tor-browser

dragdrop.js (31406B)

---

// script.aculo.us dragdrop.js v1.7.1_beta2, Tue May 15 15:15:45 EDT 2007

// Copyright (c) 2005-2007 Thomas Fuchs (http://script.aculo.us, http://mir.aculo.us)
//           (c) 2005-2007 Sammi Williams (http://www.oriontransfer.co.nz, sammi@oriontransfer.co.nz)
// 
// script.aculo.us is freely distributable under the terms of an MIT-style license.
// For details, see the script.aculo.us web site: http://script.aculo.us/

if(typeof Effect == 'undefined')
 throw("dragdrop.js requires including script.aculo.us' effects.js library");

var Droppables = {
 drops: [],

 remove: function(element) {
   this.drops = this.drops.reject(function(d) { return d.element==$(element) });
 },

 add: function(element) {
   element = $(element);
   var options = Object.extend({
     greedy:     true,
     hoverclass: null,
     tree:       false
   }, arguments[1] || {});

   // cache containers
   if(options.containment) {
     options._containers = [];
     var containment = options.containment;
     if((typeof containment == 'object') && 
       (containment.constructor == Array)) {
       containment.each( function(c) { options._containers.push($(c)) });
     } else {
       options._containers.push($(containment));
     }
   }
   
   if(options.accept) options.accept = [options.accept].flatten();

   Element.makePositioned(element); // fix IE
   options.element = element;

   this.drops.push(options);
 },
 
 findDeepestChild: function(drops) {
   deepest = drops[0];
     
   for (i = 1; i < drops.length; ++i)
     if (Element.isParent(drops[i].element, deepest.element))
       deepest = drops[i];
   
   return deepest;
 },

 isContained: function(element, drop) {
   var containmentNode;
   if(drop.tree) {
     containmentNode = element.treeNode; 
   } else {
     containmentNode = element.parentNode;
   }
   return drop._containers.detect(function(c) { return containmentNode == c });
 },
 
 isAffected: function(point, element, drop) {
   return (
     (drop.element!=element) &&
     ((!drop._containers) ||
       this.isContained(element, drop)) &&
     ((!drop.accept) ||
       (Element.classNames(element).detect( 
         function(v) { return drop.accept.include(v) } ) )) &&
     Position.within(drop.element, point[0], point[1]) );
 },

 deactivate: function(drop) {
   if(drop.hoverclass)
     Element.removeClassName(drop.element, drop.hoverclass);
   this.last_active = null;
 },

 activate: function(drop) {
   if(drop.hoverclass)
     Element.addClassName(drop.element, drop.hoverclass);
   this.last_active = drop;
 },

 show: function(point, element) {
   if(!this.drops.length) return;
   var affected = [];
   
   if(this.last_active) this.deactivate(this.last_active);
   this.drops.each( function(drop) {
     if(Droppables.isAffected(point, element, drop))
       affected.push(drop);
   });
       
   if(affected.length>0) {
     drop = Droppables.findDeepestChild(affected);
     Position.within(drop.element, point[0], point[1]);
     if(drop.onHover)
       drop.onHover(element, drop.element, Position.overlap(drop.overlap, drop.element));
     
     Droppables.activate(drop);
   }
 },

 fire: function(event, element) {
   if(!this.last_active) return;
   Position.prepare();

   if (this.isAffected([Event.pointerX(event), Event.pointerY(event)], element, this.last_active))
     if (this.last_active.onDrop) {
       this.last_active.onDrop(element, this.last_active.element, event); 
       return true; 
     }
 },

 reset: function() {
   if(this.last_active)
     this.deactivate(this.last_active);
 }
}

var Draggables = {
 drags: [],
 observers: [],
 
 register: function(draggable) {
   if(this.drags.length == 0) {
     this.eventMouseUp   = this.endDrag.bindAsEventListener(this);
     this.eventMouseMove = this.updateDrag.bindAsEventListener(this);
     this.eventKeypress  = this.keyPress.bindAsEventListener(this);
     
     Event.observe(document, "mouseup", this.eventMouseUp);
     Event.observe(document, "mousemove", this.eventMouseMove);
     Event.observe(document, "keypress", this.eventKeypress);
   }
   this.drags.push(draggable);
 },
 
 unregister: function(draggable) {
   this.drags = this.drags.reject(function(d) { return d==draggable });
   if(this.drags.length == 0) {
     Event.stopObserving(document, "mouseup", this.eventMouseUp);
     Event.stopObserving(document, "mousemove", this.eventMouseMove);
     Event.stopObserving(document, "keypress", this.eventKeypress);
   }
 },
 
 activate: function(draggable) {
   if(draggable.options.delay) { 
     this._timeout = setTimeout(function() { 
       Draggables._timeout = null; 
       window.focus(); 
       Draggables.activeDraggable = draggable; 
     }.bind(this), draggable.options.delay); 
   } else {
     window.focus(); // allows keypress events if window isn't currently focused, fails for Safari
     this.activeDraggable = draggable;
   }
 },
 
 deactivate: function() {
   this.activeDraggable = null;
 },
 
 updateDrag: function(event) {
   if(!this.activeDraggable) return;
   var pointer = [Event.pointerX(event), Event.pointerY(event)];
   // Mozilla-based browsers fire successive mousemove events with
   // the same coordinates, prevent needless redrawing (moz bug?)
   if(this._lastPointer && (this._lastPointer.inspect() == pointer.inspect())) return;
   this._lastPointer = pointer;
   
   this.activeDraggable.updateDrag(event, pointer);
 },
 
 endDrag: function(event) {
   if(this._timeout) { 
     clearTimeout(this._timeout); 
     this._timeout = null; 
   }
   if(!this.activeDraggable) return;
   this._lastPointer = null;
   this.activeDraggable.endDrag(event);
   this.activeDraggable = null;
 },
 
 keyPress: function(event) {
   if(this.activeDraggable)
     this.activeDraggable.keyPress(event);
 },
 
 addObserver: function(observer) {
   this.observers.push(observer);
   this._cacheObserverCallbacks();
 },
 
 removeObserver: function(element) {  // element instead of observer fixes mem leaks
   this.observers = this.observers.reject( function(o) { return o.element==element });
   this._cacheObserverCallbacks();
 },
 
 notify: function(eventName, draggable, event) {  // 'onStart', 'onEnd', 'onDrag'
   if(this[eventName+'Count'] > 0)
     this.observers.each( function(o) {
       if(o[eventName]) o[eventName](eventName, draggable, event);
     });
   if(draggable.options[eventName]) draggable.options[eventName](draggable, event);
 },
 
 _cacheObserverCallbacks: function() {
   ['onStart','onEnd','onDrag'].each( function(eventName) {
     Draggables[eventName+'Count'] = Draggables.observers.select(
       function(o) { return o[eventName]; }
     ).length;
   });
 }
}

/*--------------------------------------------------------------------------*/

var Draggable = Class.create();
Draggable._dragging    = {};

Draggable.prototype = {
 initialize: function(element) {
   var defaults = {
     handle: false,
     reverteffect: function(element, top_offset, left_offset) {
       var dur = Math.sqrt(Math.abs(top_offset^2)+Math.abs(left_offset^2))*0.02;
       new Effect.Move(element, { x: -left_offset, y: -top_offset, duration: dur,
         queue: {scope:'_draggable', position:'end'}
       });
     },
     endeffect: function(element) {
       var toOpacity = typeof element._opacity == 'number' ? element._opacity : 1.0;
       new Effect.Opacity(element, {duration:0.2, from:0.7, to:toOpacity, 
         queue: {scope:'_draggable', position:'end'},
         afterFinish: function(){ 
           Draggable._dragging[element] = false 
         }
       }); 
     },
     zindex: 1000,
     revert: false,
     quiet: false,
     scroll: false,
     scrollSensitivity: 20,
     scrollSpeed: 15,
     snap: false,  // false, or xy or [x,y] or function(x,y){ return [x,y] }
     delay: 0
   };
   
   if(!arguments[1] || typeof arguments[1].endeffect == 'undefined')
     Object.extend(defaults, {
       starteffect: function(element) {
         element._opacity = Element.getOpacity(element);
         Draggable._dragging[element] = true;
         new Effect.Opacity(element, {duration:0.2, from:element._opacity, to:0.7}); 
       }
     });
   
   var options = Object.extend(defaults, arguments[1] || {});

   this.element = $(element);
   
   if(options.handle && (typeof options.handle == 'string'))
     this.handle = this.element.down('.'+options.handle, 0);
   
   if(!this.handle) this.handle = $(options.handle);
   if(!this.handle) this.handle = this.element;
   
   if(options.scroll && !options.scroll.scrollTo && !options.scroll.outerHTML) {
     options.scroll = $(options.scroll);
     this._isScrollChild = Element.childOf(this.element, options.scroll);
   }

   Element.makePositioned(this.element); // fix IE    

   this.delta    = this.currentDelta();
   this.options  = options;
   this.dragging = false;   

   this.eventMouseDown = this.initDrag.bindAsEventListener(this);
   Event.observe(this.handle, "mousedown", this.eventMouseDown);
   
   Draggables.register(this);
 },
 
 destroy: function() {
   Event.stopObserving(this.handle, "mousedown", this.eventMouseDown);
   Draggables.unregister(this);
 },
 
 currentDelta: function() {
   return([
     parseInt(Element.getStyle(this.element,'left') || '0'),
     parseInt(Element.getStyle(this.element,'top') || '0')]);
 },
 
 initDrag: function(event) {
   if(typeof Draggable._dragging[this.element] != 'undefined' &&
     Draggable._dragging[this.element]) return;
   if(Event.isLeftClick(event)) {    
     // abort on form elements, fixes a Firefox issue
     var src = Event.element(event);
     if((tag_name = src.tagName.toUpperCase()) && (
       tag_name=='INPUT' ||
       tag_name=='SELECT' ||
       tag_name=='OPTION' ||
       tag_name=='BUTTON' ||
       tag_name=='TEXTAREA')) return;
       
     var pointer = [Event.pointerX(event), Event.pointerY(event)];
     var pos     = Position.cumulativeOffset(this.element);
     this.offset = [0,1].map( function(i) { return (pointer[i] - pos[i]) });
     
     Draggables.activate(this);
     Event.stop(event);
   }
 },
 
 startDrag: function(event) {
   this.dragging = true;
   
   if(this.options.zindex) {
     this.originalZ = parseInt(Element.getStyle(this.element,'z-index') || 0);
     this.element.style.zIndex = this.options.zindex;
   }
   
   if(this.options.ghosting) {
     this._clone = this.element.cloneNode(true);
     Position.absolutize(this.element);
     this.element.parentNode.insertBefore(this._clone, this.element);
   }
   
   if(this.options.scroll) {
     if (this.options.scroll == window) {
       var where = this._getWindowScroll(this.options.scroll);
       this.originalScrollLeft = where.left;
       this.originalScrollTop = where.top;
     } else {
       this.originalScrollLeft = this.options.scroll.scrollLeft;
       this.originalScrollTop = this.options.scroll.scrollTop;
     }
   }
   
   Draggables.notify('onStart', this, event);
       
   if(this.options.starteffect) this.options.starteffect(this.element);
 },
 
 updateDrag: function(event, pointer) {
   if(!this.dragging) this.startDrag(event);
   
   if(!this.options.quiet){
     Position.prepare();
     Droppables.show(pointer, this.element);
   }
   
   Draggables.notify('onDrag', this, event);
   
   this.draw(pointer);
   if(this.options.change) this.options.change(this);
   
   if(this.options.scroll) {
     this.stopScrolling();
     
     var p;
     if (this.options.scroll == window) {
       with(this._getWindowScroll(this.options.scroll)) { p = [ left, top, left+width, top+height ]; }
     } else {
       p = Position.page(this.options.scroll);
       p[0] += this.options.scroll.scrollLeft + Position.deltaX;
       p[1] += this.options.scroll.scrollTop + Position.deltaY;
       p.push(p[0]+this.options.scroll.offsetWidth);
       p.push(p[1]+this.options.scroll.offsetHeight);
     }
     var speed = [0,0];
     if(pointer[0] < (p[0]+this.options.scrollSensitivity)) speed[0] = pointer[0]-(p[0]+this.options.scrollSensitivity);
     if(pointer[1] < (p[1]+this.options.scrollSensitivity)) speed[1] = pointer[1]-(p[1]+this.options.scrollSensitivity);
     if(pointer[0] > (p[2]-this.options.scrollSensitivity)) speed[0] = pointer[0]-(p[2]-this.options.scrollSensitivity);
     if(pointer[1] > (p[3]-this.options.scrollSensitivity)) speed[1] = pointer[1]-(p[3]-this.options.scrollSensitivity);
     this.startScrolling(speed);
   }
   
   // fix AppleWebKit rendering
   if(Prototype.Browser.WebKit) window.scrollBy(0,0);
   
   Event.stop(event);
 },
 
 finishDrag: function(event, success) {
   this.dragging = false;
   
   if(this.options.quiet){
     Position.prepare();
     var pointer = [Event.pointerX(event), Event.pointerY(event)];
     Droppables.show(pointer, this.element);
   }

   if(this.options.ghosting) {
     Position.relativize(this.element);
     Element.remove(this._clone);
     this._clone = null;
   }

   var dropped = false; 
   if(success) { 
     dropped = Droppables.fire(event, this.element); 
     if (!dropped) dropped = false; 
   }
   if(dropped && this.options.onDropped) this.options.onDropped(this.element);
   Draggables.notify('onEnd', this, event);

   var revert = this.options.revert;
   if(revert && typeof revert == 'function') revert = revert(this.element);
   
   var d = this.currentDelta();
   if(revert && this.options.reverteffect) {
     if (dropped == 0 || revert != 'failure')
       this.options.reverteffect(this.element,
         d[1]-this.delta[1], d[0]-this.delta[0]);
   } else {
     this.delta = d;
   }

   if(this.options.zindex)
     this.element.style.zIndex = this.originalZ;

   if(this.options.endeffect) 
     this.options.endeffect(this.element);
     
   Draggables.deactivate(this);
   Droppables.reset();
 },
 
 keyPress: function(event) {
   if(event.keyCode!=Event.KEY_ESC) return;
   this.finishDrag(event, false);
   Event.stop(event);
 },
 
 endDrag: function(event) {
   if(!this.dragging) return;
   this.stopScrolling();
   this.finishDrag(event, true);
   Event.stop(event);
 },
 
 draw: function(point) {
   var pos = Position.cumulativeOffset(this.element);
   if(this.options.ghosting) {
     var r   = Position.realOffset(this.element);
     pos[0] += r[0] - Position.deltaX; pos[1] += r[1] - Position.deltaY;
   }
   
   var d = this.currentDelta();
   pos[0] -= d[0]; pos[1] -= d[1];
   
   if(this.options.scroll && (this.options.scroll != window && this._isScrollChild)) {
     pos[0] -= this.options.scroll.scrollLeft-this.originalScrollLeft;
     pos[1] -= this.options.scroll.scrollTop-this.originalScrollTop;
   }
   
   var p = [0,1].map(function(i){ 
     return (point[i]-pos[i]-this.offset[i]) 
   }.bind(this));
   
   if(this.options.snap) {
     if(typeof this.options.snap == 'function') {
       p = this.options.snap(p[0],p[1],this);
     } else {
     if(this.options.snap instanceof Array) {
       p = p.map( function(v, i) {
         return Math.round(v/this.options.snap[i])*this.options.snap[i] }.bind(this))
     } else {
       p = p.map( function(v) {
         return Math.round(v/this.options.snap)*this.options.snap }.bind(this))
     }
   }}
   
   var style = this.element.style;
   if((!this.options.constraint) || (this.options.constraint=='horizontal'))
     style.left = p[0] + "px";
   if((!this.options.constraint) || (this.options.constraint=='vertical'))
     style.top  = p[1] + "px";
   
   if(style.visibility=="hidden") style.visibility = ""; // fix gecko rendering
 },
 
 stopScrolling: function() {
   if(this.scrollInterval) {
     clearInterval(this.scrollInterval);
     this.scrollInterval = null;
     Draggables._lastScrollPointer = null;
   }
 },
 
 startScrolling: function(speed) {
   if(!(speed[0] || speed[1])) return;
   this.scrollSpeed = [speed[0]*this.options.scrollSpeed,speed[1]*this.options.scrollSpeed];
   this.lastScrolled = new Date();
   this.scrollInterval = setInterval(this.scroll.bind(this), 10);
 },
 
 scroll: function() {
   var current = new Date();
   var delta = current - this.lastScrolled;
   this.lastScrolled = current;
   if(this.options.scroll == window) {
     with (this._getWindowScroll(this.options.scroll)) {
       if (this.scrollSpeed[0] || this.scrollSpeed[1]) {
         var d = delta / 1000;
         this.options.scroll.scrollTo( left + d*this.scrollSpeed[0], top + d*this.scrollSpeed[1] );
       }
     }
   } else {
     this.options.scroll.scrollLeft += this.scrollSpeed[0] * delta / 1000;
     this.options.scroll.scrollTop  += this.scrollSpeed[1] * delta / 1000;
   }
   
   Position.prepare();
   Droppables.show(Draggables._lastPointer, this.element);
   Draggables.notify('onDrag', this);
   if (this._isScrollChild) {
     Draggables._lastScrollPointer = Draggables._lastScrollPointer || $A(Draggables._lastPointer);
     Draggables._lastScrollPointer[0] += this.scrollSpeed[0] * delta / 1000;
     Draggables._lastScrollPointer[1] += this.scrollSpeed[1] * delta / 1000;
     if (Draggables._lastScrollPointer[0] < 0)
       Draggables._lastScrollPointer[0] = 0;
     if (Draggables._lastScrollPointer[1] < 0)
       Draggables._lastScrollPointer[1] = 0;
     this.draw(Draggables._lastScrollPointer);
   }
   
   if(this.options.change) this.options.change(this);
 },
 
 _getWindowScroll: function(w) {
   var T, L, W, H;
   with (w.document) {
     if (w.document.documentElement && documentElement.scrollTop) {
       T = documentElement.scrollTop;
       L = documentElement.scrollLeft;
     } else if (w.document.body) {
       T = body.scrollTop;
       L = body.scrollLeft;
     }
     if (w.innerWidth) {
       W = w.innerWidth;
       H = w.innerHeight;
     } else if (w.document.documentElement && documentElement.clientWidth) {
       W = documentElement.clientWidth;
       H = documentElement.clientHeight;
     } else {
       W = body.offsetWidth;
       H = body.offsetHeight
     }
   }
   return { top: T, left: L, width: W, height: H };
 }
}

/*--------------------------------------------------------------------------*/

var SortableObserver = Class.create();
SortableObserver.prototype = {
 initialize: function(element, observer) {
   this.element   = $(element);
   this.observer  = observer;
   this.lastValue = Sortable.serialize(this.element);
 },
 
 onStart: function() {
   this.lastValue = Sortable.serialize(this.element);
 },
 
 onEnd: function() {
   Sortable.unmark();
   if(this.lastValue != Sortable.serialize(this.element))
     this.observer(this.element)
 }
}

var Sortable = {
 SERIALIZE_RULE: /^[^_\-](?:[A-Za-z0-9\-\_]*)[_](.*)$/,
 
 sortables: {},
 
 _findRootElement: function(element) {
   while (element.tagName.toUpperCase() != "BODY") {  
     if(element.id && Sortable.sortables[element.id]) return element;
     element = element.parentNode;
   }
 },

 options: function(element) {
   element = Sortable._findRootElement($(element));
   if(!element) return;
   return Sortable.sortables[element.id];
 },
 
 destroy: function(element){
   var s = Sortable.options(element);
   
   if(s) {
     Draggables.removeObserver(s.element);
     s.droppables.each(function(d){ Droppables.remove(d) });
     s.draggables.invoke('destroy');
     
     delete Sortable.sortables[s.element.id];
   }
 },

 create: function(element) {
   element = $(element);
   var options = Object.extend({ 
     element:     element,
     tag:         'li',       // assumes li children, override with tag: 'tagname'
     dropOnEmpty: false,
     tree:        false,
     treeTag:     'ul',
     overlap:     'vertical', // one of 'vertical', 'horizontal'
     constraint:  'vertical', // one of 'vertical', 'horizontal', false
     containment: element,    // also takes array of elements (or id's); or false
     handle:      false,      // or a CSS class
     only:        false,
     delay:       0,
     hoverclass:  null,
     ghosting:    false,
     quiet:       false, 
     scroll:      false,
     scrollSensitivity: 20,
     scrollSpeed: 15,
     format:      this.SERIALIZE_RULE,
     
     // these take arrays of elements or ids and can be 
     // used for better initialization performance
     elements:    false,
     handles:     false,
     
     onChange:    Prototype.emptyFunction,
     onUpdate:    Prototype.emptyFunction
   }, arguments[1] || {});

   // clear any old sortable with same element
   this.destroy(element);

   // build options for the draggables
   var options_for_draggable = {
     revert:      true,
     quiet:       options.quiet,
     scroll:      options.scroll,
     scrollSpeed: options.scrollSpeed,
     scrollSensitivity: options.scrollSensitivity,
     delay:       options.delay,
     ghosting:    options.ghosting,
     constraint:  options.constraint,
     handle:      options.handle };

   if(options.starteffect)
     options_for_draggable.starteffect = options.starteffect;

   if(options.reverteffect)
     options_for_draggable.reverteffect = options.reverteffect;
   else
     if(options.ghosting) options_for_draggable.reverteffect = function(element) {
       element.style.top  = 0;
       element.style.left = 0;
     };

   if(options.endeffect)
     options_for_draggable.endeffect = options.endeffect;

   if(options.zindex)
     options_for_draggable.zindex = options.zindex;

   // build options for the droppables  
   var options_for_droppable = {
     overlap:     options.overlap,
     containment: options.containment,
     tree:        options.tree,
     hoverclass:  options.hoverclass,
     onHover:     Sortable.onHover
   }
   
   var options_for_tree = {
     onHover:      Sortable.onEmptyHover,
     overlap:      options.overlap,
     containment:  options.containment,
     hoverclass:   options.hoverclass
   }

   // fix for gecko engine
   Element.cleanWhitespace(element); 

   options.draggables = [];
   options.droppables = [];

   // drop on empty handling
   if(options.dropOnEmpty || options.tree) {
     Droppables.add(element, options_for_tree);
     options.droppables.push(element);
   }

   (options.elements || this.findElements(element, options) || []).each( function(e,i) {
     var handle = options.handles ? $(options.handles[i]) :
       (options.handle ? $(e).getElementsByClassName(options.handle)[0] : e); 
     options.draggables.push(
       new Draggable(e, Object.extend(options_for_draggable, { handle: handle })));
     Droppables.add(e, options_for_droppable);
     if(options.tree) e.treeNode = element;
     options.droppables.push(e);      
   });
   
   if(options.tree) {
     (Sortable.findTreeElements(element, options) || []).each( function(e) {
       Droppables.add(e, options_for_tree);
       e.treeNode = element;
       options.droppables.push(e);
     });
   }

   // keep reference
   this.sortables[element.id] = options;

   // for onupdate
   Draggables.addObserver(new SortableObserver(element, options.onUpdate));

 },

 // return all suitable-for-sortable elements in a guaranteed order
 findElements: function(element, options) {
   return Element.findChildren(
     element, options.only, options.tree ? true : false, options.tag);
 },
 
 findTreeElements: function(element, options) {
   return Element.findChildren(
     element, options.only, options.tree ? true : false, options.treeTag);
 },

 onHover: function(element, dropon, overlap) {
   if(Element.isParent(dropon, element)) return;

   if(overlap > .33 && overlap < .66 && Sortable.options(dropon).tree) {
     return;
   } else if(overlap>0.5) {
     Sortable.mark(dropon, 'before');
     if(dropon.previousSibling != element) {
       var oldParentNode = element.parentNode;
       element.style.visibility = "hidden"; // fix gecko rendering
       dropon.parentNode.insertBefore(element, dropon);
       if(dropon.parentNode!=oldParentNode) 
         Sortable.options(oldParentNode).onChange(element);
       Sortable.options(dropon.parentNode).onChange(element);
     }
   } else {
     Sortable.mark(dropon, 'after');
     var nextElement = dropon.nextSibling || null;
     if(nextElement != element) {
       var oldParentNode = element.parentNode;
       element.style.visibility = "hidden"; // fix gecko rendering
       dropon.parentNode.insertBefore(element, nextElement);
       if(dropon.parentNode!=oldParentNode) 
         Sortable.options(oldParentNode).onChange(element);
       Sortable.options(dropon.parentNode).onChange(element);
     }
   }
 },
 
 onEmptyHover: function(element, dropon, overlap) {
   var oldParentNode = element.parentNode;
   var droponOptions = Sortable.options(dropon);
       
   if(!Element.isParent(dropon, element)) {
     var index;
     
     var children = Sortable.findElements(dropon, {tag: droponOptions.tag, only: droponOptions.only});
     var child = null;
           
     if(children) {
       var offset = Element.offsetSize(dropon, droponOptions.overlap) * (1.0 - overlap);
       
       for (index = 0; index < children.length; index += 1) {
         if (offset - Element.offsetSize (children[index], droponOptions.overlap) >= 0) {
           offset -= Element.offsetSize (children[index], droponOptions.overlap);
         } else if (offset - (Element.offsetSize (children[index], droponOptions.overlap) / 2) >= 0) {
           child = index + 1 < children.length ? children[index + 1] : null;
           break;
         } else {
           child = children[index];
           break;
         }
       }
     }
     
     dropon.insertBefore(element, child);
     
     Sortable.options(oldParentNode).onChange(element);
     droponOptions.onChange(element);
   }
 },

 unmark: function() {
   if(Sortable._marker) Sortable._marker.hide();
 },

 mark: function(dropon, position) {
   // mark on ghosting only
   var sortable = Sortable.options(dropon.parentNode);
   if(sortable && !sortable.ghosting) return; 

   if(!Sortable._marker) {
     Sortable._marker = 
       ($('dropmarker') || Element.extend(document.createElement('DIV'))).
         hide().addClassName('dropmarker').setStyle({position:'absolute'});
     document.getElementsByTagName("body").item(0).appendChild(Sortable._marker);
   }    
   var offsets = Position.cumulativeOffset(dropon);
   Sortable._marker.setStyle({left: offsets[0]+'px', top: offsets[1] + 'px'});
   
   if(position=='after')
     if(sortable.overlap == 'horizontal') 
       Sortable._marker.setStyle({left: (offsets[0]+dropon.clientWidth) + 'px'});
     else
       Sortable._marker.setStyle({top: (offsets[1]+dropon.clientHeight) + 'px'});
   
   Sortable._marker.show();
 },
 
 _tree: function(element, options, parent) {
   var children = Sortable.findElements(element, options) || [];
 
   for (var i = 0; i < children.length; ++i) {
     var match = children[i].id.match(options.format);

     if (!match) continue;
     
     var child = {
       id: encodeURIComponent(match ? match[1] : null),
       element: element,
       parent: parent,
       children: [],
       position: parent.children.length,
       container: $(children[i]).down(options.treeTag)
     }
     
     /* Get the element containing the children and recurse over it */
     if (child.container)
       this._tree(child.container, options, child)
     
     parent.children.push (child);
   }

   return parent; 
 },

 tree: function(element) {
   element = $(element);
   var sortableOptions = this.options(element);
   var options = Object.extend({
     tag: sortableOptions.tag,
     treeTag: sortableOptions.treeTag,
     only: sortableOptions.only,
     name: element.id,
     format: sortableOptions.format
   }, arguments[1] || {});
   
   var root = {
     id: null,
     parent: null,
     children: [],
     container: element,
     position: 0
   }
   
   return Sortable._tree(element, options, root);
 },

 /* Construct a [i] index for a particular node */
 _constructIndex: function(node) {
   var index = '';
   do {
     if (node.id) index = '[' + node.position + ']' + index;
   } while ((node = node.parent) != null);
   return index;
 },

 sequence: function(element) {
   element = $(element);
   var options = Object.extend(this.options(element), arguments[1] || {});
   
   return $(this.findElements(element, options) || []).map( function(item) {
     return item.id.match(options.format) ? item.id.match(options.format)[1] : '';
   });
 },

 setSequence: function(element, new_sequence) {
   element = $(element);
   var options = Object.extend(this.options(element), arguments[2] || {});
   
   var nodeMap = {};
   this.findElements(element, options).each( function(n) {
       if (n.id.match(options.format))
           nodeMap[n.id.match(options.format)[1]] = [n, n.parentNode];
       n.parentNode.removeChild(n);
   });
  
   new_sequence.each(function(ident) {
     var n = nodeMap[ident];
     if (n) {
       n[1].appendChild(n[0]);
       delete nodeMap[ident];
     }
   });
 },
 
 serialize: function(element) {
   element = $(element);
   var options = Object.extend(Sortable.options(element), arguments[1] || {});
   var name = encodeURIComponent(
     (arguments[1] && arguments[1].name) ? arguments[1].name : element.id);
   
   if (options.tree) {
     return Sortable.tree(element, arguments[1]).children.map( function (item) {
       return [name + Sortable._constructIndex(item) + "[id]=" + 
               encodeURIComponent(item.id)].concat(item.children.map(arguments.callee));
     }).flatten().join('&');
   } else {
     return Sortable.sequence(element, arguments[1]).map( function(item) {
       return name + "[]=" + encodeURIComponent(item);
     }).join('&');
   }
 }
}

// Returns true if child is contained within element
Element.isParent = function(child, element) {
 if (!child.parentNode || child == element) return false;
 if (child.parentNode == element) return true;
 return Element.isParent(child.parentNode, element);
}

Element.findChildren = function(element, only, recursive, tagName) {   
 if(!element.hasChildNodes()) return null;
 tagName = tagName.toUpperCase();
 if(only) only = [only].flatten();
 var elements = [];
 $A(element.childNodes).each( function(e) {
   if(e.tagName && e.tagName.toUpperCase()==tagName &&
     (!only || (Element.classNames(e).detect(function(v) { return only.include(v) }))))
       elements.push(e);
   if(recursive) {
     var grandchildren = Element.findChildren(e, only, recursive, tagName);
     if(grandchildren) elements.push(grandchildren);
   }
 });

 return (elements.length>0 ? elements.flatten() : []);
}

Element.offsetSize = function (element, type) {
 return element['offset' + ((type=='vertical' || type=='height') ? 'Height' : 'Width')];
}