Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I have a long TK program which I cannot include here. It precesses data and outputs results to a text widget. I am having a problem when cancelling my top level window, especially if the input data file is too long. The data processing keeps executing even though I had withdrawn the top level widget. Is this a common thing in Perl/Tk? Here is an abbreviation of my code: 
$tl = $mw->Toplevel(-title=>"Stupid Program");
while (<DATA>){
process data
output to a text widget
}

my $cancel_btn=$action_frame->Button(-text=>"Cancel",
       -command=> sub { 
                $tl->withdraw
                })->pack(-side =>'left', -expand=>1, -anchor => 'cente
+r');

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I have to resort to killing the application in order to stop the process. Any ideas what I can do to resolve this issue? Thank you O great Saints!

Replies are listed 'Best First'.
Re: $widget->withdraw
by zentara (Cardinal) on Jun 02, 2006 at 16:41 UTC
    It's a common mistake in Tk, to use while loops, or sleep statements. These block the gui. Your main misunderstanding, is that you think that withdraw destroys a widget and all it contains. Withdraw just removes it from being mapped onto the screen, it still exists behind the scenes and can be running. The following code is a quick fix 
    #!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = tkinit;

my $tl = $mw->Toplevel(-title=>"Stupid Program");

my $text = $tl->Text()->pack();

my $flag = 0;

my $cancel_btn=  $tl->Button(-text=>"Cancel",
         -command=> sub { 
                 $flag = 1;          
               $tl->withdraw
   })->pack(-side =>'left', -expand=>1, -anchor => 'center');         
+         

my $do_btn=  $tl->Button(-text=>"Start",
        -command=> sub { 
                 while (<DATA>){
                        #     process data
                        #     output to a text widget
                        if($flag){last}
            $text->insert('end',"$_\n");
                        $text->update;
            $mw->after(1000);
                      }
         })->pack(-side =>'left', -expand=>1, -anchor => 'center');   
+               

MainLoop;

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    [download]
    You could also do it without a flag, using the ismapped method.
    Read more... (1329 Bytes)
    I'm not really a human, but I play one on earth. flash japh
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[d/l]
[select]
      Zentara, You are a Saint! Thanks for the clarification. I would apply the ismapped function.
[reply]
        No, I'm not a Saint.......just a happy Abbot. ;-)
        I'm not really a human, but I play one on earth. flash japh
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