/* <![CDATA[ */
var _startX = 0;            // mouse starting positions
var _startY = 0;
var _offsetX = 0;           // current element offset
var _offsetY = 0;
var _dragElement;           // needs to be passed from OnMouseDown to OnMouseMove
var _oldZIndex = 0;         // we temporarily increase the z-index during drag



initDragDrop();



function initDragDrop ()
{
  document.onmousedown = onMouseDown;
  document.onmouseup   = onMouseUp;
}



function onMouseDown (e)
{
  // IE
  if (e == null) e = window.event; 
  
  // IE uses srcElement, others use target
  var target = (e.target != null)? e.target : e.srcElement;
  target = target.parentNode.parentNode;
  
  // for IE, left click == 1
  // for Firefox, left click == 0
  if ((e.button == 1 && window.event != null || e.button == 0) && target.className == 'window')
  {
    // grab the mouse position
    _startX = e.clientX;
    _startY = e.clientY;
      
    // grab the clicked element's position
    _offsetX = extractNumber(target.style.left);
    _offsetY = extractNumber(target.style.top);
    
    if (_offsetX==0) _offsetX=(document.body.clientWidth-(extractNumber(target.style.right)+extractNumber(target.style.width)));
    
    // bring the clicked element to the front while it is being dragged
    _oldZIndex = target.style.zIndex;
    target.style.zIndex = 10000;
     
    // we need to access the element in OnMouseMove
    _dragElement = target;

    // tell our code to start moving the element with the mouse
    document.onmousemove = onMouseMove;
        
    // cancel out any text selections
    document.body.focus();

    // prevent text selection in IE
    document.onselectstart = function () { return false; };
    // prevent IE from trying to drag an image
    target.ondragstart = function() { return false; };
        
    // prevent text selection (except IE)
    return false;
  }
}



function onMouseMove (e)
{
  if (e == null) var e = window.event; 

  // this is the actual "drag code"
  _dragElement.style.left = (_offsetX + e.clientX - _startX) + 'px';
  _dragElement.style.top = (_offsetY + e.clientY - _startY) + 'px';
}



function onMouseUp (e)
{
  if (_dragElement != null)
  {
    _dragElement.style.zIndex = _oldZIndex;

    // we're done with these events until the next OnMouseDown
    document.onmousemove = null;
    document.onselectstart = null;
    _dragElement.ondragstart = null;

    // this is how we know we're not dragging      
    _dragElement = null;
  }
}



function extractNumber (value)
{
  var n = parseInt(value);
  return n == null || isNaN(n) ? 0 : n;
}
/* ]]> */