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

edit: I found the problem with this. It seems that by default tk passes a ref to the object you bound to. Once I realized that that ref was also in @_ I was able to use that and trim my parameter list by one..also making it in the correct order.This works now. Thanks to all those who may have given it some thought.

I have two tk listbox's with a method bound to one of them like so. 
    #Make the file listbox and scrollbar
    my $ftp_fileList = $ftp_dialog->add("Listbox")->pack(-side=>'left'
+,-fill=>'both');
    my $ftp_fileScrollBar = $ftp_dialog->Scrollbar(-command=>['yview',
+$ftp_fileList])->pack(-side=>'left',-fill=>'y');
    
    #Bind the scrollcommand to the bar
    $ftp_fileList->configure(-yscrollcommand=>['set',$ftp_fileScrollBa
+r]);

    #Make the dir listbox and scrollbar
    my $ftp_dirList = $ftp_dialog->add("Listbox")->pack(-side=>'right'
+,fill=>'both');                                     
    my $ftp_dirScrollBar = $ftp_dialog->Scrollbar(-command=>['yview',$
+ftp_dirList])->pack(-side=>'right',-fill=>'y');
        
    #Bind the scrollcommand to the bar
    $ftp_dirList->configure(-yscrollcommand=>['set',$ftp_dirScrollBar]
+);    
    
    #Bind the double click method to change directory
    $ftp_dirList->bind('<Double-1>',[\&cd_List, \$ftp, $ftp_dirList,$f
+tp_fileList]);

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When I receive the parameters to cd_List in the function they are not passed in the order listed... does anyone have any idea how to control their order .. or tell me a secret that I'm missing on what order they go in.. I have simply two parameters previously.. and they were passed in backwards... when I switched to three and implremented the backward parameter list.. it was found to be not the case... any ideas?
Grygonos

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Re: Tk event-binding parameters
by zentara (Cardinal) on Nov 14, 2003 at 18:56 UTC
    "It seems that by default tk passes a ref to the object you bound to. Once I realized that that ref was also in @_ I was able to use that and trim my parameter list by one..also making it in the correct order"

    I'm not sure what question you are asking, other than the parameter order, but it got me thinking about your statement that tk passes a ref to the callback. At first it didn't strike me as odd, because in perl gtk, all callbacks get $self passed to it as it's first parameter. But then I tried it, and it dosn't in Tk. In Tk a hash exists with the data in it, but it isn't passed by default. The following code demonstartes what I'm talking about. It creates a bunch of "anonymous buttons" and it dosn't pass a ref to the pressed button to the callback sub-routine. The information is available from the hash returned by Tk::widget. Maybe your problem is you think the ref is being passed as an array, but it's actually in an unordered hash. Use the Dumper line to see all that is contained in $caller. Anyways....I learned something today. 

    #!/usr/bin/perl
use strict;
use Tk;
use Data::Dumper;

my $mw = MainWindow->new;

for(0..4){
$mw->Button(-text => "Hello World$_",
                     -command=>[\&change])->pack;
}
MainLoop;

sub change {
#Tk dosn't pass it's widget reference in callbacks 
#Only the bind() method will implicity pass a widget reference, and ev
+en 
#this default (and generally preferred) action can be defeated. 
#use the widget
 
my $caller = $Tk::widget;
#print Dumper([$caller]); 
print "$caller   ";
print $caller->{'_TkValue_'},'     ';
my $text = $caller->cget('-text');
print "$text\n";
$caller->configure(-text=>"Hello Stranger");
}

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[reply]
[d/l]
      Sorry .. should have clarified.. yes it is only on the bind()'d widgets. I like the idea of it passing that way. Since you're binding an event to a widget you more than likely want to do something with it when the event is processed. just a note.
      Grygonos
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