GDK3 documentation is broken
See e.g. https://developer.gnome.org/gdk3/stable/gdk3-Event-Structures.html or https://developer.gnome.org/gdk3/stable/gdk3-Windows.html#gdk3-Windows.other
The description on all of the structures are empty. This did not use to be the case - compare to the GDK2 docs: https://developer.gnome.org/gdk2/stable/gdk2-Event-Structures.html