Fetching Article Headers

["Taso N. Devetzis" <devetzis@snet.net>]

Greetings,

I have written some hooks to snarf and examine article headers (for
mail back-ends -- I am using nnml if it matters), but I have a couple
of questions regarding the available functions and their behaviour.

I can find the headers easily enough as follows:

(defun blat-find-header (hdr)
  (gnus-with-article-headers
    (message-fetch-field hdr)))

This function, however, requires the headers in question to be visible
(since it uses *gnus-article-buffer*, I presume).  I have had similar
results with manually (or using some of the built-ins) searching via
*gnus-parse-headers-hook* (wrong concept altogether on my part) and
*nnmail-prepare-incoming-header-hook* (same deal).  The hooks and
functions (such as the *gnus-with-article-headers* macro) that rely on
the article buffer will also not work unless the article is selected
(and *gnus-article-buffer* is therefore current).

*gnus-alter-header-function* seems promising, but I am not convinced
that this is its Intended Purpose.

I know enough about gnus to be a danger to myself and others, so I
would ask your indulgence in pointing me in the right direction to
examine (all of) the article headers (for mail back-ends), regardless
of whether or not the article is selected (you know, cruise through
them in Summary mode).  I understand that I may have to manually
select the article and parse the headers, but I want to make sure I am
not missing an obvious hook.  Nothing in the docs springs out at me.

Thanks.

/taso