ikiwiki/ plugins/ po

Plugin: po
Author: intrigeri
Included in ikiwiki: yes
Enabled by default: no
Included in goodstuff: no
Currently enabled: yes

This plugin adds support for multi-lingual wikis, translated with gettext, using po4a.

It depends on the Perl `Locale::Po4a::Po` library (`apt-get install po4a`). As detailed bellow in the security section, `po4a` is subject to denial-of-service attacks before version 0.35.

# 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`

# (In)Compatibility

This plugin does not support the `indexpages` mode (a.k.a. "use page/index.mdwn source files"). If you don't know what it is, you probably don't care.

# Configuration

## Supported languages

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

        po_master_language: en|English

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

        po_slave_languages:
      - fr|Français
      - es|Español
      - de|Deutsch

## Decide which pages are translatable

The `po_translatable_pages` setting configures what pages are translatable. It is a 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 PageSpec.

## Internal links

### Links targets

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.

Add 'Options MultiViews' to the wiki directory's configuration in Apache.

When `usedirs` is enabled, you should also set `DirectoryIndex index`.

These settings are also recommended, in order to avoid serving up rss files as index pages:

    AddType application/rss+xml;qs=0.8 .rss
    AddType application/atom+xml;qs=0.8 .atom

For details, see Apache's documentation.

## lighttpd

Recent versions of lighttpd should be able to use `$HTTP["language"]` to configure the translated pages to be served.

See Lighttpd Issue

TODO: Example

# Usage

## Templates

When `po_link_to` is not set to `negotiated`, one should replace some occurrences of `BASEURL` with `HOMEPAGEURL` to get correct links to the wiki homepage.

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

The `LANG_CODE` and `LANG_NAME` variables can respectively be used to display the current page's language code and pretty name.

### 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.

An example of its use can be found in the default `templates/page.tmpl`. In case you want to customize it, 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. It is used by the default `templates/page.tmpl`.

## Additional PageSpec tests

This plugin enhances the regular PageSpec syntax with some additional tests that are documented here.

## 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 and other sub-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.

Likewise, "slave" pages are not supposed to have sub-pages; WikiLinks that appear on a "slave" page therefore link to the master page's sub-pages.

## Translating

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

If untrusted git push is setup, one can edit the PO files in one's preferred `$EDITOR`, without needing to be online.

## Markup languages support

Markdown and html are well supported. Some other markup languages supported by ikiwiki mostly work, but some pieces of syntax are not rendered correctly on the slave pages:

- reStructuredText: anonymous hyperlinks and internal cross-references
- wikitext: conversion of newlines to paragraphs
- creole: verbatim text is wrapped, tables are broken
- LaTeX: not supported yet; the dedicated po4a module could be used to support it, but it would need a security audit
- other markup languages have not been tested.

## Renaming a page

A translatable page may be renamed using the web interface and the rename plugin, or using the VCS directly; in the latter case, both the "master" page and every corresponding `.po` file must be renamed in the same commit.

# Security

discussion contains a detailed security analysis of this plugin and its dependencies.

When using po4a older than 0.35, it is recommended to uninstall `Text::WrapI18N` (Debian package `libtext-wrapi18n-perl`), in order to avoid a potential denial of service.

# BUGS

# TODO