#!/usr/bin/perl

# This example exists in three different versions,
#  one using OpenGL.pm
#  one using SDL::OpenGL (this one)
#  one using PDL::Graphics::OpenGL
# It's main purpose is to show how different OpenGL-implementations in perl
# differ.

use strict;
use Gtk2 '-init';
use Gtk2::GLExt;
use SDL::OpenGL;

# Compensate for missing functionality in SDL::OpenGL
use constant GL_NICEST => 0x1102;
use constant GL_COMPILE => 0x1300;

# this is nothing, a better example should be created!

use Data::Dumper;

my $length = 20;
my $width = 12;
my $height = 8;

my $room;
my $room_rot;
my $room_ang = 0;
my @room_pos = (0, 0, 3 * -$length);

my $source;

my @corners = ();
# ceiling
push @corners, [ $width, $height,-$length];
push @corners, [-$width, $height,-$length];
push @corners, [-$width, $height, $length];
push @corners, [ $width, $height, $length];
# floor
push @corners, [ $width,-$height, $length];
push @corners, [-$width,-$height, $length];
push @corners, [-$width,-$height,-$length];
push @corners, [ $width,-$height,-$length];
# front wall
push @corners, [ $width, $height, $length];
push @corners, [-$width, $height, $length];
push @corners, [-$width,-$height, $length];
push @corners, [ $width,-$height, $length];
# back wall
push @corners, [ $width,-$height,-$length];
push @corners, [-$width,-$height,-$length];
push @corners, [-$width, $height,-$length];
push @corners, [ $width, $height,-$length];
# left wall
push @corners, [-$width, $height, $length];
push @corners, [-$width, $height,-$length];
push @corners, [-$width,-$height,-$length];
push @corners, [-$width,-$height, $length];
# right wall
push @corners, [ $width, $height,-$length];
push @corners, [ $width, $height, $length];
push @corners, [ $width,-$height, $length];
push @corners, [ $width,-$height,-$length];

my @sources = ();
# source 1
push @sources, [ 1,-1,1-$length];
push @sources, [-1,-1,1-$length];
push @sources, [-1, 1,1-$length];
push @sources, [ 1, 1,1-$length];

my @rays = ();

do_rays();

sub do_rays
{
	my ($x, $y, $z);
	$x = ($sources[0][0]+$sources[1][0]) / 2;
	$y = ($sources[1][1]+$sources[2][1]) / 2;
	$z = $sources[0][2];
	my $len = $length*2;
	my $ang = (45 * 180) / 3.14;
	my $tmp = $len*cos($ang);

	push @rays, [ [1, 1, 1, 0], [$x, $y, $z], [$x, $y, $z+$len] ];
	push @rays, [ [1, 0, 0, 0], [$x, $y, $z], [$x, $y+$tmp, $z+$len] ];
	push @rays, [ [1, 0, 0, 0], [$x, $y, $z], [$x, $y-$tmp, $z+$len] ];
	push @rays, [ [1, 0, 0, 0], [$x, $y, $z], [$x+$tmp, $y, $z+$len] ];
	push @rays, [ [1, 0, 0, 0], [$x, $y, $z], [$x-$tmp, $y, $z+$len] ];
}


main();

sub main
{

	my $glconfig;

	my $window;
	my $vbox;
	my $drawing_area;
	my $button;

	# Init GtkGLExt.
	Gtk2::GLExt->init;

	# Try double-buffered visual
	$glconfig = Gtk2::Gdk::GLExt::Config->new_by_mode
				(['rgb', 'depth', 'double']);

	unless( $glconfig )
	{
		print "*** Cannot find the double-buffered visual.\n";
		print "*** Trying single-buffered visual.\n";

		# Try single-buffered visual
		$glconfig = Gtk2::Gdk::GLExt::Config->new_by_mode
					(['rgb', 'depth']);

		unless( $glconfig )
		{
          		print "*** No appropriate OpenGL-capable "
			     ." visual found.\n";
			exit 1;
		}
	}

	# Top-level window.

	$window = Gtk2::Window->new;
	$window->set_title ("Reflections");

	# Perform the resizes immediately if on win32
	$window->set_resize_mode ('immediate') if( $^O eq 'MSWin32' );

	# Get automatically redrawn if any of their children changed allocation.
	$window->set_reallocate_redraws (1);

	$window->signal_connect (delete_event => sub { Gtk2->main_quit; 1});

	# VBox.
	$vbox = Gtk2::VBox->new (0, 0);
	$window->add($vbox);
	$vbox->show;

	# Drawing area for drawing OpenGL scene.
	$drawing_area = Gtk2::DrawingArea->new ();
	$drawing_area->set_size_request (640, 512);

	# Set OpenGL-capability to the widget.
	$drawing_area->set_gl_capability ($glconfig, undef, 1, 'rgba-type');

	$drawing_area->signal_connect_after (realize => \&realize);

	$vbox->pack_start ($drawing_area, 1, 1, 0);

	$drawing_area->show;

	# Simple quit button.
	$button = Gtk2::Button->new ("_Quit");

	$button->signal_connect (clicked => sub { Gtk2->main_quit; });

	$vbox->pack_start ($button, 0, 0, 0);

	$button->show;

	# Show window.
	$window->show;

	Glib::Timeout->add( 30, \&draw_scene, $drawing_area );

	# Main loop.
	Gtk2->main;

	return 0;
}

sub realize
{
	my $widget = shift;
	my $data = shift;

	my $glcontext = $widget->get_gl_context;
	my $gldrawable = $widget->get_gl_drawable;

	# OpenGL BEGIN
	return unless( $gldrawable->gl_begin ($glcontext) );

	my @LightAmbient = ( 0.5, 0.5, 0.5, 1.0 );
	my @LightDiffuse = ( 1.0, 1.0, 1.0, 1.0 );
	my @LightPosition = ( 0.0, 0.0, 2.0, 1.0 );

	my $alloc = $widget->allocation;
	glViewport(0, 0, $alloc->width, $alloc->height);
	glShadeModel(GL_SMOOTH);
	glClearColor(0, 0, 0, 0);
	glClearDepth(1.0);
	glEnable(GL_DEPTH_TEST);
	glDepthFunc(GL_LEQUAL);
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

	glLight(GL_LIGHT1, GL_AMBIENT, @LightAmbient);
	glLight(GL_LIGHT1, GL_DIFFUSE, @LightDiffuse);
	glLight(GL_LIGHT1, GL_POSITION, @LightPosition);
	glEnable(GL_LIGHT1);

	glPolygonMode( GL_BACK, GL_FILL );
	glPolygonMode( GL_FRONT, GL_LINE );

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45.0,$alloc->width/$alloc->height,0.1,100.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	$room = glGenLists(3);

	my @tmp = @corners;

	glNewList($room, GL_COMPILE);
		glBegin(GL_QUADS);
		glColor(0.75, 0, 0, 1);
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glColor(0, 0, 0.75, 1);
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glColor(0, 0.75, 0, 1);
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glEnd();
	glEndList();

	$source = $room+1;

	@tmp = @sources;
	glNewList($source, GL_COMPILE);
		glBegin(GL_QUADS);
		glColor(1, 1, 1, 1);
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glVertex(@{shift(@tmp)});
		glEnd();
	glEndList();


	$gldrawable->gl_end;
	# OpenGL END
}

# The main drawing function.
sub draw_scene
{
	my $widget = shift;

	my $glcontext = $widget->get_gl_context;
	my $gldrawable = $widget->get_gl_drawable;

	# OpenGL BEGIN
	return unless( $gldrawable->gl_begin ($glcontext) );

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glLoadIdentity();
	glTranslate(@room_pos);
	glRotate($room_rot, 0, 1, 0);
	glRotate(5, 1, 0, 0);
	glCallList($room);
	glCallList($source);

	glBegin(GL_LINES);
	foreach (@rays)
	{
		glColor( @{$_->[0]} );
		glVertex( @{$_->[1]} );
		glVertex( @{$_->[2]} );
	}
	glEnd();

	$room_ang += 0.1;
	$room_rot += 0.5;

	if( $gldrawable->is_double_buffered )
	{
		$gldrawable->swap_buffers;
	}
	else
	{
		glFlush ();
	}

	$gldrawable->gl_end;

	1;
}