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Edit File: peeljs.js

/*peeljs*/
(function(win) {

// Constants
  var PRECISION       = 1e2; // 2 decimals
  var VENDOR_PREFIXES = ['webkit','moz', ''];
  var SVG_NAMESPACE   = 'http://www.w3.org/2000/svg';
  var CSS_PREFIX      = 'peel-';

var clipProperty, transformProperty, boxShadowProperty, filterProperty;
  var backgroundGradientSupport;
  var docEl = document.documentElement;
  var style = docEl.style;

// Support
    function getCssProperty(name) {
	    var prefix, str;
	    for (var i = 0; i < VENDOR_PREFIXES.length; i++) {
	      prefix = VENDOR_PREFIXES[i];
	      str = prefix ? prefix + capitalize(name) : name;
	      if (str in style) {
	        return str;
	      }
	    }
    }
    function setCssProperties() {
	    clipProperty      = getCssProperty('clipPath');
	    transformProperty = getCssProperty('transform');
	    boxShadowProperty = getCssProperty('boxShadow');
	    filterProperty    = getCssProperty('filter');
	    setBackgroundGradientSupport();
	    Peel.supported = !!(clipProperty && transformProperty);
	    Peel.effectsSupported = backgroundGradientSupport;
  	}
  	function setBackgroundGradientSupport() {
	    var el = document.createElement('div');
	    var style = el.style;
	    style.cssText = 'background:linear-gradient(45deg,#9f9,white);';
	    backgroundGradientSupport = (style.backgroundImage || '').indexOf('gradient') > -1;
  	}

// General helpers
	function round(n) {
	   return Math.round(n * PRECISION) / PRECISION;
	}
 	// Clamps the number to be between 0 and 1.
	function clamp(n) {
	   return Math.max(0, Math.min(1, n));
	}
	function normalize(n, min, max) {
   	   return (n - min) / (max - min);
 	}
    // Distributes a number between 0 and 1 along a bell curve.
    function distribute(t, mult) {
    	return (mult || 1) * 2 * (.5 - Math.abs(t - .5));
 	}
 	function capitalize(str) {
    	return str.slice(0,1).toUpperCase() + str.slice(1);
  	}
  	function camelize(str) {
	    return str.replace(/-(\w)/g, function(a, b) {
	      return b.toUpperCase();
	    });
 	}
 	function prefix(str) {
   		return CSS_PREFIX + str;
 	}
 	// CSS Helpers
 	function setCSSClip(el, clip) {
    	el.style[clipProperty] = clip;
  	}
  	function setTransform(el, t) {
    	el.style[transformProperty] = t;
  	}
  	function setBoxShadow(el, x, y, blur, spread, intensity) {
    	el.style[boxShadowProperty] = getShadowCss(x, y, blur, spread, intensity);
 	}
 	function setDropShadow(el, x, y, blur, intensity) {
    	el.style[filterProperty] = 'drop-shadow(' + getShadowCss(x, y, blur, null, intensity) + ')';
  	}
  	function getShadowCss(x, y, blur, spread, intensity) {
    	return round(x) + 'px ' +
           round(y) + 'px ' +
           round(blur) + 'px ' +
           (spread ? round(spread) + 'px ' : '') +
           'rgba(0,0,0,' + round(intensity) + ')';
  	}
  	function setOpacity(el, t) {
   		el.style.opacity = t;
  	}
  	function setBackgroundGradient(el, rotation, stops) {
	    if (!backgroundGradientSupport) return;
	    var css;
	    if (stops.length === 0) {
	      css = 'none';
	    } else {
	      css = 'linear-gradient(' + round(rotation) + 'deg,' + stops.join(',') + ')';
	    }
	    el.style.backgroundImage = css;
  	}
  	// Event Helpers
  	function addEvent(el, type, fn) {
   	 	el.addEventListener(type, fn)
  	}
	function removeEvent(el, type, fn) {
	    el.removeEventListener(type, fn);
	}
 	function getEventCoordinates(evt, el) {
	    var pos = evt.changedTouches ? evt.changedTouches[0] : evt;
	    return {
	      'x': pos.clientX - el.offsetLeft + window.scrollX,
	      'y': pos.clientY - el.offsetTop + window.scrollY
	    }
 	}
 	function bindWithEvent(fn, scope, arg1, arg2) {
	    return function(evt) {
	      fn.call(scope, evt, arg1, arg2);
	    }
 	}
 	// Color Helpers
 	function getBlackStop(a, pos) {
   		return getColorStop(0, 0, 0, a, pos);
 	}
 	function getWhiteStop(a, pos) {
    	return getColorStop(255, 255, 255, a, pos);
  	}
  	function getColorStop(r, g, b, a, pos) {
	    a = round(clamp(a));
	    return 'rgba('+ r +','+ g +','+ b +','+ a +') ' + round(pos * 100) + '%';
  	}
  	// DOM Element Helpers
  	function getElement(obj, node) {
	    if (typeof obj === 'string') {
	      obj = (node || document).querySelector(obj);
	    }
    	return obj;
 	}
   function createElement(parent, className) {
	    var el = document.createElement('div');
	    addClass(el, className);
	    parent.appendChild(el);
	    return el;
 	}
    function removeClass(el, str) {
   	    el.classList.remove(str);
    }
  	function addClass(el, str) {
    	el.classList.add(str);
  	}
  	function getZIndex(el) {
    	return el.style.zIndex;
  	}
  	function setZIndex(el, index) {
   		el.style.zIndex = index;
  	}
  	// SVG Helpers
  	function createSVGElement(tag, parent, attributes) {
	    parent = parent || docEl;
	    var el = document.createElementNS(SVG_NAMESPACE, tag);
	    parent.appendChild(el);
	    for (var key in attributes) {
	      if (!attributes.hasOwnProperty(key)) continue;
	      setSVGAttribute(el, key, attributes[key]);
	    }
   		return el;
 	}
 	function setSVGAttribute(el, key, value) {
   	 	el.setAttributeNS(null, key, value);
 	}
 	/**
   	* Main class that controls the peeling effect.
    * @param {HTMLElement|string} el The main container element (can be query).
    * @param {object} options Options for the effect.
    * @constructor
    * @public
	*/

function Peel (el, opt) {
	    this.setOptions(opt);
	    this.el = getElement(el, docEl);
	    this.constraints = [];
	    this.events = [];
	    this.setupLayers();
	    this.setupDimensions();
	    this.setCorner(this.getOption('corner'));
	    this.setMode(this.getOption('mode'));
	    this.init();
  	}
  	/**
    * Four constants representing the corners of the element from which peeling can occur.
    * @constant
    * @public
    */
    Peel.Corners = {
	    TOP_LEFT:     0x0,
	    TOP_RIGHT:    0x1,
	    BOTTOM_LEFT:  0x2,
	    BOTTOM_RIGHT: 0x3
  	}
  	/**
    * Defaults
    * @constant
    */
    Peel.Defaults = {
	    'topShadow': true,
	    'topShadowBlur': 5,
	    'topShadowAlpha': .5,
	    'topShadowOffsetX': 0,
	    'topShadowOffsetY': 1,
	    'topShadowCreatesShape': true,

'backReflection': false,
	    'backReflectionSize': .02,
	    'backReflectionOffset': 0,
	    'backReflectionAlpha': .15,
	    'backReflectionDistribute': true,

'backShadow': true,
	    'backShadowSize': .04,
	    'backShadowOffset': 0,
	    'backShadowAlpha': .1,
	    'backShadowDistribute': true,

'bottomShadow': true,
	    'bottomShadowSize': 1.5,
	    'bottomShadowOffset': 0,
	    'bottomShadowDarkAlpha': .7,
	    'bottomShadowLightAlpha': .1,
	    'bottomShadowDistribute': true,

'setPeelOnInit': true,
	    'clippingBoxScale': 4,
	    'flipConstraintOffset': 5,
	    'dragPreventsDefault': true
  	}
  	/**
    * Sets the corner for the peel effect to happen from (default is bottom right).
    * @param {Mixed} [...] Either x,y or a corner id.
    * @public
    */
    Peel.prototype.setCorner = function() {
	    var args = arguments;
	    if (args[0] === undefined) {
	      args = [Peel.Corners.BOTTOM_RIGHT];
	    } else if (args[0].length) {
	      args = args[0];
	    }
   		this.corner = this.getPointOrCorner(args);
    }
    /**
    * Sets a pre-defined "mode".
    * @param {string} mode The mode to set.
    * @public
    */
    Peel.prototype.setMode = function(mode) {
	    if (mode === 'book') {
	      // The order of constraints is important here so that the peel line
	      // approaches the horizontal smoothly without jumping.
	      this.addPeelConstraint(Peel.Corners.BOTTOM_LEFT);
	      this.addPeelConstraint(Peel.Corners.TOP_LEFT);
	      // Removing effect distribution will make the book still have some
	      // depth to the effect while fully open.
	      this.setOption('backReflection', false);
	      this.setOption('backShadowDistribute', false);
	      this.setOption('bottomShadowDistribute', false);
	    } else if (mode === 'calendar') {
	      this.addPeelConstraint(Peel.Corners.TOP_RIGHT);
	      this.addPeelConstraint(Peel.Corners.TOP_LEFT);
	    }
    }
    /**
    * Sets a path along which the peel will follow.
    * Can be a flat line segment or a bezier curve.
    * @param {...number} x/y Points along the path. 4 arguments indicates a
    *     linear path along 2 points (p1 to p2), while 8 arguments indicates a
    *     bezier curve from p1 to p2 using control points c1 and c2. The first
    *     and last two arguments represent p1 and p2, respectively.
    * @public
    */
    Peel.prototype.setPeelPath = function(x1, y1) {
	    var args = arguments, p1, p2, c1, c2;
	    p1 = new Point(x1, y1);
	    if (args.length === 4) {
	      p2 = new Point(args[2], args[3]);
	      this.path = new LineSegment(p1, p2);
	    } else if (args.length === 8) {
	      c1 = new Point(args[2], args[3]);
	      c2 = new Point(args[4], args[5]);
	      p2 = new Point(args[6], args[7]);
	      this.path = new BezierCurve(p1, c1, c2, p2);
	    }
  	}
  	/**
	   * Sets a function to be called when the user drags, either with a mouse or
	   * with a finger (touch events).
	   * @param {Function} fn The function to be called on drag. This function will
	   *     be called with the Peel instance as the "this" keyword, the original
	   *     event as the first argument, and the x, y coordinates of the drag as
	   *     the 2nd and 3rd arguments, respectively.
	   * @param {HTMLElement} el The element to initiate the drag on mouse/touch start.
	   *     If not passed, this will be the element associated with the Peel
	   *     instance. Allowing this to be passed lets another element serve as a
	   *     "hit area" that can be larger than the element itself.
	   * @public
	   */
	Peel.prototype.handleDrag = function(fn, el) {
	    this.dragHandler = fn;
	    this.setupDragEvents(el);
    }
    /**
	   * Sets a function to be called when the user either clicks with a mouse or
	   * taps with a finger (touch events).
	   * @param {Function} fn The function to be called on press. This function will
	   *     be called with the Peel instance as the "this" keyword, the original
	   *     event as the first argument, and the x, y coordinates of the event as
	   *     the 2nd and 3rd arguments, respectively.
	   * @param {HTMLElement} el The element to initiate the event.
	   *     If not passed, this will be the element associated with the Peel
	   *     instance. Allowing this to be passed lets another element serve as a
	   *     "hit area" that can be larger than the element itself.
	   * @public
	   */
	Peel.prototype.handlePress = function(fn, el) {
	    this.pressHandler = fn;
	    this.setupDragEvents(el);
	}
	/**
     * Sets up the drag events needed for both drag and press handlers.
     * @param {HTMLElement} el The element to initiate the dragStart event on.
     * @private
    */
    Peel.prototype.setupDragEvents = function(el) {
	    var self = this, isDragging, moveName, endName;

if (this.dragEventsSetup) {
	      return;
	    }

el = el || this.el;

function dragStart (touch, evt) {
	      if (self.getOption('dragPreventsDefault')) {
	        evt.preventDefault();
	      }
	      moveName = touch ? 'touchmove' : 'mousemove';
	      endName  = touch ? 'touchend' : 'mouseup';

addEvent(docEl, moveName, dragMove);
	      addEvent(docEl, endName, dragEnd);
	      isDragging = false;
	    }

function dragMove (evt) {
	      if (self.dragHandler) {
	        callHandler(self.dragHandler, evt);
	      }
	      isDragging = true;
	    }

function dragEnd(evt) {
	      if (!isDragging && self.pressHandler) {
	        callHandler(self.pressHandler, evt);
	      }
	      removeEvent(docEl, moveName, dragMove);
	      removeEvent(docEl, endName, dragEnd);
	    }

function callHandler(fn, evt) {
	      var coords = getEventCoordinates(evt, self.el);
	      fn.call(self, evt, coords.x, coords.y);
	    }

this.addEvent(el, 'mousedown', dragStart.bind(this, false));
	    this.addEvent(el, 'touchstart', dragStart.bind(this, true));
	    this.dragEventsSetup = true;
    }
    /**
    * Remove all event handlers previously added to the instance.
    * @public
    */
    Peel.prototype.removeEvents = function() {
	    this.events.forEach(function(e, i) {
	      removeEvent(e.el, e.type, e.handler);
	    });
	    this.events = [];
    }
    /**
	* Sets the peel effect to a point in time along a previously
	* specified path. Will throw an error if no path exists.
    * @param {number} n The time value (between 0 and 1).
	* @public
    */
    Peel.prototype.setTimeAlongPath = function(t) {
   		t = clamp(t);
   		var point = this.path.getPointForTime(t);
   		this.timeAlongPath = t;
   		this.setPeelPosition(point.x, point.y);
    }
    /**
    * Sets a threshold above which the top layer (including the backside) layer
    * will begin to fade out. This is calculated based on the visible clipped
    * area of the polygon. If a peel path is set, it will use the progress along
    * the path instead.
    * @param {number} n A point between 0 and 1.
    * @public
    */
    Peel.prototype.setFadeThreshold = function(n) {
   		 this.fadeThreshold = n;
    }
    /**
    * Sets the position of the peel effect. This point is the position
    * of the corner that is being peeled back.
    * @param {Mixed} [...] Either x,y or a corner id.
    * @public
    */
    Peel.prototype.setPeelPosition = function() {
	    var pos = this.getPointOrCorner(arguments);
	    pos = this.getConstrainedPeelPosition(pos);
	    if (!pos) {
	      return;
	    }
	    this.peelLineSegment = this.getPeelLineSegment(pos);
	    this.peelLineRotation = this.peelLineSegment.getAngle();
	    this.setClipping();
	    this.setBackTransform(pos);
	    this.setEffects();
    }
    /**
    * Sets a constraint on the distance of the peel. This can be thought of as a
    * point on the layers that are connected and cannot be torn apart. Typically
    * this only makes sense as a point on the outer edge, such as the left edge
    * of an open book, or the top edge of a calendar. In this case, simply using
    * 2 constraint points (top-left/bottom-left for a book, etc) will create the
    * desired effect. An arbitrary point can also be used with an effect like a
    * thumbtack holding the pages together.
    * @param {Mixed} [...] Either x,y or a corner id.
    * @public
    */
    /**
    * Sets the corner for the peel effect to happen from.
    * @public
    */
    Peel.prototype.addPeelConstraint = function() {
	    var p = this.getPointOrCorner(arguments);
	    var radius = this.corner.subtract(p).getLength();
	    this.constraints.push(new Circle(p, radius));
	    this.calculateFlipConstraint();
    }
    /**
    * Sets an option to use for the effect.
    * @param {string} key The option to set.
    * @param {Mixed} value The value for the option.
    * @public
    */
    Peel.prototype.setOption = function(key, value) {
    	this.options[key] = value;
    }
    /**
    * Gets an option set by the user.
    * @param {string} key The key of the option to get.
    * @returns {Mixed}
    * @public
    */
    Peel.prototype.getOption = function(key) {
    	return this.options[camelize(key)];
    }
    /**
    * Gets the ratio of the area of the clipped top layer to the total area.
    * @returns {number} A value between 0 and 1.
    * @public
    */
  	Peel.prototype.getAmountClipped = function() {
    	var topArea = this.getTopClipArea();
    	var totalArea = this.width * this.height;
    	return normalize(topArea, totalArea, 0);
  	}
  	/**
    * Adds an event listener to the element and keeps track of it for later
    * removal.
    * @param {Element} el The element to add the handler to.
    * @param {string} type The event type.
    * @param {Function} fn The handler function.
    * @private
    */
    Peel.prototype.addEvent = function(el, type, fn) {
	    addEvent(el, type, fn);
	    this.events.push({
	      el: el,
	      type: type,
	      handler: fn
	    });
	    return fn;
    }
    /**
    * Gets the area of the clipped top layer.
    * @returns {number}
    * @private
    */
    Peel.prototype.getTopClipArea = function() {
	    var top  = new Polygon();
	    this.elementBox.forEach(function(side) {
	      this.distributeLineByPeelLine(side, top);
	    }, this);
	    return Polygon.getArea(top.getPoints());
    }
    /**
    * Determines which of the constraints should be used as the flip constraint
    * by checking which has a y value closes to the corner (because the
    * constraint operates relative to the vertical midline). Only one constraint
    * should be required - changing the order of the constraints can help to
    * achieve the proper effect and more than one will interfere with each other.
    * @private
    */
    Peel.prototype.calculateFlipConstraint = function() {
	    var corner = this.corner, arr = this.constraints.concat();
	    this.flipConstraint = arr.sort(function(a, b) {
	      var aY = corner.y - a.center.y;
	      var bY = corner.y - b.center.y;
	      return a - b;
	    })[0];
    }
    /**
    * Called when the drag event starts.
    * @param {Event} evt The original DOM event.
    * @param {string} type The event type, "mouse" or "touch".
    * @param {Function} fn The handler function to be called on drag.
    * @private
    */
    Peel.prototype.dragStart = function(evt, type, fn) {
    }
    /**
    * Calls an event handler using the coordinates of the event.
    * @param {Event} evt The original event.
    * @param {Function} fn The handler to call.
    * @private
    */
  	Peel.prototype.fireHandler = function(evt, fn) {
	    var coords = getEventCoordinates(evt, this.el);
	    fn.call(this, evt, coords.x, coords.y);
    }
    /**
    * Sets the clipping points of the top and back layers based on a line
    * segment that represents the peel line.
    * @private
    */
    Peel.prototype.setClipping = function() {
	    var top  = new Polygon();
	    var back = new Polygon();
	    this.clippingBox.forEach(function(side) {
	      this.distributeLineByPeelLine(side, top, back);
	    }, this);

this.topClip.setPoints(top.getPoints());
	    this.backClip.setPoints(back.getPoints());
    }
    /**
    * Distributes the first point in the given line segment and its intersect
    * with the peel line, if there is one.
    * @param {LineSegment} seg The line segment to check against.
    * @param {Polygon} poly1 The first polygon.
    * @param {Polygon} [poly2] The second polygon.
    * @private
    */
 	Peel.prototype.distributeLineByPeelLine = function(seg, poly1, poly2) {
	    var intersect = this.peelLineSegment.getIntersectPoint(seg);
	    this.distributePointByPeelLine(seg.p1, poly1, poly2);
	    this.distributePointByPeelLine(intersect, poly1, poly2);
    }
    /**
    * Distributes the given point to one of two polygons based on which side of
    * the peel line it falls upon (if it falls directly on the line segment
    * it is added to both).
    * @param {Point} p The point to be distributed.
    * @param {Polygon} poly1 The first polygon.
    * @param {Polygon} [poly2] The second polygon.
    * @private
    */
    Peel.prototype.distributePointByPeelLine = function(p, poly1, poly2) {
	    if (!p) return;
	    var d = this.peelLineSegment.getPointDeterminant(p);
	    if (d <= 0) {
	      poly1.addPoint(p);
	    }
	    if (d >= 0 && poly2) {
	      poly2.addPoint(this.flipPointHorizontally(p));
	    }
    }
    /**
    * Sets the options for the effect, merging in defaults.
    * @param {Object} opt User options.
    * @private
    */
  	Peel.prototype.setOptions = function(opt) {
	    var options = opt || {}, defaults = Peel.Defaults;
	    for (var key in defaults) {
	      if (!defaults.hasOwnProperty(key) || key in options) {
	        continue;
	      }
	      options[key] = defaults[key];
	    }
	    this.options = options;
    }
    /**
    * Finds or creates a layer in the dom.
    * @param {string} id The internal id of the element to be found or created.
    * @param {HTMLElement} parent The parent if the element needs to be created.
    * @param {numer} zIndex The z index of the layer.
    * @returns {HTMLElement}
    * @private
    */
    Peel.prototype.findOrCreateLayer = function(id, parent, zIndex) {
	    var optId = id + '-element';
	    var domId = prefix(id);
	    var el = getElement(this.getOption(optId) || '.' + domId, parent);
	    if (!el) {
	      el = createElement(parent, domId);
	    }
	    addClass(el, prefix('layer'));
	    setZIndex(el, zIndex);
	    return el;
    }
    /**
    * Returns either a point created from 2 arguments (x/y) or a corner point
    * created from the first argument as a corner id.
    * @param {Arguments} args The arguments object from the original function.
    * @returns {Point}
    * @private
    */
    Peel.prototype.getPointOrCorner = function(args) {
	    if (args.length === 2) {
	      return new Point(args[0], args[1]);
	    } else if(typeof args[0] === 'number') {
	      return this.getCornerPoint(args[0]);
	    }
	    return args[0];
    }
    /**
    * Returns a corner point based on an id defined in Peel.Corners.
    * @param {number} id The id of the corner.
    * @private
    */
    Peel.prototype.getCornerPoint = function(id) {
	    var x = +!!(id & 1) * this.width;
	    var y = +!!(id & 2) * this.height;
	    return new Point(x, y);
    }
    /**
    * Gets an optional clipping shape that may be set by the user.
    * @returns {Object}
    * @private
    */
    Peel.prototype.getOptionalShape = function() {
	    var shapes = ['rect', 'polygon', 'path', 'circle'], found;
	    shapes.some(function(type) {
	      var attr = this.getOption(type), obj;
	      if (attr) {
	        obj = {};
	        obj.attributes = attr;
	        obj.type = type;
	        found = obj;
	      }
	      return found;
	    }, this);
	    return found;
    }
    /**
    * Sets up the main layers used for the effect that may include a possible
    * subclip shape.
    * @private
    */
    Peel.prototype.setupLayers = function() {
	    var shape = this.getOptionalShape();

// The inner layers may be wrapped later, so keep a reference to them here.
	    var topInnerLayer  = this.topLayer  = this.findOrCreateLayer('top', this.el, 2);
	    var backInnerLayer = this.backLayer = this.findOrCreateLayer('back', this.el, 3);

this.bottomLayer = this.findOrCreateLayer('bottom', this.el, 1);

if (shape) {
	      // If there is an SVG shape specified in the options, then this needs to
	      // be a separate clipped element because Safari/Mobile Safari can't handle
	      // nested clip-paths. The current top/back element will become the shape
	      // clip, so wrap them with an "outer" clip element that will become the
	      // new layer for the peel effect. The bottom layer does not require this
	      // effect, so the shape clip can be set directly on it.
	      this.topLayer  = this.wrapShapeLayer(this.topLayer, 'top-outer-clip');
	      this.backLayer = this.wrapShapeLayer(this.backLayer, 'back-outer-clip');

this.topShapeClip    = new SVGClip(topInnerLayer, shape);
	      this.backShapeClip   = new SVGClip(backInnerLayer, shape);
	      this.bottomShapeClip = new SVGClip(this.bottomLayer, shape);

if (this.getOption('topShadowCreatesShape')) {
	        this.topShadowElement = this.setupDropShadow(shape, topInnerLayer);
	      }
	    } else {
	      this.topShadowElement = this.findOrCreateLayer('top-shadow', topInnerLayer, 1);
	    }

this.topClip = new SVGClip(this.topLayer);
	    this.backClip = new SVGClip(this.backLayer);

this.backShadowElement     = this.findOrCreateLayer('back-shadow', backInnerLayer, 1);
	    this.backReflectionElement = this.findOrCreateLayer('back-reflection', backInnerLayer, 2);
	    this.bottomShadowElement   = this.findOrCreateLayer('bottom-shadow', this.bottomLayer, 1);

this.usesBoxShadow = !shape;
    }
    /**
    * Creates an inline SVG element to be used as a layer for a drop shadow filter
    * effect. Note that drop shadow filters currently have some odd quirks in
    * Blink such as blur radius changing depending on rotation, etc.
    * @param {Object} shape A shape describing the SVG element to be used.
    * @param {HTMLElement} parent The parent element where the layer will be added.
    * @returns {SVGElement}
    * @private
    */
    Peel.prototype.setupDropShadow = function(shape, parent) {
	    var svg = createSVGElement('svg', parent, {
	      'class': prefix('layer')
	    });
	    createSVGElement(shape.type, svg, shape.attributes);
	    return svg;
    }

/**
    * Wraps the passed element in another layer, preserving its z-index. Also
    * add a "shape-layer" class to the layer which now becomes a shape clip.
    * @param {HTMLElement} el The element to become the wrapped shape layer.
    * @param {string} id The identifier for the new layer that will wrap the element.
    * @returns {HTMLElement} The new element that wraps the shape layer.
    * @private
    */
    Peel.prototype.wrapShapeLayer = function(el, id) {
	    var zIndex = getZIndex(el);
	    addClass(el, prefix('shape-layer'));
	    var outerLayer = this.findOrCreateLayer(id, this.el, zIndex);
	    outerLayer.appendChild(el);
	    return outerLayer;
    }
    /**
    * Sets up the dimensions of the element box and clipping box that area used
    * in the effect.
    * @private
    */
    Peel.prototype.setupDimensions = function() {
	    this.width  = this.el.offsetWidth;
	    this.height = this.el.offsetHeight;
	    this.center = new Point(this.width / 2, this.height / 2);

this.elementBox  = this.getScaledBox(1);
	    this.clippingBox = this.getScaledBox(this.getOption('clippingBoxScale'));
    }
    /**
    * Gets a box defined by 4 line segments that is at a scale of the main
    * element.
    * @param {number} scale The scale for the box to be.
    * @private
    */
    Peel.prototype.getScaledBox = function(scale) {

// Box scale is equal to:
	    // 1 * the bottom/right scale
	    // 0 * the top/left scale.
	    var brScale = scale;
	    var tlScale = scale - 1;

var tl = new Point(-this.width * tlScale, -this.height * tlScale);
	    var tr = new Point( this.width * brScale, -this.height * tlScale);
	    var br = new Point( this.width * brScale,  this.height * brScale);
	    var bl = new Point(-this.width * tlScale,  this.height * brScale);

return [
	      new LineSegment(tl, tr),
	      new LineSegment(tr, br),
	      new LineSegment(br, bl),
	      new LineSegment(bl, tl)
	    ];
    }
    /**
    * Returns the peel position adjusted by constraints, if there are any.
    * @param {Point} point The peel position to be constrained.
    * @returns {Point}
    * @private
    */
    Peel.prototype.getConstrainedPeelPosition = function(pos) {
	    this.constraints.forEach(function(area) {
	      var offset = this.getFlipConstraintOffset(area, pos);
	      if (offset) {
	        area = new Circle(area.center, area.radius - offset);
	      }
	      pos = area.constrainPoint(pos);
	    }, this);
	    return pos;
    }
    /**
    * Returns an offset to "pull" a corner in to prevent the peel effect from
    * suddenly flipping around its axis. This offset is intended to be applied
    * on the Y axis when dragging away from the center.
    * @param {Circle} area The constraint to check against.
    * @param {Point} point The peel position to be constrained.
    * @returns {number|undefined}
    * @private
    */
    Peel.prototype.getFlipConstraintOffset = function(area, pos) {
	    var offset = this.getOption('flipConstraintOffset');
	    if (area === this.flipConstraint && offset) {
	      var cornerToCenter = this.corner.subtract(this.center);
	      var cornerToConstraint = this.corner.subtract(area.center);
	      var baseAngle = cornerToConstraint.getAngle();

// Normalized angles are rotated to be in the same space relative
	      // to the constraint.
	      var nCornerToConstraint = cornerToConstraint.rotate(-baseAngle);
	      var nPosToConstraint = pos.subtract(area.center).rotate(-baseAngle);

// Flip the vector vertically if the corner is in the bottom left or top
	      // right relative to the center, as the effect should always pull away
	      // from the vertical midline.
	      if (cornerToCenter.x * cornerToCenter.y < 0) {
	        nPosToConstraint.y *= -1;
	      }

if (nPosToConstraint.x > 0 && nPosToConstraint.y > 0) {
	        return normalize(nPosToConstraint.getAngle(), 45, 0) * offset;
	      }

}
    }
    /**
    * Gets the line segment that represents the current peel line.
    * @param {Point} point The position of the peel corner.
    * @returns {LineSegment}
    * @private
    */
    Peel.prototype.getPeelLineSegment = function(point) {
	    // The point midway between the peel position and the corner.
	    var halfToCorner = this.corner.subtract(point).scale(.5);
	    var midpoint = point.add(halfToCorner);
	    if (halfToCorner.x === 0 && halfToCorner.y === 0) {
	      // If the corner is the same as the point, then set half to corner
	      // to be the center, and keep the midpoint where it is. This will
	      // ensure a non-zero peel line.
	      halfToCorner = point.subtract(this.center);
	    }
	    var l = halfToCorner.getLength()
	    var mult = (Math.max(this.width, this.height) / l) * 10;
	    var half = halfToCorner.rotate(-90).scale(mult);
	    var p1 = midpoint.add(half);
	    var p2 = midpoint.subtract(half);
	    return new LineSegment(p1, p2);
    }
    /**
    * Sets the transform of the back layer.
    * @param {Point} pos The position of the peeling corner.
    * @private
    */
    Peel.prototype.setBackTransform = function(pos) {
	    var mirroredCorner = this.flipPointHorizontally(this.corner);
	    var r = (this.peelLineRotation - 90) * 2;
	    var t = pos.subtract(mirroredCorner.rotate(r));
	    var css = 'translate('+ round(t.x) +'px, '+ round(t.y) +'px) rotate('+ round(r) +'deg)';
	    setTransform(this.backLayer, css);

// Set the top shadow element here as well, as the
	    // position and rotation matches that of the back layer.
	    setTransform(this.topShadowElement, css);
    }
    /**
    * Gets the distance of the peel line along an imaginary line that runs
    * between the corners that it "faces". For example, if the peel line
    * is rotated 45 degrees, then it can be considered to be between the top left
    * and bottom right corners. This function will return how far the peel line
    * has advanced along that line.
    * @returns {number} A position >= 0.
    * @private
    */
    Peel.prototype.getPeelLineDistance = function() {
	    var cornerId, opposingCornerId, corner, opposingCorner;
	    if (this.peelLineRotation < 90) {
	      cornerId = Peel.Corners.TOP_RIGHT;
	      opposingCornerId = Peel.Corners.BOTTOM_LEFT;
	    } else if (this.peelLineRotation < 180) {
	      cornerId = Peel.Corners.BOTTOM_RIGHT;
	      opposingCornerId = Peel.Corners.TOP_LEFT;
	    } else if (this.peelLineRotation < 270) {
	      cornerId = Peel.Corners.BOTTOM_LEFT;
	      opposingCornerId = Peel.Corners.TOP_RIGHT;
	    } else if (this.peelLineRotation < 360) {
	      cornerId = Peel.Corners.TOP_LEFT;
	      opposingCornerId = Peel.Corners.BOTTOM_RIGHT;
	    }
	    corner = this.getCornerPoint(cornerId);
	    opposingCorner = this.getCornerPoint(opposingCornerId);

// Scale the line segment past the original corners so that the effects
	    // can have a nice fadeout even past 1.
	    var cornerToCorner = new LineSegment(corner, opposingCorner).scale(2);
	    var intersect = this.peelLineSegment.getIntersectPoint(cornerToCorner);
	    if (!intersect) {
	      // If there is no intersect, then assume that it has run past the opposing
	      // corner and set the distance to well past the full distance.
	      return 2;
	    }
	    var distanceToPeelLine = corner.subtract(intersect).getLength();
	    var totalDistance      = corner.subtract(opposingCorner).getLength();
	    return (distanceToPeelLine / totalDistance);
    }
    /**
    * Sets shadows and fade effects.
    * @private
    */
    Peel.prototype.setEffects = function() {
	    var t = this.getPeelLineDistance();
	    this.setTopShadow(t);
	    this.setBackShadow(t);
	    this.setBackReflection(t);
	    this.setBottomShadow(t);
	    this.setFade();
    }
    /**
    * Sets the top shadow as either a box-shadow or a drop-shadow filter.
    * @param {number} t Position of the peel line from corner to corner.
    * @private
    */
    Peel.prototype.setTopShadow = function(t) {
	    if (!this.getOption('topShadow')) {
	      return;
	    }
	    var sBlur  = this.getOption('topShadowBlur');
	    var sX     = this.getOption('topShadowOffsetX');
	    var sY     = this.getOption('topShadowOffsetY');
	    var alpha  = this.getOption('topShadowAlpha');
	    var sAlpha = this.exponential(t, 5, alpha);
	    if (this.usesBoxShadow) {
	      setBoxShadow(this.topShadowElement, sX, sY, sBlur, 0, sAlpha);
	    } else {
	      setDropShadow(this.topShadowElement, sX, sY, sBlur, sAlpha);
	    }
    }
    /**
    * Gets a number either distributed along a bell curve or increasing linearly.
    * @param {number} n The number to transform.
    * @param {boolean} dist Whether or not to use distribution.
    * @param {number} mult A multiplier for the result.
    * @returns {number}
    * @private
    */
    Peel.prototype.distributeOrLinear = function(n, dist, mult) {
	    if (dist) {
	      return distribute(n, mult);
	    } else {
	      return n * mult;
	    }
    }
    /**
    * Gets a number either distributed exponentially, clamped to a range between
    * 0 and 1, and multiplied by a multiplier.
    * @param {number} n The number to transform.
    * @param {number} exp The exponent to be used.
    * @param {number} mult A multiplier for the result.
    * @returns {number}
    * @private
    */
    Peel.prototype.exponential = function(n, exp, mult) {
    	return mult * clamp(Math.pow(1 + n, exp) - 1);
    }
    /**
    * Sets reflection of the back face as a linear gradient.
    * @param {number} t Position of the peel line from corner to corner.
    * @private
    */
    Peel.prototype.setBackReflection = function(t) {
	    var stops = [];
	    if (this.canSetLinearEffect('backReflection', t)) {

var rDistribute = this.getOption('backReflectionDistribute');
	      var rSize = this.getOption('backReflectionSize');
	      var rOffset = this.getOption('backReflectionOffset');
	      var rAlpha = this.getOption('backReflectionAlpha');

var reflectionSize = this.distributeOrLinear(t, rDistribute, rSize);
	      var rStop  = t - rOffset;
	      var rMid   = rStop - reflectionSize;
	      var rStart = rMid - reflectionSize;

stops.push(getWhiteStop(0, 0));
	      stops.push(getWhiteStop(0, rStart));
	      stops.push(getWhiteStop(rAlpha, rMid));
	      stops.push(getWhiteStop(0, rStop));
	    }
	    setBackgroundGradient(this.backReflectionElement, 180 - this.peelLineRotation, stops);
    }
    /**
    * Sets shadow of the back face as a linear gradient.
    * @param {number} t Position of the peel line from corner to corner.
    * @private
    */
    Peel.prototype.setBackShadow = function(t) {
	    var stops = [];
	    if (this.canSetLinearEffect('backShadow', t)) {

var sSize       = this.getOption('backShadowSize');
	      var sOffset     = this.getOption('backShadowOffset');
	      var sAlpha      = this.getOption('backShadowAlpha');
	      var sDistribute = this.getOption('backShadowDistribute');

var shadowSize  = this.distributeOrLinear(t, sDistribute, sSize);
	      var shadowStop  = t - sOffset;
	      var shadowMid   = shadowStop - shadowSize;
	      var shadowStart = shadowMid - shadowSize;

stops.push(getBlackStop(0, 0));
	      stops.push(getBlackStop(0, shadowStart));
	      stops.push(getBlackStop(sAlpha, shadowMid));
	      stops.push(getBlackStop(sAlpha, shadowStop));
	    }
	    setBackgroundGradient(this.backShadowElement, 180 - this.peelLineRotation, stops);
    }
    /**
    * Sets the bottom shadow as a linear gradient.
    * @param {number} t Position of the peel line from corner to corner.
    * @private
    */
    Peel.prototype.setBottomShadow = function(t) {
	    var stops = [];
	    if (this.canSetLinearEffect('bottomShadow', t)) {

// Options
	      var sSize = this.getOption('bottomShadowSize');
	      var offset = this.getOption('bottomShadowOffset');
	      var darkAlpha = this.getOption('bottomShadowDarkAlpha');
	      var lightAlpha = this.getOption('bottomShadowLightAlpha');
	      var sDistribute = this.getOption('bottomShadowDistribute');

/**
    * Sets the fading effect of the top layer, if a threshold is set.
    * @private
    */
    Peel.prototype.setFade = function() {
	    var threshold = this.fadeThreshold, opacity = 1, n;
	    if (threshold) {
	      if (this.timeAlongPath !== undefined) {
	        n = this.timeAlongPath;
	      } else {
	        n = this.getAmountClipped();
	      }
	      if (n > threshold) {
	        opacity = (1 - n) / (1 - threshold);
	      }
	      setOpacity(this.topLayer, opacity);
	      setOpacity(this.backLayer, opacity);
	      setOpacity(this.bottomShadowElement, opacity);
	    }
    }
    /**
    * Flips a point along an imaginary vertical midpoint.
    * @param {Array} points The points to be flipped.
    * @returns {Array}
    * @private
    */
    Peel.prototype.flipPointHorizontally = function(p) {
    	return new Point(p.x - ((p.x - this.center.x) * 2), p.y);
    }
    /**
    * Post setup initialization.
    * @private
    */
    Peel.prototype.init = function() {
	    if (this.getOption('setPeelOnInit')) {
	      this.setPeelPosition(this.corner);
	    }
	    addClass(this.el, prefix('ready'));
    }
    /**
    * Class that clips an HTMLElement by an SVG path.
    * @param {HTMLElement} el The element to be clipped.
    * @param {Object} [shape] An object defining the SVG element to use in the new
    *     clip path. Defaults to a polygon.
    * @constructor
    */
    function SVGClip (el, shape) {
	    this.el = el;
	    this.shape = SVGClip.createClipPath(el, shape || {
	      'type': 'polygon'
	    });
	    // Chrome needs this for some reason for the clipping to work.
	    setTransform(this.el, 'translate(0px,0px)');
    }
    /**
    * Sets up the global SVG element and its nested defs object to use for new
    * clip paths.
    * @returns {SVGElement}
    * @public
    */
    SVGClip.getDefs = function() {
	    if (!this.defs) {
	      this.svg  = createSVGElement('svg', null, {
	        'class': prefix('svg-clip-element')
	      });
	      this.defs = createSVGElement('defs', this.svg);
	    }
	    return this.defs;
    }
    /**
    * Creates a new <clipPath> SVG element and sets the passed html element to be
    * clipped by it.
    * @param {HTMLElement} el The html element to be clipped.
    * @param {Object} obj An object defining the SVG element to be used in the
    *     clip path.
    * @returns {SVGElement}
    * @public
    */
    SVGClip.createClipPath = function(el, obj) {
	    var id = SVGClip.getId();
	    var clipPath = createSVGElement('clipPath', this.getDefs());
	    var svgEl = createSVGElement(obj.type, clipPath, obj.attributes);
	    setSVGAttribute(clipPath, 'id', id);
	    setCSSClip(el, 'url(#' + id + ')');
	    return svgEl;
    }
    /**
    * Gets the next svg clipping id.
    * @public
    */
    SVGClip.getId = function() {
	    if (!SVGClip.id) {
	      SVGClip.id = 1;
	    }
	    return 'svg-clip-' + SVGClip.id++;
    }
    /**
    * Sets the "points" attribute of the clip path shape. This only makes sense
    * for polygon shapes.
    * @param {Array} points The points to be used.
    * @public
    */
    SVGClip.prototype.setPoints = function(points) {
	    var str = points.map(function(p) {
	      return round(p.x) + ',' + round(p.y);
	    }).join(' ');
	    setSVGAttribute(this.shape, 'points', str);
    }
    /**
    * A class that represents a circle.
    * @param {Point} center The center point.
    * @param {Point} radius The radius.
    * @constructor
    */
    function Circle (center, radius) {
	    this.center = center;
	    this.radius = radius;
    }
    /**
    * Determines whether a point is contained within the circle.
    * @param {Point} p The point.
    * @returns {boolean}
    * @public
    */
    Circle.prototype.containsPoint = function(p) {
	    if(this.boundingRectContainsPoint(p)) {
	        var dx = this.center.x - p.x;
	        var dy = this.center.y - p.y;
	        dx *= dx;
	        dy *= dy;
	        var distanceSquared = dx + dy;
	        var radiusSquared = this.radius * this.radius;
	        return distanceSquared <= radiusSquared;
	    }
	    return false;
    }
    /**
    * Determines whether a point is contained within the bounding box of the circle.
    * @param {Point} p The point.
    * @returns {boolean}
    * @private
    */
    Circle.prototype.boundingRectContainsPoint = function(p) {
        return p.x >= this.center.x - this.radius && p.x <= this.center.x + this.radius &&
           p.y >= this.center.y - this.radius && p.y <= this.center.y + this.radius;
    }
    /**
    * Moves a point outside the circle to the closest point on the circumference.
    * Rotated angle from the center point should be the same.
    * @param {Point} p The point.
    * @returns {boolean}
    * @public
    */
    Circle.prototype.constrainPoint = function(p) {
	    if (!this.containsPoint(p)) {
	      var rotation = p.subtract(this.center).getAngle();
	      p = this.center.add(new Point(this.radius, 0).rotate(rotation));
	    }
	    return p;
    }
    /**
    * A class that represents a polygon.
    * @constructor
    */
    function Polygon() {
    	this.points = [];
    }
    /**
    * Gets the area of the polygon.
    * @param {Array} points The points describing the polygon.
    * @public
    */
    Polygon.getArea = function(points) {
	    var sum1 = 0, sum2 = 0;
	    points.forEach(function(p, i, arr) {
	      var next = arr[(i + 1) % arr.length];
	      sum1 += (p.x * next.y);
	      sum2 += (p.y * next.x);
	    });
	    return (sum1 - sum2) / 2;
    }
    /**
    * Adds a point to the polygon.
    * @param {Point} point
    * @public
    */
    Polygon.prototype.addPoint = function(point) {
   		 this.points.push(point);
    }
    /**
    * Gets the points of the polygon as an array.
    * @returns {Array}
    * @public
    */
    Polygon.prototype.getPoints = function() {
   		 return this.points;
    }
    /**
    * A class representing a bezier curve.
    * @param {Point} p1 The starting point.
    * @param {Point} c1 The control point of p1.
    * @param {Point} c2 The control point of p2.
    * @param {Point} p2 The ending point.
    * @constructor
    */
    function BezierCurve (p1, c1, c2, p2) {
	    this.p1 = p1;
	    this.c1 = c1;
	    this.p2 = p2;
	    this.c2 = c2;
    }
    /**
    * Gets a point along the line segment for a given time.
    * @param {number} t The time along the segment, between 0 and 1.
    * @returns {Point}
    */
    BezierCurve.prototype.getPointForTime = function(t) {
	    var b0 = Math.pow(1 - t, 3);
	    var b1 = 3 * t * Math.pow(1 - t, 2);
	    var b2 = 3 * Math.pow(t, 2) * (1 - t);
	    var b3 = Math.pow(t, 3);

function crossProduct(p1, p2) {
	      return p1.x * p2.y - p1.y * p2.x;
	    }

var r = seg1.p2.subtract(seg1.p1);
	    var s = seg2.p2.subtract(seg2.p1);

var uNumerator = crossProduct(seg2.p1.subtract(seg1.p1), r);
	    var denominator = crossProduct(r, s);

if (denominator == 0) {
	      // ignoring colinear and parallel
	      return null;
	    }

var u = uNumerator / denominator;
	    var t = crossProduct(seg2.p1.subtract(seg1.p1), s) / denominator;

if ((t >= 0) && (t <= 1) && (u >= 0) && (u <= 1)) {
	      return seg1.p1.add(r.scale(t));
	    }

return null;
    }
    /**
    * Returns the angle of the line segment in degrees.
    * @returns {number}
    * @public
    */
    LineSegment.prototype.getAngle = function() {
   		 return this.getVector().getAngle();
    }
    /**
    * Gets the vector that represents the line segment.
    * @returns {Point}
    * @private
    */
    LineSegment.prototype.getVector = function() {
	    if (!this.vector) {
	      this.vector = this.p2.subtract(this.p1);
	    }
	    return this.vector;
    }
    /**
    * A class representing a point or 2D vector.
    * @param {number} x The x coordinate.
    * @param {number} y The y coordinate.
    * @constructor
    */
	function Point (x, y) {
	    this.x = x;
	    this.y = y;
	}
	/**
    * @constant
    */
    Point.DEGREES_IN_RADIANS = 180 / Math.PI;

/**
    * Gets degrees in radians.
    * @param {number} deg
    * @returns {number}
    */
    Point.degToRad = function(deg) {
   		 return deg / Point.DEGREES_IN_RADIANS;
    };
    /**
    * Gets radians in degrees.
    * @param {number} rad
    * @returns {number}
    */
    Point.radToDeg = function(rad) {
	    var deg = rad * Point.DEGREES_IN_RADIANS;
	    while(deg < 0) deg += 360;
	    return deg;
    };
    /**
    * Creates a new point given a rotation in degrees and a length.
    * @param {number} deg The rotation of the vector.
    * @param {number} len The length of the vector.
    * @returns {Point}
    */
	Point.vector = function(deg, len) {
	    var rad = Point.degToRad(deg);
	    return new Point(Math.cos(rad) * len, Math.sin(rad) * len);
	};
	/**
    * Adds a point.
    * @param {Point} p
    * @returns {Point}
    */
    Point.prototype.add = function(p) {
   		 return new Point(this.x + p.x, this.y + p.y);
    };
    /**
    * Subtracts a point.
    * @param {Point} p
    * @returns {Point}
    */
    Point.prototype.subtract = function(p) {
   		 return new Point(this.x - p.x, this.y - p.y);
    };
    /**
    * Scales a point by a scalar.
    * @param {number} n
    * @returns {Point}
    */
 	Point.prototype.scale = function(n) {
  	  return new Point(this.x * n, this.y * n);
  	};
  	/**
    * Gets the length of the distance to the point.
    * @returns {number}
    */
 	Point.prototype.getLength = function() {
   		 return Math.sqrt(Math.pow(this.x, 2) + Math.pow(this.y, 2));
  	};
  	/**
    * Gets the angle of the point in degrees.
    * @returns {number}
    */
    Point.prototype.getAngle = function() {
    	return Point.radToDeg(Math.atan2(this.y, this.x));
    };
    /**
    * Returns a new point of the same length with a different angle.
    * @param {number} deg The angle in degrees.
    * @returns {Point}
    */
    Point.prototype.setAngle = function(deg) {
   		 return Point.vector(deg, this.getLength());
    };
    /**
    * Rotates the point.
    * @param {number} deg The amount to rotate by in degrees.
    * @returns {Point}
    */
 	 Point.prototype.rotate = function(deg) {
    	return this.setAngle(this.getAngle() + deg);
 	};
 	setCssProperties();
  	win.Peel = Peel;
})(window);