wxWidgets

Tk (ツールキット)

FLTK – a light, cross platform, non-native widget toolkit

FOX toolkit – a fast, open source, cross-platform widget toolkit

GTK – the GIMP toolkit, a widget toolkit used by GNOME applications

gtkmm – C++ version of GTK

Juce – an extensive cross-platform widget toolkit

IUP – a multi-platform toolkit for building native graphical user interfaces

Qt (toolkit) – an application framework used by KDE applications

U++ – a C++ cross-platform development framework

List of widget toolkits