Starts up the Tcl/Tk GUI
Starts a GUI console implemented via a Tk text widget. This should
probably be called at most once per session. Also redefines the file
pager (as used by
help()) to be the Tk pager.
tkStartGUI() saves its evaluation environment as
.GUIenv. This means that the user interface elements can be
accessed in order to extend the interface. The three main objects are
Toolbar, and the various
submenus and callback functions can be seen with
ls(envir = .GUIenv).