Scheme Widget Library
The Scheme Widget Library (SWL) is no longer being maintained, but the source code is still available.
The Scheme Widget Library (SWL) is a windowing and graphics package for Chez Scheme developed in the Indiana University Computer Science Department with support from the National Science Foundation and Cadence Research Systems. It includes an object system for Scheme, a threaded windowing and graphics library, and various tools, including a window-based REPL (read-eval-print loop) window, a simple editor, a source-file viewer, and a document viewer. See the reference manual for more information on the windowing and graphics library.
SWL runs on each of the platforms supported by Chez Scheme: Windows, Linux, MacOS, FreeBSD, OpenBSD, and SunOS, with either Chez Scheme or Petite Chez Scheme. It can be built from sources only by Chez Scheme, since building it requires the compiler. SWL is documented in the SWL Reference Manual.
SWL is based on Tcl/Tk.