cellrenderer_spinbutton.pl example. Gtk2::Entry where from?

[Mitchell Laks <mlaks post harvard edu>]

Hi group,

I have been puzzling over the cellrenderer_spinbutton.pl example
in the Gtk2-1.153 distribution
and can't seem to figure this out.

If you hover over the window with your mouse, without clicking on any cell,
then type a keyboard entry such as any letter, then a Gtk2::Entry widget
 opens up below the main window and your typed info goes into it.

What line in the code creates a Gtk2::Entry widget that sits outside of
the main window?? 
This Gtk2::Entry  goes away completely if you remove the mouse
from hovering over the window, or type enter. Puzzling.

Thank you,

Mitchell