I have a 13" MBP (Early 2011) plugged it to a Dell U2711 monitor via DisplayPort.
I have successfully enabled HiDPI mode, using Quartz Debug the problem is that the screen won't run at the HiDPI equivalent of the screen's native resolution. i.e 1440×720 HiDPI (2560×1440). The screen's maximum resolution of 2560×1440 is recognised & working.
The best it will do is 960x720HiDPI (1920×1440), which seems strange as most of the documentation suggests HiDPI will only work at pixel doubling resolutions.
Is it possible to force the MBP to run the display at 1440×720 HiDPI on a screen that supports 2560×1440 native pixel resolution?
Best Answer
After a lot of messing about I managed to get this working in two ways.
Screenshot 1 (Warning, large file)
This mode is actually 1280x720 HiDPI (2560x1440).
Screenshot 2 (Warning, large file)
Yay!
I was going to embed screenshots of these new menus, but they are now insanely huge due to HiDPI mode, so I just linked to them instead.