add doc for chill_print_or_message

source/development/user-interface/layout-template-usage.rst

@@ -14,6 +14,38 @@ We recommand the use of the existing layouts to ensure the consistency of the de
 
 The layouts are twig templates.
 
+Twig templating helper
+======================
+
+`chill_print_or_message`
+------------------------
+
+Print a value or use a default template if the value is empty.
+
+The template can be customized. 
+
+Two default templates are registered: 
+
+- :code:`default`, do not decorate the value ;
+- :code:`blockquote`: wrap the value into a blockquote if exists
+
+.. code-block:: html+twig
+
+  {{ "This is a message"|chill_print_or_message("No message") }} 
+  <!-- will print "This is a message" -->
+
+  {{ ""|chill_print_or_message("No message")}} 
+  <!-- will print <span class="chill-no-data-statement">No message</span> -->
+
+  {{ "This is a comment\n with multiples lines"|chill_print_or_message("No comment", 'blockquote') }} 
+  <!-- will print <blockquote class="chill-user-quote">This is a comment<br/>with multiples lines</blockquote> -->
+
+When customizing the template, two arguments are passed to the template: 
+
+- :code:`value`: the actual value ;
+- :code:`message`: the message, given as argument
+
+
 Organisation of the layouts
 ===========================
 
@@ -159,7 +191,7 @@ The accepted parameters are :
 Usage : 
 
 
-.. code-block:: html+jinja2
+.. code-block:: html+twig
 
        {{ include('ChillMainBundle:Util:confirmation_template.html.twig',
            {