Could Tk be D's ideal widget set?

[Mars]

I think this one is not a proof-of-concept implementation but the real deal.

"As its core, KWWidgets is an object-oriented C++ layer on top of the 
Tcl/Tk UI toolkit. It uses the same coding framework and guidelines as 
VTK. It can interact and co-exist with Tcl/Tk directly from C++, 
allowing you to load or execute Tcl modules directly from a C++ 
application."

http://www.kwwidgets.org/Wiki/KWWidgets