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