Hello, guys. My research in possible screenshot system implementations with OpenGL all pointed to glReadPixels.
iirc, it is safe to call OpenGL functions additionally to OpenLayer, as long as it's guaranteed that such functions do not meddle with OpenGL's state.
I couldn't find the info whether glReadPixels is state-changing or not (I could imagine it is not, but you never know ...), so I'd go for that approach, unless someone now convinces me there's a better method
P.S.: For the case it is not clear what I meant with "screenshot system": I want the current screen saved to a .png file (or whatever) on keypress. Nothing of all that is much of a problem, except of the screen-grabbing part.