#!/usr/bin/perl

use strict;
use warnings;

use Tk;

my $mw = tkinit();
$mw->geometry('200x200');

$mw->update;

for my $x ( 1 .. 50 )
{
	my $y  = sin($x)*100;
	my $x1 = 100;
	my $x2 = $x1 + $y;

	($x1, $x2) = ($x2, $x1) if $x2 < $x1;

	$mw -> draw_hl(
		$x1,
		$x*4,
		$x2-$x1,
		'darkblue',
	);

	$mw -> update;
} # for

MainLoop;

#
# draw an horizontal line using a Frame widget
#
sub Tk::Toplevel::draw_hl {
	my( $mw, $x, $y, $w, $c ) = @_;

	$mw -> Frame(
		-width      => $w,
		-height     => 1,
		-bd         => 0,
		-background => $c,
	) -> place(
		-x          => $x,
		-y          => $y,
	);
} # draw_hl

__END__