Re: odt file instant open

[Kevin Rodgers]

Andreas Röhler wrote:
> Am 27.07.2010 18:58, schrieb Eli Zaretskii:
> > > Date: Tue, 27 Jul 2010 09:30:32 +0200
> > > From: Andreas Röhler<andreas.roehler@easy-emacs.de>
> > >
> > > Am 26.07.2010 18:29, schrieb Olwe Melwasul:
> > > > I'm trying to grok the open document format, so I took the first wild
> > > > and crazy step of simply trying to open it in Emacs (23.2.1) -- and it
> > > > opened up to a "Zip-Archive Narrow" view of all the files contained
> > > > therein Poking around on the Internet, I found that Emacs
> > > > automatically unpacks a .odt file, which is nothing more than a zip
> > > > file. My question is this: How is Emacs doing this?
> > >
> > > by calling a shell-command resp. to the ending found.
> >
> > No.  For most archive types, arc-mode.el (and tar-mode.el) can list
> > the contents directly, just by reading the archive file itself.
> > Extracting the individual files in the archive sometimes needs to run
> > an external program.
>
> Hi,
>
> think you mistook the question.
> As the OP wrote, he just opened the file without any precaution. The 
> surprise was: it worked.
>
> Ignoring so for how opening was done in detail --via find-file or from 
> dired probably--

I think you misread the question, that is exactly what the OP asked about:

How is Emacs doing this? What code is
running (what .el is invoked) to make this happen?

> arc-mode seems not involved, but auto-compression-mode 
> from jka-cmpr-hook.el etc.

This entry from auto-mode-alist suggests otherwise:

 ("\\.\\(sx[dmicw]\\|od[fgpst]\\|oxt\\)\\'" . archive-mode)

> BTW arc-mode too recurs to shell-commands AFAIS,
>       (apply 'call-process
> in archive-*-extract for example

Good point, which Eli made above as well.  Here's what arc-mode.el says:

;; This code does not decode any files internally, although it does
;; understand the directory level of the archives.

--
Kevin Rodgers
Denver, Colorado, USA