dev/js/src/menu.js - KorAP/Kalamar - Gitiles

 /**
  * Create scrollable drop-down menus.
  *
  * @author Nils Diewald
  */
 /*
  * TODO: space is not a valid prefix!
  */
 define([
   'menu/item',
   'menu/prefix',
   'util'
 ], function (defaultItemClass,
 	     defaultPrefixClass) {

   // Todo: This may not be necessary
   // Default maximum number of menu items
   var menuLimit = 8;

   function _codeFromEvent (e) {
     if (e.charCode && (e.keyCode == 0))
       return e.charCode
     return e.keyCode;
   };


   /**
    * List of items for drop down menu (complete).
    * Only a sublist of the menu is filtered (live).
    * Only a sublist of the filtered menu is visible (shown).
    */
   return {
     /**
      * Create new Menu based on the action prefix
      * and a list of menu items.
      *
      * @this {Menu}
      * @constructor
      * @param {string} Context prefix
      * @param {Array.<Array.<string>>} List of menu items
      */
     create : function (params) {
       return Object.create(this)._init(params);
     },

     /**
      * Destroy this menu
      * (in case you don't trust the
      * mark and sweep GC)!
      */
     destroy : function () {
       if (this._element != undefined)
 	delete this._element["menu"];

       for (var i = 0; i < this._items.length; i++) {
 	delete this._items[i]["_menu"];
       };
       delete this._prefix['_menu'];
     },

     focus : function () {
       this._element.focus();
     },

     // mouse wheel treatment
     _mousewheel : function (e) {
       var delta = 0;

       delta = e.deltaY / 120;
       if (delta > 0)
 	this.next();
       else if (delta < 0)
 	this.prev();
       e.halt();
     },

     // Arrow key and prefix treatment
     _keypress : function (e) {
       var code = _codeFromEvent(e);

       switch (code) {
       case 27: // 'Esc'
 	e.halt();
 	this.hide();
 	break;

       case 38: // 'Up'
 	e.halt();
 	this.prev();
 	break;
       case 33: // 'Page up'
 	e.halt();
 	this.prev();
 	break;
       case 40: // 'Down'
 	e.halt();
 	this.next();
 	break;
       case 34: // 'Page down'
 	e.halt();
 	this.next();
 	break;
       case 39: // 'Right'
 	if (this._prefix.active())
 	  break;

 	var item = this.liveItem(this._position);
 	if (item["further"] !== undefined) {
 	  item["further"].bind(item).apply();
 	  e.halt();
 	};
 	break;
       case 13: // 'Enter'

 	// Click on prefix
 	if (this._prefix.active())
 	  this._prefix.onclick(e);

 	// Click on item
 	else
 	  this.liveItem(this._position).onclick(e);
 	e.halt();
 	break;
       case 8: // 'Backspace'
 	this._prefix.backspace();
 	this.show();
 	e.halt();
 	break;
       default:
 	if (e.key !== undefined &&
 	    e.key.length != 1)
 	  return;

 	// Add prefix
 	this._prefix.add(e.key.toLowerCase());

 	if (!this.show()) {
 	  this.prefix('').show();
 	};
       };
     },

     // Initialize list
     _init : function (itemClass, prefixClass, params) {
       var that = this;
       this._itemClass = itemClass || defaultItemClass;

       if (prefixClass !== undefined)
 	this._prefix = prefixClass.create();
       else
 	this._prefix = defaultPrefixClass.create();

       this._prefix._menu = this;

       var e = document.createElement("ul");
       e.style.opacity = 0;
       e.style.outline = 0;
       e.setAttribute('tabindex', 0);
       e.classList.add('menu');
       e.classList.add('roll');
       e.appendChild(this._prefix.element());

       // This has to be cleaned up later on
       e["menu"] = this;

       // Arrow keys
       e.addEventListener(
 	'keypress',
 	function (ev) {
 	  that._keypress(ev)
 	},
 	false
       );

       // Mousewheel
       e.addEventListener(
 	'wheel',
 	function (ev) {
 	  that._mousewheel(ev)
 	},
 	false
       );

       this._element = e;
       this.active = false;
       this._items = new Array();
       var i;

       // Initialize item list based on parameters
       for (i in params) {
 	var obj = this._itemClass.create(params[i]);

 	// This may become circular
 	obj["_menu"] = this;

 	this._items.push(obj);
       };
       this._limit    = menuLimit;
       this._position = 0;  // position in the active list
       this._active   = -1; // active item in the item list
       this._reset();
       return this;
     },

     /**
      * Get the instantiated HTML element
      */
     element : function () {
       return this._element;
     },

     /**
      * Get the creator object for items
      */
     itemClass : function () {
       return this._itemClass;
     },

     /**
      * Get and set numerical value for limit,
      * i.e. the number of items visible.
      */
     limit : function (limit) {
       if (arguments.length === 1) {
 	this._limit = limit;
 	return this;
       };
       return this._limit;
     },

     /**
      * Upgrade this object to another object,
      * while private data stays intact.
      *
      * @param {Object} An object with properties.
      */
     upgradeTo : function (props) {
       for (var prop in props) {
 	this[prop] = props[prop];
       };
       return this;
     },

     // Reset chosen item and prefix
     _reset : function () {
       this._offset = 0;
       this._pos    = 0;
       this._prefix.value('');
     },

     /**
      * Filter the list and make it visible
      *
      * @param {string} Prefix for filtering the list
      */
     show : function () {

       // Initialize the list
       if (!this._initList())
 	return false;

       // show based on initial offset
       this._showItems(0);

       // Set the first element to active
       // Todo: Or the last element chosen
       this.liveItem(0).active(true);
       this._prefix.active(false);

       this._active = this._list[0];
       this._position = 0;
       this._element.style.opacity = 1;

       // Add classes for rolling menus
       this._boundary(true);
       return true;
     },

     hide : function () {
       this.active = false;
       this.delete();
       this._element.style.opacity = 0;
       this.onHide();
       /* this._element.blur(); */
     },

     // To be override
     onHide : function () {},

     // Initialize the list
     _initList : function () {

       // Create a new list
       if (this._list === undefined) {
 	this._list = [];
       }
       else if (this._list.length != 0) {
 	this._boundary(false);
 	this._list.length = 0;
       };

       // Offset is initially zero
       this._offset = 0;

       // There is no prefix set
       if (this.prefix().length <= 0) {
 	var i = 0;
 	for (; i < this._items.length; i++)
 	  this._list.push(i);
 	while (this._items[++i] !== undefined) {
 	  this._items[i].lowlight();
 	  // console.log(this._item);
 	};
 	return true;
       };

       // There is a prefix set, so filter the list
       var pos;
       var paddedPrefix = " " + this.prefix();

       // Iterate over all items and choose preferred matching items
       // i.e. the matching happens at the word start
       for (pos = 0; pos < this._items.length; pos++) {
 	if ((this.item(pos).lcField().indexOf(paddedPrefix)) >= 0)
 	  this._list.push(pos);
       };

       // The list is empty - so lower your expectations
       // Iterate over all items and choose matching items
       // i.e. the matching happens anywhere in the word
       if (this._list.length == 0) {
 	for (pos = 0; pos < this._items.length; pos++) {
 	  if ((this.item(pos).lcField().indexOf(this.prefix())) >= 0)
 	    this._list.push(pos);
 	};
       };

       // Filter was successful - yeah!
       return this._list.length > 0 ? true : false;
     },

     // Set boundary for viewport
     _boundary : function (bool) {
       this.item(this._list[0]).noMore(bool);
       this.item(this._list[this._list.length - 1]).noMore(bool);
     },

     /**
      * Get the prefix for filtering,
      * e.g. &quot;ve&quot; for &quot;verb&quot;
      */
     prefix : function (pref) {
       if (arguments.length === 1) {
 	this._prefix.value(pref);
 	return this;
       };
       return this._prefix.value();
     },

     // Append Items that should be shown
     _showItems : function (offset) {
       this.delete();

       // Use list
       var shown = 0;
       var i;
       for (i in this._list) {

 	// Don't show - it's before offset
 	if (shown++ < offset)
 	  continue;

 	this._append(this._list[i]);

 	if (shown >= (this.limit() + this._offset))
 	  break;
       };
     },

     /**
      * Delete all visible items from the menu element
      */
     delete : function () {
       var child;

       /*
       // Iterate over all visible items
       for (var i = 0; i <= this.limit(); i++) {

 	// there is a visible element
 	// unhighlight!
 	if (child = this.shownItem(i)) {
 	  child.lowlight();
 	  child.active(false);
 	};
       };
       */

       for (var i in this._list) {
 	var item = this._items[this._list[i]];
 	item.lowlight();
 	item.active(false);
       };

       // Remove all children
       var children = this._element.childNodes;
       for (var i = children.length - 1; i >= 1; i--) {
 	this._element.removeChild(
 	  children[i]
 	);
       };
     },


     // Append item to the shown list based on index
     _append : function (i) {
       var item = this.item(i);

       // Highlight based on prefix
       if (this.prefix().length > 0)
 	item.highlight(this.prefix());

       // Append element
       this.element().appendChild(item.element());
     },


     // Prepend item to the shown list based on index
     _prepend : function (i) {
       var item = this.item(i);

       // Highlight based on prefix
       if (this.prefix().length > 0)
 	item.highlight(this.prefix());

       var e = this.element();
       // Append element
       e.insertBefore(
 	item.element(),
 	e.children[1]
       );
     },


     /**
      * Get a specific item from the complete list
      *
      * @param {number} index of the list item
      */
     item : function (index) {
       return this._items[index]
     },


     /**
      * Get a specific item from the filtered list
      *
      * @param {number} index of the list item
      *        in the filtered list
      */
     liveItem : function (index) {
       if (this._list === undefined)
 	if (!this._initList())
 	  return;

       return this._items[this._list[index]];
     },


     /**
      * Get a specific item from the visible list
      *
      * @param {number} index of the list item
      *        in the visible list
      */
     shownItem : function (index) {
       if (index >= this.limit())
 	return;
       return this.liveItem(this._offset + index);
     },


     /**
      * Get the length of the full list
      */
     length : function () {
       return this._items.length;
     },


     /**
      * Make the next item in the filtered menu active
      */
     next : function () {

       // No active element set
       if (this._position === -1)
 	return;

       var newItem;

       // Set new live item
       if (!this._prefix.active()) {
 	var oldItem = this.liveItem(this._position);
 	oldItem.active(false);
       };

       this._position++;

       newItem = this.liveItem(this._position);

       // The next element is undefined - roll to top or to prefix
       if (newItem === undefined) {

 	// Activate prefix
 	var prefix = this._prefix;

 	// Mark prefix
 	if (prefix.isSet() && !prefix.active()) {
 	  this._position--;
 	  prefix.active(true);
 	  return;
 	}
 	else {
 	  this._offset = 0;
 	  this._position = 0;
 	  newItem = this.liveItem(0);
 	  this._showItems(0);
 	};
       }

       // The next element is outside the view - roll down
       else if (this._position >= (this.limit() + this._offset)) {
 	this._removeFirst();
 	this._offset++;
 	this._append(this._list[this._position]);
       };

       this._prefix.active(false);
       newItem.active(true);
     },

     /*
      * Page down to the first item on the next page
      */
     /*
     nextPage : function () {

       // Prefix is active
       if (this._prefix.active()) {
 	this._prefix.active(false);
       }

       // Last item is chosen
       else if (this._position >= this.limit() + this._offset) {

 	this._position = this.limit() + this._offset - 1;
 	newItem = this.liveItem(this._position);
 	var oldItem = this.liveItem(this._position--);
 	oldItem.active(false);
       }

       // Last item of page is chosen
       else if (0) {

       // Jump to last item
       else {
 	var oldItem = this.liveItem(this._position);
 	oldItem.active(false);

 	this._position = this.limit() + this._offset - 1;
 	newItem = this.liveItem(this._position);
       };

       newItem.active(true);
     },
 	*/


     /*
      * Make the previous item in the menu active
      */
     prev : function () {

       // No active element set
       if (this._position === -1) {
 	return;
 	// TODO: Choose last item
       };

       var newItem;

       // Set new live item
       if (!this._prefix.active()) {
 	var oldItem = this.liveItem(this._position--);
 	oldItem.active(false);
       };

       newItem = this.liveItem(this._position);

       // The previous element is undefined - roll to bottom
       if (newItem === undefined) {

 	// Activate prefix
 	var prefix = this._prefix;
 	this._offset = this.liveLength() - this.limit();

 	// Normalize offset
 	this._offset = this._offset < 0 ? 0 : this._offset;

 	this._position = this.liveLength() - 1;

 	if (prefix.isSet() && !prefix.active()) {
 	  this._position++;
 	  prefix.active(true);
 	  return;
 	}
 	else {
 	  newItem = this.liveItem(this._position);
 	  this._showItems(this._offset);
 	};
       }

       // The previous element is outside the view - roll up
       else if (this._position < this._offset) {
 	this._removeLast();
 	this._offset--;
 	this._prepend(this._list[this._position]);
       };

       this._prefix.active(false);
       newItem.active(true);
     },


     // Length of the filtered list
     liveLength : function () {
       if (this._list === undefined)
 	this._initList();
       return this._list.length;
     },


     // Remove the HTML node from the first item
     _removeFirst : function () {
       this.item(this._list[this._offset]).lowlight();
       this._element.removeChild(this._element.children[1]);
     },


     // Remove the HTML node from the last item
     _removeLast : function () {
       this.item(this._list[this._offset + this.limit() - 1]).lowlight();
       this._element.removeChild(this._element.lastChild);
     }
   };
 });
	/**
	* Create scrollable drop-down menus.
	*
	* @author Nils Diewald
	*/
	/*
	* TODO: space is not a valid prefix!
	*/
	define([
	'menu/item',
	'menu/prefix',
	'util'
	], function (defaultItemClass,
	defaultPrefixClass) {

	// Todo: This may not be necessary
	// Default maximum number of menu items
	var menuLimit = 8;

	function _codeFromEvent (e) {
	if (e.charCode && (e.keyCode == 0))
	return e.charCode
	return e.keyCode;
	};


	/**
	* List of items for drop down menu (complete).
	* Only a sublist of the menu is filtered (live).
	* Only a sublist of the filtered menu is visible (shown).
	*/
	return {
	/**
	* Create new Menu based on the action prefix
	* and a list of menu items.
	*
	* @this {Menu}
	* @constructor
	* @param {string} Context prefix
	* @param {Array.<Array.<string>>} List of menu items
	*/
	create : function (params) {
	return Object.create(this)._init(params);
	},

	/**
	* Destroy this menu
	* (in case you don't trust the
	* mark and sweep GC)!
	*/
	destroy : function () {
	if (this._element != undefined)
	delete this._element["menu"];

	for (var i = 0; i < this._items.length; i++) {
	delete this._items[i]["_menu"];
	};
	delete this._prefix['_menu'];
	},

	focus : function () {
	this._element.focus();
	},

	// mouse wheel treatment
	_mousewheel : function (e) {
	var delta = 0;

	delta = e.deltaY / 120;
	if (delta > 0)
	this.next();
	else if (delta < 0)
	this.prev();
	e.halt();
	},

	// Arrow key and prefix treatment
	_keypress : function (e) {
	var code = _codeFromEvent(e);

	switch (code) {
	case 27: // 'Esc'
	e.halt();
	this.hide();
	break;

	case 38: // 'Up'
	e.halt();
	this.prev();
	break;
	case 33: // 'Page up'
	e.halt();
	this.prev();
	break;
	case 40: // 'Down'
	e.halt();
	this.next();
	break;
	case 34: // 'Page down'
	e.halt();
	this.next();
	break;
	case 39: // 'Right'
	if (this._prefix.active())
	break;

	var item = this.liveItem(this._position);
	if (item["further"] !== undefined) {
	item["further"].bind(item).apply();
	e.halt();
	};
	break;
	case 13: // 'Enter'

	// Click on prefix
	if (this._prefix.active())
	this._prefix.onclick(e);

	// Click on item
	else
	this.liveItem(this._position).onclick(e);
	e.halt();
	break;
	case 8: // 'Backspace'
	this._prefix.backspace();
	this.show();
	e.halt();
	break;
	default:
	if (e.key !== undefined &&
	e.key.length != 1)
	return;

	// Add prefix
	this._prefix.add(e.key.toLowerCase());

	if (!this.show()) {
	this.prefix('').show();
	};
	};
	},

	// Initialize list
	_init : function (itemClass, prefixClass, params) {
	var that = this;
	this._itemClass = itemClass \|\| defaultItemClass;

	if (prefixClass !== undefined)
	this._prefix = prefixClass.create();
	else
	this._prefix = defaultPrefixClass.create();

	this._prefix._menu = this;

	var e = document.createElement("ul");
	e.style.opacity = 0;
	e.style.outline = 0;
	e.setAttribute('tabindex', 0);
	e.classList.add('menu');
	e.classList.add('roll');
	e.appendChild(this._prefix.element());

	// This has to be cleaned up later on
	e["menu"] = this;

	// Arrow keys
	e.addEventListener(
	'keypress',
	function (ev) {
	that._keypress(ev)
	},
	false
	);

	// Mousewheel
	e.addEventListener(
	'wheel',
	function (ev) {
	that._mousewheel(ev)
	},
	false
	);

	this._element = e;
	this.active = false;
	this._items = new Array();
	var i;

	// Initialize item list based on parameters
	for (i in params) {
	var obj = this._itemClass.create(params[i]);

	// This may become circular
	obj["_menu"] = this;

	this._items.push(obj);
	};
	this._limit = menuLimit;
	this._position = 0; // position in the active list
	this._active = -1; // active item in the item list
	this._reset();
	return this;
	},

	/**
	* Get the instantiated HTML element
	*/
	element : function () {
	return this._element;
	},

	/**
	* Get the creator object for items
	*/
	itemClass : function () {
	return this._itemClass;
	},

	/**
	* Get and set numerical value for limit,
	* i.e. the number of items visible.
	*/
	limit : function (limit) {
	if (arguments.length === 1) {
	this._limit = limit;
	return this;
	};
	return this._limit;
	},

	/**
	* Upgrade this object to another object,
	* while private data stays intact.
	*
	* @param {Object} An object with properties.
	*/
	upgradeTo : function (props) {
	for (var prop in props) {
	this[prop] = props[prop];
	};
	return this;
	},

	// Reset chosen item and prefix
	_reset : function () {
	this._offset = 0;
	this._pos = 0;
	this._prefix.value('');
	},

	/**
	* Filter the list and make it visible
	*
	* @param {string} Prefix for filtering the list
	*/
	show : function () {

	// Initialize the list
	if (!this._initList())
	return false;

	// show based on initial offset
	this._showItems(0);

	// Set the first element to active
	// Todo: Or the last element chosen
	this.liveItem(0).active(true);
	this._prefix.active(false);

	this._active = this._list[0];
	this._position = 0;
	this._element.style.opacity = 1;

	// Add classes for rolling menus
	this._boundary(true);
	return true;
	},

	hide : function () {
	this.active = false;
	this.delete();
	this._element.style.opacity = 0;
	this.onHide();
	/* this._element.blur(); */
	},

	// To be override
	onHide : function () {},

	// Initialize the list
	_initList : function () {

	// Create a new list
	if (this._list === undefined) {
	this._list = [];
	}
	else if (this._list.length != 0) {
	this._boundary(false);
	this._list.length = 0;
	};

	// Offset is initially zero
	this._offset = 0;

	// There is no prefix set
	if (this.prefix().length <= 0) {
	var i = 0;
	for (; i < this._items.length; i++)
	this._list.push(i);
	while (this._items[++i] !== undefined) {
	this._items[i].lowlight();
	// console.log(this._item);
	};
	return true;
	};

	// There is a prefix set, so filter the list
	var pos;
	var paddedPrefix = " " + this.prefix();

	// Iterate over all items and choose preferred matching items
	// i.e. the matching happens at the word start
	for (pos = 0; pos < this._items.length; pos++) {
	if ((this.item(pos).lcField().indexOf(paddedPrefix)) >= 0)
	this._list.push(pos);
	};

	// The list is empty - so lower your expectations
	// Iterate over all items and choose matching items
	// i.e. the matching happens anywhere in the word
	if (this._list.length == 0) {
	for (pos = 0; pos < this._items.length; pos++) {
	if ((this.item(pos).lcField().indexOf(this.prefix())) >= 0)
	this._list.push(pos);
	};
	};

	// Filter was successful - yeah!
	return this._list.length > 0 ? true : false;
	},

	// Set boundary for viewport
	_boundary : function (bool) {
	this.item(this._list[0]).noMore(bool);
	this.item(this._list[this._list.length - 1]).noMore(bool);
	},

	/**
	* Get the prefix for filtering,
	* e.g. "ve" for "verb"
	*/
	prefix : function (pref) {
	if (arguments.length === 1) {
	this._prefix.value(pref);
	return this;
	};
	return this._prefix.value();
	},

	// Append Items that should be shown
	_showItems : function (offset) {
	this.delete();

	// Use list
	var shown = 0;
	var i;
	for (i in this._list) {

	// Don't show - it's before offset
	if (shown++ < offset)
	continue;

	this._append(this._list[i]);

	if (shown >= (this.limit() + this._offset))
	break;
	};
	},

	/**
	* Delete all visible items from the menu element
	*/
	delete : function () {
	var child;

	/*
	// Iterate over all visible items
	for (var i = 0; i <= this.limit(); i++) {

	// there is a visible element
	// unhighlight!
	if (child = this.shownItem(i)) {
	child.lowlight();
	child.active(false);
	};
	};
	*/

	for (var i in this._list) {
	var item = this._items[this._list[i]];
	item.lowlight();
	item.active(false);
	};

	// Remove all children
	var children = this._element.childNodes;
	for (var i = children.length - 1; i >= 1; i--) {
	this._element.removeChild(
	children[i]
	);
	};
	},


	// Append item to the shown list based on index
	_append : function (i) {
	var item = this.item(i);

	// Highlight based on prefix
	if (this.prefix().length > 0)
	item.highlight(this.prefix());

	// Append element
	this.element().appendChild(item.element());
	},


	// Prepend item to the shown list based on index
	_prepend : function (i) {
	var item = this.item(i);

	// Highlight based on prefix
	if (this.prefix().length > 0)
	item.highlight(this.prefix());

	var e = this.element();
	// Append element
	e.insertBefore(
	item.element(),
	e.children[1]
	);
	},


	/**
	* Get a specific item from the complete list
	*
	* @param {number} index of the list item
	*/
	item : function (index) {
	return this._items[index]
	},


	/**
	* Get a specific item from the filtered list
	*
	* @param {number} index of the list item
	* in the filtered list
	*/
	liveItem : function (index) {
	if (this._list === undefined)
	if (!this._initList())
	return;

	return this._items[this._list[index]];
	},


	/**
	* Get a specific item from the visible list
	*
	* @param {number} index of the list item
	* in the visible list
	*/
	shownItem : function (index) {
	if (index >= this.limit())
	return;
	return this.liveItem(this._offset + index);
	},


	/**
	* Get the length of the full list
	*/
	length : function () {
	return this._items.length;
	},


	/**
	* Make the next item in the filtered menu active
	*/
	next : function () {

	// No active element set
	if (this._position === -1)
	return;

	var newItem;

	// Set new live item
	if (!this._prefix.active()) {
	var oldItem = this.liveItem(this._position);
	oldItem.active(false);
	};

	this._position++;

	newItem = this.liveItem(this._position);

	// The next element is undefined - roll to top or to prefix
	if (newItem === undefined) {

	// Activate prefix
	var prefix = this._prefix;

	// Mark prefix
	if (prefix.isSet() && !prefix.active()) {
	this._position--;
	prefix.active(true);
	return;
	}
	else {
	this._offset = 0;
	this._position = 0;
	newItem = this.liveItem(0);
	this._showItems(0);
	};
	}

	// The next element is outside the view - roll down
	else if (this._position >= (this.limit() + this._offset)) {
	this._removeFirst();
	this._offset++;
	this._append(this._list[this._position]);
	};

	this._prefix.active(false);
	newItem.active(true);
	},

	/*
	* Page down to the first item on the next page
	*/
	/*
	nextPage : function () {

	// Prefix is active
	if (this._prefix.active()) {
	this._prefix.active(false);
	}

	// Last item is chosen
	else if (this._position >= this.limit() + this._offset) {

	this._position = this.limit() + this._offset - 1;
	newItem = this.liveItem(this._position);
	var oldItem = this.liveItem(this._position--);
	oldItem.active(false);
	}

	// Last item of page is chosen
	else if (0) {

	// Jump to last item
	else {
	var oldItem = this.liveItem(this._position);
	oldItem.active(false);

	this._position = this.limit() + this._offset - 1;
	newItem = this.liveItem(this._position);
	};

	newItem.active(true);
	},
	*/


	/*
	* Make the previous item in the menu active
	*/
	prev : function () {

	// No active element set
	if (this._position === -1) {
	return;
	// TODO: Choose last item
	};

	var newItem;

	// Set new live item
	if (!this._prefix.active()) {
	var oldItem = this.liveItem(this._position--);
	oldItem.active(false);
	};

	newItem = this.liveItem(this._position);

	// The previous element is undefined - roll to bottom
	if (newItem === undefined) {

	// Activate prefix
	var prefix = this._prefix;
	this._offset = this.liveLength() - this.limit();

	// Normalize offset
	this._offset = this._offset < 0 ? 0 : this._offset;

	this._position = this.liveLength() - 1;

	if (prefix.isSet() && !prefix.active()) {
	this._position++;
	prefix.active(true);
	return;
	}
	else {
	newItem = this.liveItem(this._position);
	this._showItems(this._offset);
	};
	}

	// The previous element is outside the view - roll up
	else if (this._position < this._offset) {
	this._removeLast();
	this._offset--;
	this._prepend(this._list[this._position]);
	};

	this._prefix.active(false);
	newItem.active(true);
	},


	// Length of the filtered list
	liveLength : function () {
	if (this._list === undefined)
	this._initList();
	return this._list.length;
	},


	// Remove the HTML node from the first item
	_removeFirst : function () {
	this.item(this._list[this._offset]).lowlight();
	this._element.removeChild(this._element.children[1]);
	},


	// Remove the HTML node from the last item
	_removeLast : function () {
	this.item(this._list[this._offset + this.limit() - 1]).lowlight();
	this._element.removeChild(this._element.lastChild);
	}
	};
	});