#!/usr/bin/perl -w
#
# pf.pl
#

use strict;
use Tk;

my %all;
$all{mw} = MainWindow -> new();
$all{mw} -> bind("<Key-q>","exit");

$all{canvas} = $all{mw} ->
Canvas (-background => "#000000",
            -highlightthickness => 0,
            -relief => "flat",
            -bd => 0)->
    pack(-fill => "both",
           -expand => 1);

my ($screenx,$screeny) =
($all{mw} -> screenwidth(),
$all{mw} -> screenheight());

$all{photo} = $all{mw} ->
Photo (-width => $screenx,
          -height => $screeny);

$all{canvas} ->
createImage (0,0,
                   -image => $all{photo},
                   -anchor => "nw");

$all{mw} -> FullScreen(1);
$all{mw} -> geometry  ("${screenx}x$screeny");

for (0..$screenx) {

  my $y = $_;
  $y = $screeny / 2 if $y >= $screeny / 2;

  point($_,$y);

  for (0..10000) {}
  $all{mw} -> update;
}
for (0..$screenx) {

  my $y = $_;
  $y = $screeny / 2 if $y >= $screeny / 2;

  my $x = $screenx - $_;

  point($x,$y);

  for (0..10000) {}
  $all{mw} -> update;
}

MainLoop;

sub point {
  my ($x,$y,$color);

  if ($#_ >= 0) {
    $x = shift;
    if ($#_ >= 0) {
      $y = shift;
      if ($#_ >= 0) {
        $color = shift;
      }
      else {
        $color = "#ff0000";
      }
    }
    else {
      $y = 0;
      $color = "#ff0000";
    }
  }
  else {
    $x = 0;
    $y = 0;
    $color = "#ff0000";
  }

  $all{photo} ->
  put ("$color",
        -to => $x,$y);
}