#!/usr/local/bin/perl 
# Embedding OpenGL in a Tk Toplevel.

use Tk;
use OpenGL;

$mw = MainWindow->new;
$mw->Button(-text => 'OpenGL Demo', -command => \&opengl)->pack;
$mw->Button(-text => 'Quit', -command => \&exit)->pack;

sub opengl {
    $top = $mw->Toplevel(qw/-width 500 -height 500 -background pink/);
    $top->title('OpenGL Demo');
    $top->waitVisibility;
   glpOpenWindow(parent=> hex($top->id), width => 450, height => 450);
    glClearColor(0, 0, 1, 1);
    glClear(GL_COLOR_BUFFER_BIT);
    glOrtho(-1, 1, -1, 1, -1, 1);
    glColor3f(0, 1, 0);
    glBegin(GL_POLYGON);
   
    $pi =  3.141592654;
    $d2r = $pi / 180.0;
    $nvert = 8;
    $dangle = 360 / $nvert;
    for ($angle = 0; $angle <= 359; $angle += $dangle) {
        $x = cos($angle * $d2r);
        $y = sin($angle * $d2r);
	glVertex2f($x, $y);
    }
    glEnd;
    glFlush;
}

MainLoop;