#!/usr/bin/perl

use strict;
use Time::HiRes qw(ualarm);
use Tk;
BEGIN {*Tk::Clock::time = sub { time * -1 } }
use Tk::Clock;
my $wm = MainWindow->new;
my $ck = $wm->Clock->pack(-side => 'top');
my $b  = $wm->Button(-text => 'Start Process', -command => \&mainprocess)->pack;
$ck->config(dateFormat => "dd-mm-yyy");

MainLoop;

#
# simulate a long running, CPU-intensive task
#
sub mainprocess {

    local $SIG{ALRM} = sub {
        DoOneEvent(Tk::Event::DONT_WAIT);
        ualarm(1000);
    }
    ualarm(1000);

    # task body begin

    my $c;
    $b->configure(-text => 'running...');
    while (1) {
        $c++; 
        print $c,"\n" unless $c % 1000;
        last if $c == 10000000;
    }
    $b->configure(-text => 'Start Process');

    # task body end

    ualarm(0);
}