ak.arjun has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I am using Perl/Tk to build a gui application and i need some advice. my issue is that i want to use a check-button in three states, i.e. i want to have a partial selection mode for check-button. But tk provide check-button with only two states.

Now with each check-button there is a variable associated on changing the value for that variable reflects the change in the corresponding check-button. What i want to do is alter this part of in such way that this variable can operate on three values rather than two(current behavior). What i mean is that instead of just having two values associated to that variable , i want to associate a third value in which i will change the select color property. Can this be done???

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Re: Tk Checkbutton
by zentara (Cardinal) on Apr 24, 2012 at 12:12 UTC
    You would be better off making your own widget on a sub-classed Canvas. However you could bind a right mouse button click to each checkbutton, to simulate 3 states. 
    #!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::Pane;

my @states = qw(Alaska Hawaii Michigan Georgia Arizona Washington Oreg
+on California Texas Utah Minnesota);

my $mw = tkinit();
$mw->geometry('300x300+100+100');

my $sp = $mw->Scrolled('Pane', -scrollbars=>'osoe', sticky=>'nwse')
     ->pack(-expand=>1, -fill=>'both' );

my %cbs;
my @cbvalues;
my @cbnames;
my $count = 0;

foreach my $d( @states){

  $cbnames[$count] = $d;

  $cbs{$count} = $sp->Checkbutton(-text => $d,
        -font=>[arial => 12],
        -onvalue => 1,
        -offvalue => 0,
        -variable => \$cbvalues[$count],
        -font => 'big',
        -bg => 'white',
     )->pack(-anchor=>'w')->pack();

  $cbs{$count}->bind('<ButtonRelease-3>', sub{  
                              print "@_\n";
                              print "do you 3rd state thing here\n"; 
                             });


$count++;
}

my $showbutton= $mw->Button(-text=>'Show Selected',
-bg => 'lightyellow',
-command => sub{ 
       my @selected = ();
       foreach my $c( 0.. $count ){
            if ( $cbvalues[$c] ){
                push @selected, $cbnames[$c];
              }
         }
  
      print "@selected\n"; 
      } )->pack();

MainLoop();

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[reply]
[d/l]

      Well making my own widget is an option, and can't use right mouse click because my requirement is to make a hierarchical tree structure with each entry of tree containing a check-button. Hence whenever each check-button is selected all its child node should get selected, but when de-select a check-button, the parent check-button will get partially de-selected(third state) or or totally de-selected(only if all its child node are de-selected))

      What i was thinking that each check-button has a variable associated to it, and when i change the value of that variable to on/off state, the check-button gets selected/de-selected automatically. So if i know how does tk is exactly implementing this behavior, i can make changes in that area of code to add my functionality. Is it possible?

[reply]
[reply]
Re: Tk Checkbutton
by Anonymous Monk on Apr 24, 2012 at 12:03 UTC

    Not with a checkbutton, they're meant to be on or off

    You can however create your own button class like Tk::StyledButton or Tk::ImageButton but with more states than normal/active/disabled

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