slackbuilds_ponce/libraries/fltk13

The Fast Light Tool Kit ("FLTK", pronounced "fulltick") is a a cross-platform 
C++ GUI toolkit for UNIX(r)/Linux(r) (X11), Microsoft(r) Windows(r), and 
MacOS(r) X.  FLTK provides modern GUI functionality without the bloat and 
supports 3D graphics via OpenGL(r) and its built-in GLUT emulation.  It was 
originally developed by Mr. Bill Spitzak and is currently maintained by a 
small group of developers across the world with a central repository in the US.

CAVEATS:
1) fltk13 can be installed alongside fltk (1.1.x), but in order to build it,
you may need to remove fltk first (with removepkg); you can then reinstall it
afterwards. YMMV.

If you want cairo support, you need to pass CAIRO=1 to the build script.