$item->set_simple_transform ($x, $y, $scale, $rotation) 

##</code><code>##

sub event_handler{

my ( $widget, $event ) = @_;
 print $widget ,' ',$event->type,"\n";

my ($x,$y) = ($event->x,$event->y);
        print "$x  $y\n";

}

##</code><code>##

#!/usr/bin/perl
use warnings;
use strict;
use Gnome2::Canvas;
use Gtk2 '-init';


my $window = Gtk2::Window->new();
my $sw = Gtk2::ScrolledWindow->new();
 $sw->set_shadow_type ('etched-out');
 $sw->set_policy ('automatic', 'always');
 $sw->set_placement('top-right');
 $sw->set_size_request (500, 500);
 $sw->set_border_width(0);
 
 my $black = Gtk2::Gdk::Color->new (0x0000,0x0000,0x0000);
 my $white = Gtk2::Gdk::Color->new (0xFFFF,0xFFFF,0xFFFF);

  my $canvas = Gnome2::Canvas->new_aa();
  $canvas->set_size_request(500,500);
  $canvas->set_scroll_region(0,0,1000,1000);
  $canvas->modify_bg('normal',$white);
  $canvas->set_center_scroll_region (0);

  my $root = $canvas->root();


  my @points = (50,50,80,20,90,100);
  my $poly = Gnome2::Canvas::Item->new ($root, 'Gnome2::Canvas::Polygon',
                 points => \@points,
                 fill_color_rgba => 0x0000ff80,
                 outline_color => 'black');
 
  $poly->{'points'} = \@points;    
 
  my $id = Glib::Timeout->add (100, sub {
             &rotate($poly,10);
             return 1;
        	    });


# $ztree->set_pixels_per_unit(2);

 $sw->add($canvas);
 $window->signal_connect('destroy'=>sub { Gtk2->main_quit(); });
 $window->set_default_size(450,350);
 $window->add($sw);
 $window->show_all();

 Gtk2->main();

############################################################################    
sub rotate {
    my ( $item, $degree ) = @_;

	my @points = @{$item->{'points'}};
        $item->destroy;

       @points = &rotate_poly($item, $degree);

       $poly = Gnome2::Canvas::Item->new ($root, 'Gnome2::Canvas::Polygon',
                   points => \@points,
                  fill_color_rgba => 0xff000080,
	          outline_color => 'black');

        $poly->{'points'} =  \@points;
}
####################################################################3
sub rotate_poly {
    my ($ind, $angle, $midx, $midy) = @_;
    
    # Get the old coordinates.
    my @coords = @{$ind->{'points'}};

    # Get the center of the poly. We use this to translate the
    # above coords back to the origin, and then rotate about
    # the origin, then translate back. (old)

    ($midx, $midy) = _get_CM( @coords ) unless defined $midx;

    my @new;

    # Precalculate the sin/cos of the angle, since we'll call
    # them a few times.
    my $rad = 3.1416*$angle/180;
    my $sin = sin $rad;
    my $cos = cos $rad;

    # Calculate the new coordinates of the line.
    while (my ($x, $y) = splice @coords, 0, 2) {
	my $x1 = $x - $midx;
	my $y1 = $y - $midy;

	push @new => $midx + ($x1 * $cos - $y1 * $sin);
	push @new => $midy + ($x1 * $sin + $y1 * $cos);
    }

    # Redraw the poly.
    return @new;
}
#################################################################
# This sub finds the center of mass of a polygon.
# I grabbed the algorithm somewhere from the web.
# I grabbed it from Ala Qumsieh's RotCanvas :-)
sub _get_CM {
    my ($x, $y, $area);

    my $i = 0;

    while ($i < $#_) {
	my $x0 = $_[$i];
	my $y0 = $_[$i+1];

	my ($x1, $y1);
	if ($i+2 > $#_) {
	    $x1 = $_[0];
	    $y1 = $_[1];
	} else {
	    $x1 = $_[$i+2];
	    $y1 = $_[$i+3];
	}

	$i += 2;

	my $a1 = 0.5*($x0 + $x1);
	my $a2 = ($x0**2 + $x0*$x1 + $x1**2)/6;
	my $a3 = ($x0*$y1 + $y0*$x1 + 2*($x1*$y1 + $x0*$y0))/6;
	my $b0 = $y1 - $y0;

	$area += $a1 * $b0;
	$x    += $a2 * $b0;
	$y    += $a3 * $b0;
    }

    return split ' ', sprintf "%.0f %0.f" => $x/$area, $y/$area;
}
####################################################################