displayhdmimacosthunderbolt
I messed up the settings for the clamshell display mode on my MacBook Pro. I can't get my external display to work when I close my laptop. I can get all other modes working (standard mirroring and shared desktop) except for clamshell.
I've tried using defaults to remove com.apple.windowserver, but that hasn't helped.
According to this source, this should work. This other source confirms it. These are the troubleshooting steps I would try:
Run all software updates on both the iMac and MacBook Air. A lot of times there are firmware updates that address issues like this.
Open System Preferences > Displays and click Detect Displays.
Reset the PRAM on both the iMac and the MacBook Air by restarting the computer and holding ⌘+⌥+P+R on boot but until you hear the POST chime twice. Then you can let go and boot normally. Be sure to do this on both machines.
Try going through these steps and let me know if you're able to resolve the issue.
DockSpaces is nice and convenient, but annoyingly unscriptable. So, I wrote two little shell scripts, one to change to my desktop Dock and one to change to my mobile Dock.
The desktop script is triggered on arrival in my Home context in ControlPlane, and the mobile script is triggered by departure from it.
The desktop context is defined based on the presence of my external displays:
Here's how the scripts work:
I save a copy of both Docks in my Documents folder (the Dock configuration is stored in ~/Library/Preferences/com.apple.dock.plist).
When I switch from one to the other, I replace the appropriate file in my Documents folder with the current file in my Preferences so that changes I've made to the Dock are saved. Then I copy the alternate Dock from my Documents to my Preferences. Finally, the Dock process is restarted so that the changes take effect.
The Scripts:
To Desktop:
#!/bin/bash
cp ~/Library/Preferences/com.apple.dock.plist ~/Documents/Docks/mobile.plist
cp ~/Documents/Docks/desktop.plist ~/Library/Preferences/com.apple.dock.plist
killall Dock
To Mobile:
#!/bin/bash
cp ~/Library/Preferences/com.apple.dock.plist ~/Documents/Docks/desktop.plist
cp ~/Documents/Docks/mobile.plist ~/Library/Preferences/com.apple.dock.plist
killall Dock
Best Answer
Neither of the above two answers has solved the problem. Maybe I can move the ball forward a couple of inches ...
I, too, clicked on the wrong resolution for my external monitor and now I can only use the monitor in "Mirror Displays" mode. When in separate mode, the external monitor is black except for a message saying "DVI NO SIGNAL". I cannot see the System Preferences > Displays control dialog for that monitor because it's on the black screen. When I return to Mirror Displays mode, I can see that the wrong resolution is set and when I set the proper one, I get both monitors work -- but ONLY if I stay in Mirror Displays mode.
This sounds like exactly the problem that @CyberSkull reported, same cause, same results.
I can verify that
Colorsync Utility.appdoes nothing for resolution, only color profile, and my profile is likewise set to Factory Default.Similarly, the answer about
hmscreenis about Arrangement, not Resolution. I looked at the doc forhmscreenand it confirms that it deals with ScreenIDs, screen positions, and which screen is the main screen, not resolution. I'm afraid to try it to set the black external monitor to be my main screen, and that seems to be the only experiment it might be useful for.Finally, I found a solution that worked for me! In another Ask Different question, "change screen resolution with AppleScript", more than one AppleScript solution was offered (which I didn't try) AND @user332214 posted a link to a utility developed at the University of Utah, Display Manager which worked for me.
Display Manager supposedly has a GUI interface available, but I couldn't find where it had been installed to invoke it, so I used the command line interface. Once it was installed, the command line:
successfully changed my external monitor to 1920x1200 resolution, my usual, from the erroneous 1920x1080 that I had accidentally set and which resulted in a black screen except in Mirror Displays mode.
It works.