
It's my understanding that the next release of UIM/X, due out
last February :-) has full support for C++.

I use XDesigner which does not have the interpreter or UI meta languages
of these other tools but does fully support C++ code generation,
reusable templates via C++ classes which are generated, a variety of
other handy features for using C++ and layout functions in different
ways, and generates Motif 1.2 code (including drag 'n drop, 
internationalization, etc.).  Fits in quite nicely with Doug Young's
paradigm for C++/Motif.

Available in the US from VI Corp, in Europe from Imperial Software,
London (see FAQ for details).