Thank you for your reply, Zentara.

>I was musing over it last night, and guessed it has to do with column headers getting counted as a row, maybe ? :-)

When I commented out the code constructing column headers, nothing changed.

>If you want some real consistency in widget design, move up to Perl-Gtk2. All of it's widgets descend from well laid out ancestors, so the style remains the same across widgets.

Unfortunately, I have no enough time to study Gtk2. It's already more than a year that I'm writing this gui on Tk (in free time by evening); imagine how much time will it take from me - total rewriting all the code :)

>so just hack around it, with a few lines of code.

Yes, I'll do it. I have already begun to do it, before creating this page on perlmonks, but then I thought, may be it's not a bug, may be I don't understand something...