#!/usr/bin/perl

use Tk;

my $mw = MainWindow->new;
    $mw->bind( "<Configure>" => sub { print "reconfigure ".ref($_[0])."\n" } );

my $topFr = $mw->Frame
     ->pack( -fill => "both", -expand => 1 );

$topFr->Button( -text => "bigger", -command => sub { changeSize(50) } )
     ->pack( -side => "bottom", -expand => 1 );

$topFr->Button( -text => "smaller", -command => sub { changeSize(-50) } )
     ->pack( -side => "bottom", -expand => 1 );

my $interior = $topFr->Frame(
         -label => "Hello world", -height => 100, -width => 100,
         -background => "white", -relief => "groove" )
     ->pack( -side => "bottom", -fill => "both", -expand => 1 );
    $interior->packPropagate(0);

MainLoop;

sub changeSize
{
my ($sizeDelta) = @_;
$interior->configure(
   -width => $interior->width+$sizeDelta,
   -height => $interior->height+$sizeDelta );
    printf("interior %d x %d, topFr %d x %d\n",
         $interior->width, $interior->height,
         $topFr->width, $topFr->height );
}