I have some complicated cart validation logic that I need to check every time the qty of a product in the cart changes. I don't need to check the logic when a product is added or removed entirely, just when the qty changes.
I am observing
sales_quote_item_qty_set_after but that fires every time you load the cart, add a product, remove a product, etc. I would assume that I would want to grab the qty of all products in the cart to start with and then compare that with the items in the sales_quote_item_qty_set_after event. I should then be able to identify the product that started with a qty > 0, ended with a qty > 0, and a delta <> 0. I'm having trouble figuring out the logic for that.