I recently upgraded my Mac mini to OS X Lion (from Snow Leopard) and discovered two very annoying problems that were not present in Snow Leopard. Both stem from the fact that I have a two-monitor setup: a regular computer monitor connected to the display port as my primary display, and a television connected to the HDMI port as my secondary display.
The first problem I encountered was when I tried to select HDMI as the audio source. I couldn’t. I tried to select it in the Sound panel of the System Preferences, but it kept reverting back to “headphones” as the output (“headphones” means anything plugged into the headphone jack—in my case it’s desktop speakers). After some Google searching that lead nowhere, I decided to unplug the speakers to see what happened and low and behold, I was able to select HDMI for audio output. After further searching, I discovered that Apple considers this a feature and not a bug. This Apple support article says this behavior was added “to mimic the mutually exclusive speaker behavior of iMac and Apple display products that use Mini DisplayPort or Thunderbolt,” whatever the heck that means. Their only “solution” is to unplug the speakers from the back of the Mac mini every time you want to use HDMI for sound. What a pain (and a bunch of wear and tear on the headphone jack).
The second problem is that apps will not display full screen in a secondary monitor. If you attempt to set them to full screen, they will jump to the primary monitor. I used to be able to play video full screen on the television while working (or surfing the Web or whatever) on my main monitor; I can no longer do that. I can view video in the secondary monitor in a window, but then I’m stuck with the window title and status bars, and the video is never as big as it could be.
The HDMI sound issue is an inconvenience, but the full screen video issue is ridiculously bad. A quick Google search turns up a ton of forum posts about this (even in Apple’s own support forums) by people who are scratching their heads at best and outraged at worst. Lion was released almost a year ago, and Apple shows no signs of wanting to address this issue. Shame on them.