The handler executes the following snippets in a restricted environment: _onattributechanged (self, name, value) : The snippet is executed when the an attribute changes value; unless its name begins with an underscore. self : Secure frame handle to the frame. name : String - attribute name. value : Mixed - new attribute value. Note that if the value is not a string, boolean or a number, it'll be replaced with nil -- this a limitation enforced by the restricted environment.