ikiwiki/doc/plugins/po.mdwn

[[!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 chosen as the "master" one, and any other supported
language is a "slave" one.

A page written in the "master" language is a "master" page. It can be
of any page type supported by ikiwiki, except `po`. It does not have to be
named a special way: migration to this plugin does not imply any page
renaming work.

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

Any translation of a "master" page into a "slave" language is called
a "slave" page; it is written in the gettext PO format. `po` is now
a page type supported by ikiwiki.

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.fr.html`, else as `bla/page.fr.html`


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

Supported languages
-------------------

`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' => 'Français',
                                'es' => 'Castellano',
                                'de' => 'Deutsch',
        }

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

The `po_translatable_pages` setting configures what pages are
translatable. It is a [[ikiwiki/PageSpec]], so you have lots of
control over what kind of pages are translatable.

The `.po` files are not considered as being translatable, so you don't need to
worry about excluding them explicitly from this [[ikiwiki/PageSpec]].

Internal links
--------------

The `po_link_to` option in `ikiwiki.setup` is used to decide how
internal links should be generated, depending on web server features
and site-specific preferences.

### Default linking behavior

If `po_link_to` is unset, or set to `default`, ikiwiki's default
linking behavior is preserved: `\[[destpage]]` links to the master
language's page.

### Link to current language

If `po_link_to` is set to `current`, `\[[destpage]]` links to the
`destpage`'s version written in the current page's language, if
available, *i.e.*:

- `foo/destpage/index.LL.html` if `usedirs` is enabled
- `foo/destpage.LL.html` if `usedirs` is disabled

### Link to negotiated language

If `po_link_to` is set to `negotiated`, `\[[page]]` links to the
negotiated preferred language, *i.e.* `foo/page/`.

(In)compatibility notes:

- if `usedirs` is disabled, it does not make sense to set `po_link_to`
  to `negotiated`; this option combination is neither implemented
  nor allowed.
- if the web server does not support Content Negotiation, setting
  `po_link_to` to `negotiated` will produce a unusable website.


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

Apache
------

Using Apache `mod_negotiation` makes it really easy to have Apache
serve any 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` (replace `LL` with your default MIME
language code) for the wiki context can help to ensure
`bla/page/index.en.html` is served as `Content-Language: LL`.

lighttpd
--------

lighttpd unfortunately does not support content negotiation.

**FIXME**: does `mod_magnet` provide the functionality needed to
 emulate this?


Usage
=====

Templates
---------

The `ISTRANSLATION` and `ISTRANSLATABLE` variables can be used to
display things only on translatable or translation pages.

### Display page's versions in other languages

The `OTHERLANGUAGES` loop provides ways to display other languages'
versions of the same page, and the translations' status.

One typically adds the following code to `templates/page.tmpl`:

	<TMPL_IF NAME="OTHERLANGUAGES">
	<div id="otherlanguages">
	  <ul>
	  <TMPL_LOOP NAME="OTHERLANGUAGES">
	    <li>
	      <a href="<TMPL_VAR NAME="URL">"><TMPL_VAR NAME="LANGUAGE"></a>
	      <TMPL_UNLESS NAME="MASTER">
	        (<TMPL_VAR NAME="PERCENT">&nbsp;%)
	      </TMPL_UNLESS>
	    </li>
	  </TMPL_LOOP>
	  </ul>
	</div>
	</TMPL_IF>

The following variables are available inside the loop (for every page in):

- `URL` - url to the page
- `CODE` - two-letters language code
- `LANGUAGE` - language name (as defined in `po_slave_languages`)
- `MASTER` - is true (1) if, and only if the page is a "master" page
- `PERCENT` - for "slave" pages, is set to the translation completeness, in percents

### Display the current translation status

The `PERCENTTRANSLATED` variable is set to the translation
completeness, expressed in percent, on "slave" pages.

One can use it this way:

	<TMPL_IF NAME="ISTRANSLATION">
	<div id="percenttranslated">
	  <TMPL_VAR NAME="PERCENTTRANSLATED">
	</div>
	</TMPL_IF>

Additional PageSpec tests
-------------------------

This plugin enhances the regular [[ikiwiki/PageSpec]] syntax with some
additional tests that are documented [[here|ikiwiki/pagespec/po]].

Automatic PO file update
------------------------

Committing changes to a "master" page:

1. updates the POT file and the PO files for the "slave" languages;
   the updated PO files are then put under version control;
2. triggers a refresh of the corresponding HTML slave pages.

Also, when the plugin has just been enabled, or when a page has just
been declared as being translatable, the needed POT and PO files are
created, and the PO files are checked into version control.

Discussion pages
----------------

Discussion should happen in the language in which the pages are
written for real, *i.e.* the "master" one. If discussion pages are
enabled, "slave" pages therefore link to the "master" page's
discussion page.

Translating
-----------

One can edit the PO files using ikiwiki's CGI (a message-by-message
interface could also be implemented at some point).

If [[tips/untrusted_git_push]] is setup, one can edit the PO files in one's
preferred `$EDITOR`, without needing to be online.

TODO
====

Security checks
---------------

- Can any sort of directives be put in po files that will
  cause mischief (ie, include other files, run commands, crash gettext,
  whatever). The [PO file
  format](http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files)
  should contain the answer.
- Any security issues on running po4a on untrusted content?

### Security history

#### GNU gettext
- [CVE-2004-0966](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0966)
  / [Debian bug #278283](http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=278283):
  the autopoint and gettextize scripts in the GNU gettext package
  1.14 and later versions, as used in Trustix Secure Linux 1.5
  through 2.1 and other operating systems, allows local users to
  overwrite files via a symlink attack on temporary files.

#### po4a
-
  [CVE-2007-4462](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4462):
  lib/Locale/Po4a/Po.pm in po4a before 0.32 allows local users to
  overwrite arbitrary files via a symlink attack on the
  gettextization.failed.po temporary file.

gettext/po4a rough corners
--------------------------

- fix infinite loop when synchronizing two ikiwiki (when checkouts
  live in different directories): say bla.fr.po has been updated in
  repo2; pulling repo2 from repo1 seems to trigger a PO update, that
  changes bla.fr.po in repo1; then pushing repo1 to repo2 triggers
  a PO update, that changes bla.fr.po in repo2; etc.; fixed in
  `629968fc89bced6727981c0a1138072631751fee`?
- new translations created in the web interface must get proper
  charset/encoding gettext metadata, else the next automatic PO update
  removes any non-ascii chars; possible solution: put such metadata
  into the Pot file, and let it propagate; should be fixed in
  `773de05a7a1ee68d2bed173367cf5e716884945a`, time will tell.

Misc. improvements
------------------

### page titles

Use nice page titles from meta plugin in links, as inline already
does. This is actually a duplicate for
[[bugs/pagetitle_function_does_not_respect_meta_titles]], which might
be fixed by something like [[todo/using_meta_titles_for_parentlinks]].

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

Modifying a PO file via the CGI must be forbidden if the new version
is not 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.