XGui is a multiplatform, multilanguage native widget set. Developed at OS3 and used for several commercial projects, the project has been released under LGPL license.
This means you can write your code once in your favorite language (C, C++ or Python) and then compile it to run on Linux or Windows with the native look of the OS.
XGui is developed keeping in mind the MVC pattern. Lists and Tress are just views of a Model. Even styles which define how to show the model in every different view are separated. Guis, Models and styles can be saved and loaded from XML files.
XGui also supports loading of widgets and subclasses of xgui::Object from shared objects.
XGui cames with its own gui-creation tool. Plan and its own inspection tool pexplorer. Both use the powerfull support for dynamic methods and introspection of xgui::Object to make possible to create on the fly guis and save them to xml files or to see which methods and properties a widget exports.