incr widgets (aka iwidgets) consists of a series of Tk widgets, built out of other widgets using the incr Tk/incr Tcl foundation classes.
The source for iwidgets can be found at the http://sf.net/projects/incrtcl/ project CVS.
Also, see http://incrtcl.sourceforge.net/iwidgets http://incrtcl.sourceforge.net/iwidgets/index.html
They include: