updated 03:45 pm EST, Thu February 24, 2011
Lion first with true high DPI display support
Among the changes found in the Mac OS X Lion preview is a new discovery of very high resolution technology that would be first in a mainstream desktop OS. Referred to as "HiDPI display modes," they would mimic the fourfold increase in resolution from scaling an iPhone app on an iPad but adjust every interface element to have the same relative size. The method spotted by MacRumors would greatly increase the detail but in a much more elegant way than before, where it had to use only vector scaling or multiple bitmaps and often couldn't scale at all.
The technique might need higher resolution artwork from developers, although Apple already has developers use very large icon sizes that in most cases would scale properly.
No clear sign exists of when the technology would be used in practice, and Apple is so far only exposing HiDPI when manually switched on in the Quartz debug mode.
A number of technical hurdles exist that revolve mostly around cost: even a 13-inch MacBook Pro would need a 2560x1600 screen, and a 27-inch iMac would need a difficult to achieve 5120x3200 resolution. Many of these extremely dense displays can sometimes have issues with slow response times and would need video chipsets with fast performance and a large amount of RAM to handle the frame buffer for the image.
The advancement may be a further clue that Apple's mystery large-scale investment relates to displays. Most have assumed that it related to mobile devices such as the rumored 2048x1536 iPad 3, but it could ultimately represent a comprehensive cash infusion that affects every screened product Apple makes.
Many operating systems can handle these resolutions by themselves, but the interface seldom scales and often requires manually boosting font and interface sizes to make the resolution usable.