use Tk;
use Tk::PNG;
use strict;
use warnings;
use FindBin;

my $main = new MainWindow;

our $DiagramWin;
our $DiagramWin_open = 0;

my $butShow1 = $main -> Button(-text=>" Show 1 ", -command =>\&butShow1_clicked) ->pack(-side => 'top');
my $butShow2 = $main -> Button(-text=>" Show 2 ", -command =>\&butShow2_clicked) ->pack(-side => 'top');
my $butQuit  = $main -> Button(-text=>" Close  ", -command =>\&DiagramWin_close) ->pack(-side => 'top');

MainLoop;

sub butShow1_clicked { &DiagramWin_show("wetterdiagramm1.png") };
sub butShow2_clicked { &DiagramWin_show("wetterdiagramm2.png") };

sub DiagramWin_show 
{
        my $png_filename = shift;
        if ($DiagramWin_open eq 0)
        {
                $DiagramWin = $main -> Toplevel (-title=> "Unterfenster", -width=>1024, -height=>768);
                $DiagramWin -> OnDestroy(\&DiagramWin_destroyed);               
        }
        
        my $canv = $DiagramWin -> Canvas(-width => 1024, -height => 768, -background => 'dark slate gray')->pack;
        
        my $diagram = $FindBin::Bin . "/" . $png_filename;
        $canv -> create ('image', 0, 0, -image => $main->Photo(-file=> $diagram), -anchor => 'nw');             
        $DiagramWin_open = 1;
} 

sub DiagramWin_close
{
        if ($DiagramWin_open) { $DiagramWin -> destroy(); }
        $DiagramWin_open = 0;
}

sub DiagramWin_destroyed
{
        $DiagramWin_open = 0;
}