How does Gmail do comet on Opera?

Question

I would like to know how Gmail (or anyone else) does comet on Opera.

Here is what I know so far from my experiments.

1. It doesn't use the event-source tag which is broken in Opera 10.51.
2. It doesn't use iframe which displays a spinning throbber and a busy mouse cursor.
3. It doesn't use responseText on xmlhttprequest when readyState = 3 which is known to be broken on Opera.

I tried seeing how it was done in mibbit and etherpad, and I found that they both use long-polling.

Bounty

The bounty goes to whoever can tell me a method better than "event-source" for Opera comet streaming, or how gmail does streaming (or long-polling if it does that).

Answer 1

GMail uses BrowserChannel (Docs | Source), which is included in Google's Closure Library.

• @fileoverview Definition of the BrowserChannel class. A BrowserChannel
• simulates a bidirectional socket over HTTP. It is the basis of the
• Gmail Chat IM connections to the server.