[mod_python] sending headers directly to the client

Hi all,

I need to send headers directly to the client; that is, before
mod_python sends its headers (I know that I have to handle the status
line specially).

Background: I need to detect when the user hits the 'Cancel' button of
the browser. The only reliable way to do this seems to send something
periodically to the client. My idea is now to send dummy headers to
the client until the possibly long running HTML code generating
function is finished. Then I stop sending dummy headers and send the
HTML code to the client. If the client hits 'Cancel' while the
HTML code generating function is running, I'm able to detect this
because I get some kind of error when sending a dummy header.

The problem is now: how can I send the dummy headers?

I cannot use 'req.write' because this flushes all headers (note that
some headers can be set only *after* HTML has been generated).  My
idea was then to use 'req.connection.write'. The problem with this
approach is that this function does *not* trigger an error if the
connection is closed. I also fiddled around with the
'req.connection.aborted' field without success.

Any help would be greatly appreciated.

Cheers, Stefan