[gtkmm] Triggering of a combo's popup?

[Markus Gerwinski <markus gerwinski de>]

Hi folks,

is there a way in Gtkmm-2.0 to "manually" trigger a combo's popup from the
source?

I want to overload the "activate" signal of a combo->entry, but to do so, I
have to disable_activate it, and don't find another way to show the popup list.

Thanks in advance,

  Markus