> FLTK widgets can appear *around* an opengl drawing area, but not inside it.

I make extensive use of the Fl_Gl_Window widget. In fact I actually do place widgets INSIDE the OpenGL window. They don't visually 'appear' because the OGL graphics is written on top of them. However they provide useful functionality. For example I often split the GL window into 3 or 4 viewports. To 'activate' a viewport the user left clicks anywhere inside it. This is implemented by putting a large FLTK button under the entire viewport with an appropriate callback.

> But perhaps elsewhere on that page, one of the mentions of openGL
> might seem to indicate FLTK was /implemented/ with openGL ...

I didn't get my misconception from the documentation. It just sunk in slowly over the years.