#!/usr/bin/perl -w

###############
## Libraries ##
###############
use strict;
use warnings;
use Tk;
use Tk::Font;

##################
## Instructions ##
##################
my $help = qq{
   Instructions:  (1) Click "Minimize" followed by "Maximize", and
   notice how the Canvas alternates between visible and hidden.
   (2) While the Canvas is maximized, resize the GUI with the mouse,
   by clicking on and dragging any corner of the GUI to a new place.
   (3) Finally, click "Minimize" again, and note that the GUI keeps
   the size of Maximized window, rather than shrinking as before.
};

##################
## Main Program ##
##################
my $state = 'max';

# Create the Toplevel
my $mw    = new MainWindow(-title => "Pack/Repack Example");

# Assign colors, fonts, reliefs
my $font1 = $mw->Font(-family => 'arial', -size => 24);
my $font2 = $mw->Font(-family => 'arial', -size => 16);
my @btn   = (-font => $font1, -bg => '#ffef3f');
my @lbl   = (-font => $font2, -bg => 'pink', -relief => 'groove');

# Assign widgets
my $frm1  = $mw->Frame->pack(-fill => 'x'); 
my $frm2  = $mw->Frame->pack(-fill => 'x'); 
my $frm3  = $mw->Frame->pack(-expand => 1, -fill => 'both'); 
my $btn1  = $frm1->Button(@btn, -text => 'Minimize');
my $btn2  = $frm1->Button(@btn, -text => 'Maximize');
my $btn3  = $frm1->Button(@btn, -text => 'Exit (^X)');
my $can   = $frm3->Canvas(-bg => 'white');
my $lbl   = $frm2->Label(-text => $help, @lbl)->pack(-fill => 'x');

# Pack the buttons and canvas
$btn1->pack($btn2, $btn3, -side => 'left');
$can->pack(-expand => 1, -fill => 'both');

# Draw some random circles in the Canvas for fun
for (my $i = 0; $i < 512; $i++) {
    my $radius    = 8 + int rand(64);
    my ($x0, $y0) = (int rand(800), int rand(800));
    my ($x1, $y1) = ($x0 + $radius, $y0 + $radius);
    my $fill = sprintf "#%02x%02x%02x", rand 256, rand 256, rand 256;
    $can->createOval($x0, $y0, $x1, $y1, -fill => $fill);
}

# Attach callbacks and bindings
$btn1->configure(-command => sub { minimize() });
$btn2->configure(-command => sub { maximize() });
$btn3->configure(-command => sub { exit });
$mw->bind("<Control-x>" => sub { $btn3->invoke });

MainLoop;


#################
## Subroutines ##
#################
sub minimize {
    ($state eq 'min') and return;
    $state = 'min';
    $frm3->packForget;
}

sub maximize {
    ($state eq 'max') and return;
    $state = 'max';
    $frm3->packConfigure(-expand => 1, -fill => 'both'); 
}