#!/usr/bin/perl
use warnings;
use strict;
use threads;
use threads::shared;
use Tk;
use Thread::Queue;
use Tk::ProgressBar;

my $percent_done;
share $percent_done;
$percent_done = 0;

my $comm = new Thread::Queue;
my $progressbar;

threads->new(\&go, $comm, $percent_done)->detach;

my $mw;
($mw, $percent_done) = create_gui();

$mw->repeat( 100, [\&updateScreen, $comm, $percent_done] );

MainLoop();

sub create_gui {
    $percent_done=0;

    my $mw = MainWindow->new( -title => 'Test');
    $mw->Label( -text => "percent_done" )->pack;

    $progressbar = $mw->ProgressBar()->pack;
    $progressbar->value($percent_done);

    $mw->Button (
        -text => "Clear",
        -command => sub { $percent_done = 0;
                          $progressbar->value(0);
                          $mw->update; }
        )->pack;

    return ($mw, $percent_done);
    }

sub go {
    my ($comm, $percent_done) = @_;
    $comm->enqueue( $percent_done + 5);
    while(1) {
    $comm->enqueue( $percent_done + 5);
        select undef, undef, undef, 1;
        $percent_done += 5;
        if($percent_done == 100){last}
        }

    }

sub updateScreen {
    my ($comm, $percent_d) = @_;

    $progressbar->value($percent_done);
    ($percent_done = $comm->dequeue ) if $comm->pending;
    $progressbar->value($percent_done);

    }