Re: forked process exiting before output read

["Jeffrey Ratcliffe" <jeffrey ratcliffe gmail com>]

On 27/07/07, zentara <zentara1 sbcglobal net> wrote:
> If you use a thread, you can avoid this by placing the results in a shared variable.

Thanks for the tip. I have always avoided threads as I had the
impression that they don't play well with Gtk2-Perl. I have reworked
my original example with threads. Are there any obvious pitfalls with
this approach?

Jeff

#!/usr/bin/perl

use warnings;
use strict;
use threads;
use threads::shared;
use Thread::Semaphore;
use Gtk2 qw/-init -threads-init/;
use Glib qw(TRUE FALSE);             # To get TRUE and FALSE

my $semaphore = Thread::Semaphore->new(0);
my @queue:shared;
my $thread = threads->new(\&worker);

# Create the windows
my $window = Gtk2::Window->new('toplevel');
my $box = Gtk2::VBox->new;
my $pbar = Gtk2::ProgressBar->new;
my $buttonQuit = Gtk2::Button->new('Quit');
my $buttonStart = Gtk2::Button->new('Start');

$window->add ($box);
$box->add ($pbar);
$box->add($buttonQuit);
$box->add($buttonStart);

my %helperTag;

# We should also link this to the destroy message on the main window,
# this is just quick and dirty
$buttonQuit->signal_connect(clicked => sub{Gtk2->main_quit});
$buttonStart->signal_connect(clicked => sub{
 $semaphore->up;
 Glib::Timeout->add (200, sub{
  if (@queue) {
   my $fraction = shift @queue;
   my $text = shift @queue;
   $pbar->set_fraction($fraction);
   $pbar->set_text($text);
   if ($fraction == 1) {
    $thread->join;
    $semaphore->down;
    return FALSE;
   }
  }
  return TRUE;
 });
});
$window->show_all;
Gtk2->main;

sub worker {
 $semaphore->down;
 my $n = 4;
 for (my $i = 0; $i <= $n; $i++) {
  sleep(1);
  push @queue, $i/$n;
  push @queue, "Running $i of $n";
 }
 $semaphore->up;
}