sub keep_on_top {
    my $w = shift;
    my($wrapper) = $w->toplevel->wrapper;
    eval {
        if (!grep { $_ eq '_NET_WM_STATE_STAYS_ON_TOP' } $w->property('get', '_NET_SUPPORTED', 'root')) {
            die "_NET_WM_STATE_STAYS_ON_TOP not supported";
        }
        $w->property('set', '_NET_WM_STATE', "ATOM", 32,
                     ["_NET_WM_STATE_STAYS_ON_TOP"], $wrapper);
    };
    if ($@) {
        warn $@;
        0;
    } else {
        1;
    }
}