[Sommaire] [Imprimer]

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