All those naked 'new's in the example make me nervous. I see that the library uses exceptions, if one of the widget constructor throws while composing the overall widget hierarchy, it would leak memory.
You should be able to make it work with a value-based interface and allocating behind the scenes (this would also enable a few optimization opportunities).
You should be able to make it work with a value-based interface and allocating behind the scenes (this would also enable a few optimization opportunities).