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 dragobj = null;

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

function setmousemove(o,n)
{
  switch (n)
  {
    case 1:
      o.onmousemove = onmousemove1; // update(event) implied on NS, update(null) implied on IE
      break;
    case 2:
      o.onmousemove = onmousemove2; // update(event) implied on NS, update(null) implied on IE
      break;
    case 3:
      o.onmousemove = onmousemove3; // update(event) implied on NS, update(null) implied on IE
      break;
    case 4:
      o.onmousemove = onmousemove4; // update(event) implied on NS, update(null) implied on IE
      break;
    default:
      o.onmousemove = onmousemove1;
      break;
  } 
}

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;
    }
    else if (e.clientX || e.clientY)
    { // works on IE6,FF,Moz,Opera7
      mousex = e.clientX + document.body.scrollLeft;
      mousey = e.clientY + document.body.scrollTop;
    }  
  }
}

function grab(o,n)
{
  document.onmousedown = falsefunc; // in NS this prevents cascading of events, thus disabling text selection
  dragobj = o;
  switch (n)
  {
    case 1:
      document.onmousemove = drag1; // update(event) implied on NS, update(null) implied on IE
      break;
    case 2:
      document.onmousemove = drag2; // update(event) implied on NS, update(null) implied on IE
      break;
    case 3:
      document.onmousemove = drag3; // update(event) implied on NS, update(null) implied on IE
      break;
    case 4:
      document.onmousemove = drag4; // update(event) implied on NS, update(null) implied on IE
      break;
    default:
      document.onmousemove = drag;
      break;
  } 
  document.onmouseup = drop;
}

function drag(e) // parameter passing is important for NS family 
{
  if (dragobj)
  {
    getMouseXY(e);
    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';
  }
  return false; // in IE this prevents cascading of events, thus text selection is disabled
}

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