SilverStripe Translatable defaults snippets

_config.php

<?php
// file: mysite/_config.php
...

// limit the CMS user to the following locales
Translatable::set_allowed_locales(array(
	'de_DE',
	'en_US',
	'es_ES',
	'it_IT',
));

// set default locale
i18n::set_locale('de_DE');
Translatable::set_default_locale('de_DE');

config.yml

# file: mysite/_config/config.yml

...

Controller:
  extensions:
    - 'TranslatableControllerExtension'

TranslatableControllerExtension.php

<?php
// file: mysite/code/TranslatableControllerExtension.php

class TranslatableControllerExtension extends Extension {
	/**
	 * save the current controller to ensure we have access to it,
	 * this is necessary because Security crates a fake Page_Controller to render templates
	 * @var Controller
	 */
	protected static $actual_current_controller;

	/**
	 * hook into Controller->init() to set current locale
	 */
	public function onBeforeInit() {
		static::$actual_current_controller = $this->owner;
		$locale = Session::get('current_locale');
		if ($locale && !static::$actual_current_controller->is_a('ContentController')) {
			// current controller is a static controller, such as Security
			// lets set the default locale to what we have stored in session
			// the reason we set default locale rather than current local is, that default
			// locale will only be used if there is no ?locale=xx_XX
			// so we keep locale switching in tact
			try {
				Translatable::set_default_locale($locale);
			} catch (InvalidArgumentException $e) {
			}
		}
		$locale = Translatable::get_current_locale();
		i18n::set_locale($locale);
		Session::set('current_locale', $locale);
	}

	/**
	 * Returns a list of all locales that have at least 1 Page, with a Link to the current Page in all languages if available, or the home page otherwise.
	 * Example usage in template: <% loop getAvailableLocales %><a href="$Link" title="$NativeTitle">$ShortCode</a><% end_loop %>
	 * Eg: The Page has German and English and you are on /about-us-de it will give you: "DE EN" with the links to /about-us-de and /about-us-en
	 */
	public function getAvailableLocales() {
		$return = ArrayList::create();
		$isStaticRoute = !static::$actual_current_controller->is_a('ContentController');
		$request = static::$actual_current_controller->getRequest();
		$page = $isStaticRoute ? null : static::$actual_current_controller->data();
		foreach (Translatable::get_existing_content_languages('SiteTree') as $code => $val) {
			$short = i18n::get_lang_from_locale($code);
			$link = false;
			if ($isStaticRoute) {
				// static controller, just preserve the URL and append ?locale=xx_XX
				$getVars = $request->getVars();
				unset($getVars['locale'], $getVars['url']);
				$getVars['locale'] = $code;
				$link = array($request->getURL());
				foreach ($getVars as $k => $v) {
					$link[] = "?$k=$v";
				}
				$link = call_user_func_array('Controller::join_links', $link);
			} elseif ($page && $page->hasMethod('hasTranslation') && $page->hasTranslation($code) && $translation = $page->getTranslation($code)) {
				$link = $translation->Link();
			}
			if (!$link) {
				// no link, simply create one to the homepage of the locale
				$homeLink = Translatable::get_homepage_link_by_locale($code);
				$link = $homeLink ? $homeLink : "/home?locale=$code";
			}
			$return->push(ArrayData::create(array(
				'Code' => $code,
				'ShortCode' => $short,
				'Title' => i18n::get_language_name($short, false),
				'NativeTitle' => i18n::get_language_name($short, true),
				'Link' => $link,
				'Current' => $code == Translatable::get_current_locale(),
			)));
		}
		return $return;
	}
}

TranslatableLanguageNavigation.ss

<%-- file: mysite/templates/Includes/LanguageNavigation.ss or themes/yourtheme/Includes/LanguageNavigation.ss --%>
<% loop getAvailableLocales %>
	<%-- $Title: full name of the local in english. eg: German --%>
	<%-- $NativeTitle: full name of the local in nativ language. eg: Deutsch --%>
	<%-- $Code: locale code. eg: de_DE --%>
	<%-- $ShortCode: language code. eg: de (will also be de for de_AT) --%>
	<a href="$Link" class="<% if $Current %>current<% end_if %>" title="$NativeTitle">$ShortCode</a>
<% end_loop %>