MP All Models desktops swapped: there has GOT to be a solution!

[larrytheo]

I have a Late 2013 Mac Pro trashcan running Monterey. (Yeah, it's about time for a new machine, but not quite yet.) I have two identical ACER displays that I use, let's call them Left and Right, since that his how the physical devices are configured. Left has always been designated as the main monitor and has the menu. Right is set up as the Extension monitor.

One day, a week or so ago, I booted up and the desktops were reversed. The main monitor display and menu were now on Right. To get the cursor from Right to Left, I had to move it to the far right edge of Right and then continue moving it to the right, at which point the cursor would enter from the left edge of Left. When I open the Displays control panel, it shows the main monitor display and menu still on Left, but that conflicts with the reality that the main monitor is on Right.

Now, I have seen numerous threads that seem to discuss this issue, but none have had a definitive fix for it, which is kind of crazy. I have tried SO much stuff, including:

- In the Display control panel, moving Right over to become Left. Although the control panel shows the switch, the actuality does not change.
- Resetting NVRAM and SMC
- unplugging the Mac for 15 seconds, then plugging back in and rebooting
- swapping the monitor cables at the Mac end (both monitors are plugged directly into Thunderbolt ports)
- swapping the monitor cables at the cable end
- unplugging Right so that the Mac is forced to use only Left, then plugging Right back in. It just reverts to Right.
- trashing Library>Preferences>com.apple.windowserver.plist
- cold booting (duh)

Nothing has worked. Everything was fine for years now, then suddenly, for no apparent reason, this happens. Clearly, the issue is software, not hardware, and it has got to be a setting or preference somewhere. What IS the answer to this?

 

[Bigwaff]

I have two identical ACER displays that I use

Model number and specs of displays?

 

[larrytheo]

Acer V246HQL.

But I managed to fix it by reinstalling the OS. It was NOT fixed immediately; it took quite a while to install, and then I had to fool around the Displays control panel a few times rearranging the displays, restart once or twice, and do a cold boot. And then it suddenly was OK and continues to be.

I guess that's the fix. That's gotta be some deep corruption going on in some register somewhere.

 

[Bigwaff]

Most likely the issue is related to this long standing feature request (or bug, depending on your perspective) for macOS

Weird monitor bugs people sent me in the last 5 years - Alin Panaitiu

I develop 🌕 Lunar, a macOS app for getting intelligent adaptive brightness on external monitors and controlling every aspect of your monitor using DDC and other obscure protocols. I get tons of email about Lunar, especially after it became my full time “job” in 2021. A lot of those emails...

notes.alinpanaitiu.com

 

[supremegopher]

For future reference, you might try (this is in Ventura, not sure the steps in Monterey) going to System Preferences -> Displays -> Advanced -> Click "Prevent automatic sleeping when the display is off". That fixed the problem for me on my M1 Mini. Not ideal to prevent the Mac from sleeping but it works for me. The issue actually started after a fresh reinstall for me. Macs apparently are finicky about displays.