Wrapping a layer with a div with margin:auto messes up the display of wires when you're dragging them

<div id="wrapper">
   <div id="layer">

#wrapper { margin:auto; width:800px; }

var layer = document.getElementById('layer');
new WireIt.Layer({parentEl:layer});

The above wraps the layer in a div that centres everything. You will note that if you try to drag a wire around, the end of the wire is not connected to your mouse cursor but is displaced by the same distance as the wrapper is moved from the side of the screen.