#!/usr/bin/perl
use Tk;
my $mw = new MainWindow;

my $canvas = $mw->Canvas(-bg=>'white')->pack(-expand=>1, -fill => 'both');

my $currentSize = $mw->reqwidth . "x" . $mw->reqheight;

$mw->bind( '<Configure>', [ \&OnResize, \$currentSize ] );

MainLoop;

sub OnResize {
    my ( $mw, $oldSize ) = @_;

    my $newSize = $mw->width . "x" . $mw->height;
    if ( $$oldSize ne $newSize ) {
        ## Resize has occurred do something:
         printf( "Resize happened - old size: %s, new size: %s\n",
            $$oldSize, $newSize );
         ## set the old size to the new size
        $$oldSize = $newSize;
    }

}