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

Hi there,

I have an application which needs to perform some action when a radio button is deselected. This is what happens when the radio button has previously been clicked, then another radio button is clicked.

The Tk::Radiobutton widget has a callback, -command, but this is only called when the button is clicked, i.e. selected. It is not called when a different button sharing the same -variable is clicked

I know it's possible to code a common subroutine for all the radio buttons in the group, but this is outside my control as I am trying to write a new composite widget (which by implication will not know about other radio buttons outside the widget, unless its -variable changes).

Presumably, there is some internal method in the widget that is called in order for the radio button to get visually unclicked. All I am after is access to this event as a callback, in the manner of -deselect_command below: 


my $foo;

for (qw/eenie meenie minie mo/) {
    $mw->Radiobutton(
         -text => $_,
         -command => sub { print "$_ selected\n" },
#        -deselect_command => sub { print "$_ unselected\n" },
         -variable => \$foo,
         -value => $_
    ) ->pack( -side => 'left');
}

[download]
--
I'm Not Just Another Perl Hacker

Replies are listed 'Best First'.
Re: Need a callback for Tk radio button deselect
by zentara (Cardinal) on Sep 30, 2003 at 16:35 UTC
    Does this give you ideas? 
    #!/usr/bin/perl
use Tk;
use strict;

my $val;

my $mw = new MainWindow;
$mw->Checkbutton(onvalue => "I am selected",
                offvalue => "I am deselected",
                variable => \$val)
  ->pack;
$mw->Entry(textvariable => \$val)->pack;

MainLoop;

    [download]
[reply]
[d/l]
      zentara, I'm not sure your example helps.

      What I am after is a callback for a radiobutton. My radiobutton widget is detecting changes of value of the common -variable, and visibly changes its appearance. It looks like you are doing something equivalent by typing into the entry box. However, no callback results; this is what I am really after, in order to do some processing when the widget is deselected.

      --
      I'm Not Just Another Perl Hacker
[reply]
Re: Need a callback for Tk radio button deselect
by zentara (Cardinal) on Oct 01, 2003 at 15:53 UTC
    I'm really just a beginner at Tk. Sorry. Maybe you could separate out the Radio Buttons into single units, and do something like the following: 
    #!/usr/bin/perl
use Tk;

my $mw = MainWindow->new;
my $lastbutton = 0;

my $rb1 = $mw->Radiobutton(-text => "Button One",
                            -value => 'button1',
                            -variable => \$rb,
                            -command => [ \&showRB, \$rb ])->pack;
my $rb2 = $mw->Radiobutton(-text => "Button Two",
                            -value => 'button2',
                            -variable => \$rb,
                            -command => [ \&showRB, \$rb ])->pack;
my $rb3 = $mw->Radiobutton(-text => "Button Three",
                            -value => 'button3',
                            -variable => \$rb,
                            -command => [ \&showRB, \$rb ])->pack;
my $rb2 = $mw->Radiobutton(-text => "Button Four",
                            -value => 'button4',
                            -variable => \$rb,
                            -command => [ \&showRB, \$rb ])->pack;

MainLoop;

sub showRB
{
     print "Arg list is @_\n";
     my $state_ref = shift;
     my $state = $$state_ref;
     $mw->messageBox(-title => 'Status',
                     -type  => 'OK',
                     -message  => "Status is :$state:. Previous State 
+was $lastbutton");
     $lastbutton = $state;
}

    [download]
[reply]
[d/l]
Re: Need a callback for Tk radio button deselect
by rinceWind (Monsignor) on Oct 03, 2003 at 09:19 UTC
    For those interested in this thread, I posted this question to the ptk list, and I was pointed in the direction of Tk::Trace, which looks like it will do what I want.

    I will be able to set a trace on the radiobutton variable, which results in a callback when its value is changed. I will need to filter the cases for when the button is being deselected.

    $me =~ /happy bunny/

[reply]

Back to Seekers of Perl Wisdom