Formulator DateTimeField: when timezone should be displayed,regenerate sub form

When want to display timezone in datetimefield, some time timezone
attribute is lost in sub form for the backward compatibility
reason. So to display timezone, a new sub form should be regenerated

product/Formulator/StandardFields.py

@@ -151,6 +151,11 @@ class DateTimeField(ZMIField):
       assert 0, "Unknown input_style."
     self.on_value_css_class_changed(self.values['css_class'])
 
+  def on_value_timezone_style_changed(self, value):
+    if value:
+      input_style = self.get_value('input_style')
+      self.on_value_input_style_changed(input_style)
+
   def on_value_css_class_changed(self, value):
     for field in self.sub_form.get_fields():
       field.values['css_class'] = value

product/Formulator/tests/testForm.py

@@ -118,6 +118,20 @@ class FormTestCase(unittest.TestCase):
         self.assertEqual({'int_field': 3}, result)
 
 
+    def test_datetime_timezone_rendering(self):
+        self.form.manage_addProduct['Formulator']\
+                 .manage_addField('date_time','Test Field','DateTimeField')
+        field = self.form.date_time
+        sub_form = field.sub_form
+        if sub_form.has_field('timezone'):
+          del sub_form.fields['timezone']
+        #now timezone is not presented
+        self.assertFalse(self.form.date_time.sub_form.has_field('timezone'))
+        field._edit({'timezone_style': 1})
+        #test if timezone's presented
+        self.assertTrue(self.form.date_time.sub_form.has_field('timezone'))
+
+
     def test_datetime_css_class_rendering(self):
         # test that a bug is fixed, which causing the css_class value
         # not to be rendered