Alpar had the key, focus can be set in the window class. But it is not enough, the focused widget has to be activated, as well! Was a hard task to find out... By the way, two compilation warnings are removed.
1 /// The namespace of LEMON
3 /// \todo Some more detailed description would be nice here.
7 /// The namespace of LEMON concepts and concept checking classes
9 /// \todo Some more detailed description would be nice here.