Define a subclass of the selected implementation object class.

Define a subclass of the selected public class. It is not necessary to subclass both the public and the implementation object class, but this is the typical use case.

Use the factory's get_container_impl() method. This returns an x::w::container_impl that refers the parent container widget's implementation object. The custom implementation object class's parent class is x::w::child_elementObj whose constructor takes the parent container widget's implementation object as a parameter. The custom subclass's constructor typically takes the parent container widget reference as the first parameter to its constructor, and the subclass's constructor typically passes it to its parent class together with any other parameters.

The custom public object class gets constructed with the custom implementation object class as its parameter. This typically gets forwarded to the public class's parent class. The implementation subclass is typically a subclass of the public object's implementation class. The public parent class's constructor's first parameter is usually its implementation object. Because of this, the custom public object subclass's constructor simply forwards its implementation class to the public object's parent class's constructor.

The constructed public object gets passed to the factory's created_internally() method. This method places the new widget into its container. Just creating the implementation object and the public object is not the entire story. The story doesn't end until the factory's created_internally() gets called.