Returns the ID of the active row of @combo_box. This value is taken
from the active row and the column specified by the #GtkComboBox:id-column
property of @combo_box (see gtk_combo_box_set_id_column()).
The returned value is an interned string which means that you can
compare the pointer by value to other interned strings and that you
must not free it.
If the #GtkComboBox:id-column property of @combo_box is not set, or if
no row is active, or if the active row has a %NULL ID value, then %NULL
is returned.
Returns the ID of the active row of @combo_box. This value is taken from the active row and the column specified by the #GtkComboBox:id-column property of @combo_box (see gtk_combo_box_set_id_column()).
The returned value is an interned string which means that you can compare the pointer by value to other interned strings and that you must not free it.
If the #GtkComboBox:id-column property of @combo_box is not set, or if no row is active, or if the active row has a %NULL ID value, then %NULL is returned.