About read/unread topics (again!) - howto? Brainstorming..

Ok, in order to get that (at least to me) important feature, as Rickard said he was in little trouble to implement it, I suggest a little brainstorming to implement that properly.

Jansson proposed a solution with a cookie for every read topic; i must say, I really dislike that one; imagine, when reading a big forum, with hundreds of topics... you get hundreds of cookies...

What do I suggest... In fact, my primary idea was to stock in a cookie the serialized id's of read topics. How can that work? Each time the "last visit" is updated, you have to look if there have been any new messages since last one. I currently use such a system for one of my forums , works great, but i had to add a request for each page where last visit gets updated... _but_ i think the sql request i added is certainly already done anywhere else in the script... maybe in looking in that direction...

So, how it works, quite easy, you add each time "last visit" get's updated every new topic to the cookie, and delete in viewtopic.php the id from the topic being currently read from the cookie.

Any other idea? What do you think? How could we implement that? I really like that feature... Thanks for brainstorming