wxWindows gives you a single, easy-to-use API for writing
GUI applications on multiple platforms. Link with the appropriate library
for your platform (Windows/Unix/Mac, others coming shortly) and compiler
(almost any popular C++ compiler), and your application will adopt the look
and feel appropriate to that platform. On top of great GUI functionality,
wxWindows gives you: online help, network programming, streams, clipboard
and drag and drop, multithreading, image loading and saving in a variety
of popular formats, database support, HTML viewing and printing, and much
much more.