Make the web app select the language based on browser values

Language also can be selected using the `?l=langcode` query string.

.gitignore

@@ -1,2 +1,4 @@
 __pycache__/
-app/local.db
+/app/local.db
+/messages.pot
+/app/translations/*/LC_MESSAGES/*.mo

app/__init__.py

@@ -17,10 +17,32 @@
 import os
 
 from flask import Flask, current_app, redirect, render_template, url_for
-from flask_babel import Babel
+from flask_babel import Babel, get_locale as babel_get_locale
 from flask_security import SQLAlchemyUserDatastore, current_user
 
 
+def get_locale():
+    """Locale selector
+
+    Selects the best locale based on values sent by the browser.
+    """
+
+    from flask import request
+
+    supported_languages = ['en', 'hu']
+
+    if 'l' in request.args and request.args['l'].lower() in supported_languages:
+        return request.args['l'].lower()
+
+    return request.accept_languages.best_match(supported_languages)
+
+
+def template_vars():
+    return {
+        'lang': babel_get_locale().language,
+    }
+
+
 class CalendarSocialApp(Flask):
     def __init__(self, name, config=None):
         from app.models import db, User, Role
@@ -34,10 +56,13 @@ class CalendarSocialApp(Flask):
         self.config['SECURITY_USER_IDENTITY_ATTRIBUTES'] = ('username', 'email')
         db.init_app(self)
         babel = Babel(app=self)
+        babel.localeselector(get_locale)
 
         user_store = SQLAlchemyUserDatastore(db, User, Role)
         security.init_app(self, datastore=user_store)
 
+        self.context_processor(template_vars)
+
 
 app = CalendarSocialApp(__name__)
 

app/translations/hu/LC_MESSAGES/messages.po

@@ -0,0 +1,61 @@
+# Hungarian translations for PROJECT.
+# Copyright (C) 2018 ORGANIZATION
+# This file is distributed under the same license as the PROJECT project.
+# FIRST AUTHOR <EMAIL@ADDRESS>, 2018.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: 0.1\n"
+"Report-Msgid-Bugs-To: gergely@polonkai.eu\n"
+"POT-Creation-Date: 2018-06-29 14:14+0200\n"
+"PO-Revision-Date: 2018-06-29 14:26+0200\n"
+"Last-Translator: Gergely Polonkai <gergely@polonkai.eu>\n"
+"Language: hu\n"
+"Language-Team: hu <gergely@polonkai.eu>\n"
+"Plural-Forms: nplurals=1; plural=0\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=utf-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Generated-By: Babel 2.6.0\n"
+
+#: app/forms.py:8
+msgid "Username"
+msgstr "Felhasználónév"
+
+#: app/forms.py:9
+msgid "Email address"
+msgstr "E-mail cím"
+
+#: app/forms.py:10
+msgid "Password"
+msgstr "Jelszó"
+
+#: app/forms.py:11
+msgid "Password, once more"
+msgstr "Jelszó még egszer"
+
+#: app/forms.py:15
+msgid "The two passwords must match!"
+msgstr "A két jelszónak egyeznie kell!"
+
+#: app/templates/base.html:21
+#, python-format
+msgid "Logged in as %(username)s"
+msgstr "Bejelentkezve %(username)s néven"
+
+#: app/templates/base.html:25
+msgid "Login"
+msgstr "Bejelentkezés"
+
+#: app/templates/base.html:27
+msgid "Logout"
+msgstr "Kijelentkezés"
+
+#: app/templates/index.html:4
+#, python-format
+msgid "Welcome to Calendar.social, %(username)s!"
+msgstr "Üdv a Calendar.social-ben, %(username)s!"
+
+#: app/templates/registration.html:27
+msgid "Register"
+msgstr "Regisztráció"

babel.cfg

@@ -0,0 +1,6 @@
+[python: **/*.py]
+encoding=utf-8
+[jinja2: **/templates/**.html]
+encoding=utf-8
+extensions=jinja2.ext.autoescape
+