#!/usr/local/bin/perl -w
#
# Show how to set a watchpoint on a Tk Entry variable.  Using this technique
# you can do data verification on the user's input.  SOL

use Tk;
use Tie::Watch;

my $MW = MainWindow->new;
my $foo='cow';
my $e = $MW->Entry(-textvariable => \$foo)->pack;
$e->icursor('end');
$e->focus;

sub store_callback {
    print "In store_callback, self=$_[0], new_value=$_[1].\n";
    $_[0]->Store($_[1]);
}
my $w = Tie::Watch->new(-variable => \$foo, -store => \&store_callback);

my $u = $MW->Button(-text => 'UnWatch $foo', -command => sub {
    $w->Unwatch;
    print "Unwatch() value=$foo.\n";
})->pack;

my $l = $MW->Button(-text => 'Quit', -command => sub {
    print "Final value=$foo.\n";
    exit;
})->pack;

MainLoop;