[[!template id=plugin name=po core=0 author="[[intrigeri]]"]]
[[!tag type/format]]

This plugin adds support for multi-lingual wikis, translated with
gettext, using [po4a|http://po4a.alioth.debian.org/].

It depends on the Perl `Locale::Po4a::Po` library (`apt-get install po4a`).

Introduction
============

A language is decided to be the "master" one, and any other supported
language is a "slave" one. A page written in the "master" language is
a "master" page, and is written in any supported format but PO.

Example: `bla/page.mdwn` is a "master" Markdown page written in
English; if `usedirs` is enabled, it is rendered as
`bla/page/index.html`, else as `bla/page.html`.

Translations of a "master" page into a "slave" language are called
"slave" pages, and is a in gettext PO format. PO is thus promoted to
the wiki page type status.

Example: `bla/page.fr.po` is the PO "message catalog" used to
translate `bla/page.mdwn` into French; if `usedirs` is enabled, it is
rendered as `bla/page/index.html.fr`, else as `bla/page.html.fr`


Configuration
=============

`po_master_language` is used to set the master language in
`ikiwiki.setup`, such as:

        po_master_language => { 'code' => 'en', 'name' => 'English' }

`po_slave_languages` is used to set the list of supported "slave"
languages, such as:

        po_slave_languages => { 'fr' => { 'name' => 'Français', },
                                'es' => { 'name' => 'Castellano', },
                                'de' => { 'name' => 'Deutsch', },
        },


Server support
==============

Apache
------

Using `mod_negotiation` makes it really easy to have Apache serve the
page in the client's preferred language, if available. This is the
default Debian Apache configuration.

When `usedirs` is enabled, one has to set `DirectoryIndex index` for
the wiki context.

Setting `DefaultLanguage LL` for the wiki context can be needed, to
ensure `bla/page/index.html` is served as `Content-Language: LL`
(replace `LL` with your default MIME language).

lighttpd
--------

lighttpd unfortunately does not support content negotiation.


TODO
====

Display available translations
------------------------------

The [[linguas|plugins/contrib/linguas]] plugin has some code that can
be used as a basis to display the existing translations, and allow to
navigate between them.

View translation status
-----------------------

One should be able to view some freshness information about the
translation status, either for a given page or for the whole wiki.

This should not be too hard using gettext tools. If this is
implemented as a
[[HTML::Template|http://search.cpan.org/search?mode=dist&query=HTML%3A%3ATemplate]]
loop, a page using it should depend on any "master" and "slave" pages
whose status is being displayed.

Decide which pages are translatable
-----------------------------------

The subset of ("master") pages supporting translation must be
configurable:

- a `[[!translatable ]]` directive, when put on a page, makes it
  translatable
- this [[ikiwiki/directive]] can be used with an optional `match=PageSpec`
  argument, to render translatable a bunch of pages at once

Automatic PO files update
-------------------------

Committing changes to a "master" page must:

1. update the POT file, the PO files for the supported languages, and
   put them under version control
2. trigger a refresh of the corresponding HTML slave pages

The former can be implemented as a `needsbuild` hook, which is the
first type of hook to run after the list of files that need to be
built is known: that is, at a time when we know which "master" page
was modified, and thus, which POT/PO files have to be updated.

The latter can be implemented by making any "slave" page depend on the
corresponding "master" page. The `add_depends` function can achieved
this, if used in a FIXME hook.

UI consistency: rename "Edit" button on slave pages
---------------------------------------------------

It may be surprising to some, after having pressed *Edit* on a wiki
page, to end up editing a strange PO file. The *Edit* button must then
be be renamed to *Improve translation* on "slave" pages.

Translation quality assurance
-----------------------------

Modifying a PO file via the CGI must only be allowed if the new
version is a valid PO file. As a bonus, check that it provides a more
complete translation than the existing one.

A new `cansave` type of hook would be needed to implement this.

Note: committing to the underlying repository is a way to bypass
this check.

Translating online
------------------

As PO is a wiki page type, we already have an online PO editor, that
is ikiwiki's CGI.

A message-by-message interface could be implemented later, providing
a nice way to translate offline (without VCS access) is provided.

Translating offline without VCS access
--------------------------------------

The following workflow should be made possible for translators without
VCS access who need to edit the PO files in another editor than a web
browser:

- download the PO file for the page
- use any PO editor to update the translation
- upload the updated PO file

A generic mechanism to download and upload a page's source is needed.
It's only an alternative way to do Edit/edit/Save.

### Short-term workflow

- pretend to edit the PO file online
- copy the PO file content from the textarea
- cancel the edit
- paste the content into a local file.