380 lines
13 KiB
Markdown
380 lines
13 KiB
Markdown
[[!template id=plugin name=po core=0 author="[[intrigeri]]"]]
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[[!tag type/format]]
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This plugin adds support for multi-lingual wikis, translated with
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gettext, using [po4a](http://po4a.alioth.debian.org/).
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It depends on the Perl `Locale::Po4a::Po` library (`apt-get install po4a`).
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As detailed bellow in the security section, `po4a` is subject to
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denial-of-service attacks before version 0.35.
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[[!toc levels=2]]
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Introduction
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============
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A language is chosen as the "master" one, and any other supported
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language is a "slave" one.
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A page written in the "master" language is a "master" page. It can be
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of any page type supported by ikiwiki, except `po`. It does not have to be
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named a special way: migration to this plugin does not imply any page
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renaming work.
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Example: `bla/page.mdwn` is a "master" Markdown page written in
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English; if `usedirs` is enabled, it is rendered as
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`bla/page/index.en.html`, else as `bla/page.en.html`.
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Any translation of a "master" page into a "slave" language is called
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a "slave" page; it is written in the gettext PO format. `po` is now
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a page type supported by ikiwiki.
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Example: `bla/page.fr.po` is the PO "message catalog" used to
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translate `bla/page.mdwn` into French; if `usedirs` is enabled, it is
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rendered as `bla/page/index.fr.html`, else as `bla/page.fr.html`
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(In)Compatibility
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=================
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This plugin does not support the `indexpages` mode. If you don't know
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what it is, you probably don't care.
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Configuration
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=============
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Supported languages
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-------------------
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`po_master_language` is used to set the "master" language in
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`ikiwiki.setup`, such as:
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po_master_language => { 'code' => 'en', 'name' => 'English' }
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`po_slave_languages` is used to set the list of supported "slave"
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languages, such as:
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po_slave_languages => { 'fr' => 'Français',
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'es' => 'Español',
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'de' => 'Deutsch',
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}
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Decide which pages are translatable
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-----------------------------------
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The `po_translatable_pages` setting configures what pages are
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translatable. It is a [[ikiwiki/PageSpec]], so you have lots of
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control over what kind of pages are translatable.
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The `.po` files are not considered as being translatable, so you don't need to
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worry about excluding them explicitly from this [[ikiwiki/PageSpec]].
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Internal links
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--------------
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### Links targets
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The `po_link_to` option in `ikiwiki.setup` is used to decide how
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internal links should be generated, depending on web server features
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and site-specific preferences.
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#### Default linking behavior
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If `po_link_to` is unset, or set to `default`, ikiwiki's default
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linking behavior is preserved: `\[[destpage]]` links to the master
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language's page.
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#### Link to current language
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If `po_link_to` is set to `current`, `\[[destpage]]` links to the
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`destpage`'s version written in the current page's language, if
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available, *i.e.*:
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* `foo/destpage/index.LL.html` if `usedirs` is enabled
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* `foo/destpage.LL.html` if `usedirs` is disabled
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#### Link to negotiated language
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If `po_link_to` is set to `negotiated`, `\[[page]]` links to the
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negotiated preferred language, *i.e.* `foo/page/`.
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(In)compatibility notes:
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* if `usedirs` is disabled, it does not make sense to set `po_link_to`
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to `negotiated`; this option combination is neither implemented
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nor allowed.
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* if the web server does not support Content Negotiation, setting
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`po_link_to` to `negotiated` will produce a unusable website.
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Server support
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==============
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Apache
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------
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Using Apache `mod_negotiation` makes it really easy to have Apache
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serve any page in the client's preferred language, if available.
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Add 'Options MultiViews' to the wiki directory's configuration in Apache.
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When `usedirs` is enabled, one has to set `DirectoryIndex index` for
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the wiki context.
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Setting `DefaultLanguage LL` (replace `LL` with your default MIME
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language code) for the wiki context can help to ensure
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`bla/page/index.en.html` is served as `Content-Language: LL`.
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For details, see [Apache's documentation](http://httpd.apache.org/docs/2.2/content-negotiation.html).
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lighttpd
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--------
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Recent versions of lighttpd should be able to use
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`$HTTP["language"]` to configure the translated pages to be served.
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See [Lighttpd Issue](http://redmine.lighttpd.net/issues/show/1119)
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TODO: Example
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Usage
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=====
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Templates
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---------
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When `po_link_to` is not set to `negotiated`, one should replace some
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occurrences of `BASEURL` with `HOMEPAGEURL` to get correct links to
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the wiki homepage.
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The `ISTRANSLATION` and `ISTRANSLATABLE` variables can be used to
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display things only on translatable or translation pages.
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### Display page's versions in other languages
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The `OTHERLANGUAGES` loop provides ways to display other languages'
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versions of the same page, and the translations' status.
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An example of its use can be found in the default
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`templates/page.tmpl`. In case you want to customize it, the following
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variables are available inside the loop (for every page in):
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* `URL` - url to the page
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* `CODE` - two-letters language code
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* `LANGUAGE` - language name (as defined in `po_slave_languages`)
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* `MASTER` - is true (1) if, and only if the page is a "master" page
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* `PERCENT` - for "slave" pages, is set to the translation completeness, in percents
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### Display the current translation status
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The `PERCENTTRANSLATED` variable is set to the translation
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completeness, expressed in percent, on "slave" pages. It is used by
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the default `templates/page.tmpl`.
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Additional PageSpec tests
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-------------------------
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This plugin enhances the regular [[ikiwiki/PageSpec]] syntax with some
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additional tests that are documented [[here|ikiwiki/pagespec/po]].
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Automatic PO file update
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------------------------
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Committing changes to a "master" page:
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1. updates the POT file and the PO files for the "slave" languages;
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the updated PO files are then put under version control;
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2. triggers a refresh of the corresponding HTML slave pages.
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Also, when the plugin has just been enabled, or when a page has just
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been declared as being translatable, the needed POT and PO files are
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created, and the PO files are checked into version control.
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Discussion pages and other sub-pages
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------------------------------------
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Discussion should happen in the language in which the pages are
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written for real, *i.e.* the "master" one. If discussion pages are
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enabled, "slave" pages therefore link to the "master" page's
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discussion page.
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Likewise, "slave" pages are not supposed to have sub-pages;
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[[WikiLinks|wikilink]] that appear on a "slave" page therefore link to
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the master page's sub-pages.
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Translating
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-----------
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One can edit the PO files using ikiwiki's CGI (a message-by-message
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interface could also be implemented at some point).
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If [[tips/untrusted_git_push]] is setup, one can edit the PO files in one's
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preferred `$EDITOR`, without needing to be online.
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Markup languages support
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------------------------
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[[Markdown|mdwn]] and [[html]] are well supported. Some other markup
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languages supported by ikiwiki mostly work, but some pieces of syntax
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are not rendered correctly on the slave pages:
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* [[reStructuredText|rst]]: anonymous hyperlinks and internal
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cross-references
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* [[wikitext]]: conversion of newlines to paragraphs
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* [[creole]]: verbatim text is wrapped, tables are broken
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* LaTeX: not supported yet; the dedicated po4a module
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could be used to support it, but it would need a security audit
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* other markup languages have not been tested.
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Security
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========
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[[po/discussion]] contains a detailed security analysis of this plugin
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and its dependencies.
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When using po4a older than 0.35, it is recommended to uninstall
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`Text::WrapI18N` (Debian package `libtext-wrapi18n-perl`), in order to
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avoid a potential denial of service.
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TODO
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====
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Better links
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------------
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Once the fix to
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[[bugs/pagetitle_function_does_not_respect_meta_titles]] from
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[[intrigeri]]'s `meta` branch is merged into ikiwiki upstream, the
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generated links' text will be optionally based on the page titles set
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with the [[meta|plugins/meta]] plugin, and will thus be translatable.
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It will also allow displaying the translation status in links to slave
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pages. Both were implemented, and reverted in commit
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ea753782b222bf4ba2fb4683b6363afdd9055b64, which should be reverted
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once [[intrigeri]]'s `meta` branch is merged.
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An integration branch, called `meta-po`, merges [[intrigeri]]'s `po`
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and `meta` branches, and thus has this additional features.
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Language display order
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----------------------
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Jonas pointed out that one might want to control the order that links to
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other languages are listed, for various reasons. Currently, there is no
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order, as `po_slave_languages` is a hash. It would need to be converted
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to an array to support this. (If twere done, twere best done quickly.)
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--[[Joey]]
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> Done in my po branch, preserving backward compatibility. Please
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> review :) --[[intrigeri]]
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>> Right, well my immediate concern is that using an array to hold
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>> hash-like pairs is not very clear to the user. It will be displayed
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>> in a confusing way by websetup; dumping a setup file will probably
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>> also cause it to be formatted in a confusing way. And the code
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>> seems to assume that the array length is even, and probably blows
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>> up if it is not.. and the value is marked safe so websetup can be
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>> used to modify it and break that way too. --[[Joey]]
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>>> I have added a sanity check for the even array problem. This was
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>>> the easy part.
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>>>
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>>> About the hash-like vs. dump and websetup issue,
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>>> I can think of a few solutions:
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>>>
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>>> - keep the current hash-like pairs and unmark this setting as safe
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>>> for websetup: this does not solve the dump setup issue, though;
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>>> - replace the array of pairs with an array of
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>>> "LANGUAGECODE|LANGUAGENAME" elements, using a pipe or whatever
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>>> separator seems adequate;
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>>> - add support for ordered hashes to `$config`, websetup and
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>>> dumpsetup, using Tie-IxHash or any similar module;
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>>> - replace the array of hash-like pairs with an array of real
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>>> pairs, such as `[ ['de', 'Deutsch'], ['fr', 'Français'] ]`; this
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>>> brings once again the need for `$config` to support arrays of
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>>> arrays, which I have already implemented in my mirrorlist branch
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>>> (see [[todo/mirrorlist_with_per-mirror_usedirs_settings]] for
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>>> details).
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>>>
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>>> Joey, which of these solutions do you prefer? Or another one?
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>>> I tend to prefer the last one. --[[intrigeri]]
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Pagespecs
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---------
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I was suprised that, when using the map directive, a pagespec of "*"
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listed all the translated pages as well as regular pages. That can
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make a big difference to an existing wiki when po is turned on,
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and seems generally not wanted.
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(OTOH, you do want to match translated pages by
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default when locking pages.) --[[Joey]]
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Edit links on untranslated pages
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--------------------------------
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If a page is not translated yet, the "translated" version of it
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displays wikilinks to other, existing (but not yet translated?)
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pages as edit links, as if those pages do not exist.
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That's really confusing, especially as clicking such a link
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brings up an edit form to create a new, english page.
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This is with po_link_to=current or negotiated. With default, it doesn't
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happen..
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Also, this may only happen if the page being linked to is coming from an
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underlay, and the underlays lack translation to a given language.
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--[[Joey]]
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> Any simple testcase to reproduce it, please? I've never seen this
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> happen yet. --[[intrigeri]]
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>> Sure, go here <http://l10n.ikiwiki.info/smiley/smileys/index.sv.html>
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>> (Currently 0% translateed) and see the 'WikiLink' link at the bottom,
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>> which goes to <http://l10n.ikiwiki.info/ikiwiki.cgi?page=ikiwiki/wikilink&from=smiley/smileys&do=create>
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>> Compare with eg, the 100% translated Dansk version, where
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>> the WikiLink link links to the English WikiLink page. --[[Joey]]
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Double commits of po files
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--------------------------
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When adding a new english page, the po files are created, committed,
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and then committed again. The second commit makes this change:
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-"Content-Type: text/plain; charset=utf-8\n"
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-"Content-Transfer-Encoding: ENCODING"
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+"Content-Type: text/plain; charset=UTF-8\n"
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+"Content-Transfer-Encoding: ENCODING\n"
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Same thing happens when a change to an existing page triggers a po file
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update. --[[Joey]]
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> * The s/utf-8/UTF-8 part is fixed in my po branch.
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> * The ENCODING\n part is due to an inconsistency in po4a, which
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> I've just send a patch for. --[[intrigeri]]
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Ugly messages with empty files
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------------------------------
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If there are empty .mdwn files, the po plugin displays some ugly messages.
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> This is due to a bug in po4a (not checking definedness of a
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> variable). One-liner patch sent. --[[intrigeri]]
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Translation of directives
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-------------------------
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If a translated page contains a directive, it may expand to some english
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text, or text in whatever single language ikiwiki is configured to "speak".
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Maybe there could be a way to switch ikiwiki to speaking another language
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when building a non-english page? Then the directives would get translated.
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(We also will need this in order to use translated templates, when they are
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available.)
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Documentation
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-------------
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Maybe write separate documentation depending on the people it targets:
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translators, wiki administrators, hackers. This plugin may be complex
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enough to deserve this.
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