Make jQuery-ui draggable handle cover entire page

What would be the best way to make an element draggable when clicking anywhere in the window?

Would I have to use a container <div> that covers the whole window?

I tried making the body draggable but that didn't work.

The problem with using a container <div> is that it moves and therefore doesn't cover the whole of the screen any more after it has been dragged.

What about making a really vast container <div> that spans a large number of pixels in every direction so you would never get to the edge of it. Is that a bad idea?

The idea (simplified) is to have a page with a square in the middle that can be dragged by dragging any part of the window.

Here's a wonderfully unnecessary mockup :)

I'm trying with a full screen div, but when I reset it, the elemen开发者_开发知识库t within it moves back with it.. http://jsfiddle.net/LUFf6/

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EDIT: revised to include mouse offset from the div.

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.js"></script>
<script>
function doMove(e) {
  var $d = $('#myDiv');
  var off = $d.offset();
  var left = e.pageX + $d.data('left');
  var top = e.pageY + $d.data('top');
  $d.offset({left: left, top: top});
};
$(function() {
  $(document).mousedown(function(e) {
     var $d = $('#myDiv');
     var off = $d.offset();
     $d.data('left',off.left - e.pageX);
     $d.data('top',off.top - e.pageY);     
     $(document).bind('mousemove', doMove);
  }).mouseup(function(e) {
     $(document).unbind('mousemove',doMove);
  });
});
</script>
<style>
div#myDiv {
  width: 50px;
  height: 50px;
  background-color: red;
  position: absolute;
  top: 100px;
  left: 100px;
}
</style>
<div id="myDiv"></div>

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it really depends on what you are trying to achieve, so we'll need to know a bit more really.
You could just move the draggable div to the top left of the screen and full width/height after each "drop" event?

I personally wouldn't go down the 'vast container' route though.