Derive a widget from a custom widget??

I derived a custom widget class from another custom widget class.
When calling PtCreateWidget(), the Defaults class methods of its superclasses are not ivoked.
I encounter this problem whenever deriving a custom widget class from another non built-in class.

For example:
I derived a custom class from PtContainer. It’s working fine.
I derived a class from this custom class. The Defaults method of PtContainer -and above- is not inovked!

Perhaps I forget to register it with the Photon widget hierarchy?