[gtkmm] custom cellrenderer bug

[Peter Gasper <pgasper designadvantage com>]

I'm trying to learn how to implement a custom cellrenderer. I looked through and
compiled the gtkmm examples as well as the example found here:

http://mail.gnome.org/archives/gtkmm-list/2003-January/msg00107.html

The above was the most helpful. However there seems to be a bug in it which is also
present in my attempts at custom cellrenderers. If one selects
a combo cell and hits enter it changes to its editable state. But if you want to use
the keyboard keys up/down to navigate it you are forced to click on it,
otherwise it arrows out of that cell. Nor can you type in the combo until you physically
click it with the mouse. Additionally, in a normal editable cell if you hit 
enter a second time it commits the changes and goes back to its normal state. However,
in the combo example if you haven't yet clicked on the combo it will throws the
error:

(example:29764): Gtk-CRITICAL **: file ../../gtk/gtktreeviewcolumn.c: line 3222 (_gtk_tree_view_column_start_editing): assertion `tree_column->editable_widget == NULL' failed


The spinbutton in the example doesn't suffer from either of these two errors.


any help will be appreciated. thanks.