Re: Please install: Some improvements to doc-view.el

[Juri Linkov <juri@jurta.org>]

>     DocView and the Gnus mailcap mechanism are unrelated features.
>
> They are related because they do the same job: display non-textual
> formats for Emacs.  They work in different ways, but each can still
> substitute for the other.  If you have a PDF or PS or DVI file, you
> can display it either with doc-view or with the Gnus mailcap
> mechanism.
>
> So do we really want both methods?  If so, when should each
> method be used?  Or how should the user choose?

I think both methods are very useful.

The Gnus mailcap mechanism provides several alternatives of external
programs to run.  There are many different file types associated with
programs in the mailcap file, not only documents supported by doc-view.
But OTOH, doc-view provides more convenient way of viewing supported
file types (PDF/PS/DVI) inside Emacs, not in external programs.

> The current code chooses the mailcap mechanism when in Gnus,
> and now we have a proposal for Dired to use the doc-view mechanism.

There is already a file lisp/gnus/gnus-dired.el that binds `C-c C-m C-l'
in Dired to the command that runs the program found in the mailcap file.

But I think a better way would be to allow the user to select the
preferred program, inspect the command line and be able to edit the
command line before running a command.  This can be achieved by putting
program names found by the Gnus mailcap mechanism to the default value
in the minibuffer activated after typing !  in Dired.

A for doc-view, since it displays rendered images inside Emacs buffers,
there is no need to activate it only from Dired.  Visiting a PDF/PS/DVI
file in any way including `C-x C-f' could put it in doc-view mode.
And if the user want to see its source text, then the user can type
`C-c C-c' just like in image-mode.

-- 
Juri Linkov
http://www.jurta.org/emacs/