sub centre_text{
  # centre_text( $text_control, $container );
  # Not enough error checking, really ...
  my ( $text_control, $container ) = @_;
  my ($container_width) = $container->GetSizeWH();
  my ($text_width) = $container->GetTextExtent( $text_control->GetLabel() );
  my ( $text_x, $text_y ) = $text_control->GetPositionXY();
  $text_control->Move( ($container_width-$text_width)/2, $text_y );
}