Rudif has asked for the wisdom of the Perl Monks concerning the following question:

Estimated Tk monks

In the example below, I would like to keep the bindings provides by the Scrolled widget - when user clicks or or drags the scrollbar elements - but I'd like to be called so that I can add some behavior. Specifically, when user scrolls down to the last planet, I'd like to add to the list some exoplanets, for example. When called, I would also need to know/find out what is the current scroll position. Is there a general pattern for doing this in Tk? Pointers to doc, tutorials or working examples would be welcome.

#perl -w use strict; use Tk; my @planets = qw / Mercury Venus Earth Mars Jupiter Saturn Uranus Nept +un Pluto /; my $mw = MainWindow->new(); my $plist = $mw->Scrolled( "Listbox", -scrollbars => 'oe', -selectmode => 'single', -height => 4, -setgrid => 1 ); foreach my $planet (@planets) { $plist->insert( 'end', $planet ); } $plist->pack(); MainLoop();