Custom widget based on PtComboBox

I want to build my custom widget based on PtComboBox. But I’ve got some
With other widget like PtText, PtList or PtCompound, my widget works.

But with PtComboBox, I’ve got problems withs focus and the button for
extended list.
I’ve got CoreDump with this widget on PhAb and on my application.

I try some parameter on widget class’s flags, and on inherited resources but
without result…

Does anyone build a widget based on PtComboBox ???