Dell Display Detected as Apple Hardware

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• [X] Updated MonitorControl to the latest version (if applicable)

Describe the issue

A Dell U3415W display previously successfully controlled by DDC is detected as "Control method: Hardware (Apple)" after another monitor changed. As the control method is not correctly detected, controlling the brightness of the display does not work.

Controlling the Dell display with m1ddc works as expected.

Expected behavior

Dell U3415W display can be controlled via DDC as before.

Anything else?

❯ ./m1ddc display list
1 - StudioDisplay (…)
2 - DELL U3415W (…)
❯ ./m1ddc display 2 set luminance 50

These work fine.

Environment Information (please complete the following information)

- macOS version: 12.4
- Mac model: MacBook Pro (16-inch, 2021)
- MonitorControl version: 4.1.0
- Monitor(s): internal, Dell U3415W, Apple Studio Display
- Monitor Cable(s)/Connection(s): 
  - MacBook Pro → OWC Thunderbolt 3 Dock → MiniDP/DP → Dell U3415W
  - MacBook Pro → OWC Thunderbolt 3 Dock → Thunderbolt 3 → Apple Studio Display
- Apple Silicon/M1 (yes or no): yes

Hmm. This might be because the display identifiers get messed up somehow maybe? You should try resetting the app preferences. Also you can try BetterDisplay and see if that works since that is a full rewrite from ground-up and uses a different method for identifying displays.

Let me know if any of these help! Thank you!

You should try resetting the app preferences.

Using "Reset Preferences" or deleting the apps plist does not seem to change anything.

Also you can try BetterDisplay and see if that works since that is a full rewrite from ground-up and uses a different method for identifying displays.

It seems to have the same issue. Regardless if Use alternative method to identify displays is enabled or not. Enable advanced display control is enabled, Enable hardware brightness control is also enabled. Brightness does not change.

In BetterDisplay, please click on both displays' name and attach as a screenshot the details so I can understnd better how the app sees the displays.

It is either the OS reports the display as it can change its brightness (DisplayServicesCanChangeBrightness(CGDirectDisplayID display) returns true) or DisplayServicesGetBrightness(displayID, &brightness) returns with a valid brightness (which means the OS can read the display's brightness). This is why it is detected as an Apple external display by both apps.

Does this happen if you directly connect the displays without the dock?

Does this happen if you directly connect the displays without the dock?

Yes this also happened if the displays were directly connected. There was also a very strange issue where video content on the Dell display was rotated 90° (as is the Studio Display) in some applications (e.g Safari, looks like some kind of video acceleration mode). Seems to be an incompatibility with the Studio Display on Apples side, I will also report a Feedback.

I think a possible fix for MonitorControl would be a Force DDC option.

What happens if only the Dell display is connected? Does the issue happen then as well? It is super interesting that the OS reports as controllable. There does not seem to be a confusion in identifiers though.

There should be a setting to treat the display as a non-Apple display.

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