8 files changed, 198 insertions, 2 deletions

diff --git a/doc/md/Download-and-Installation.md b/doc/md/Download-and-Installation.md
index e5e929ef..59a1b7da 100644
--- a/doc/md/Download-and-Installation.md
+++ b/doc/md/Download-and-Installation.md
@@ -36,6 +36,7 @@ In most cases, download Shaarli from the [releases](https://github.com/shaarli/S
 $ mkdir -p /path/to/shaarli && cd /path/to/shaarli/
 $ git clone -b v0.9 https://github.com/shaarli/Shaarli.git .
 $ composer install --no-dev --prefer-dist
+$ make translate
 ```
 
 ## Stable version
@@ -83,13 +84,14 @@ $ git clone https://github.com/shaarli/Shaarli.git -b master /path/to/shaarli/
 # install/update third-party dependencies
 $ cd /path/to/shaarli
 $ composer install --no-dev --prefer-dist
+$ make translate
 ```
 
 ## Finish Installation
 
 Once Shaarli is downloaded and files have been placed at the correct location, open it this location your favorite browser.
 
-![install screenshot](http://i.imgur.com/wuMpDSN.png)
+![install screenshot](images/install-shaarli.png)
 
 Setup your Shaarli installation, and it's ready to use!
 
diff --git a/doc/md/Server-requirements.md b/doc/md/Server-requirements.md
index 707af762..400b85a9 100644
--- a/doc/md/Server-requirements.md
+++ b/doc/md/Server-requirements.md
@@ -39,3 +39,4 @@ Extension | Required? | Usage
 [`php-gd`](http://php.net/manual/en/book.image.php) | optional | thumbnail resizing
 [`php-intl`](http://php.net/manual/en/book.intl.php) | optional | localized text sorting (e.g. `e->è->f`)
 [`php-curl`](http://php.net/manual/en/book.curl.php) | optional | using cURL for fetching webpages and thumbnails in a more robust way
+[`php-gettext`](http://php.net/manual/en/book.gettext.php) | optional | Use the translation system in gettext mode (faster)
diff --git a/doc/md/Shaarli-configuration.md b/doc/md/Shaarli-configuration.md
index 99b25ba7..920c7e27 100644
--- a/doc/md/Shaarli-configuration.md
+++ b/doc/md/Shaarli-configuration.md
@@ -81,6 +81,20 @@ _These settings should not be edited_
 - **page_cache**: Shaarli's internal cache directory.  
 - **ban_file**: Banned IP file path.
 
+### Translation
+
+- **language**: translation language (also see [Translations](Translations))
+    - **auto** (default): The translation language is chosen from the browser locale. 
+    It means that the language can be different for 2 different visitors depending on their locale.  
+    - **en**: Use the English translation.
+    - **fr**: Use the French translation.
+- **mode**: 
+    - **auto** or **php** (default): Use the PHP implementation of gettext (slower)
+    - **gettext**: Use PHP builtin gettext extension 
+    (faster, but requires `php-gettext` to be installed and to reload the web server on update)
+- **extension**: Translation extensions for custom themes or plugins. 
+Must be an associative array: `translation domain => translation path`.
+
 ### Updates
 
 - **check_updates**: Enable or disable update check to the git repository.  
@@ -211,6 +225,13 @@ _These settings should not be edited_
     "plugins": {
         "WALLABAG_URL": "http://demo.wallabag.org",
         "WALLABAG_VERSION": "1"
+    },
+    "translation": {
+        "language": "fr",
+        "mode": "php",
+        "extensions": {
+            "demo": "plugins/demo_plugin/languages/"
+        }
     }
 } ?>
 ```
diff --git a/doc/md/Translations.md b/doc/md/Translations.md
new file mode 100644
index 00000000..54a36655
--- /dev/null
+++ b/doc/md/Translations.md
@@ -0,0 +1,152 @@
+## Translations
+
+Shaarli supports [gettext](https://www.gnu.org/software/gettext/manual/gettext.html) translations
+since `>= v0.9.2`.
+
+Note that only the `default` theme supports translations.
+
+### Contributing
+
+We encourage the community to contribute to Shaarli's translation either by improving existing 
+translations or submitting a new language. 
+
+Contributing to the translation does not require development skill.
+
+Please submit a pull request with the `.po` file updated/created. Note that the compiled file (`.mo`)
+is not stored on the repository, and is generated during the release process.
+
+### How to
+
+First, install [Poedit](https://poedit.net/) tool.
+
+Poedit will extract strings to translate from the PHP source code.
+
+**Important**: due to the usage of a template engine, it's important to generate PHP cache files to extract 
+every translatable string. 
+
+You can either use [this script](https://gist.github.com/ArthurHoaro/5d0323f758ab2401ef444a53f54e9a07)  (recommended)
+or visit every template page in your browser to generate cache files, while logged in.
+
+Here is a list :
+
+```
+http://<replace_domain>/
+http://<replace_domain>/?nonope
+http://<replace_domain>/?do=addlink
+http://<replace_domain>/?do=changepasswd
+http://<replace_domain>/?do=changetag
+http://<replace_domain>/?do=configure
+http://<replace_domain>/?do=tools
+http://<replace_domain>/?do=daily
+http://<replace_domain>/?post
+http://<replace_domain>/?do=export
+http://<replace_domain>/?do=import
+http://<replace_domain>/?do=login
+http://<replace_domain>/?do=picwall
+http://<replace_domain>/?do=pluginadmin
+http://<replace_domain>/?do=tagcloud
+http://<replace_domain>/?do=taglist
+```
+
+#### Improve existing translation
+
+In Poedit, click on "Edit a Translation", and from Shaarli's directory open 
+`inc/languages/<lang>/LC_MESSAGES/shaarli.po`. 
+
+The existing list of translatable strings should have been loaded, then click on the "Update" button.
+
+You can start editing the translation.
+
+![poedit-screenshot](images/poedit-1.jpg)
+
+Save when you're done, then you can submit a pull request containing the updated `shaarli.po`.
+
+#### Add a new language
+
+Open Poedit and select "Create New Translation", then from Shaarli's directory open 
+`inc/languages/<lang>/LC_MESSAGES/shaarli.po`.
+
+Then select the language you want to create. 
+
+Click on `File > Save as...`, and save your file in `<shaarli directory>/inc/language/<new language>/LC_MESSAGES/shaarli.po`.  
+`<new language>` here should be the language code respecting the [ISO 3166-1 alpha-2](https://en.wikipedia.org/wiki/ISO_3166-2) 
+format in lowercase (e.g. `de` for German).
+
+Then click on the "Update" button, and you can start to translate every available string.
+
+Save when you're done, then you can submit a pull request containing the new `shaarli.po`.
+
+### Extend Shaarli's translation
+
+If you're writing a custom theme, or a non official plugin, you might want to use the translation system,
+but you won't be able to able to override Shaarli's translation.
+
+However, you can add your own translation domain which extends the main translation list.
+
+> Note that you can find a live example of translation extension in the `demo_plugin`.
+
+First, create your translation files tree directory:
+
+```
+<your_module>/languages/<ISO 3166-1 alpha-2 language code>/LC_MESSAGES/
+```
+
+Your `.po` files must be named like your domain. E.g. if your translation domain is `my_theme`, then your file will be
+`my_theme.po`.
+
+Users have to register your extension in their configuration with the parameter 
+`translation.extensions.<domain>: <translation files path>`.
+
+Example:
+
+```php
+if (! $conf->exists('translation.extensions.my_theme')) {
+    $conf->set('translation.extensions.my_theme', '<your_module>/languages/');
+    $conf->write(true);
+}
+```
+
+> Note that the page needs to be reloaded after the registration.
+
+It is then recommended to create a custom translation function which will call the `t()` function with your domain.
+For example :
+
+```php
+function my_theme_t($text, $nText = '', $nb = 1)
+{
+    return t($text, $nText, $nb, 'my_theme'); // the last parameter is your translation domain.
+}
+```
+
+All strings which can be translated should be processed through your function:
+
+```php
+my_theme_t('Comment');
+my_theme_t('Comment', 'Comments', 2);
+```
+
+Or in templates:
+
+```php
+{'Comment'|my_theme_t}
+{function="my_theme_t('Comment', 'Comments', 2)"}
+```
+
+> Note than in template, you need to visit your page at least once to generate a cache file.
+
+When you're done, open Poedit and load translation strings from sources:
+
+  1. `File > New`
+  2. Choose your language
+  3. Save your `PO` file in `<your_module>/languages/<language code>/LC_MESSAGES/my_theme.po`.
+  4. Go to `Catalog > Properties...` 
+  5. Fill the `Translation Properties` tab
+  6. Add your source path in the `Sources Paths` tab
+  7. In the `Sources Keywords` tab uncheck "Also use default keywords" and add the following lines:
+  
+```
+my_theme_t
+my_theme_t:1,2
+```
+
+Click on the "Update" button and you're free to start your translations!
diff --git a/doc/md/Upgrade-and-migration.md b/doc/md/Upgrade-and-migration.md
index 7033cd41..1dc07339 100644
--- a/doc/md/Upgrade-and-migration.md
+++ b/doc/md/Upgrade-and-migration.md
@@ -39,7 +39,10 @@ We recommend that you use the latest release tarball with the `-full` suffix. It
 
 Once downloaded, extract the archive locally and update your remote installation (e.g. via FTP) -be sure you keep the content of the `data` directory!
 
-After upgrading, access your fresh Shaarli installation from a web browser; the configuration and data store will then be automatically updated, and new settings added to `data/config.json.php` (see [Shaarli configuration](Shaarli-configuration) for more details).
+If you use translations in gettext mode - meaning you manually changed the default mode -, 
+reload your web server.
+
+After upgrading, access your fresh Shaarli installation from a web browser; the configuration and data store will then be automatically updated, and new settings added to `data/config.json.php` (see [Shaarli configuration](Shaarli configuration) for more details).
 
 ## Upgrading with Git
 
@@ -72,6 +75,14 @@ Updating dependencies
     Downloading: 100%
 ```
 
+Shaarli >= `v0.9.2` supports translations:
+
+```bash
+$ make translate
+```
+
+If you use translations in gettext mode, reload your web server.
+
 ### Migrating and upgrading from Sebsauvage's repository
 
 If you have installed Shaarli from [Sebsauvage's original Git repository](https://github.com/sebsauvage/Shaarli), you can use [Git remotes](https://git-scm.com/book/en/v2/Git-Basics-Working-with-Remotes) to update your working copy.
@@ -151,6 +162,14 @@ Updating dependencies
     Downloading: 100%
 ```
 
+Shaarli >= `v0.9.2` supports translations:
+
+```bash
+$ make translate
+```
+
+If you use translations in gettext mode, reload your web server.
+
 Optionally, you can delete information related to the legacy version:
 
 ```bash
diff --git a/doc/md/images/install-shaarli.png b/doc/md/images/install-shaarli.png
new file mode 100644
index 00000000..7ae33816
--- /dev/null
+++ b/doc/md/images/install-shaarli.png
diff --git a/doc/md/images/poedit-1.jpg b/doc/md/images/poedit-1.jpg
new file mode 100644
index 00000000..673ae6d6
--- /dev/null
+++ b/doc/md/images/poedit-1.jpg
diff --git a/mkdocs.yml b/mkdocs.yml
index 03a7a34e..8617ea45 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -43,6 +43,7 @@ pages:
     - Versioning and Branches: Versioning-and-Branches.md
     - Security: Security.md
     - Static analysis: Static-analysis.md
+    - Translations: Translations.md
     - Theming: Theming.md
     - Unit tests: Unit-tests.md
     - Unit tests inside Docker: Unit-tests-Docker.md