I haven't used Windows for ages, but will try to find it.

No, it' not enough. "not declared in this scope". 
Is that a Qt problem (old Qt?) or a gl.h problem?

where to get it? Which one will work with the Mingw QtCreator tools?
I remember I used to use a newer gl.h on Windows, but
I haven't used Windows for 6 years.
Will try to find it, though.
Maybe google GL3 gl.h or GL2.1 gl.h.

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