I have a situation where I would like to know the 'absolute' position of an item in a set with respect to DataObjectSet pagination. We inherited a site where comment participants referenced other comments by the ID/number -- e.g. first comment is always #1, 2nd comment #2, and so fourth.. and dialog looks like "Ditto what #39 says".
Anyhow... I thought this would be simple to implement but soon found it nearly impossible to access the current DataObjectSet of a <% control %> loop in order to determine page offset (e.g. PageLength * (CurrentPage -1)).
I ended up writing a patch to extend the DataObjectSet Iterators to include PageOffset, as well as a $PosInSet method to viewable data which essentially returns $Pos(PageOffset).
Perhaps there is a graceful out-of-box method to do this that I have overlooked -- or perhaps there's a more desirable approach in extending Sapphire to accomplish this; please let me know...
I've opened a ticket regarding this: http://open.silverstripe.org/ticket/6252 which includes the patch.