Which framework/toolkit for modern unity applications?

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http://askubuntu.com – I want to code some applications for ubuntu (no other platforms), but which gui-toolkit would be the "official" one... in the past (gnome) gtk+ was my choice, but afaik unity uses Nux. I don't want to use these standard buttons and "old style ui". Qt would be great for KDE but what's the latest "unity" toolkit suggestion? ps: programming language would be C/C++ or python. (HowTos)