wxWidgets is a C++ library that lets developers create applications for Windows, Mac OS X, Linux and other platforms with a single code base. It has popular language bindings for Python, Perl, Ruby and many other languages, and unlike other cross-platform toolkits, wxWidgets gives applications a
... [More] truly native look and feel because it uses the platform's native API rather than emulating the GUI. It's also extensive, free, open-source and mature. [Less]
libNUI is a hardware accelerated GUI framework that makes it possible to build rich multi-platform applications based on 3D rendered dynamic layouts. Interfaces are built as a composition of widgets and behaviors, and the framework handles positioning, resizing, anchoring, and texture stretching.
... [More] Objects are connected with synchronous events and delegates for mono-threaded communication, or asynchronous notifications and message queues are used for multi-threaded applications. It also supports strings (including Unicode), paths, files, data streams, fonts, threads, critical sections, audio buffer rendering, and more. [Less]