I think SDL also mostly started like that (just a window where you fill pixels, and very basic kb/mouse events). You can also very easily use it just like that

I think SDL also mostly started like that (just a window where you fill pixels, and very basic kb/mouse events). You can also very easily use it just like that (which is why this looked so similar to me like MiniFB). Then over time, more and more people used it, and had special request. E.g. to be able to setup an OpenGL context. Use gamepad input (as this was used mostly for games). Multiple windows. Etc.