sub OnPreview {
  my( $this, $event ) = @_;

  my $prev = Wx::DemoModules::wxPrinting::Printout->new( $this->canvas, "Preview" );
  my $print = Wx::DemoModules::wxPrinting::Printout->new( $this->canvas, "Print" );
  my $preview = Wx::PrintPreview->new( $prev, $print );
  my $frame = Wx::DemoModules::wxPrinting::PreviewFrame->new( $preview, wxTheApp->GetTopWindow,
                                     "Printing Demo Preview", [-1, -1], [600, -1] );
  $frame->Initialize();

  $frame->Show( 1 );
}