#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = MainWindow->new;
my $vh = $mw->vrootheight;
my $vw = $mw->vrootwidth;
$mw->geometry($vw.'x'.$vh.'+0+0');
$mw->overrideredirect(1); #grabs full control

$mw->fontCreate('big',
   -family=>'arial',
  -weight=>'bold',
  -size=>int(-18*18/14));

my $topframe = $mw->Frame->pack();
my $frame = $mw->Frame->pack();
my $txt;  #make these globals so you reuse them
my $canvas; #and avoid memory gains of making too many 
            #redundant widgets
my $count = 0;

# instead of a button you could make navigation arrows
$topframe->Button(-text => "Change Screen",
          -command => sub{
         	  #clean out frame's children
         	  my @w = $frame->packSlaves;
	          foreach (@w) { $_->packForget; }
	          #clean out frame
	          $frame->packForget;
      
                  $count++;
                  &build($count);
            })->pack(-side=>'left',-padx=>20);

$topframe->Button(-text => "Exit",
         -command => sub {exit})->pack(-side=>'right',-padx=>20);

&build(0); #setup first screen

MainLoop;
			 
sub build {
my $count = shift;

 $txt = $frame->Text(-bg=>'white',-font=>'big',-height=>5)->pack(-fill=>'x');
 $txt->insert('end',"\t\t\t\t Page $count");
# Note that the 'virtual window' height and width are $vh and $vw
# respectively, so we use those dimensions for our Canvas height 
# and width, and let the Canvas expand and fill in both x and y
# directions.
#
$canvas = $frame->Canvas(
   -width => $vw, 
   -height => $vh, 
   -background =>'blue', 
  )->pack(-expand => 1, -fill => 'both');

$canvas->createRectangle(80, 80, 200, 200, -fill => 'yellow'); 

$canvas->createText(125, 125, 
                -fill => 'black',
                -text => "page $count",
                -font => 'big',
                ); 

$frame->pack(); #reshow it
$mw->update;

}