Digging through the build of Mac OS X Lion that was seeded to developers yesterday, MacRumors discovered the presence of “HiDPI display modes” which suggests that Apple is planning for the possibility of Mac displays running something similar to a Retina display sometime in the near future.
Developers would, as they have done on the iPhone, provide each UI element in two sizes, one in the size they currently are and then one at twice the resolution. It would work virtually identically to how Apple implemented the Retina display for the iPhone, with the high-resolution displays using the double sized UI elements so that physically the size of the elements would stay the same.
MacRumors gives the example of a 15” MacBook Pro that has a resolution of 1440x900 that could be doubled to 2880x1800 and then use an app’s UI 2X elements and which would leave the application’s UI elements the same physical size, but with much greater detail. Apple had previously dabbled in the notion of creating OS X a resolution independent OS through a number of methods from using vector graphics to providing bitmaps for multiple screen resolutions, but none had previously eventuated.
The HiDPI mode is not turned on by default and must be done so through Lion’s Quartz debug in Xcode.