I have solved this problem in the other way. How I wrote before, the pagination in this situation is working (when I put a &start=0, &start=1 in site-url). I have installed the countDocs extender in DItto:
http://forums.modx.com/thread/32686/count-child-documents-and-output-them
And I have written stupid simple snippet "mypager" to calculate link in pagination based on count of documents calling by ditto:
calling the pager:
[[mypager?c=`[[Ditto? &documents=`<?php echo $result ?>` &showInMenuOnly=`1` &tpl=`item_subdocs` &extenders=`countDocs` &display=`1` &tpl=`count` ]]`]]
($result is a dinamically created string like '9,12,23,123,123,412,1232')
mypager Snippet code:
<?php
if (is_numeric($c)) {
$marker = 0;
$i=1;
while ($c>$marker) {
echo '<a href="[(site_url)][~[*id*]~]?tag='.$_GET['tag'].'&start='.$marker.'">'.$i.'</a> ';
$marker+=4;
$i++;
}
}
?>
maybe it helps to someone