Add basic support for themes. Theme can be configured in config file …

app/__init__.py

@@ -1,8 +1,9 @@
-from flask import Flask
+from flask import Flask, url_for
 from flask_login import LoginManager
 from flask_sqlalchemy import SQLAlchemy
 from importlib import import_module
 from logging import basicConfig, DEBUG, getLogger, StreamHandler
+from os import path
 
 db = SQLAlchemy()
 login_manager = LoginManager()
@@ -36,6 +37,36 @@ def configure_logs(app):
     logger.addHandler(StreamHandler())
 
 
+def apply_themes(app):
+    """
+    Add support for themes.
+
+    If DEFAULT_THEME is set then all calls to
+      url_for('static', filename='')
+      will modfify the url to include the theme name
+
+    The theme parameter can be set directly in url_for as well:
+      ex. url_for('static', filename='', theme='')
+
+    If the file cannot be found in the /static/<theme>/ lcation then
+      the url will not be modified and the file is expected to be
+      in the default /static/ location
+    """
+    @app.context_processor
+    def override_url_for():
+        return dict(url_for=_generate_url_for_theme)
+
+    def _generate_url_for_theme(endpoint, **values):
+        if endpoint.endswith('static'):
+            themename = values.get('theme', None) or \
+                app.config.get('DEFAULT_THEME', None)
+            if themename:
+                theme_file = "{}/{}".format(themename, values.get('filename', ''))
+                if path.isfile(path.join(app.static_folder, theme_file)):
+                    values['filename'] = theme_file
+        return url_for(endpoint, **values)
+
+
 def create_app(config, selenium=False):
     app = Flask(__name__, static_folder='base/static')
     app.config.from_object(config)
@@ -45,4 +76,5 @@ def create_app(config, selenium=False):
     register_blueprints(app)
     configure_database(app)
     configure_logs(app)
+    apply_themes(app)
     return app