture);
        }

        return interact;
    };

    /*\
     * interact.off
     [ method ]
     *
     * Removes a global InteractEvent listener or DOM event from `document`
     *
     - type       (string | array | object) The types of events that were listened for
     - listener   (function) The listener function to be removed
     - useCapture (boolean) #optional useCapture flag for removeEventListener
     = (object) interact
     \*/
    interact.off = function (type, listener, useCapture) {
        if (isString(type) && type.search(' ') !== -1) {
            type = type.trim().split(/ +/);
        }

        if (isArray(type)) {
            for (var i = 0; i < type.length; i++) {
                interact.off(type[i], listener, useCapture);
            }

            return interact;
        }

        if (isObject(type)) {
            for (var prop in type) {
                interact.off(prop, type[prop], listener);
            }

            return interact;
        }

        if (!contains(eventTypes, type)) {
            events.remove(document, type, listener, useCapture);
        }
        else {
            var index;

            if (type in globalEvents
                && (index = indexOf(globalEvents[type], listener)) !== -1) {
                globalEvents[type].splice(index, 1);
            }
        }

        return interact;
    };

    /*\
     * interact.enableDragging
     [ method ]
     *
     * Deprecated.
     *
     * Returns or sets whether dragging is enabled for any Interactables
     *
     - newValue (boolean) #optional `true` to allow the action; `false` to disable action for all Interactables
     = (boolean | object) The current setting or interact
    \*/
    interact.enableDragging = warnOnce(function (newValue) {
        if (newValue !== null && newValue !== undefined) {
            actionIsEnabled.drag = newValue;

            return interact;
        }
        return actionIsEnabled.drag;
    }, 'interact.enableDragging is deprecated and will soon be removed.');

    /*\
     * interact.enableResizing
     [ method ]
     *
     * Deprecated.
     *
     * Returns or sets whether resizing is enabled for any Interactables
     *
     - newValue (boolean) #optional `true` to allow the action; `false` to disable action for all Interactables
     = (boolean | object) The current setting or interact
    \*/
    interact.enableResizing = warnOnce(function (newValue) {
        if (newValue !== null && newValue !== undefined) {
            actionIsEnabled.resize = newValue;

            return interact;
        }
        return actionIsEnabled.resize;
    }, 'interact.enableResizing is deprecated and will soon be removed.');

    /*\
     * interact.enableGesturing
     [ method ]
     *
     * Deprecated.
     *
     * Returns or sets whether gesturing is enabled for any Interactables
     *
     - newValue (boolean) #optional `true` to allow the action; `false` to disable action for all Interactables
     = (boolean | object) The current setting or interact
    \*/
    interact.enableGesturing = warnOnce(function (newValue) {
        if (newValue !== null && newValue !== undefined) {
            actionIsEnabled.gesture = newValue;

            return interact;
        }
        return actionIsEnabled.gesture;
    }, 'interact.enableGesturing is deprecated and will soon be removed.');

    interact.eventTypes = eventTypes;

    /*\
     * interact.debug
     [ method ]
     *
     * Returns debugging data
     = (object) An object with properties that outline the current state and expose internal functions and variables
    \*/
    interact.debug = function () {
        var interaction = interactions[0] || new Interaction();

        return {
            interactions          : interactions,
            target                : interaction.target,
            dragging              : interaction.dragging,
            resizing              : interaction.resizing,
            gesturing             : interaction.gesturing,
            prepared              : interaction.prepared,
            matches               : interaction.matches,
            matchElements         : interaction.matchElements,

            prevCoords            : interaction.prevCoords,
            startCoords           : interaction.startCoords,

            pointerIds            : interaction.pointerIds,
            pointers              : interaction.pointers,
            addPointer            : listeners.addPointer,
            removePointer         : listeners.removePointer,
            recordPointer        : listeners.recordPointer,

            snap                  : interaction.snapStatus,
            restrict              : interaction.restrictStatus,
            inertia               : interaction.inertiaStatus,

            downTime              : interaction.downTimes[0],
            downEvent             : interaction.downEvent,
            downPointer           : interaction.downPointer,
            prevEvent             : interaction.prevEvent,

            Interactable          : Interactable,
            interactables         : interactables,
            pointerIsDown         : interaction.pointerIsDown,
            defaultOptions        : defaultOptions,
            defaultActionChecker  : defaultActionChecker,

            actionCursors         : actionCursors,
            dragMove              : listeners.dragMove,
            resizeMove            : listeners.resizeMove,
            gestureMove           : listeners.gestureMove,
            pointerUp             : listeners.pointerUp,
            pointerDown           : listeners.pointerDown,
            pointerMove           : listeners.pointerMove,
            pointerHover          : listeners.pointerHover,

            events                : events,
            globalEvents          : globalEvents,
            delegatedEvents       : delegatedEvents
        };
    };

    // expose the functions used to calculate multi-touch properties
    interact.getTouchAverage  = touchAverage;
    interact.getTouchBBox     = touchBBox;
    interact.getTouchDistance = touchDistance;
    interact.getTouchAngle    = touchAngle;

    interact.getElementRect   = getElementRect;
    interact.matchesSelector  = matchesSelector;
    interact.closest          = closest;

    /*\
     * interact.margin
     [ method ]
     *
     * Returns or sets the margin for autocheck resizing used in
     * @Interactable.getAction. That is the distance from the bottom and right
     * edges of an element clicking in which will start resizing
     *
     - newValue (number) #optional
     = (number | interact) The current margin value or interact
    \*/
    interact.margin = function (newvalue) {
        if (isNumber(newvalue)) {
            margin = newvalue;

            return interact;
        }
        return margin;
    };

    /*\
     * interact.supportsTouch
     [ method ]
     *
     = (boolean) Whether or not the browser supports touch input
    \*/
    interact.supportsTouch = function () {
        return supportsTouch;
    };

    /*\
     * interact.supportsPointerEvent
     [ method ]
     *
     = (boolean) Whether or not the browser supports PointerEvents
    \*/
    interact.supportsPointerEvent = function () {
        return supportsPointerEvent;
    };

    /*\
     * interact.stop
     [ method ]
     *
     * Cancels all interactions (end events are not fired)
     *
     - event (Event) An event on which to call preventDefault()
     = (object) interact
    \*/
    interact.stop = function (event) {
        for (var i = interactions.length - 1; i > 0; i--) {
            interactions[i].stop(event);
        }

        return interact;
    };

    /*\
     * interact.dynamicDrop
     [ method ]
     *
     * Returns or sets whether the dimensions of dropzone elements are
     * calculated on every dragmove or only on dragstart for the default
     * dropChecker
     *
     - newValue (boolean) #optional True to check on each move. False to check only before start
     = (boolean | interact) The current setting or interact
    \*/
    interact.dynamicDrop = function (newValue) {
        if (isBool(newValue)) {
            //if (dragging && dynamicDrop !== newValue && !newValue) {
                //calcRects(dropzones);
            //}

            dynamicDrop = newValue;

            return interact;
        }
        return dynamicDrop;
    };

    /*\
     * interact.pointerMoveTolerance
     [ method ]
     * Returns or sets the distance the pointer must be moved before an action
     * sequence occurs. This also affects tolerance for tap events.
     *
     - newValue (number) #optional The movement from the start position must be greater than this value
     = (number | Interactable) The current setting or interact
    \*/
    interact.pointerMoveTolerance = function (newValue) {
        if (isNumber(newValue)) {
            pointerMoveTolerance = newValue;

            return this;
        }

        return pointerMoveTolerance;
    };

    /*\
     * interact.maxInteractions
     [ method ]
     **
     * Returns or sets the maximum number of concurrent interactions allowed.
     * By default only 1 interaction is allowed at a time (for backwards
     * compatibility). To allow multiple interactions on the same Interactables
     * and elements, you need to enable it in the draggable, resizable and
     * gesturable `'max'` and `'maxPerElement'` options.
     **
     - newValue (number) #optional Any number. newValue <= 0 means no interactions.
    \*/
    interact.maxInteractions = function (newValue) {
        if (isNumber(newValue)) {
            maxInteractions = newValue;

            return this;
        }

        return maxInteractions;
    };

    interact.createSnapGrid = function (grid) {
        return function (x, y) {
            var offsetX = 0,
                offsetY = 0;

            if (isObject(grid.offset)) {
                offsetX = grid.offset.x;
                offsetY = grid.offset.y;
            }

            var gridx = Math.round((x - offsetX) / grid.x),
                gridy = Math.round((y - offsetY) / grid.y),

                newX = gridx * grid.x + offsetX,
                newY = gridy * grid.y + offsetY;

            return {
                x: newX,
                y: newY,
                range: grid.range
            };
        };
    };

    function endAllInteractions (event) {
        for (var i = 0; i < interactions.length; i++) {
            interactions[i].pointerEnd(event, event);
        }
    }

    function listenToDocument (doc) {
        if (contains(documents, doc)) { return; }

        var win = doc.defaultView || doc.parentWindow;

        // add delegate event listener
        for (var eventType in delegatedEvents) {
            events.add(doc, eventType, delegateListener);
            events.add(doc, eventType, delegateUseCapture, true);
        }

        if (PointerEvent) {
            if (PointerEvent === win.MSPointerEvent) {
                pEventTypes = {
                    up: 'MSPointerUp', down: 'MSPointerDown', over: 'mouseover',
                    out: 'mouseout', move: 'MSPointerMove', cancel: 'MSPointerCancel' };
            }
            else {
                pEventTypes = {
                    up: 'pointerup', down: 'pointerdown', over: 'pointerover',
                    out: 'pointerout', move: 'pointermove', cancel: 'pointercancel' };
            }

            events.add(doc, pEventTypes.down  , listeners.selectorDown );
            events.add(doc, pEventTypes.move  , listeners.pointerMove  );
            events.add(doc, pEventTypes.over  , listeners.pointerOver  );
            events.add(doc, pEventTypes.out   , listeners.pointerOut   );
            events.add(doc, pEventTypes.up    , listeners.pointerUp    );
            events.add(doc, pEventTypes.cancel, listeners.pointerCancel);

            // autoscroll
            events.add(doc, pEventTypes.move, autoScroll.edgeMove);
        }
        else {
            events.add(doc, 'mousedown', listeners.selectorDown);
            events.add(doc, 'mousemove', listeners.pointerMove );
            events.add(doc, 'mouseup'  , listeners.pointerUp   );
            events.add(doc, 'mouseover', listeners.pointerOver );
            events.add(doc, 'mouseout' , listeners.pointerOut  );

            events.add(doc, 'touchstart' , listeners.selectorDown );
            events.add(doc, 'touchmove'  , listeners.pointerMove  );
            events.add(doc, 'touchend'   , listeners.pointerUp    );
            events.add(doc, 'touchcancel', listeners.pointerCancel);

            // autoscroll
            events.add(doc, 'mousemove', autoScroll.edgeMove);
            events.add(doc, 'touchmove', autoScroll.edgeMove);
        }

        events.add(win, 'blur', endAllInteractions);

        try {
            if (win.frameElement) {
                var parentDoc = win.frameElement.ownerDocument,
                    parentWindow = parentDoc.defaultView;

                events.add(parentDoc   , 'mouseup'      , listeners.pointerEnd);
                events.add(parentDoc   , 'touchend'     , listeners.pointerEnd);
                events.add(parentDoc   , 'touchcancel'  , listeners.pointerEnd);
                events.add(parentDoc   , 'pointerup'    , listeners.pointerEnd);
                events.add(parentDoc   , 'MSPointerUp'  , listeners.pointerEnd);
                events.add(parentWindow, 'blur'         , endAllInteractions );
            }
        }
        catch (error) {
            interact.windowParentError = error;
        }

        if (events.useAttachEvent) {
            // For IE's lack of Event#preventDefault
            events.add(doc, 'selectstart', function (event) {
                var interaction = interactions[0];

                if (interaction.currentAction()) {
                    interaction.checkAndPreventDefault(event);
                }
            });

            // For IE's bad dblclick event sequence
            events.add(doc, 'dblclick', doOnInteractions('ie8Dblclick'));
        }

        documents.push(doc);
    }

    listenToDocument(document);

    function indexOf (array, target) {
        for (var i = 0, len = array.length; i < len; i++) {
            if (array[i] === target) {
                return i;
            }
        }

        return -1;
    }

    function contains (array, target) {
        return indexOf(array, target) !== -1;
    }

    function matchesSelector (element, selector, nodeList) {
        if (ie8MatchesSelector) {
            return ie8MatchesSelector(element, selector, nodeList);
        }

        // remove /deep/ from selectors if shadowDOM polyfill is used
        if (window !== realWindow) {
            selector = selector.replace(/\/deep\//g, ' ');
        }

        return element[prefixedMatchesSelector](selector);
    }

    function matchesUpTo (element, selector, limit) {
        while (isElement(element)) {
            if (matchesSelector(element, selector)) {
                return true;
            }

            element = parentElement(element);

            if (element === limit) {
                return matchesSelector(element, selector);
            }
        }

        return false;
    }

    // For IE8's lack of an Element#matchesSelector
    // taken from http://tanalin.com/en/blog/2012/12/matches-selector-ie8/ and modified
    if (!(prefixedMatchesSelector in Element.prototype) || !isFunction(Element.prototype[prefixedMatchesSelector])) {
        ie8MatchesSelector = function (element, selector, elems) {
            elems = elems || element.parentNode.querySelectorAll(selector);

            for (var i = 0, len = elems.length; i < len; i++) {
                if (elems[i] === element) {
                    return true;
                }
            }

            return false;
        };
    }

    // requestAnimationFrame polyfill
    (function() {
        var lastTime = 0,
            vendors = ['ms', 'moz', 'webkit', 'o'];

        for(var x = 0; x < vendors.length && !realWindow.requestAnimationFrame; ++x) {
            reqFrame = realWindow[vendors[x]+'RequestAnimationFrame'];
            cancelFrame = realWindow[vendors[x]+'CancelAnimationFrame'] || realWindow[vendors[x]+'CancelRequestAnimationFrame'];
        }

        if (!reqFrame) {
            reqFrame = function(callback) {
                var currTime = new Date().getTime(),
                    timeToCall = Math.max(0, 16 - (currTime - lastTime)),
                    id = setTimeout(function() { callback(currTime + timeToCall); },
                  timeToCall);
                lastTime = currTime + timeToCall;
                return id;
            };
        }

        if (!cancelFrame) {
            cancelFrame = function(id) {
                clearTimeout(id);
            };
        }
    }());

    /* global exports: true, module, define */

    // http://documentcloud.github.io/underscore/docs/underscore.html#section-11
    if (typeof exports !== 'undefined') {
        if (typeof module !== 'undefined' && module.exports) {
            exports = module.exports = interact;
        }
        exports.interact = interact;
    }
    // AMD
    else if (typeof define === 'function' && define.amd) {
        define('interact', function() {
            return interact;
        });
    }
    else {
        realWindow.interact = interact;
    }

} (window));