var mousex = 0;
var mousey = 0;
var grabx = 0;
var graby = 0;
var orix = 0;
var oriy = 0;
var elex = 0;
var eley = 0;
var algor = 0;

var dragobj = null;
var initialz=10;

function falsefunc() { return false; } // used to block cascading events

function init()
{
  document.onmousemove = update; // update(event) implied on NS, update(null) implied on IE
  update();
}



function getMouseXY(e) // works on IE6,FF,Moz,Opera7
{
  if (!e) e = window.event; // works on IE, but not NS (we rely on NS passing us the event)

  if (e)
  {
    if (e.pageX || e.pageY)
    { // this doesn't work on IE6!! (works on FF,Moz,Opera7)
      mousex = e.pageX;
      mousey = e.pageY;
      algor = '[e.pageX]';
      if (e.clientX || e.clientY) algor += ' [e.clientX] '
    }
    else if (e.clientX || e.clientY)
    { // works on IE6,FF,Moz,Opera7
      // Note: I am adding together both the "body" and "documentElement" scroll positions
      //       this lets me cover for the quirks that happen based on the "doctype" of the html page.
      //         (example: IE6 in compatibility mode or strict)
      //       Based on the different ways that IE,FF,Moz,Opera use these ScrollValues for body and documentElement
      //       it looks like they will fill EITHER ONE SCROLL VALUE OR THE OTHER, NOT BOTH
      //         (from info at http://www.quirksmode.org/js/doctypes.html)
      mousex = e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft;
      mousey = e.clientY + document.body.scrollTop + document.documentElement.scrollTop;
      algor = '[e.clientX]';
      if (e.pageX || e.pageY) algor += ' [e.pageX] '
    }
  }
}
function update(e)
{
  getMouseXY(e); // NS is passing (event), while IE is passing (null)
}

function grab(context)
{
  getMouseXY();
  document.onmousedown = falsefunc; // in NS this prevents cascading of events, thus disabling text selection
  dragobj = context;
  dragobj.style.zIndex = initialz; // move it to the top
  initialz++;
  document.onmousemove = drag;
  document.onmouseup = drop;
  grabx = mousex;
  graby = mousey;
  elex = orix = dragobj.offsetLeft;
  eley = oriy = dragobj.offsetTop;
  update();
}

function drag(e) // parameter passing is important for NS family
{
  if (dragobj)
  {
    if(graby==0)graby=mousey;
    if(grabx==0)grabx=mousex;
    elex = orix + (mousex-grabx);
    eley = oriy + (mousey-graby);
    dragobj.style.position = "absolute";
    dragobj.style.left = (elex).toString(10) + 'px';
    dragobj.style.top  = (eley).toString(10) + 'px';
  }
  update(e);
  return false; // in IE this prevents cascading of events, thus text selection is disabled
}

function drop()
{
  if (dragobj)
  {
    //dragobj.style.zIndex = 0;
    dragobj = null;
  }
  update();
  document.onmousemove = update;
  document.onmouseup = null;
  document.onmousedown = null;   // re-enables text selection on NS
}