im using C++ and SFML
I see the following options:
- use a gui library created specifically for the sfml such as sfgui
- use a standard and cross platform c++ gui library and create your specific widget which use SFML under the hood. (there are examples on how to make a sfml widget for Qt or wxWidgets)
- create your app with a high level language such as Python or C#. To make the glue between your app and your c++ library you can create custom bindings (look at swig or cython) or use a tcp/ip connection.