Re: Executing functions in Perl::Tk

[liverpole]

Yes, there are a couple of ways.

The really simple approach is just to call the method update() on the main window object at appropriate times during the subroutine execution:

# Assuming my $mw = MainWindow(...)

sub button_press {
    # Do some work
    $mw->update;

    # Do some more work
    $mw->update;

    # etc...

The more complex (but very powerful) approach is to use threads, as long as you're very careful not to do anything Tk-related within the thread.  (That's because Tk is not "thread-safe").

Here's an example of a way you could use threads, especially if there are parts of the worker subroutine that have long delays during which you don't have the luxury of using $mw->update:

#!/usr/bin/perl -w
#

# Libraries
use strict;
use warnings;
use threads;
use Tk;
use Tk::Font;
use Tk::ROText;


# Main Program
my $mw  = new MainWindow(-title => 'Tk thread example');
my $fnt = $mw->Font(-family => 'tahoma', -size => '24');
my $btn = $mw->Button(-text => 'Press Me', -font => $fnt)->pack(-fill 
+=> 'x');
$btn->configure(-bg => '#ff7f3f', -command => \&button_press);
my $txt = $mw->ROText(-bg => 'white')->pack(-fill => 'both');
$mw->bind('<Escape>' => sub { exit });
$mw->repeat(1000 => \&gui_loop);
MainLoop;


# Subroutines
sub gui_loop {
    $txt->insert('end', sprintf "Time is %s\n", scalar localtime time(
+));
    $txt->see('end');
}


sub button_press {
    my $sthread = threads->new(sub { worker_thread() });
    $sthread->detach();

    # Here we "return immediately" :)
    return;
}


sub worker_thread {
    my $tid = threads->tid;

    # But DON'T do this ... !!!
    # my $thread_mw = new MainWindow();

    for (my $i = 0; $i < 1024; $i++) {
        printf "Thread %s:  Doing more work ...\n", $tid;
        sleep 1;
    }
}

Please note that once you're in the worker thread, you must refrain from the urge to use Tk.  If you want to pass data back to the main program, you should look into shared data between threads.

If you try putting back in the code where it says "But DON'T do this", you'll get an error message like:

Thread 1:  Doing more work ...
Attempt to free non-existent shared string '_ErrorInfo_', Perl interpr
+eter: 0x23
3f3c at C:/Perl/site/lib/Tk.pm line 423.