bug#44504: 27.1; feature request: doc-view support for Djvu documents

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Roland Winkler]

I suggest to add a backend for Djvu documents to doc-view.  (See the
website http://djvu.sourceforge.net/ describing the Djvu format and
hosting the DjVuLibre library.)  While I am maintaining djvu.el in
GNU Elpa, the purpose of this package is to edit Djvu documents.  So
the relation between djvu.el and doc-view is similar to the relation
between ps-mode and doc-view.  For users who only want to view Djvu
documents, the fairly big machinery of djvu.el can be rather
confusing.

The command line tool ddjvu from DjVuLibre converts Djvu documents
to various bitmap formats (pbm, pgm, ppm, pnm, rle, and tiff).
So I believe this should be sufficient for doc-view.  It is also
possible to extract the text layer of Djvu documents.


In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2020-08-31 built on regnitz
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description: Ubuntu 16.04.7 LTS

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Eli Zaretskii]

> Date: Sat, 7 Nov 2020 09:55:04 -0600
> From: "Roland Winkler" <winkler@gnu.org>
> 
> I suggest to add a backend for Djvu documents to doc-view.  (See the
> website http://djvu.sourceforge.net/ describing the Djvu format and
> hosting the DjVuLibre library.)  While I am maintaining djvu.el in
> GNU Elpa, the purpose of this package is to edit Djvu documents.  So
> the relation between djvu.el and doc-view is similar to the relation
> between ps-mode and doc-view.  For users who only want to view Djvu
> documents, the fairly big machinery of djvu.el can be rather
> confusing.
> 
> The command line tool ddjvu from DjVuLibre converts Djvu documents
> to various bitmap formats (pbm, pgm, ppm, pnm, rle, and tiff).
> So I believe this should be sufficient for doc-view.  It is also
> possible to extract the text layer of Djvu documents.

SGTM, thanks.  Patches to this effect are welcome.

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Jean Louis]

* Roland Winkler <winkler@gnu.org> [2020-11-07 18:56]:
> 
> I suggest to add a backend for Djvu documents to doc-view.  (See the
> website http://djvu.sourceforge.net/ describing the Djvu format and
> hosting the DjVuLibre library.)  While I am maintaining djvu.el in
> GNU Elpa, the purpose of this package is to edit Djvu documents.  So
> the relation between djvu.el and doc-view is similar to the relation
> between ps-mode and doc-view.  For users who only want to view Djvu
> documents, the fairly big machinery of djvu.el can be rather
> confusing.

I read systematically djvu documents in Emacs. Reading works in doc-view

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Roland Winkler]

On Sat Nov 7 2020 Jean Louis wrote:
> I read systematically djvu documents in Emacs. Reading works in doc-view

Thank you, you are right!  I looked at the Commentary section of
doc-view which starts out by explaining

  DocView is a document viewer for Emacs.  It converts PDF, PS and
  DVI files to a set of PNG files...

So I suggest to update this line and mention Djvu documents, too,
plus odf documents (mentioned in the docstring for
doc-view-doc-type).

(Of course, the real reason I did not notice this is djvu.el in GNU
Elpa, which I use for editing djvu documents.)

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Lars Ingebrigtsen]

"Roland Winkler" <winkler@gnu.org> writes:

> So I suggest to update this line and mention Djvu documents, too,
> plus odf documents (mentioned in the docstring for
> doc-view-doc-type).

OK, done on the Emacs 27 branch.  

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Roland Winkler]

On Mon Nov 9 2020 Lars Ingebrigtsen wrote:
> "Roland Winkler" <winkler@gnu.org> writes:
> 
> > So I suggest to update this line and mention Djvu documents, too,
> > plus odf documents (mentioned in the docstring for
> > doc-view-doc-type).
> 
> OK, done on the Emacs 27 branch.  

Thank you!  My apologies for being picky: How about also updating
the first line of doc-view.el to

;;; doc-view.el --- Document viewer for Emacs -*- lexical-binding: t -*-

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Lars Ingebrigtsen]

"Roland Winkler" <winkler@gnu.org> writes:

> Thank you!  My apologies for being picky: How about also updating
> the first line of doc-view.el to
>
> ;;; doc-view.el --- Document viewer for Emacs -*- lexical-binding: t -*-

Makes sense; I've now pushed that, too, to emacs-27.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Roland Winkler]

On Mon Nov 9 2020 Roland Winkler wrote:
> Thank you!  My apologies for being picky: How about also updating
> the first line of doc-view.el to
> 
> ;;; doc-view.el --- Document viewer for Emacs -*- lexical-binding: t -*-

...And the section "Requirements" is likewise outdated. How about
adding:

;; Djvu documents require `ddjvu' (from DjVuLibre).
;; ODF files require `soffice' (from LibreOffice).

Actually, I do not know about `soffice'.  Is this also part of
some (outdated?) Openoffice?

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Rudolf Schlatte]

"Roland Winkler" <winkler@gnu.org> writes:

> On Mon Nov 9 2020 Roland Winkler wrote:
>> Thank you!  My apologies for being picky: How about also updating
>> the first line of doc-view.el to
>> 
>> ;;; doc-view.el --- Document viewer for Emacs -*- lexical-binding: t -*-
>
> ...And the section "Requirements" is likewise outdated. How about
> adding:
>
> ;; Djvu documents require `ddjvu' (from DjVuLibre).
> ;; ODF files require `soffice' (from LibreOffice).
>
> Actually, I do not know about `soffice'.  Is this also part of
> some (outdated?) Openoffice?

OpenOffice started life in Germany as StarOffice, so the executable name
would make sense.

bug#44504: 27.1; feature request: doc-view support for Djvu documents

[Lars Ingebrigtsen]

"Roland Winkler" <winkler@gnu.org> writes:

> ...And the section "Requirements" is likewise outdated. How about
> adding:
>
> ;; Djvu documents require `ddjvu' (from DjVuLibre).
> ;; ODF files require `soffice' (from LibreOffice).

OK; added.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no