#!/usr/bin/perl -w
# This code was created by Jeff Molofee '99
# (ported to SDL by Sam Lantinga '2000)
# (ported to Perl/SDL by Wayne Keenan '2000)
#
# If you've found this code useful, please let me know.
#
# Visit me at www.demonews.com/hosted/nehe

use strict;
use Getopt::Long;

use SDL;
use SDLx::App;
use SDL::OpenGL;
use SDL::Event;

my $arg_screen_width  = 640;
my $arg_screen_height = 512;
my $arg_fullscreen    = 0;

GetOptions(
	"width:i"     => \$arg_screen_width,
	"height:i"    => \$arg_screen_height,
	"fullscreen!" => \$arg_fullscreen,

) or die $!;

main();
exit;

sub main {
	my $done = 0;

	my $app = SDLx::App->new(
		-title  => "Jeff Molofee's GL Code Tutorial ... NeHe '99",
		-icon   => "icon.png",
		-width  => $arg_screen_width,
		-height => $arg_screen_height,
		-d      => 16,
		-gl     => 1,

	);
	$app->fullscreen() if ($arg_fullscreen);

	SDL::ShowCursor(0);

	my $event = SDL::Event->new;
	$event->set( SDL_SYSWMEVENT, SDL_IGNORE ); #

	InitGL( $arg_screen_width, $arg_screen_height );

	while ( !$done ) {

		DrawGLScene();

		$app->sync();

		$event->pump;
		$event->poll;

		if ( $event->type == SDL_QUIT ) {
			$done = 1;
		}

		if ( $event->type == SDL_KEYDOWN ) {
			if ( $event->key_sym == SDLK_ESCAPE ) {
				$done = 1;
			}
		}
	}
}

#########################################################################
#Pretty much in original form, but 'Perlised'

sub InitGL {
	my ( $Width, $Height ) = @_;

	glViewport( 0, 0, $Width, $Height );
	glClearColor( 0.0, 0.0, 0.0, 0.0 ); # This Will Clear The Background Color To Black
	glClearDepth(1.0);                  # Enables Clearing Of The Depth Buffer
	glDepthFunc( GL_LESS() );           # The Type Of Depth Test To Do
	glEnable( GL_DEPTH_TEST() );        # Enables Depth Testing
	glShadeModel( GL_SMOOTH() );        # Enables Smooth Color Shading

	glMatrixMode( GL_PROJECTION() );
	glLoadIdentity();                   # Reset The Projection Matrix

	gluPerspective( 45.0, $Width / $Height, 0.1, 100.0 ); # Calculate The Aspect Ratio Of The Window

	glMatrixMode( GL_MODELVIEW() );
}

# The main drawing function.
sub DrawGLScene {
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); # Clear The Screen And The Depth Buffer
	glLoadIdentity();                                     # Reset The View

	glTranslate( -1.5, 0.0, -6.0 );                       # Move Left 1.5 Units And Into The Screen 6.0

	# draw a triangle
	glBegin(GL_POLYGON);                                  # start drawing a polygon
	glVertex( 0.0,  1.0,  0.0 );                          # Top
	glVertex( 1.0,  -1.0, 0.0 );                          # Bottom Right
	glVertex( -1.0, -1.0, 0.0 );                          # Bottom Left
	glEnd();                                              # we're done with the polygon

	glTranslate( 3.0, 0.0, 0.0 );                         # Move Right 3 Units

	# draw a square (quadrilateral)
	glBegin(GL_QUADS);                                    # start drawing a polygon (4 sided)
	glVertex( -1.0, 1.0,  0.0 );                          # Top Left
	glVertex( 1.0,  1.0,  0.0 );                          # Top Right
	glVertex( 1.0,  -1.0, 0.0 );                          # Bottom Right
	glVertex( -1.0, -1.0, 0.0 );                          # Bottom Left
	glEnd();                                              # done with the polygon

}