Code used when a bag is opened?
 

Does anyone know where this is handled in the emu code? It seems to be hiding from me.

Seeing as how slots inside a bag are just other item slots (251 through 260 according to the Wiki), I assume this is done client side, just like the bank (it is moving items from 1 slot to another).

Is there something in particular you're trying to do with it?

Well, I imagine that there has to be code in the source for when a tradeskill object (like a forge) is opened and closed, so maybe there is something for bags as well. Not to derail this post, but I would love to see code in for when a forge (or aug pool, etc) is closed with no drop items in it that it will return the items like it does on live.