XForms is a handy and relatively simple user interface toolkit for X11. Many Geomview external modules, including the examples in this manual, use XForms to create and manage control panels. XForms is available from http://www.nongnu.org/xforms/. XForms is free-ware. If you wish you may use any other interface toolkit instead of XForms in an external module. We chose FORMS because it is free and relatively simple.
There is a complete autoconf'ed package `gvemod-xforms-example' available from Geomview's Sourceforge.NET page.