I’ll start with a basic NSURL object as the value and see how far that takes things.
From my not so fresh memory, I think the limit you will hit there will be that the link in a NSURL/NSString form cannot be activated using VO-Space, for that I think you would need a custom link accessibility object with AXPress action. As mentioned, VO-Space had trouble to determine based on cursor position which link object to AXPress (e.g. when I last tried, it might not AXPress the link object at which cursor is - either fail or AXPress a different link object), but that might have changed in the meantime (e.g. in El Capitan), so as I suggested earlier you should do your own experiments here :-)
I don’t suppose there’s been any discussion on here about getting Apple to document these things?
I probably did not get to report it to rdar (no time for it at the moment), which you should, as there is the known truth of “what does not exists in rdar does not exist”. I think there might be at least 3 reasons for Apple not documenting these attributes:
1. Intentional - Apple wants to still have the leeway of changing the attribute semantics/names etc. in future OS releases and break things, before committing to a public API
2. Apple knows about the fact that the attributes have not been documented, but just did not get to documenting them yet.
3. Apple does not know about it.
Filing a rdar definitely helps for 3., could quite help for 2., and might theoretically speed things a little bit with 1.
Maybe someone else already filed the rdar, but it still helps to have your own rdar reported nevertheless (more rdars for the same issue could mean more priority given to them, you might formulate the rdar more clearly than someone else, etc.).
BR,
Boris
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