Touch datatype questions


Whilst writing my events binding, I came across 3 types:

SDL_TouchID, SDL_GestureID and SDL_FingerID.

I was wondering if they really should be signed entities. I found
SDL_RecordGesture which takes a SDL_TouchID and allows, -1, is that the
only negative value it allows? Do the other 2 allow negative values and
which if any? Just -1?

Also, do they really need to be 64 bit? Seems a rather huge available slots.