I used the Spine-C runtime and then the actual rendering of the Skeletons is done with OpenGL. My windowing library is SDL2 but the code shouldn't need to change much if you use a different windowing library as long as you are using OpenGL. A great place to start would be looking at the Spine-SFML implementation that is already provided in the Github Repo, and writing your own code in the place of the SFML code that is being called.
I am working on writing up a blog post that walks you through the process of writing an implementation to help those who may not be using SDL2. In the mean time, feel free to ask any questions you have and I'll gladly help out.
