use Tk::widgets qw/Canvas/;                                        
use base  qw/Tk::Derived Tk::Canvas/;

sub ClassInit 
{  
    my ($class, $mw) = @_; 
    $class->SUPER::ClassInit($mw); 
    $mw->bind($class, "<1>" =>'pick_one' ); 
    return $class; 
}