I'm curious to know how Mac handles apps moving between a Retina Display Mac and a non-Retina display (Thunderbolt, whatever). Apps need to be updated to handle retina, otherwise they draw double pixels.. so what happens when you have a window that's halfway between a Retina and non-Retina?
My two guesses:
1. The entire window draws as doubled pixels, as if it didn't support Retina at all
2. The window gets two separate paint events, one retina and one non-retina.
I don't think apps need to be updated, the OS will just send two separate screen redraws to the app. If you put a window half on an 8-bit color screen and half on a 16-bit color screen it works fine too, I don't see why this would be different.
I'm pretty sure that the drawing system emulates the x2 resolution boost introduced in iOS devices - apps will draw in points, and 1pt = 2px for a retina Macbook. Switching between 1x and 2x drawing should be seamless - one exception being that images would have to be reloaded when going from 1x to 2x.
1 happens, as long as the bigger part of the window is on the non-Retina display. If the bigger part of the window is on the Retina display, the window only gets a Retina paint event and the non-Retina display shows a downscaled version.
Source: manual testing under 10.7.4 with HiDPI resolutions activated using QuartzDebug
My two guesses: 1. The entire window draws as doubled pixels, as if it didn't support Retina at all 2. The window gets two separate paint events, one retina and one non-retina.
Anyone know how this works yet?