Subject: Re: bug#21331: 24.5; LibreOffice documents have less support than Microsoft Office docs (in Gnus?)

From: [email-masked] (N. Jackson)
Date: Tue, 25 Aug 2015 20:41:34 -0300

At 19:13 -0300 on Tuesday 2015-08-25, Richard Stallman wrote:

> Where does mailcap come from?

Mailcap is Network Working Group RFC 1524 [1]. "A mailcap file can be
used to find the correct program to open a file with, based on MIME
information. While the name is "mailcap" and is related to MIME (mail
filetypes) it actually has use outside the domain of electronic mail"
[2].

My mailcap file came with my OS distribution (Fedora 21 GNU/Linux) and I
would guess their distribution is where most users' mailcap files come
from.

I suspect (but am not certain), that I, rather than Red Hat, am guilty
of adding the line to it that allowed Gnus to open Microsoft Word file
attachments, inadvertently kicking off this bug report. Otherwise Gnus
would have failed to open all office suite file attachments equally.

> How can we get this fixed in everyone's mailcap file?

I don't see how that could be possible for Emacs. Presumably each user
must edit their own mailcap files to add support for the MIME types they
choose. The only support that Emacs could provide for this IIUC would be
to provide more explicit and more easily-found documentation.

An alternative solution, at least for users using desktop environments
such as Gnome, KDE, and Xfce, would be for Emacs to make use of
freedesktop.org facilities such as xdg-utils. I envisage users being
able to launch from within Emacs (from dired, say), not only LibreOffice
to open it's associated files, but to launch the correct program to open
any file on their system (provided their desktop environment knows how
to open the file) -- when Emacs is unable to open it internally. [But
perhaps this functionality already exists and I just haven't discovered
it yet?]

[1] Network Working Group, RFC 1524: A User Agent Configuration
Mechanism For Multimedia Mail Format Information.
https://tools.ietf.org/html/rfc1524

[2] Wikipedia, Mailcap. https://en.wikipedia.org/wiki/Mailcap