TK: button update

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

Beginner TK question:

If a button label changes, how does one ask the widget to refresh itself? Thanks.

my $on_off = $left_frame->Button(
    -text => $FILTER_IS_ON ? 'turn off ' : 'turn on',
    -command => sub {
        $FILTER_IS_ON = $FILTER_IS_ON ? 0 : 1;
    },
    -anchor => 'w',
)->pack( side => 'left' );
[download]

Comment on TK: button update Download Code

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Re: TK: button update by mawe (Hermit) on Sep 11, 2004 at 18:39 UTC
Hi! You could do it like this: `use Tk; my $FILTER_IS_ON = 0; my $top = new MainWindow(); my $b = $top->Button(-text=>$FILTER_IS_ON ? 'turn off' : 'turn on', -command => \&turn)->pack(); MainLoop(); sub turn { $FILTER_IS_ON = $FILTER_IS_ON ? 0 : 1; $b->configure(-text=> $FILTER_IS_ON ? 'turn off' : 'turn on'); }` [download] mawe	[reply] [d/l]
Re: TK: button update by davidj (Priest) on Sep 12, 2004 at 09:36 UTC
Another way to do it is to use the `-textvariable` attribute of the `Button` widget. What that does is bind the button text to a variable and whenever the variable changes, the button text will automatically change. A modification of the code above: `#!/usr/bin/perl use strict; use Tk; my $FILTER_IS_ON = 0; my $tv = $FILTER_IS_ON ? 'turn off' : 'turn on'; my $top = new MainWindow(); my $b = $top->Button(-textvariable=> \$tv, -command => \&turn)->pack(); MainLoop(); sub turn { $FILTER_IS_ON = $FILTER_IS_ON ? 0 : 1; $tv = $FILTER_IS_ON ? 'turn off' : 'turn on'; }` [download] The benefit of doing it this way is that you don't have to worry about explicitly updating the widget yourself. It happens automatically whenever the value of the bounded variable changes. hope this helps, davidj	[reply] [d/l] [select]