Re: downloading attachments on demand

[Simon Josefsson <jas@extundo.com>]

Lars Magne Ingebrigtsen <larsi@gnus.org> writes:

> Jouni K Seppanen <jks@iki.fi> writes:
>
>> From what I understand about the internal workings of Gnus, you'd have
>> to alter the backend protocol to make use of this. Instead of getting
>> a buffer filled with a message that it can parse for MIME structure,
>> the frontend would ask for some sort of a pre-parsed message object,
>> with stubs for the attachments, and only if the user wants to do
>> anything with them, would the frontend query the backend for their
>> contents.
>
> Well, nnimap could just return a valid MIME document with
> message/external-body parts, I think.  Gnus and nnimap would have to
> implement a special external-body scheme to download the parts, but
> that shouldn't be too much work...

I think we've discussed this approach before, and I'm not sure it is
the right one.  For example, how will this work with the various
caches in Gnus?  There is the backlog and the agent article cache.
Maybe others?

I'm afraid I don't have time to work on this.  Would someone else be
willing to make a stab at it?  Perhaps just ignore the backlog and
agent cache issues, and see if it is possible to make nnimap return
only partial articles if the article is larger than x KB should not be
too complex.  Then add a command that asks nnimap to really download
the entire article.  Once this is done, we can see if it is possible
to prune the agent/backlog caches correctly.

Alternatively, as I believe I have proposed before, we could add a new
backend interface to allow Gnus to query the MIME structure of
articles, and then only request partial articles, and handle the Gnus
cache coherency stuff in Gnus instead of in some nnimap-specific
command.