1 // script.aculo.us dragdrop.js v1.7.0, Fri Jan 19 19:16:36 CET 2007
  2 
  3 // Copyright (c) 2005, 2006 Thomas Fuchs (http://script.aculo.us, http://mir.aculo.us)
  4 //           (c) 2005, 2006 Sammi Williams (http://www.oriontransfer.co.nz, sammi@oriontransfer.co.nz)
  5 // 
  6 // script.aculo.us is freely distributable under the terms of an MIT-style license.
  7 // For details, see the script.aculo.us web site: http://script.aculo.us/
  8 
  9 if(typeof Effect == 'undefined')
 10   throw("dragdrop.js requires including script.aculo.us' effects.js library");
 11 
 12 var Droppables = {
 13   drops: [],
 14 
 15   remove: function(element) {
 16     this.drops = this.drops.reject(function(d) { return d.element==$(element) });
 17   },
 18 
 19   add: function(element) {
 20     element = $(element);
 21     var options = Object.extend({
 22       greedy:     true,
 23       hoverclass: null,
 24       tree:       false
 25     }, arguments[1] || {});
 26 
 27     // cache containers
 28     if(options.containment) {
 29       options._containers = [];
 30       var containment = options.containment;
 31       if((typeof containment == 'object') && 
 32         (containment.constructor == Array)) {
 33         containment.each( function(c) { options._containers.push($(c)) });
 34       } else {
 35         options._containers.push($(containment));
 36       }
 37     }
 38     
 39     if(options.accept) options.accept = [options.accept].flatten();
 40 
 41     Element.makePositioned(element); // fix IE
 42     options.element = element;
 43 
 44     this.drops.push(options);
 45   },
 46   
 47   findDeepestChild: function(drops) {
 48     deepest = drops[0];
 49       
 50     for (i = 1; i < drops.length; ++i)
 51       if (Element.isParent(drops[i].element, deepest.element))
 52         deepest = drops[i];
 53     
 54     return deepest;
 55   },
 56 
 57   isContained: function(element, drop) {
 58     var containmentNode;
 59     if(drop.tree) {
 60       containmentNode = element.treeNode; 
 61     } else {
 62       containmentNode = element.parentNode;
 63     }
 64     return drop._containers.detect(function(c) { return containmentNode == c });
 65   },
 66   
 67   isAffected: function(point, element, drop) {
 68     return (
 69       (drop.element!=element) &&
 70       ((!drop._containers) ||
 71         this.isContained(element, drop)) &&
 72       ((!drop.accept) ||
 73         (Element.classNames(element).detect( 
 74           function(v) { return drop.accept.include(v) } ) )) &&
 75       Position.within(drop.element, point[0], point[1]) );
 76   },
 77 
 78   deactivate: function(drop) {
 79     if(drop.hoverclass)
 80       Element.removeClassName(drop.element, drop.hoverclass);
 81     this.last_active = null;
 82   },
 83 
 84   activate: function(drop) {
 85     if(drop.hoverclass)
 86       Element.addClassName(drop.element, drop.hoverclass);
 87     this.last_active = drop;
 88   },
 89 
 90   show: function(point, element) {
 91     if(!this.drops.length) return;
 92     var affected = [];
 93     
 94     if(this.last_active) this.deactivate(this.last_active);
 95     this.drops.each( function(drop) {
 96       if(Droppables.isAffected(point, element, drop))
 97         affected.push(drop);
 98     });
 99         
100     if(affected.length>0) {
101       drop = Droppables.findDeepestChild(affected);
102       Position.within(drop.element, point[0], point[1]);
103       if(drop.onHover)
104         drop.onHover(element, drop.element, Position.overlap(drop.overlap, drop.element));
105       
106       Droppables.activate(drop);
107     }
108   },
109 
110   fire: function(event, element) {
111     if(!this.last_active) return;
112     Position.prepare();
113 
114     if (this.isAffected([Event.pointerX(event), Event.pointerY(event)], element, this.last_active))
115       if (this.last_active.onDrop) 
116         this.last_active.onDrop(element, this.last_active.element, event);
117   },
118 
119   reset: function() {
120     if(this.last_active)
121       this.deactivate(this.last_active);
122   }
123 }
124 
125 var Draggables = {
126   drags: [],
127   observers: [],
128   
129   register: function(draggable) {
130     if(this.drags.length == 0) {
131       this.eventMouseUp   = this.endDrag.bindAsEventListener(this);
132       this.eventMouseMove = this.updateDrag.bindAsEventListener(this);
133       this.eventKeypress  = this.keyPress.bindAsEventListener(this);
134       
135       Event.observe(document, "mouseup", this.eventMouseUp);
136       Event.observe(document, "mousemove", this.eventMouseMove);
137       Event.observe(document, "keypress", this.eventKeypress);
138     }
139     this.drags.push(draggable);
140   },
141   
142   unregister: function(draggable) {
143     this.drags = this.drags.reject(function(d) { return d==draggable });
144     if(this.drags.length == 0) {
145       Event.stopObserving(document, "mouseup", this.eventMouseUp);
146       Event.stopObserving(document, "mousemove", this.eventMouseMove);
147       Event.stopObserving(document, "keypress", this.eventKeypress);
148     }
149   },
150   
151   activate: function(draggable) {
152     if(draggable.options.delay) { 
153       this._timeout = setTimeout(function() { 
154         Draggables._timeout = null; 
155         window.focus(); 
156         Draggables.activeDraggable = draggable; 
157       }.bind(this), draggable.options.delay); 
158     } else {
159       window.focus(); // allows keypress events if window isn't currently focused, fails for Safari
160       this.activeDraggable = draggable;
161     }
162   },
163   
164   deactivate: function() {
165     this.activeDraggable = null;
166   },
167   
168   updateDrag: function(event) {
169     if(!this.activeDraggable) return;
170     var pointer = [Event.pointerX(event), Event.pointerY(event)];
171     // Mozilla-based browsers fire successive mousemove events with
172     // the same coordinates, prevent needless redrawing (moz bug?)
173     if(this._lastPointer && (this._lastPointer.inspect() == pointer.inspect())) return;
174     this._lastPointer = pointer;
175     
176     this.activeDraggable.updateDrag(event, pointer);
177   },
178   
179   endDrag: function(event) {
180     if(this._timeout) { 
181       clearTimeout(this._timeout); 
182       this._timeout = null; 
183     }
184     if(!this.activeDraggable) return;
185     this._lastPointer = null;
186     this.activeDraggable.endDrag(event);
187     this.activeDraggable = null;
188   },
189   
190   keyPress: function(event) {
191     if(this.activeDraggable)
192       this.activeDraggable.keyPress(event);
193   },
194   
195   addObserver: function(observer) {
196     this.observers.push(observer);
197     this._cacheObserverCallbacks();
198   },
199   
200   removeObserver: function(element) {  // element instead of observer fixes mem leaks
201     this.observers = this.observers.reject( function(o) { return o.element==element });
202     this._cacheObserverCallbacks();
203   },
204   
205   notify: function(eventName, draggable, event) {  // 'onStart', 'onEnd', 'onDrag'
206     if(this[eventName+'Count'] > 0)
207       this.observers.each( function(o) {
208         if(o[eventName]) o[eventName](eventName, draggable, event);
209       });
210     if(draggable.options[eventName]) draggable.options[eventName](draggable, event);
211   },
212   
213   _cacheObserverCallbacks: function() {
214     ['onStart','onEnd','onDrag'].each( function(eventName) {
215       Draggables[eventName+'Count'] = Draggables.observers.select(
216         function(o) { return o[eventName]; }
217       ).length;
218     });
219   }
220 }
221 
222 /*--------------------------------------------------------------------------*/
223 
224 var Draggable = Class.create();
225 Draggable._dragging    = {};
226 
227 Draggable.prototype = {
228   initialize: function(element) {
229     var defaults = {
230       handle: false,
231       reverteffect: function(element, top_offset, left_offset) {
232         var dur = Math.sqrt(Math.abs(top_offset^2)+Math.abs(left_offset^2))*0.02;
233         new Effect.Move(element, { x: -left_offset, y: -top_offset, duration: dur,
234           queue: {scope:'_draggable', position:'end'}
235         });
236       },
237       endeffect: function(element) {
238         var toOpacity = typeof element._opacity == 'number' ? element._opacity : 1.0;
239         new Effect.Opacity(element, {duration:0.2, from:0.7, to:toOpacity, 
240           queue: {scope:'_draggable', position:'end'},
241           afterFinish: function(){ 
242             Draggable._dragging[element] = false 
243           }
244         }); 
245       },
246       zindex: 1000,
247       revert: false,
248       scroll: false,
249       scrollSensitivity: 20,
250       scrollSpeed: 15,
251       snap: false,  // false, or xy or [x,y] or function(x,y){ return [x,y] }
252       delay: 0
253     };
254     
255     if(!arguments[1] || typeof arguments[1].endeffect == 'undefined')
256       Object.extend(defaults, {
257         starteffect: function(element) {
258           element._opacity = Element.getOpacity(element);
259           Draggable._dragging[element] = true;
260           new Effect.Opacity(element, {duration:0.2, from:element._opacity, to:0.7}); 
261         }
262       });
263     
264     var options = Object.extend(defaults, arguments[1] || {});
265 
266     this.element = $(element);
267     
268     if(options.handle && (typeof options.handle == 'string'))
269       this.handle = this.element.down('.'+options.handle, 0);
270     
271     if(!this.handle) this.handle = $(options.handle);
272     if(!this.handle) this.handle = this.element;
273     
274     if(options.scroll && !options.scroll.scrollTo && !options.scroll.outerHTML) {
275       options.scroll = $(options.scroll);
276       this._isScrollChild = Element.childOf(this.element, options.scroll);
277     }
278 
279     Element.makePositioned(this.element); // fix IE    
280 
281     this.delta    = this.currentDelta();
282     this.options  = options;
283     this.dragging = false;   
284 
285     this.eventMouseDown = this.initDrag.bindAsEventListener(this);
286     Event.observe(this.handle, "mousedown", this.eventMouseDown);
287     
288     Draggables.register(this);
289   },
290   
291   destroy: function() {
292     Event.stopObserving(this.handle, "mousedown", this.eventMouseDown);
293     Draggables.unregister(this);
294   },
295   
296   currentDelta: function() {
297     return([
298       parseInt(Element.getStyle(this.element,'left') || '0'),
299       parseInt(Element.getStyle(this.element,'top') || '0')]);
300   },
301   
302   initDrag: function(event) {
303     if(typeof Draggable._dragging[this.element] != 'undefined' &&
304       Draggable._dragging[this.element]) return;
305     if(Event.isLeftClick(event)) {    
306       // abort on form elements, fixes a Firefox issue
307       var src = Event.element(event);
308       if((tag_name = src.tagName.toUpperCase()) && (
309         tag_name=='INPUT' ||
310         tag_name=='SELECT' ||
311         tag_name=='OPTION' ||
312         tag_name=='BUTTON' ||
313         tag_name=='TEXTAREA' ||
314         tag_name=='IMG')) return;
315         
316       var pointer = [Event.pointerX(event), Event.pointerY(event)];
317       var pos     = Position.cumulativeOffset(this.element);
318       this.offset = [0,1].map( function(i) { return (pointer[i] - pos[i]) });
319       
320       Draggables.activate(this);
321       Event.stop(event);
322     }
323   },
324   
325   startDrag: function(event) {
326     this.dragging = true;
327     
328     if(this.options.zindex) {
329       this.originalZ = parseInt(Element.getStyle(this.element,'z-index') || 0);
330       this.element.style.zIndex = this.options.zindex;
331     }
332     
333     if(this.options.ghosting) {
334       this._clone = this.element.cloneNode(true);
335       Position.absolutize(this.element);
336       this.element.parentNode.insertBefore(this._clone, this.element);
337     }
338     
339     if(this.options.scroll) {
340       if (this.options.scroll == window) {
341         var where = this._getWindowScroll(this.options.scroll);
342         this.originalScrollLeft = where.left;
343         this.originalScrollTop = where.top;
344       } else {
345         this.originalScrollLeft = this.options.scroll.scrollLeft;
346         this.originalScrollTop = this.options.scroll.scrollTop;
347       }
348     }
349     
350     Draggables.notify('onStart', this, event);
351         
352     if(this.options.starteffect) this.options.starteffect(this.element);
353   },
354   
355   updateDrag: function(event, pointer) {
356     if(!this.dragging) this.startDrag(event);
357     Position.prepare();
358     Droppables.show(pointer, this.element);
359     Draggables.notify('onDrag', this, event);
360     
361     this.draw(pointer);
362     if(this.options.change) this.options.change(this);
363     
364     if(this.options.scroll) {
365       this.stopScrolling();
366       
367       var p;
368       if (this.options.scroll == window) {
369         with(this._getWindowScroll(this.options.scroll)) { p = [ left, top, left+width, top+height ]; }
370       } else {
371         p = Position.page(this.options.scroll);
372         p[0] += this.options.scroll.scrollLeft + Position.deltaX;
373         p[1] += this.options.scroll.scrollTop + Position.deltaY;
374         p.push(p[0]+this.options.scroll.offsetWidth);
375         p.push(p[1]+this.options.scroll.offsetHeight);
376       }
377       var speed = [0,0];
378       if(pointer[0] < (p[0]+this.options.scrollSensitivity)) speed[0] = pointer[0]-(p[0]+this.options.scrollSensitivity);
379       if(pointer[1] < (p[1]+this.options.scrollSensitivity)) speed[1] = pointer[1]-(p[1]+this.options.scrollSensitivity);
380       if(pointer[0] > (p[2]-this.options.scrollSensitivity)) speed[0] = pointer[0]-(p[2]-this.options.scrollSensitivity);
381       if(pointer[1] > (p[3]-this.options.scrollSensitivity)) speed[1] = pointer[1]-(p[3]-this.options.scrollSensitivity);
382       this.startScrolling(speed);
383     }
384     
385     // fix AppleWebKit rendering
386     if(navigator.appVersion.indexOf('AppleWebKit')>0) window.scrollBy(0,0);
387     
388     Event.stop(event);
389   },
390   
391   finishDrag: function(event, success) {
392     this.dragging = false;
393 
394     if(this.options.ghosting) {
395       Position.relativize(this.element);
396       Element.remove(this._clone);
397       this._clone = null;
398     }
399 
400     if(success) Droppables.fire(event, this.element);
401     Draggables.notify('onEnd', this, event);
402 
403     var revert = this.options.revert;
404     if(revert && typeof revert == 'function') revert = revert(this.element);
405     
406     var d = this.currentDelta();
407     if(revert && this.options.reverteffect) {
408       this.options.reverteffect(this.element, 
409         d[1]-this.delta[1], d[0]-this.delta[0]);
410     } else {
411       this.delta = d;
412     }
413 
414     if(this.options.zindex)
415       this.element.style.zIndex = this.originalZ;
416 
417     if(this.options.endeffect) 
418       this.options.endeffect(this.element);
419       
420     Draggables.deactivate(this);
421     Droppables.reset();
422   },
423   
424   keyPress: function(event) {
425     if(event.keyCode!=Event.KEY_ESC) return;
426     this.finishDrag(event, false);
427     Event.stop(event);
428   },
429   
430   endDrag: function(event) {
431     if(!this.dragging) return;
432     this.stopScrolling();
433     this.finishDrag(event, true);
434     Event.stop(event);
435   },
436   
437   draw: function(point) {
438     var pos = Position.cumulativeOffset(this.element);
439     if(this.options.ghosting) {
440       var r   = Position.realOffset(this.element);
441       pos[0] += r[0] - Position.deltaX; pos[1] += r[1] - Position.deltaY;
442     }
443     
444     var d = this.currentDelta();
445     pos[0] -= d[0]; pos[1] -= d[1];
446     
447     if(this.options.scroll && (this.options.scroll != window && this._isScrollChild)) {
448       pos[0] -= this.options.scroll.scrollLeft-this.originalScrollLeft;
449       pos[1] -= this.options.scroll.scrollTop-this.originalScrollTop;
450     }
451     
452     var p = [0,1].map(function(i){ 
453       return (point[i]-pos[i]-this.offset[i]) 
454     }.bind(this));
455     
456     if(this.options.snap) {
457       if(typeof this.options.snap == 'function') {
458         p = this.options.snap(p[0],p[1],this);
459       } else {
460       if(this.options.snap instanceof Array) {
461         p = p.map( function(v, i) {
462           return Math.round(v/this.options.snap[i])*this.options.snap[i] }.bind(this))
463       } else {
464         p = p.map( function(v) {
465           return Math.round(v/this.options.snap)*this.options.snap }.bind(this))
466       }
467     }}
468     
469     var style = this.element.style;
470     if((!this.options.constraint) || (this.options.constraint=='horizontal'))
471       style.left = p[0] + "px";
472     if((!this.options.constraint) || (this.options.constraint=='vertical'))
473       style.top  = p[1] + "px";
474     
475     if(style.visibility=="hidden") style.visibility = ""; // fix gecko rendering
476   },
477   
478   stopScrolling: function() {
479     if(this.scrollInterval) {
480       clearInterval(this.scrollInterval);
481       this.scrollInterval = null;
482       Draggables._lastScrollPointer = null;
483     }
484   },
485   
486   startScrolling: function(speed) {
487     if(!(speed[0] || speed[1])) return;
488     this.scrollSpeed = [speed[0]*this.options.scrollSpeed,speed[1]*this.options.scrollSpeed];
489     this.lastScrolled = new Date();
490     this.scrollInterval = setInterval(this.scroll.bind(this), 10);
491   },
492   
493   scroll: function() {
494     var current = new Date();
495     var delta = current - this.lastScrolled;
496     this.lastScrolled = current;
497     if(this.options.scroll == window) {
498       with (this._getWindowScroll(this.options.scroll)) {
499         if (this.scrollSpeed[0] || this.scrollSpeed[1]) {
500           var d = delta / 1000;
501           this.options.scroll.scrollTo( left + d*this.scrollSpeed[0], top + d*this.scrollSpeed[1] );
502         }
503       }
504     } else {
505       this.options.scroll.scrollLeft += this.scrollSpeed[0] * delta / 1000;
506       this.options.scroll.scrollTop  += this.scrollSpeed[1] * delta / 1000;
507     }
508     
509     Position.prepare();
510     Droppables.show(Draggables._lastPointer, this.element);
511     Draggables.notify('onDrag', this);
512     if (this._isScrollChild) {
513       Draggables._lastScrollPointer = Draggables._lastScrollPointer || $A(Draggables._lastPointer);
514       Draggables._lastScrollPointer[0] += this.scrollSpeed[0] * delta / 1000;
515       Draggables._lastScrollPointer[1] += this.scrollSpeed[1] * delta / 1000;
516       if (Draggables._lastScrollPointer[0] < 0)
517         Draggables._lastScrollPointer[0] = 0;
518       if (Draggables._lastScrollPointer[1] < 0)
519         Draggables._lastScrollPointer[1] = 0;
520       this.draw(Draggables._lastScrollPointer);
521     }
522     
523     if(this.options.change) this.options.change(this);
524   },
525   
526   _getWindowScroll: function(w) {
527     var T, L, W, H;
528     with (w.document) {
529       if (w.document.documentElement && documentElement.scrollTop) {
530         T = documentElement.scrollTop;
531         L = documentElement.scrollLeft;
532       } else if (w.document.body) {
533         T = body.scrollTop;
534         L = body.scrollLeft;
535       }
536       if (w.innerWidth) {
537         W = w.innerWidth;
538         H = w.innerHeight;
539       } else if (w.document.documentElement && documentElement.clientWidth) {
540         W = documentElement.clientWidth;
541         H = documentElement.clientHeight;
542       } else {
543         W = body.offsetWidth;
544         H = body.offsetHeight
545       }
546     }
547     return { top: T, left: L, width: W, height: H };
548   }
549 }
550 
551 /*--------------------------------------------------------------------------*/
552 
553 var SortableObserver = Class.create();
554 SortableObserver.prototype = {
555   initialize: function(element, observer) {
556     this.element   = $(element);
557     this.observer  = observer;
558     this.lastValue = Sortable.serialize(this.element);
559   },
560   
561   onStart: function() {
562     this.lastValue = Sortable.serialize(this.element);
563   },
564   
565   onEnd: function() {
566     Sortable.unmark();
567     if(this.lastValue != Sortable.serialize(this.element))
568       this.observer(this.element)
569   }
570 }
571 
572 var Sortable = {
573   SERIALIZE_RULE: /^[^_\-](?:[A-Za-z0-9\-\_]*?)[_](.*)$/,
574   
575   sortables: {},
576   
577   _findRootElement: function(element) {
578     while (element.tagName.toUpperCase() != "BODY") {  
579       if(element.id && Sortable.sortables[element.id]) return element;
580       element = element.parentNode;
581     }
582   },
583 
584   options: function(element) {
585     element = Sortable._findRootElement($(element));
586     if(!element) return;
587     return Sortable.sortables[element.id];
588   },
589   
590   destroy: function(element){
591     var s = Sortable.options(element);
592     
593     if(s) {
594       Draggables.removeObserver(s.element);
595       s.droppables.each(function(d){ Droppables.remove(d) });
596       s.draggables.invoke('destroy');
597       
598       delete Sortable.sortables[s.element.id];
599     }
600   },
601 
602   create: function(element) {
603     element = $(element);
604     var options = Object.extend({ 
605       element:     element,
606       tag:         'li',       // assumes li children, override with tag: 'tagname'
607       dropOnEmpty: false,
608       tree:        false,
609       treeTag:     'ul',
610       overlap:     'vertical', // one of 'vertical', 'horizontal'
611       constraint:  'vertical', // one of 'vertical', 'horizontal', false
612       containment: element,    // also takes array of elements (or id's); or false
613       handle:      false,      // or a CSS class
614       only:        false,
615       delay:       0,
616       hoverclass:  null,
617       ghosting:    false,
618       scroll:      false,
619       scrollSensitivity: 20,
620       scrollSpeed: 15,
621       format:      this.SERIALIZE_RULE,
622       onChange:    Prototype.emptyFunction,
623       onUpdate:    Prototype.emptyFunction
624     }, arguments[1] || {});
625 
626     // clear any old sortable with same element
627     this.destroy(element);
628 
629     // build options for the draggables
630     var options_for_draggable = {
631       revert:      true,
632       scroll:      options.scroll,
633       scrollSpeed: options.scrollSpeed,
634       scrollSensitivity: options.scrollSensitivity,
635       delay:       options.delay,
636       ghosting:    options.ghosting,
637       constraint:  options.constraint,
638       handle:      options.handle };
639 
640     if(options.starteffect)
641       options_for_draggable.starteffect = options.starteffect;
642 
643     if(options.reverteffect)
644       options_for_draggable.reverteffect = options.reverteffect;
645     else
646       if(options.ghosting) options_for_draggable.reverteffect = function(element) {
647         element.style.top  = 0;
648         element.style.left = 0;
649       };
650 
651     if(options.endeffect)
652       options_for_draggable.endeffect = options.endeffect;
653 
654     if(options.zindex)
655       options_for_draggable.zindex = options.zindex;
656 
657     // build options for the droppables  
658     var options_for_droppable = {
659       overlap:     options.overlap,
660       containment: options.containment,
661       tree:        options.tree,
662       hoverclass:  options.hoverclass,
663       onHover:     Sortable.onHover
664     }
665     
666     var options_for_tree = {
667       onHover:      Sortable.onEmptyHover,
668       overlap:      options.overlap,
669       containment:  options.containment,
670       hoverclass:   options.hoverclass
671     }
672 
673     // fix for gecko engine
674     Element.cleanWhitespace(element); 
675 
676     options.draggables = [];
677     options.droppables = [];
678 
679     // drop on empty handling
680     if(options.dropOnEmpty || options.tree) {
681       Droppables.add(element, options_for_tree);
682       options.droppables.push(element);
683     }
684 
685     (this.findElements(element, options) || []).each( function(e) {
686       // handles are per-draggable
687       var handle = options.handle ? 
688         $(e).down('.'+options.handle,0) : e;    
689       options.draggables.push(
690         new Draggable(e, Object.extend(options_for_draggable, { handle: handle })));
691       Droppables.add(e, options_for_droppable);
692       if(options.tree) e.treeNode = element;
693       options.droppables.push(e);      
694     });
695     
696     if(options.tree) {
697       (Sortable.findTreeElements(element, options) || []).each( function(e) {
698         Droppables.add(e, options_for_tree);
699         e.treeNode = element;
700         options.droppables.push(e);
701       });
702     }
703 
704     // keep reference
705     this.sortables[element.id] = options;
706 
707     // for onupdate
708     Draggables.addObserver(new SortableObserver(element, options.onUpdate));
709 
710   },
711 
712   // return all suitable-for-sortable elements in a guaranteed order
713   findElements: function(element, options) {
714     return Element.findChildren(
715       element, options.only, options.tree ? true : false, options.tag);
716   },
717   
718   findTreeElements: function(element, options) {
719     return Element.findChildren(
720       element, options.only, options.tree ? true : false, options.treeTag);
721   },
722 
723   onHover: function(element, dropon, overlap) {
724     if(Element.isParent(dropon, element)) return;
725 
726     if(overlap > .33 && overlap < .66 && Sortable.options(dropon).tree) {
727       return;
728     } else if(overlap>0.5) {
729       Sortable.mark(dropon, 'before');
730       if(dropon.previousSibling != element) {
731         var oldParentNode = element.parentNode;
732         element.style.visibility = "hidden"; // fix gecko rendering
733         dropon.parentNode.insertBefore(element, dropon);
734         if(dropon.parentNode!=oldParentNode) 
735           Sortable.options(oldParentNode).onChange(element);
736         Sortable.options(dropon.parentNode).onChange(element);
737       }
738     } else {
739       Sortable.mark(dropon, 'after');
740       var nextElement = dropon.nextSibling || null;
741       if(nextElement != element) {
742         var oldParentNode = element.parentNode;
743         element.style.visibility = "hidden"; // fix gecko rendering
744         dropon.parentNode.insertBefore(element, nextElement);
745         if(dropon.parentNode!=oldParentNode) 
746           Sortable.options(oldParentNode).onChange(element);
747         Sortable.options(dropon.parentNode).onChange(element);
748       }
749     }
750   },
751   
752   onEmptyHover: function(element, dropon, overlap) {
753     var oldParentNode = element.parentNode;
754     var droponOptions = Sortable.options(dropon);
755         
756     if(!Element.isParent(dropon, element)) {
757       var index;
758       
759       var children = Sortable.findElements(dropon, {tag: droponOptions.tag, only: droponOptions.only});
760       var child = null;
761             
762       if(children) {
763         var offset = Element.offsetSize(dropon, droponOptions.overlap) * (1.0 - overlap);
764         
765         for (index = 0; index < children.length; index += 1) {
766           if (offset - Element.offsetSize (children[index], droponOptions.overlap) >= 0) {
767             offset -= Element.offsetSize (children[index], droponOptions.overlap);
768           } else if (offset - (Element.offsetSize (children[index], droponOptions.overlap) / 2) >= 0) {
769             child = index + 1 < children.length ? children[index + 1] : null;
770             break;
771           } else {
772             child = children[index];
773             break;
774           }
775         }
776       }
777       
778       dropon.insertBefore(element, child);
779       
780       Sortable.options(oldParentNode).onChange(element);
781       droponOptions.onChange(element);
782     }
783   },
784 
785   unmark: function() {
786     if(Sortable._marker) Sortable._marker.hide();
787   },
788 
789   mark: function(dropon, position) {
790     // mark on ghosting only
791     var sortable = Sortable.options(dropon.parentNode);
792     if(sortable && !sortable.ghosting) return; 
793 
794     if(!Sortable._marker) {
795       Sortable._marker = 
796         ($('dropmarker') || Element.extend(document.createElement('DIV'))).
797           hide().addClassName('dropmarker').setStyle({position:'absolute'});
798       document.getElementsByTagName("body").item(0).appendChild(Sortable._marker);
799     }    
800     var offsets = Position.cumulativeOffset(dropon);
801     Sortable._marker.setStyle({left: offsets[0]+'px', top: offsets[1] + 'px'});
802     
803     if(position=='after')
804       if(sortable.overlap == 'horizontal') 
805         Sortable._marker.setStyle({left: (offsets[0]+dropon.clientWidth) + 'px'});
806       else
807         Sortable._marker.setStyle({top: (offsets[1]+dropon.clientHeight) + 'px'});
808     
809     Sortable._marker.show();
810   },
811   
812   _tree: function(element, options, parent) {
813     var children = Sortable.findElements(element, options) || [];
814   
815     for (var i = 0; i < children.length; ++i) {
816       var match = children[i].id.match(options.format);
817 
818       if (!match) continue;
819       
820       var child = {
821         id: encodeURIComponent(match ? match[1] : null),
822         element: element,
823         parent: parent,
824         children: [],
825         position: parent.children.length,
826         container: $(children[i]).down(options.treeTag)
827       }
828       
829       /* Get the element containing the children and recurse over it */
830       if (child.container)
831         this._tree(child.container, options, child)
832       
833       parent.children.push (child);
834     }
835 
836     return parent; 
837   },
838 
839   tree: function(element) {
840     element = $(element);
841     var sortableOptions = this.options(element);
842     var options = Object.extend({
843       tag: sortableOptions.tag,
844       treeTag: sortableOptions.treeTag,
845       only: sortableOptions.only,
846       name: element.id,
847       format: sortableOptions.format
848     }, arguments[1] || {});
849     
850     var root = {
851       id: null,
852       parent: null,
853       children: [],
854       container: element,
855       position: 0
856     }
857     
858     return Sortable._tree(element, options, root);
859   },
860 
861   /* Construct a [i] index for a particular node */
862   _constructIndex: function(node) {
863     var index = '';
864     do {
865       if (node.id) index = '[' + node.position + ']' + index;
866     } while ((node = node.parent) != null);
867     return index;
868   },
869 
870   sequence: function(element) {
871     element = $(element);
872     var options = Object.extend(this.options(element), arguments[1] || {});
873     
874     return $(this.findElements(element, options) || []).map( function(item) {
875       return item.id.match(options.format) ? item.id.match(options.format)[1] : '';
876     });
877   },
878 
879   setSequence: function(element, new_sequence) {
880     element = $(element);
881     var options = Object.extend(this.options(element), arguments[2] || {});
882     
883     var nodeMap = {};
884     this.findElements(element, options).each( function(n) {
885         if (n.id.match(options.format))
886             nodeMap[n.id.match(options.format)[1]] = [n, n.parentNode];
887         n.parentNode.removeChild(n);
888     });
889    
890     new_sequence.each(function(ident) {
891       var n = nodeMap[ident];
892       if (n) {
893         n[1].appendChild(n[0]);
894         delete nodeMap[ident];
895       }
896     });
897   },
898   
899   serialize: function(element) {
900     element = $(element);
901     var options = Object.extend(Sortable.options(element), arguments[1] || {});
902     var name = encodeURIComponent(
903       (arguments[1] && arguments[1].name) ? arguments[1].name : element.id);
904     
905     if (options.tree) {
906       return Sortable.tree(element, arguments[1]).children.map( function (item) {
907         return [name + Sortable._constructIndex(item) + "[id]=" + 
908                 encodeURIComponent(item.id)].concat(item.children.map(arguments.callee));
909       }).flatten().join('&');
910     } else {
911       return Sortable.sequence(element, arguments[1]).map( function(item) {
912         return name + "[]=" + encodeURIComponent(item);
913       }).join('&');
914     }
915   }
916 }
917 
918 // Returns true if child is contained within element
919 Element.isParent = function(child, element) {
920   if (!child.parentNode || child == element) return false;
921   if (child.parentNode == element) return true;
922   return Element.isParent(child.parentNode, element);
923 }
924 
925 Element.findChildren = function(element, only, recursive, tagName) {    
926   if(!element.hasChildNodes()) return null;
927   tagName = tagName.toUpperCase();
928   if(only) only = [only].flatten();
929   var elements = [];
930   $A(element.childNodes).each( function(e) {
931     if(e.tagName && e.tagName.toUpperCase()==tagName &&
932       (!only || (Element.classNames(e).detect(function(v) { return only.include(v) }))))
933         elements.push(e);
934     if(recursive) {
935       var grandchildren = Element.findChildren(e, only, recursive, tagName);
936       if(grandchildren) elements.push(grandchildren);
937     }
938   });
939 
940   return (elements.length>0 ? elements.flatten() : []);
941 }
942 
943 Element.offsetSize = function (element, type) {
944   return element['offset' + ((type=='vertical' || type=='height') ? 'Height' : 'Width')];
945 }
946