As can be seen in my presentation APWTCL at the 10th European Tcl/Tk Users Meeting 2012 this year and on the wiki page there has been a reimplementation of incr tcl in javascript based on Jim Tcl. This version was the first version wtk from Mark Roseman as an interface for handling basic widget support. Following that APWTCL (Javascript) version there was another implementation of APWTCL (Java) for supporting Android smartphones and an implementation in Objective-C for support of iPhone s.
When arriving at the point for building support for wtk widgets the first approach was to use the administrative part of wtk mostly as it was and to replace sending of javascript code to the displaying part by a generic message (string based) interface.
On the client side there should be a small interpreter for decoding the messages and for switching and dispatching to the appropriate functions for doing the displaying and event handling work.
This was first implemented for the iOS version, later on there was a port of that code to Java to support Android.