This one is pretty short and simple once you get down to it.
I recently set up a client’s boardroom with a really sweet 75″ Sony 4K Android TV, a Logitech Group video conferencing webcam, a Mac mini and a Sonos Playbar. Everything was really sweet, except that the Mac mini refused to treat the TV as a Retina or HiDPI screen.
The result of this was that the Mac mini would use the TV at it’s native resolution – it saw the TV as a monitor running at 3840 x 2160. What I wanted it to do was treat it as a 1920 x 1080 display, but in Retina mode, so UI elements would be a reasonable size from across the room but text and graphical elements would still be sharp.
I was able to enable HiDPI modes by first running the following command in Terminal:
sudo defaults write /Library/Preferences/com.apple.windowserver.plist DisplayResolutionEnabled -bool true
Once this had been applied, I rebooted and logged in again. Then, when I went into my Displays preferences, instead of selecting Resolution: Best for built-in display, I held down the Option key and clicked on Scaled.
Scrolling down to the bottom of the list revealed the HiDPI modes – I selected 1920 x 1080 (HiDPI) and voila! I was running in Retina mode and could comfortably use the Mac mini from across the other side of the room.