PerlTk - bind callbacks with arguments

Author

bind callbacks with arguments

listmail@triad.rr.com

2005-09-22, 6:57 pm

Sorry to beat this to death, but I do have a solution to resizing
widgets by using GeometryRequest. Right now a fundamental problem has
cropped up with the callback in the bind definition. For some reason
when I shift the parameters to the variable $parm, $parm becomes the
HASH for the actual Text widget and not the value 0 or 1 as I believe I
have defined it. Please run this scripts and double click one of the
text widgets and review the print output. I really dont know how this
is possible.

#Script
use strict;
use warnings;
use Tk;
use Tk::Adjuster;

my $mw = MainWindow->new(-title => "Adjuster example");

my $frame1=$mw->Frame();
$frame1->pack();

my $topw = $frame1->pack(-side => 'top', -fill => 'x');
my $botw = $frame1->pack(-side => 'bottom', -fill => 'both', -expand =>
1);

my $tw = $topw->Scrolled('Text', -scrollbars => 'osoe', -height => 10)-
>pack(-expand => 1, -fill => 'both');
my $adj1 = $mw->Adjuster();
$adj1->packAfter($tw, -side => 'top');
my $bw = $botw->Scrolled('Text', -scrollbars => 'osoe', -height => 10)-
>pack(-expand => 1, -fill => 'both');

#here value of 0 or 1 is passed when doubleclicking the Text widget
$tw->bind('<Double-Button-1>', [ \&resize, 0 ]);
$bw->bind('<Double-Button-1>', [ \&resize, 1 ]);

MainLoop();

sub resize () {
my $parm=shift;

#after double-clicking either Text widget for some reason $parm
is a HASH pointing to the widget and not
#a value of 0 or 1 ???
print "PARM: $parm\n";
}
#
#Output is as follows (clicked both widgets)
#PARM: Tk::Text=HASH(0x315ddbc)
#PARM: Tk::Text=HASH(0x32c3964)
-++**==--++**==--++**==--++**==--++**==--++**==--++**==
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dgordon@micron.com

2005-09-22, 6:57 pm

Tk supplies the widget reference as the first argument passed to your
callback, and your argument(s) will be next in line:

sub resize () {
my $widget=shift;
my $parm=shift;

print "WIDGET: $widget\n";
print "PARM: $parm\n";
}

-- Dave

-----Original Message-----
From: owner-ptk@lists.Stanford.EDU [mailto:owner-ptk@lists.Stanford.EDU]
On Behalf Of listmail@triad.rr.com
Sent: Thursday, September 22, 2005 9:40 AM
To: Perl TK Mailing List
Subject: bind callbacks with arguments

Sorry to beat this to death, but I do have a solution to resizing
widgets by using GeometryRequest. Right now a fundamental problem has
cropped up with the callback in the bind definition. For some reason
when I shift the parameters to the variable $parm, $parm becomes the
HASH for the actual Text widget and not the value 0 or 1 as I believe I
have defined it. Please run this scripts and double click one of the
text widgets and review the print output. I really dont know how this
is possible.

#Script
use strict;
use warnings;
use Tk;
use Tk::Adjuster;

my $mw = MainWindow->new(-title => "Adjuster example");

my $frame1=$mw->Frame();
$frame1->pack();

my $topw = $frame1->pack(-side => 'top', -fill => 'x');
my $botw = $frame1->pack(-side => 'bottom', -fill => 'both', -expand =>
1);

my $tw = $topw->Scrolled('Text', -scrollbars => 'osoe', -height => 10)-
>pack(-expand => 1, -fill => 'both');
my $adj1 = $mw->Adjuster();
$adj1->packAfter($tw, -side => 'top');
my $bw = $botw->Scrolled('Text', -scrollbars => 'osoe', -height => 10)-
>pack(-expand => 1, -fill => 'both');

#here value of 0 or 1 is passed when doubleclicking the Text widget
$tw->bind('<Double-Button-1>', [ \&resize, 0 ]);
$bw->bind('<Double-Button-1>', [ \&resize, 1 ]);

MainLoop();

sub resize () {
my $parm=shift;

#after double-clicking either Text widget for some reason $parm
is a HASH pointing to the widget and not
#a value of 0 or 1 ???
print "PARM: $parm\n";
}
#
#Output is as follows (clicked both widgets)
#PARM: Tk::Text=HASH(0x315ddbc)
#PARM: Tk::Text=HASH(0x32c3964)
-++**==--++**==--++**==--++**==--++**==--++**==--++**==
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Ala Qumsieh

2005-09-22, 6:57 pm

--- listmail@triad.rr.com wrote:

> Sorry to beat this to death, but I do have a
> solution to resizing
> widgets by using GeometryRequest. Right now a
> fundamental problem has
> cropped up with the callback in the bind definition.
> For some reason
> when I shift the parameters to the variable $parm,
> $parm becomes the
> HASH for the actual Text widget and not the value 0
> or 1 as I believe I
> have defined it. Please run this scripts and double
> click one of the
> text widgets and review the print output. I really
> dont know how this
> is possible.

It is a by-product of how Perl/Tk glue logic evaluates
callbacks. In this case, there are two arguments
passed to resize:

$tw (or $bw), 0 (or 1)

one fix:

> sub resize () {
> my $parm=shift;

my $parm = pop;

--Ala

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