At this point, it has only been tested with versions 7.0-7.3. It was designed to support more structured programming in Tcl. Scripts that grow beyond a few thousand lines become extremely difficult to maintain. These widgets are defined as object classes, and pack primitive widgets together to provide higher-level functionality. Allows colors to be changed in another Tk application.
Widgets provide a natural domain for object-oriented programming techniques.
They are not, however, the only domain.