Help or issue (?) with Virtual Displays and multiple users

[BrentEubanks]

I am using Virtual Displays to get 3840x1620 HiDPI resolution on a Dell Ultrasharp U4021QW with an M2 Macbook Air. (Without Virtual Displays the best HiDPI resolution I can get is 3072x1296.)

So far this works great when logged in as one user. However, I have two user accounts on this machine, one that I use for work and one for personal stuff. When I switch between them, I start having problems.

I'm not sure if what I am running into is a bug/issue or if this is a problem with how I am using VDs or how I have BetterDisplays configured, so before posting an Issue I wanted to see if I could get any advice here.

Behavior:

• Log in as User A, BetterDisplays launches with VD mirroring the Dell display at 3840x1620 HiDPI. Built in display is off/lid is closed. Though mirroring is being used, Mac's "screen mirroring" is NOT shown as active in the menu bar. Everything works great.
• Switch to User B. Everything works great. User B display is at 3840x1620 HiDPI. Everything works great.
• Switch back to User A. Menu bar icon now shows that "screen mirroring" IS active. Left side of menu bar (Apple icon, File/ Edit/View etc menu) is no longer responsive to mouse clicks, though everything else works.

To restore normal behavior, I have to kill and restart BetterDisplays.

Note that the same issue seems to arise whether I have BetterDisplays set to run on login for both accounts, or just for User A. Originally I had though this was happening because I was running two instantiations of BetterDisplays but after some testingt that does not seem to be the issue.

Is this a?

1. configuration error that I can correct
2. a known issue with a known workaround
3. a new issue/bug that I should write up

Thanks!

[waydabber]

Huhh. Although BetterDisplay should work mostly fine when it is running in multiple instances for different users (for some operations the app checks if the user has console or not), using virtual screen mirroring like this is totally untested. One BD instance for sure should recognize the virtual screen created by the other instance as a foreign system virtual screen, but should not be able to manage it properly.

Generally macOS have various issues with mirrored virtual screens even without the added complexity of a multi-user scenario, so I am not really sure whether you experience is an other of such macOS bugs or not (I suppose it is).

[BrentEubanks]

Thanks for the reply.

When I disable BetterDisplays, I run at 3072x1296 but the default is 2560x1080. What's interesting is that in the lock screen (whether I log out or not) the resolution reverts to the default. However, when I am running VD, that doesn't happen - the adjusted resolution (and the VD) persists across the lock screen and the second user.

What I am wondering is if there is some way to sandbox the VD session, or indeed BetterDisplays altogether, to a single user session. I don't really need the higher resolution in the second user session - it would be nice, but it's much more important to me to have it available in my primary user session, and to be able to switch between users without screwing anything up.

Can you think of a way to make that work?

[waydabber]

You should be able to interact with an other user's BetterDisplay process using betterdisplaycli and turn the virtual screen on/off. You'll need to disable CLI integration on the secondary user to avoid confusion/race condition between the two running apps when using CLI though. This might be be to a simple solution to the problem.

[BrentEubanks]

Still hoping for some clarity on these instructions (see earlier reply below - I realize I probably should have been replying in this box rather than in the "suggest an answer" box - sorry). Thanks!

[BrentEubanks]

Can you tell me how to do that, or point me to the relevant section of the documentation? I'm afraid that what you're referring to is part of the program that is entirely unfamiliar to me.

I'm not entirely sure I even understand what you are suggesting. For reference, User A is the primary user who needs the higher resolution enabled by Betterdisplays Virtual Display. User B is the secondary user who can run a native resolution without Betterdisplays.

My thought was to somehow run Betterdisplays in a "sandboxed" fashion that keeps it confined to User A's session so that User B is simply not affected - assuming that's even possible.

Your suggestion sound instead like somehow User B would disable (?) Betterdisplays for themselves through the command line interface? I'm not sure how that would work, but I'm also not sure I'm understanding the suggestion correctly to begin with.

Can you clarify?

Thanks

[waydabber]

Hi there, yes, here is the documentation on CLI features: https://github.com/waydabber/BetterDisplay/wiki/Integration-features,-CLI

Here are some examples on how to manage virtual screens using CLI: #2521 (comment)

[BrentEubanks]

Thanks! Just to clarify the intent of your suggestion, you were proposing that I use the CLI to "discard" the VD automatically when I log in as User B. Is that correct?

I ask for the sake of understanding, and for the sake of anyone else who finds this thread later on, because - Haha! - it turns out that I was wrong about the etiology of this whole situation.

Yesterday, while I was NOT running BetterDisplays at all, I had the exact same bug appear! At first I was dismayed, thinking that BD was somehow running in the background. Then I did a little googling and realized that what I was seeing was some version of a well-known screen mirroring bug that seems to have been introduced in OS 15.1 or 15.2.

A couple of interesting things about this, which I report here just for your information:

• It seems to happen pretty randomly and inconsistently. It doesn't happen every time I switch users, only occassionally.
• It appears to be made more common by having a Virtual Display enabled. When I was running a VD, it happened probably 50% of the time when I switched users. Without a VD running, it happened so infrequently that I didn't figure out that it wasn't a VD-specific bug for several days.
• A number of places (https://www.reddit.com/r/MacOS/comments/1hc5to9/macos_152_has_a_new_setting_when_using_a_tv_as/) where they discuss a bug that is at least very similar if not the same bug, using Betterdisplays is one of the suggested workarounds!

The fix I ultimately landed on was recommended in a post that I unfortunately can no longer find. That post recommended a couple of solutions.

• One was to delete com.apple.windowserver.displays.plist in /Library/Preferences. I didn't actually have to do this, but I mention it again for the record and your information.
• The other was to change the system setting for Control Center for screen mirroring to display in the menu bar from "show when active" to "never". I did this, and so far the issue has not recurred, when when running Betterdisplays with a Virtual Display. Fingers crossed that it stays fixed!

Anyway, sorry about the confusion and the false alarm, and thank you for your support and patience as I worked through this. I apologize for blaming your program incorrectly - I really did think it was being cased by the VD! Hopefully my report is sufficient to provide some useful information in compensation for wasting your time. And I will be registering Betterdisplays Pro shortly!

Thanks for helping me get the most out of my (stupidly expensive) new monitor! (Dell Ultrasharp U4025QW. My gods it's gorgeous. It's probably going to save me at least a diopter of eyestrain over the next decade.)

[waydabber]

Thanks @BrentEubanks for the explanation and write-up!

[BrentEubanks]

So it turns out that I had to address this issue after all. Switching accounts continued to give problems intermittently, usually in the form of missing/lagged mouse tracking and sometimes menu freezing.

I started experimenting with command line solutions, and I figured out how to recreate the virtual screen from the command line but I couldn't figure out how to associate it with the physical external screen.

HOWEVER, I found a setting in BetterDisplays that seems to have helped: I turned on both "Reconnect Virtual Screens After Wake" and "Disconnect Virtual Screens Upon Lock...". I'm not sure which of these did the trick (both?) and I'm not 100% certain it's a fix because the problem did not consistently appear but... so far, so good. Fingers crossed!