Is it definitely upscaling a 320x568 buffer, or is it fractionally scaling the UIView hierarchy to render at 375x667 or 414x736? My impression from the article was that it is doing the latter.
In the keynote they seemed to imply that existing apps would appear sharp on the new displays, and this sort of rendering trick would achieve that.
In the keynote they seemed to imply that existing apps would appear sharp on the new displays, and this sort of rendering trick would achieve that.