I\'m developing a graphical application to present data (not a game but a real workhorse app). It needs to be cross platform, so I have chosen:
In the latest releases of QT you can draw widgets into your OpenGL context, if you really would like to do something like that. Otherwise there is CEGui that is used in some game engines.
Implementing GUI Widgets yourself unless you want to edify yourself is a waste of your time, unless you would be satisfied with the most rudimentary of looks and functionality.