#!/usr/bin/perl
use warnings;
use strict;
use threads;
use threads::shared;

my $work:shared = 0;
my $die:shared = 0;

#create thread before any tk code is called
my $thr = threads->create( \&worker );

use Tk;

my $mw = MainWindow->new();
$mw->protocol('WM_DELETE_WINDOW' => sub { &clean_exit }); 

my $button_stop = $mw->Button(-text => 'Stop thread',
							  -command =>
							  sub
							  {						  
								  $work = 0;
							  })->pack();

my $button_start = $mw->Button(-text => '(Re)Start thread',
							   -command =>
							   sub
							   {
								   $work = 0;
								   sleep(1);
								   $work = 1;
							   })->pack();

MainLoop;

sub clean_exit
{
	my @running_threads = threads->list;
	if (scalar(@running_threads) > 1)
	{
		print "ERROR: Too many threads are active. This was not planned!\n";
	}
	elsif (scalar(@running_threads) == 1)
    {
		$work = 0;
		$die = 1;
		$thr->join;
		exit;
	}
	else
	{
		print "ERROR: There should be at least one thread started!\n";
	}
}

# no Tk code in thread
sub worker
{
	my $i;

  THREAD_START:	
	while($work == 0)
	{
		# just wait
		if( $die == 1 )
		{
			return;
		}			
	}

	$i = 0;
	while($work == 1)
	{
		print $i . "\n";		
		$i++;
    }

	if( $die == 0 )
	{
		goto THREAD_START;
	}
}