// Global holds reference to selected element
var selectedObj;

// Globals hold location of click relative to element
var offsetX, offsetY;

// Set global reference to element being engaged and dragged
function setSelectedElem(evt)
{
   var target = (evt.target) ? evt.target : evt.srcElement;
   var divID = (target.id == "titlebar") ? "pseudoWindow" : "";

   if(divID)
   {
      if(document.layers)
         selectedObj = document.layers[divID];
      else if(document.all)
         selectedObj = document.all(divID);
      else if(document.getElementById)
         selectedObj = document.getElementById(divID);
   
      setZIndex(selectedObj, 100);
      return;
   }

   selectedObj = null;
   return;
}

// Turn selected element on
function engage(evt)
{
   evt = (evt) ? evt : event;
   setSelectedElem(evt);
   if(selectedObj)
   {
      if(document.body && document.body.setCapture)
      {
         // engage event capture in IE/Win
         document.body.setCapture();
      }
      if(evt.pageX)
      {
         offsetX = evt.pageX - ((typeof selectedObj.offsetLeft != "undefined") ? 
            selectedObj.offsetLeft : selectedObj.left);
         offsetY = evt.pageY - ((selectedObj.offsetTop) ? 
            selectedObj.offsetTop : selectedObj.top);
      }
      else if(typeof evt.clientX != "undefined")
      {
         offsetX = evt.clientX - ((selectedObj.offsetLeft) ? 
            selectedObj.offsetLeft : 0);
         offsetY = evt.clientY - ((selectedObj.offsetTop) ? 
            selectedObj.offsetTop : 0);
      }
      else if(evt.offsetX || evt/offsetY)
      {
         offsetX = evt.offsetX - ((evt.offsetX < -2) ? 
            0 : document.body.scrollLeft);
         offsetX -= (document.body.parentElement && 
            document.body.parentElement.scrollLeft) ? 
            document.body.parentElement.scrollLeft : 0
            offsetY = evt.offsetY - ((evt.offsetY < -2) ? 
            0 : document.body.scrollTop);
         offsetY -= (document.body.parentElement && 
            document.body.parentElement.scrollTop) ? 
            document.body.parentElement.scrollTop : 0
      }
      evt.cancelBubble = true;
      return false;
   }
}

// Drag an element
function dragIt(evt)
{
   evt = (evt) ? evt : event;
   if(selectedObj)
   {
      if(evt.pageX)
         shiftTo(selectedObj, (evt.pageX - offsetX), (evt.pageY - offsetY));
      else if(evt.clientX || evt.clientY)
         shiftTo(selectedObj, (evt.clientX - offsetX), (evt.clientY - offsetY));
      
      evt.cancelBubble = true;
      return false;
   }
}

// Turn selected element off
function release(evt)
{
   if(selectedObj)
   {
      setZIndex(selectedObj, 0);
      if(document.body && document.body.releaseCapture)
      {
         // stop event capture in IE/Win
         document.body.releaseCapture();
      }
      selectedObj = null;
   }
}

function blockEvents(evt)
{
   evt = (evt) ? evt : event;
   evt.cancelBubble = true;
   return false;
}

// Assign event handlers used by both Navigator and IE
function initDrag()
{
   if(document.layers)
   {
      // turn on event capture for these events in NN4 event model
      document.captureEvents(Event.MOUSEDOWN | Event.MOUSEMOVE | Event.MOUSEUP);
      return;
   }
   else if(document.body & document.body.addEventListener)
   {
      // turn on event capture for these events in W3C DOM event model
      document.addEventListener("mousedown", engage, true);
      document.addEventListener("mousemove", dragIt, true);
      document.addEventListener("mouseup", release, true);
      return;
   }
   
  	document.onmousedown = engage;
   document.onmousemove = dragIt;
   document.onmouseup = release;
   return;
}