[gtkmm] CustomCellRenderer - how to commit edits when losing focus?

[Igor Gorbounov <igorbounov voronezh serw ru>]

I use the custom SpinCellRenderer and ComboCellRenderer, described in
http://mail.gnome.org/archives/gtkmm-list/2003-January/msg00090.html.
They work fine but there is a problem that I cannot solve:
when any of these cell renderers are in an editing mode, removing
focus from them does not complete the changes (or discards them -
no matter, I only need that the cell became inactive, not in an
edit mode), though a "normal" CellRendererText completes the
editing when losing its focus.
So what makes the difference between those two types of renderers,
what am I missing?
	Igor Gorbounov