Algui is a project mainly written in C, it's free.
A C gui library for Allegro 5
C GUI library for Allegro 5.
Converted the skin and resource management APIs to use UTF-8 strings internally.
Added/changed several things:
-init and cleanup functions. -logging API. -resource manager. -bitmaps and fonts loaded via skins are managed via the resource manager. -a widget 'display', used as the toplevel widget. -a 'game' event loop in the example.
-added tab order and cursor/tab focus.
Added the following APIs:
-translation
Various small bug fixes.
Features implemented so far:
-widget management API -mouse and keyboard events API -drag and drop API -timer API -skinning API -layout management API