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

my $window = Gtk2::Window->new;
$window ->signal_connect( 'destroy' => \&delete_event );

my $canvas = Gnome2::Canvas->new();
$canvas->set_size_request(256,256);
$canvas->set_scroll_region(0,0,256,256);
my $root = $canvas->root();

my $item = Gnome2::Canvas::Item->new($root,
"Gnome2::Canvas::Ellipse",
x1 => 0,
y1 => 0,
x2 => 200,
y2 => 180,
fill_color=>"red",
outline_color=>"black"
);

$item->signal_connect(event=>sub {print "I got an event!\n"; });

$canvas->signal_connect (event => \&event_handler);
$window->add ($canvas);
$window->show_all;

Gtk2->main;
###########################################################3

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

    if ( $event->type eq "button-press" ) {
        print 'x->',$event->x,'  ','y->',$event->y,"\n";
    }    
}

sub delete_event {
Gtk2->main_quit;
return 0;
}
[download]

I have encountered a small problem when zooming. It seems that when you double click to drop a point it is not exactly where the mouse pointer is, it is off slightly. when you zoom in it gets worse. When you zoom closer it drops the point far to the right and vise versa when you zoom out. maybe someone can see why that is?

#Draggability of window
my $adj = Gtk2::Adjustment->new (1.00, 0.05, 5.00, 0.05, 0.50, 0.50);
my $dragger = Gtk2::Ex::Dragger->new( widget => $scwin,
    hadjustment => $scwin->get_hadjustment,
    vadjustment => $scwin->get_vadjustment,
    #update_policy => 'continous',
    #cursor => 'hand1'
    );

#Setup zooming
my $zoom = Gtk2::Label->new ("Zoom:");
$table->attach_defaults($zoom, 0, 1, 1, 2);
$adj->signal_connect (value_changed => \&zoom_changed, $canvas);
$zoom = Gtk2::SpinButton->new ($adj, 0.0, 2);
$zoom->set_size_request (50, -1);
$table->attach_defaults($zoom, 1, 2, 1, 2);

#handle the events
$canvas->signal_connect (event => \&event_handler);

$window->show_all;

Gtk2->main;
#------------------------------------------------
sub event_handler {
    my ( $widget, $event ) = @_;
    # print $widget ,' ',$event->type,"\n";
    
    #on 2 mouse presses, place waypoint 
    if ( $event->type eq "2button-press" ) {
        print 'x->',$event->x,'  ','y->',$event->y;
        
        #convert UTM to Lat and Long
        my $easting = $ps[0] * $event->x + 0.0 * $event->y + $mtp[3];
        my $northing = (-$ps[1]) * $event->y + 0.0 * $event->x + $mtp[
+4];
        my ($latitude,$longitude)=utm_to_latlon($ellipsoid,$zone,$east
+ing,$northing);
        print " ($latitude, $longitude)\n";
        
        #Drop icon
        my $tgroup = Gnome2::Canvas::Item->new ($root, 'Gnome2::Canvas
+::Group', x => $event->x, y => $event->y);
        Gnome2::Canvas::Item->new($tgroup, 'Gnome2::Canvas::Ellipse',
            x1 => 0,
            y1 => 0,
            x2 => 10,
            y2 => 10,
            fill_color => 'purple',
            outline_color => 'black');
            $tgroup->raise_to_top();
    }
    
    #on mouse press, pan the window
    if ( $event->type eq "button-press" ) {
        $dragger->start ($event);
    }
}
#------------------------------------------------
sub zoom_changed {
    my ($adj, $canvas) = @_;
    $canvas->set_pixels_per_unit ($adj->value);
}
[download]

UPDATE: I am receiving this error:

Gdk-CRITICAL **: gdk_property_change: assertion `type != GDK_TARGET_ST
+RING' fail
ed at C:/camelbox/site/lib/Gtk2/Ex/SyncCall.pm line 62.
[download]

I mentioned in the previous post, that "pixel zooming" is tricky to handle....it is only a "screen illusion" where the screen pixels are magnfied. Also you must be aware of the "center point of zoom"... it will default to (0,0) ... the upper left corner(accounting for the right-downward shift when zooming). Read perldoc Gnome2::Canvas and search for zoom. Also look at window-to-world and c2w.

I don't have an example handy, and you might want to ask on the Perl/Gtk2 maillist.

Before you get too deep into the Gnome2::Canvas, you may want to switch to the Goo::Canvas because it will save better. You can save the whole canvas as svg. Also it's demo shows how to change the center-point of zooming by setting the anchor, ( I don't know if it will work on Gnome2::Canvas)

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I'm not really a human, but I play one on earth CandyGram for Mongo