Unread count for items in Mail.app-styled NSOutlineView

FROM : Leonardo Cassarani
DATE : Sat Mar 01 23:35:18 2008

Hi all

I'm trying to make a lateral sidebar that is similar to Mail.app's or 
iTunes'. It all works well with a NSOutlineView with the "Data source" 
display option, but I was wondering how could I get the single items 
to draw the equivalent of the "unread count" for folders in Mail.app's 
sidebar, or the number of active downloads in iTunes'.

I guess it's a fairly common UI element, and I was wondering if there 
was an "official" way to do it, and if not is there any sample source 
code that you know of which I can take some inspiration from?

Thanks.
Leonardo Cassarani