var MoverBehaviour = {
  mo: null, // reference to the movable obj,
  x: 0, y: 0,
  
  // ----- Events -----
  onmousedown: function (evt) {
    evt = evt || window.event;
    var src = jcl.FindBehaviourElement(evt.srcElement, MoverBehaviour);
    src.MoveStart(evt);
  }, // onmousedown


  // track mouse moves. This handler will be attached to the document level !
  _onmousemove: function (evt) {
    evt = evt || window.event;
    MoverBehaviour.MoveIt(evt);
  }, // onmousemove


  // track mouse button up. This handler will be attached to the document level !
  _onmouseup: function (evt) {
    evt = evt || window.event;
    MoverBehaviour.MoveEnd(evt);
  }, // onmouseup


  // ----- Methods -----
  MoveStart: function (evt) {
    // find the moving part (position:absolute or class="VEPart")
    var mo = this;
    while ((mo != null) && (mo.className != "VEPart"))
      mo = mo.parentNode;

    if (mo == null)
      return; // don't move
    MoverBehaviour.mo = mo;
      
    // calculate mousepointer-object distance
    mo.x = mo.y = 0;
    obj = mo;
    while (obj != null) {
      mo.x += obj.offsetLeft;
      mo.y += obj.offsetTop;
      obj = obj.offsetParent;
    } // while
    mo.x = evt.clientX - mo.x;
    mo.y = evt.clientY - mo.y;

    // make the moving object globally evailable when mouse is leaving this object.
    jcl.AttachEvent(document, "onmousemove", this._onmousemove);
    jcl.AttachEvent(document, "onmouseup", this._onmouseup);
  }, // MoveStart
  

  MoveIt: function (evt) {
    var mo = MoverBehaviour.mo;
    if (mo != null) {
      var p = (evt.clientX - mo.x) + "px";
      if (p != mo.style.left) mo.style.left = p;
      p = (evt.clientY - mo.y) + "px";
      if (p != mo.style.top) mo.style.top = p;
    } // if
    // cancel selecting anything
    evt.cancelBubble = true;
    evt.returnValue = false;
  }, // MoveIt
  

  MoveEnd: function () {
    var mo = MoverBehaviour.mo;
    if (mo != null) {
      MoverBehaviour.mo = null;
      jcl.DetachEvent(document, "onmousemove", this._onmousemove);
      jcl.DetachEvent(document, "onmouseup", this._onmouseup);
    } // if
  } // MoveEnd
    
} // MoverBehaviour