Uize.Node.getCoords.seen and Firefox

[timcarter]

The value of Uize.Node.getCoords.seen does not always match what is visually observed in Firefox. This seems to stem from Firefox allowing DOM elements to escape the boundaries of the body element. Once a DOM element has exited the interior of the body, the "seen" property is set to false in subsequent calls to Uize.Node.getCoords, even though it is clearly still visible onscreen.

I've created a test page to demonstrate the problem: http://timcarter.github.com/javascript.html. When the square is moved below the body element (highlighted in pink), "seen" is set to false. This does not occur in Chrome, which restricts the vertical movement of the DOM element. I have yet to figure out why that is the case, considering that the body element appears to span the height of the browser window.

There is also a separate issue of the "seen" property initially being set to false, which I believe is due to the square's positioning being set to "absolute".