Extensions
There are some megawidgets written in Tk and Itk whose handling is exact as the normal widgets.
You can always use these mega widgets. If there is a tcl file "megaspinbox.tcl" containing a widget megaspinbox, use this lines:
(start-tk)
(eval-wish "source {megaspinbox.tcl}")
(define mbox (tk 'create-widget 'megaspinbox))
Because it is frequently used, the megawidget scrolledtext is hard-wired in chicken/Tk so that you don't need to source it yourself.