Otk is a portable widget library for making graphical user interfaces for
application programs. It emphasizes simplicity without eliminating capability.
It is based on OpenGL, and C. Otk provides the following basic widgets:

 * Panel -		The "container" widget,
 * Text Label -		Text labels,
 * Button -		Buttons with labels and call-backs
		  	  to user functions,
 * Text Form Box -	Accept text with function call-back,
			  also scrollable editor window,
 * Pull-down Menu -	Display hierarchical menu-lists with user
			  function call-backs on mouse release,
 * Slider Control -	Slider control with call-back,
 * Sub-windows -	Detachable self-managed windows,
 * Gadgets -		High level widgets

and many others.

WWW:	http://otk.sourceforge.net/