I suspect compression from the UA to the server will need support on the
XHR object in order to work. I don't think the right way to do it is
through setRequestHeader though, that seems like a hack at best.
I would have thought this would be negotiated by the server sending a
Accept-Encoding header to indicate what forms of encoding it could handle
for request entities. XHR requests are almost always proceeded by a
separate response from a server (the web page) that can indicate the
server's ability to decode request entities.
I think that this would go against the spirit of HTTP. The idea of HTTP is
that it is state-less, so you should not carry state from one request to
the next.
Encoding capability isn't really a state in the HTTP sense, since it is
presumably an immutable characteristic of the server, rather than a mutable
state of an application (the latter being what HTTP abhors). It seems
completely analagous to Accept-Ranges which works exactly the same
(communicates the server's ability to handle Range requests and what range
units are acceptable).
Kris
