External display used to work perfectly on my Macbook Air (Nov 2011 model, I think 4.2). It stopped working after upgrading to Ubuntu 13.04.
External displays are no longer detected. xrandr always shows external ports as disconnected.
This bug makes the laptop essentially useless, since the ability to make presentations is an essential feature for me.
I've seen a bug report on this: http://email@example.com/msg4037538.html But no solution or workaround.
Does anyone have a workaround?