comment on

Hello,

I have written a small example how I use threads with TK at the moment.

It is working, but it is polluting my design and code. So I'm sure that there has to be a better solution than mine.

First I want to present you my solution:

thread_example.pl:

#!/usr/bin/perl

###########################################################
# USES
###########################################################
use strict;
use warnings;

use Tk;

use My::Gui;
use My::ThreadManager;

###########################################################
# MAIN FUNCTION
###########################################################
&createMyThread();
&createMyGui();
&MainLoop();
[download]

My/Globals.pm:

package My::Globals;

###########################################################
# USES
###########################################################
use strict;
use warnings;

use base 'Exporter';

use constant
{
    FALSE  => 0,
    TRUE   => 1,
    CANCEL => 2
};


###########################################################
# EXPORT
###########################################################
our @EXPORT = qw(TRUE FALSE CANCEL);

###########################################################
# VARIABLES
###########################################################
# NONE

###########################################################
# PUBLIC FUNCTIONS
###########################################################
# NONE

###########################################################
# PRIVATE FUNCTIONS
###########################################################
# NONE

1;
[download]

My/Gui.pm:

package My::Gui;

###########################################################
# USES
###########################################################
use strict;
use warnings;

use base 'Exporter';

use Tk;

use My::ThreadManager;

###########################################################
# EXPORT
###########################################################
our @EXPORT = qw(createMyGui);

###########################################################
# VARIABLES
###########################################################
my %gui;
my %thread_data = ( 'number' => 7 );

###########################################################
# PUBLIC FUNCTIONS
###########################################################
sub createMyGui
{
    $gui{'mw'} = new MainWindow;
    $gui{'mw'}->title("Thread Example");
    $gui{'mw'}->protocol('WM_DELETE_WINDOW' => sub
                         {
                             evWorkCancel() unless isWorkFinished();
                             killMyThread();
                         });
    fillMainWindow($gui{'mw'});
}

###########################################################
# PRIVATE FUNCTIONS
###########################################################
sub fillMainWindow
{
    my $mw = $_[0];

    $mw->{'start_b'} = $mw->Button('-relief' => 'raised',
                                   '-text' => 'START',
                                   '-command' => sub
                                   {
                                       evWorkStart(\%thread_data);
                                       
                                   });

    $mw->{'cancel_b'} = $mw->Button('-relief' => 'raised',
                                    '-text' => 'CANCEL',
                                    '-command' => sub
                                    {
                                        evWorkCancel();
                                    });
    
    
    $mw->{'start_b'}->pack();
    $mw->{'cancel_b'}->pack();
}

1;
[download]

My/ThreadManager.pm:

package My::ThreadManager;

###########################################################
# USES
###########################################################
use strict;
use warnings;

use base 'Exporter';

use Data::Dumper;

use threads;
use threads::shared;
use Thread::Queue;

use My::Globals;
use My::ThreadWorker;

use feature qw(say);

use constant
{
    EV_NONE        => 0,
    EV_KILL        => 1,
    EV_WORK_START  => 2,
    EV_WORK_CANCEL => 3,
    EV_WORK_FINISH => 4
};

use constant
{
    STATE_IDLE => 0,
    STATE_WORK => 1
};

###########################################################
# EXPORT
###########################################################
our @EXPORT = qw(createMyThread killMyThread
                 evWorkStart evWorkCancel
                 isWorkFinished shallWorkBeCancelled );

###########################################################
# VARIABLES
###########################################################
my $thread;

my $thread_event:shared = EV_NONE;
my $thread_state:shared = STATE_IDLE;

my $q = Thread::Queue->new();    

###########################################################
# PUBLIC FUNCTIONS
###########################################################
sub createMyThread
{
    $thread = threads->create( \&execMyThread );
}

sub execMyThread
{
  STATE_IDLE:
    $thread_state = STATE_IDLE;
    say "STATE_IDLE";

    while(1)
    {
        if( $thread_event == EV_WORK_START )
        {
            say "EV_WORK_START";
            $thread_event = EV_NONE;
            goto STATE_WORK;
        }
        elsif( $thread_event == EV_KILL )
        {
            say "EV_KILL";
            $thread_event = EV_NONE;
            return;
        }
        else
        {
            # wait
            select(undef,undef,undef,0.1);
        }
    }

  STATE_WORK:
    $thread_state = STATE_WORK;
    say "STATE_WORK";

    while(1)
    {        
        if( ($thread_event == EV_WORK_FINISH) ||
            ($thread_event == EV_WORK_CANCEL) )
        {
            say "EV_WORK_FINISH" if( $thread_event == EV_WORK_FINISH )
+;
            say "EV_WORK_CANCEL" if( $thread_event == EV_WORK_CANCEL )
+;
            
            $thread_event = EV_NONE;
            goto STATE_IDLE;
        }
        elsif( $thread_event == EV_KILL )
        {
            say "EV_KILL";
            $thread_event = EV_NONE;
            return;
        }
        else
        {
            my %thread_data;
            
            select(undef,undef,undef,0.1);
           
            while( my $thread_data_str1 = $q->dequeue )
            {                
                %thread_data = %{ eval $thread_data_str1 };
            };            

            if( &work(\%thread_data) == CANCEL )
            {
                $thread_event = EV_WORK_CANCEL;
            }
            else
            {
                $thread_event = EV_WORK_FINISH;
            }
        }
    }       
}

sub killMyThread
{
    
    $thread_event = EV_KILL;
    $thread->join;
    exit 0;
}

sub evWorkStart
{    
    my $ref_thread_data = $_[0];

    my $thread_data_str1 = "";

    $Data::Dumper::Varname = "thread_data_str";
    $thread_data_str1 = Dumper($ref_thread_data);

    $q->enqueue( $thread_data_str1 );
    $q->enqueue( undef ); 
    
    $thread_event = EV_WORK_START;
    while( $thread_state != STATE_WORK )
    {
        select(undef, undef, undef, 0.1);
    }
}

sub evWorkCancel
{
    $thread_event = EV_WORK_CANCEL;
    while( $thread_state != STATE_IDLE )
    {
        select(undef, undef, undef, 0.1);
    }    
}

sub isWorkFinished
{
    if( $thread_state == STATE_IDLE )
    {
        return TRUE;
    }
    else
    {
        return FALSE;
    }
}

sub shallWorkBeCancelled
{
    if( $thread_event == EV_WORK_CANCEL )
    {
        return TRUE;
    }
    else
    {
        return FALSE;
    }        
}

###########################################################
# PRIVATE FUNCTIONS
###########################################################
# NONE

1;
[download]

My/ThreadWorker:

package My::ThreadWorker;

###########################################################
# USES
###########################################################
use strict;
use warnings;

use base 'Exporter';

use My::Globals;
use My::ThreadManager;

use Data::Dumper;
use feature qw(say);

###########################################################
# EXPORT
###########################################################
our @EXPORT = qw( work );

###########################################################
# VARIABLES
###########################################################
# NONE

###########################################################
# PUBLIC FUNCTIONS
###########################################################
sub work
{
    my ($ref_thread_data) = @_;

    while( $ref_thread_data->{'number'} <= 100 )
    {
        print $ref_thread_data->{'number'} . " ";
        select(undef, undef, undef, 0.1);
        $ref_thread_data->{'number'} += 1;

        # NOTE:
        # Bad design because My::ThreadWorker needs 
        # My::ThreadManager and My::ThreadManager 
        # needs MyThreadWorker
        if( My::ThreadManager::shallWorkBeCancelled() == TRUE )
        {
            print "\n";
            return CANCEL;
        }
    }

    print "\n";        
}
[download]

In reality the work function of package "My::ThreadWorker" is a complex function which is calling a lot of other modules. I want to be able to cancel this work function to every time and NOT only when it is calling My::ThreadManager::shallWorkBeCancelled.

I do not like to make the call to this function. Because I have to enter this call to a lot of code. In my opinion the code is polluted.

Is there a solution to return from the work function when the user is pressing the cancel-button without polluting the code with My::ThreadManager::shallWorkBeCancelled?

And the other problem is the design. "ThreadWorker" needs "ThreadManager" and "ThreadManager" needs "ThreadWorker".

Thank you alot for your help

Greetings,

Dirk

In reply to Tk and Threads by Dirk80

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