Re: Scale widget executes it's command when mapped

On Jan 21, 2005, at 2:24 AM, [email protected] wrote:

> Hi all,
>
> talking about the Scale widget, I remembered another issue.
> Unlike other widgets (like Button, Checkbutton, ...), the Scale
> widget executes it's -command code, when it's mapped (or
> close to that time).

Yes, that's known .. IIRC a few other widgets do that as well. I think 
I (at one time) had a reasonable work-around, but nothing comes to 
mind.

> See this little example:
>
> use Tk;
> my $mw = MainWindow->new();
> $mw->Scale(-from => 0, -to => 10, -length => 300, -width => 10,
>            -command => sub { print "*" })->pack();
> $mw->Button(-text => "Test", -command => sub { print "+" })->pack();
> MainLoop;
>
> When you start it, it immediately prints a * to the shell, but
> no +. So the Button behaves as expected, the Scale
> act 'prematurely'.

Here's a kluge:

#!/usr/local/bin/perl -w
use Tk;
my $mw = MainWindow->new();
my $s = $mw->Scale(-from => 0, -to => 10, -length => 300, -width => 
10)->pack();
$mw->update; $s->configure( -command => sub { print "*" } );
$mw->Button(-text => "Test", -command => sub { print "+" })->pack();
MainLoop;



>
> That is does so is annoying and doesn't make sense to me.
> I always have to build this 'return unless ($first++)' type of
> code into the command code of the Scale.

With luck an expected snow storm will trap me in front of my computer 
this weekend  and I'll address this and all your previous mails ;)

>
> Regards,
> Gerhard
>
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