The usage of an unique upload ID ensures at their end
that the progressbar
iframe always gets the right data. It refreshes using AJAX technology:
http://pastebin.com/f56b8c8f4
I'll take a look if this might be applicable to put into MW.
Yes, that seems similar to the original proposal: track the status of the opload
on the server side, store the status in some cross-request cache (like APC), and
query it using JavaSCript (as an iframe or by injecting html doesn't really
matter). That's a *little* lighter on the client, but still quite a fugly hack,
ant not very reliable, IMHO.
-- daniel