PerlTk - Callbacks and Subroutines

Author

Callbacks and Subroutines

doni

2007-03-05, 7:06 pm

Hi,

I am right now learning about Perl/TK and have a basic question
regarding subroutines and callbacks.

I was wondering how can I have the subroutine output to display in the
MainWindow if the subroutine is called using a button widget from the
MainWindow.

Here is the code that I wrote to test my above question.

#!/usr/bin/perl

use strict;
use Tk;

my $mw = MainWindow->new;
$mw->title("Demo Program");
$mw->Button(-text => "Test",
-command => sub{test()})->pack;
$mw->Button(-text => "Exit",
-command => sub{exit})->pack;
MainLoop;

sub test {
print "We have reached the subroutine part \n";
}

>From the above code, I wanted the print statement "We have reached the
subroutine part" to display in the MainWindow when I press the "test"
button.

When I press the "Test" button the result is getting displayed on the
command line and not on the MainWindow.

Thanks,
doni

felix.da.ru

2007-03-06, 4:18 am

On Mar 6, 2:18 am, "doni" <doni.se...@gmail.com> wrote:
> Hi,
>
> I am right now learning about Perl/TK and have a basic question
> regarding subroutines and callbacks.
>
> I was wondering how can I have the subroutine output to display in the
> MainWindow if the subroutine is called using a button widget from the
> MainWindow.
>
> Here is the code that I wrote to test my above question.
>
> #!/usr/bin/perl
>
> use strict;
> use Tk;
>
> my $mw = MainWindow->new;
> $mw->title("Demo Program");
> $mw->Button(-text => "Test",
> -command => sub{test()})->pack;
> $mw->Button(-text => "Exit",
> -command => sub{exit})->pack;
> MainLoop;
>
> sub test {
> print "We have reached the subroutine part \n";
>
> }
>
> subroutine part" to display in the MainWindow when I press the "test"
> button.
>
> When I press the "Test" button the result is getting displayed on the
> command line and not on the MainWindow.
>
> Thanks,
> doni

Hi,

Looks like you've to learn more about Perl/Tk and GUI development in
general.
You are trying to use graphic widget as text terminal, and it for sure
wouldn't work.
To solve your task you've to create respective text widget (Label/
Message/ROText) and insert your text message there.

Example:

#!/usr/bin/perl -w

# test

use strict;

use Tk;
use Tk::Button;
use Tk::Frame;
use Tk::ROText;

my $mw=MainWindow->new(-title=>'test');
#===vptk widgets definition===< DO NOT WRITE UNDER THIS LINE >===
my $w_ROText_003 = $mw -> Scrolled ( 'ROText', -height=>10, -
scrollbars=>'osoe', -width=>30 ) -> pack(-fill=>'both', -expand=>1);
my $w_Frame_002 = $mw -> Frame ( -relief=>'flat' ) -> pack();
my $w_Button_004 = $w_Frame_002 -> Button ( -text=>'Test', -command=>
\&test ) -> pack(-anchor=>'nw', -side=>'left');
my $w_Button_005 = $w_Frame_002 -> Button ( -text=>'Exit', -
command=>sub {exit} ) -> pack(-anchor=>'nw', -side=>'left');

MainLoop;

#===vptk end===< DO NOT CODE ABOVE THIS LINE >===

sub test
{
$w_ROText_003->insert('end',"your text to indicate event\n");
}

Ch Lamprecht

2007-03-06, 4:18 am

doni schrieb:
> Hi,
>
> I am right now learning about Perl/TK and have a basic question
> regarding subroutines and callbacks.
>
> I was wondering how can I have the subroutine output to display in the
> MainWindow if the subroutine is called using a button widget from the
> MainWindow.

You need a widget to display the message. The Labels -textvariable option takes
a reference to a Scalar variable. The widget will automagically update on
changes of that variable.

Christoph

use warnings;
use strict;
use Tk;

my $mw = MainWindow->new;
$mw->title("Demo Program");
my $message = '';
$mw->Label(-textvariable => \$message)->pack;
$mw->Button(-text => "Test",
-command => sub{test(\$message)})->pack;
$mw->Button(-text => "Exit",
-command => sub{exit})->pack;
MainLoop;

sub test {
my $msg = shift;
$$msg = "We have reached the subroutine part \n";
}

--
use Tk;use Tk::GraphItems;$c=tkinit->Canvas->pack;push@i,Tk::GraphItems->
TextBox(text=>$_,canvas=>$c,x=>$x+=70,y=>100)for(Just=>another=>Perl=>Hacker);
Tk::GraphItems->Connector(source=>$i[$_],target=>$i[$_+1])for(0..2);
$c->repeat(30,sub{$_->move(0,4*cos($d+=3.16))for(@i)});MainLoop

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