Sdl/opengl window saving

I am new here.
I’d like to ask about the subject that a day ago emerged here.
It’s about screen shooting - saving the window view as a .bmp file.
I tried to use method presented by Ben Campbell, but it doesn’t work for me:
I’m getting pure black window only in my .bmp.

If you have a while to have a look on my code - it is here:

After pressing F2 key you should get “save.bmp”.

I have another problem also, but not related to the first one.
Which SDL or GL or GLU function allows me to check if a point marked e.g.
by the mouse either is or not on the cubic area.
And how can I read the 2D coordinates of the points that I am drawing with
glVertex3f( -1.0f, 1.0f, -1.0f);
where exactly on the 2D screen will it be placed?
(I know it’s the basic question, but I am beginner in this stuff).

Thanks a lot for any help.

nell aka Justyna Bia?a