Inventory System Question

How would one begin to attempt a drag and drop inventory system that did not rely on a grid system, but rather a coordinate system. The language used doesn’t bother me much, so feel free to respond with examples in whatever is comfortable.

The best example I could find was from Darkfall Online.

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I know this is an incredibly general question, but I need a good foundation before I start butchering it from the start.

Since Darkfall had no limit other then weight should be achievable with a simple array of items. As new items were added I would say change the depth of the items that are older to larger numbers(so they properly don’t clip new items coming in) but if they are selected by the mouse click change them to be a small number depth again.

If your trying to save it out… I’d definitely just say keep the coordinates of each item inside the bag.