How to never draw "Jaggies" in the first place considering resolution and scale
Well you can render at higher resolution and sample down thhis is called FSAA and should just work without much change to render code. FSAA has the benefit of not having a conflation problem whereas smoothing does.


No, something has to emit this info.
You take the derivate (the gfx card does this for you) of the surface varying to determine how far the step would take you in your pixel. if its over the edge then you antialias.