We have some users with visibility issues and typically run their webapps using the browser's zoom. We are using packager, which doesn't have any default 'zoom' functions. The closest I have found is to use "document.body.style.zoom='125%'".
The page does zoom, but the viewport doesn't seem to notice. So the extra 25% just flows off the screen on the right and bottom. Re-sizing the window just carries the problem with.
The only thing I can see is that viewport.setWidth() (& height) could possibly be used to compensate, but any event that causes re-layout will bring back the 'wrong' dimensions.