[gtkmm] possible bug in ComboBox behavior

["Meier, Elke" <elke meier sysde eads net>]

Hi,
I am experiencing a rather enervating behavior in Gtk::ComboBox: 

When I click on the button to the right and accidently drag the mouse a
little *within the button* (with the mouse button still pressed), the value
of the entry jumps to the first item in the list.
The expected behavior would be to change the value only when the user clicks
in the list.
That's the kind of thing that drives users nuts... . 

Is this a bug ? If not, how can turn off this "feature" ?

Thanks,
	Elke Meier