FOX toolkit
http://fox-toolkit.org/
Dependencies
Open GL
OpenGL Utility Library
libjpeg
libpng
LibTIFF
zlib (lz)
bzip2 for file compression
FLTK – a light, cross-platform, non-native widget toolkit
fpGUI – a cross-platform GUI toolkit with a Visual Form Designer and a custom help document reader
GTK – a widget toolkit used by GNOME applications
gtkmm – the official C++ interface to GTK
IUP – a multi-platform toolkit for building native graphical user interfaces
Juce
Qt – a widget toolkit used by KDE
Ultimate++
Widget toolkit
wxWidgets – a cross-platform open-source C++ widget library, wrapping native widget toolkits
List of widget toolkits
https://en.wikipedia.org/wiki/Fox_toolkit