Add translations

changedetectionio/blueprint/ui/__init__.py

@@ -1,6 +1,6 @@
 import time
 import threading
-from flask import Blueprint, request, redirect, url_for, flash, render_template, session
+from flask import Blueprint, request, redirect, url_for, flash, render_template, session, current_app
 from flask_babel import gettext
 from loguru import logger
 
@@ -404,4 +404,25 @@ def construct_blueprint(datastore: ChangeDetectionStore, update_q, worker_handle
 
         return redirect(url_for('watchlist.index'))
 
+    @ui_blueprint.route("/language/auto-detect", methods=['GET'])
+    def delete_locale_language_session_var_if_it_exists():
+        """Clear the session locale preference to auto-detect from browser Accept-Language header"""
+        if 'locale' in session:
+            session.pop('locale', None)
+            # Refresh Flask-Babel to clear cached locale
+            from flask_babel import refresh
+            refresh()
+            flash(gettext("Language set to auto-detect from browser"))
+
+        # Check if there's a redirect parameter to return to the same page
+        redirect_url = request.args.get('redirect')
+
+        # If redirect is provided and safe, use it
+        from changedetectionio.is_safe_url import is_safe_url
+        if redirect_url and is_safe_url(redirect_url, current_app):
+            return redirect(redirect_url)
+
+        # Otherwise redirect to watchlist
+        return redirect(url_for('watchlist.index'))
+
     return ui_blueprint

changedetectionio/flask_app.py

@@ -94,6 +94,14 @@ if os.getenv('FLASK_SERVER_NAME'):
 app.config['BABEL_TRANSLATION_DIRECTORIES'] = str(Path(__file__).parent / 'translations')
 app.config['BABEL_DEFAULT_LOCALE'] = 'en_GB'
 
+# Session configuration
+# NOTE: Flask session (for locale, etc.) is separate from Flask-Login's remember-me cookie
+# - Flask session stores data like session['locale'] in a signed cookie
+# - Flask-Login's remember=True creates a separate authentication cookie
+# - Setting PERMANENT_SESSION_LIFETIME controls how long the Flask session cookie lasts
+from datetime import timedelta
+app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(days=3650)  # ~10 years (effectively unlimited)
+
 #app.config["EXPLAIN_TEMPLATE_LOADING"] = True
 
 
@@ -550,6 +558,9 @@ def changedetection_app(config=None, datastore_o=None):
 
         # Validate the locale against available languages
         if locale in language_codes:
+            # Make session permanent so language preference persists across browser sessions
+            # NOTE: This is the Flask session cookie (separate from Flask-Login's remember-me auth cookie)
+            session.permanent = True
             session['locale'] = locale
 
             # CRITICAL: Flask-Babel caches the locale in the request context (ctx.babel_locale)

changedetectionio/templates/base.html

@@ -265,6 +265,9 @@
           </a>
           {% endfor %}
         </div>
+        <div>
+            <a href="{{ url_for('ui.delete_locale_language_session_var_if_it_exists', redirect=request.path) }}" >{{ _('Auto-detect from browser') }}</a>
+        </div>
         <div>
             {{ _('Language support is in beta, please help us improve by opening a PR on GitHub with any updates.') }}
         </div>

changedetectionio/tests/test_i18n.py

@@ -160,7 +160,7 @@ def test_invalid_locale(client, live_server, measure_memory_usage, datastore_pat
 def test_language_persistence_in_session(client, live_server, measure_memory_usage, datastore_path):
     """
     Test that the language preference persists across multiple requests
-    within the same session.
+    within the same session, and that auto-detect properly clears the preference.
     """
 
     # Establish session cookie
@@ -184,6 +184,34 @@ def test_language_persistence_in_session(client, live_server, measure_memory_usa
         assert res.status_code == 200
         assert b"Annulla" in res.data, "Italian text should persist across requests"
 
+    # Verify locale is in session
+    with client.session_transaction() as sess:
+        assert sess.get('locale') == 'it', "Locale should be set in session"
+
+    # Call auto-detect to clear the locale
+    res = client.get(
+        url_for("ui.delete_locale_language_session_var_if_it_exists"),
+        follow_redirects=True
+    )
+
+    assert res.status_code == 200
+    # Verify the flash message appears (in English since we cleared the locale)
+    assert b"Language set to auto-detect from browser" in res.data, "Should show flash message"
+
+    # Verify locale was removed from session
+    with client.session_transaction() as sess:
+        assert 'locale' not in sess, "Locale should be removed from session after auto-detect"
+
+    # Now requests should use browser default (English in test environment)
+    res = client.get(
+        url_for("watchlist.index"),
+        follow_redirects=True
+    )
+
+    assert res.status_code == 200
+    assert b"Cancel" in res.data, "Should show English after auto-detect clears Italian"
+    assert b"Annulla" not in res.data, "Should not show Italian after auto-detect"
+
 
 def test_set_language_with_redirect(client, live_server, measure_memory_usage, datastore_path):
     """

changedetectionio/translations/README.md

@@ -0,0 +1,101 @@
+# Translation Guide
+
+## Updating Translations
+
+To maintain consistency and minimize unnecessary changes in translation files, run these commands:
+
+```bash
+python setup.py extract_messages   # Extract translatable strings
+python setup.py update_catalog     # Update all language files
+python setup.py compile_catalog    # Compile to binary .mo files
+```
+
+## Configuration
+
+All translation settings are configured in **`../../setup.cfg`** (single source of truth).
+
+The configuration below is shown for reference - **edit `setup.cfg` to change settings**:
+
+```ini
+[extract_messages]
+# Extract translatable strings from source code
+mapping_file = babel.cfg
+output_file = changedetectionio/translations/messages.pot
+input_paths = changedetectionio
+keywords = _ _l gettext
+# Options to reduce unnecessary changes in .pot files
+sort_by_file = true       # Keeps entries ordered by file path
+width = 120               # Consistent line width (prevents rewrapping)
+add_location = file       # Show file path only (not line numbers)
+
+[update_catalog]
+# Update existing .po files with new strings from .pot
+# Note: 'locale' is omitted - Babel auto-discovers all catalogs in output_dir
+input_file = changedetectionio/translations/messages.pot
+output_dir = changedetectionio/translations
+domain = messages
+# Options for consistent formatting
+width = 120               # Consistent line width
+no_fuzzy_matching = true  # Avoids incorrect automatic matches
+
+[compile_catalog]
+# Compile .po files to .mo binary format
+directory = changedetectionio/translations
+domain = messages
+```
+
+**Key formatting options:**
+- `sort_by_file = true` - Orders entries by file path (consistent ordering)
+- `width = 120` - Fixed line width prevents text rewrapping
+- `add_location = file` - Shows file path only, not line numbers (reduces git churn)
+- `no_fuzzy_matching = true` - Prevents incorrect automatic fuzzy matches
+
+## Why Use These Commands?
+
+Running pybabel commands directly without consistent options causes:
+- ❌ Entries get reordered differently each time
+- ❌ Text gets rewrapped at different widths
+- ❌ Line numbers change every edit (if not configured)
+- ❌ Large diffs that make code review difficult
+
+Using `python setup.py` commands ensures:
+- ✅ Consistent ordering (by file path, not alphabetically)
+- ✅ Consistent line width (120 characters, no rewrapping)
+- ✅ File-only locations (no line number churn)
+- ✅ No fuzzy matching (prevents incorrect auto-translations)
+- ✅ Minimal diffs (only actual changes show up)
+- ✅ Easier code review and git history
+
+These commands read settings from `../../setup.cfg` automatically.
+
+## Supported Languages
+
+- `cs` - Czech (Čeština)
+- `de` - German (Deutsch)
+- `en_GB` - English (UK)
+- `en_US` - English (US)
+- `fr` - French (Français)
+- `it` - Italian (Italiano)
+- `ko` - Korean (한국어)
+- `zh` - Chinese Simplified (中文简体)
+- `zh_Hant_TW` - Chinese Traditional (繁體中文)
+
+## Adding a New Language
+
+1. Initialize the new language catalog:
+   ```bash
+   pybabel init -i changedetectionio/translations/messages.pot -d changedetectionio/translations -l NEW_LANG_CODE
+   ```
+2. Compile it:
+   ```bash
+   python setup.py compile_catalog
+   ```
+
+Babel will auto-discover the new language on subsequent translation updates.
+
+## Translation Notes
+
+From CLAUDE.md:
+- Always use "monitor" or "watcher" terminology (not "clock")
+- Use the most brief wording suitable
+- When finding issues in one language, check ALL languages for the same issue

setup.cfg

@@ -0,0 +1,28 @@
+# Translation configuration for changedetection.io
+# See changedetectionio/translations/README.md for full documentation on updating translations
+
+[extract_messages]
+# Extract translatable strings from source code
+mapping_file = babel.cfg
+output_file = changedetectionio/translations/messages.pot
+input_paths = changedetectionio
+keywords = _ _l gettext
+# Options to reduce unnecessary changes in .pot files
+sort_by_file = true
+width = 120
+add_location = file
+
+[update_catalog]
+# Update existing .po files with new strings from .pot
+# Note: Omitting 'locale' makes Babel auto-discover all catalogs in output_dir
+input_file = changedetectionio/translations/messages.pot
+output_dir = changedetectionio/translations
+domain = messages
+# Options for consistent formatting
+width = 120
+no_fuzzy_matching = true
+
+[compile_catalog]
+# Compile .po files to .mo binary format
+directory = changedetectionio/translations
+domain = messages