[GH-ISSUE #437] Can't change MB brightness in mirror mode #350

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opened 2026-05-05 05:48:21 -06:00 by gitea-mirror · 7 comments
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Originally created by @felixradtke on GitHub (May 7, 2021).
Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/437

Originally assigned to: @waydabber on GitHub.

Checklist

  • I have searched for existing issues
  • I have looked through the wiki
  • I have updated MonitorControl to the latest version

Describe the bug
When using both the MacBook display and the external display (through USB-C), you can change the internal brightness with ctrl+F1/F2, and the monitor's brightness with F1/F2. However, when both displays are in mirror mode, you can't change the internal brightness anymore.
To Reproduce
Steps to reproduce the behavior:

  1. Activate display mirror mode in settings
  2. Try to change the brightness of the MacBook display with ctrl+F1/F2
    Expected behavior
    The internal display's brightness should change.

Environment Information (please complete the following information):

  • macOS version: 11.3.1
  • Mac model: MacBook Pro 16" late 2019
  • MonitorControl version: 2.1.0
  • Monitor(s): LG UltraFine
  • Apple Silicon/M1 (yes or no): no
Originally created by @felixradtke on GitHub (May 7, 2021). Original GitHub issue: https://github.com/MonitorControl/MonitorControl/issues/437 Originally assigned to: @waydabber on GitHub. **Checklist** - [x] I have searched for existing issues - [x] I have looked through [the wiki](https://github.com/MonitorControl/MonitorControl/wiki) - [x] I have updated MonitorControl to the latest version **Describe the bug** When using both the MacBook display and the external display (through USB-C), you can change the internal brightness with ctrl+F1/F2, and the monitor's brightness with F1/F2. However, when both displays are in mirror mode, you can't change the internal brightness anymore. **To Reproduce** Steps to reproduce the behavior: 1. Activate display mirror mode in settings 2. Try to change the brightness of the MacBook display with ctrl+F1/F2 **Expected behavior** The internal display's brightness should change. **Environment Information (please complete the following information):** - macOS version: 11.3.1 - Mac model: MacBook Pro 16" late 2019 - MonitorControl version: 2.1.0 - Monitor(s): LG UltraFine - Apple Silicon/M1 (yes or no): no
gitea-mirror 2026-05-05 05:48:21 -06:00
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@waydabber commented on GitHub (Aug 17, 2021):

This should be fixed in the latest betas which improves handling of mirrored displays. Please retest it and close if you find it working! Thank you!

<!-- gh-comment-id:900128158 --> @waydabber commented on GitHub (Aug 17, 2021): This should be fixed in the latest betas which improves handling of mirrored displays. Please retest it and close if you find it working! Thank you!
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@felixradtke commented on GitHub (Aug 17, 2021):

Hi @waydabber thank you for your reply. I have tested it a bit on 3.0b8. ctrl+brightness now works to control just the internal monitor, which is great!

Controlling the external monitor isn't as reliable anymore as in previous versions. (1) It is "kind of" is changing the brightness on internal+external monitor even though the setting isn't active in MonitorControl's settings, but this just happens when display mirroring is active on macOS. (2) When mirroring is disabled, it works as expected but with much more lagging than in previous versions.

I expect that at least (2) might be the known intel issue 'Changing the volume/brightness on Intel devices might be a bit choppy/laggy'. Thanks a lot!

<!-- gh-comment-id:900192729 --> @felixradtke commented on GitHub (Aug 17, 2021): Hi @waydabber thank you for your reply. I have tested it a bit on 3.0b8. ctrl+brightness now works to control just the internal monitor, which is great! Controlling the external monitor isn't as reliable anymore as in previous versions. (1) It is "kind of" is changing the brightness on internal+external monitor even though the setting isn't active in MonitorControl's settings, but this just happens when display mirroring is active on macOS. (2) When mirroring is disabled, it works as expected but with much more lagging than in previous versions. I expect that at least (2) might be the known intel issue 'Changing the volume/brightness on Intel devices might be a bit choppy/laggy'. Thanks a lot!
Author
Owner

@waydabber commented on GitHub (Aug 17, 2021):

Hi,

if you are on Intel, then the choppiness is probably due to the issue @JoniVR mentioned. Unfortunatelly I can't test that.

It is intentional that the app changes both the main and the mirrored display's brightness now (as these are basically regarded as one screen, the app can't decide which display should be controlled via keyboard based on which screen is active since both are active) - imagine a situation when one external display is mirrored to an other. In the past there was no way to change the brightness of displays that were 'slaves' (shadows) in a mirrored set.

<!-- gh-comment-id:900228651 --> @waydabber commented on GitHub (Aug 17, 2021): Hi, if you are on Intel, then the choppiness is probably due to the issue @JoniVR mentioned. Unfortunatelly I can't test that. It is intentional that the app changes both the main and the mirrored display's brightness now (as these are basically regarded as one screen, the app can't decide which display should be controlled via keyboard based on which screen is active since both are active) - imagine a situation when one external display is mirrored to an other. In the past there was no way to change the brightness of displays that were 'slaves' (shadows) in a mirrored set.
Author
Owner

@waydabber commented on GitHub (Aug 21, 2021):

Hi, we have relased the 3.0.0 version. Could you please test if this issue is resolved and report back? Thank you!

<!-- gh-comment-id:903128624 --> @waydabber commented on GitHub (Aug 21, 2021): Hi, we have relased the [3.0.0 version](https://github.com/MonitorControl/MonitorControl/releases/tag/v3.0.0-rc1). Could you please test if this issue is resolved and report back? Thank you!
Author
Owner

@felixradtke commented on GitHub (Aug 21, 2021):

Thanks, @waydabber , the RC appears much more stable on my end!

  • laggy behaviour on Intel seems to be fixed

  • I have the same display twice in settings (see attached). When I disable one of them, it actually works as expected: Brightness with buttons and slider just regulates the external brightness, and ctrl+brightness regulates the internal brightness, even if mirroring is active.

Bildschirmfoto 2021-08-21 um 22 55 45
  • There is currently just a slider for the external monitor when using the menu bar icon, I am not sure if we had multiple sliders in the past (If not: Would be nice to have)

Nevertheless, it looks like this issue is solved - thank you!

<!-- gh-comment-id:903175816 --> @felixradtke commented on GitHub (Aug 21, 2021): Thanks, @waydabber , the RC appears much more stable on my end! - laggy behaviour on Intel seems to be fixed - I have the same display twice in settings (see attached). When I disable one of them, it actually works as expected: Brightness with buttons and slider just regulates the external brightness, and ctrl+brightness regulates the internal brightness, even if mirroring is active. <img width="687" alt="Bildschirmfoto 2021-08-21 um 22 55 45" src="https://user-images.githubusercontent.com/5154969/130334559-7d906553-a3c8-4d42-8f77-10429dca14dc.png"> - There is currently just a slider for the external monitor when using the menu bar icon, I am not sure if we had multiple sliders in the past (If not: Would be nice to have) Nevertheless, it looks like this issue is solved - thank you!
Author
Owner

@waydabber commented on GitHub (Aug 21, 2021):

Hi, Farb-LCD, which is the built in display seems to be a mirror of LG HDR 4K (the wave indicates the mirrored relationship). When mirroring is enabled and both displays are Enabled for control, then both displays should be controlled at the same time. This is by design works like this and is not a bug (since the app cannot tell which one you want to control by the location of the mouse, since both has the mouse). If you want to control only one, then you have disable keyboard control for the other in a mirrored scenario. Hope this helps!

You can add the volume and contrast slider if you turn them on under the "General" ("Allgemein") tab. The internal display has no slider since it can be direclty controlled by the macOS slider.

<!-- gh-comment-id:903176716 --> @waydabber commented on GitHub (Aug 21, 2021): Hi, Farb-LCD, which is the built in display seems to be a mirror of LG HDR 4K (the wave indicates the mirrored relationship). When mirroring is enabled and both displays are Enabled for control, then both displays should be controlled at the same time. This is by design works like this and is not a bug (since the app cannot tell which one you want to control by the location of the mouse, since both has the mouse). If you want to control only one, then you have disable keyboard control for the other in a mirrored scenario. Hope this helps! You can add the volume and contrast slider if you turn them on under the "General" ("Allgemein") tab. The internal display has no slider since it can be direclty controlled by the macOS slider.
Author
Owner

@waydabber commented on GitHub (Aug 25, 2021):

I'll close this one since it should be solved. If there is any issue with this, please feel free to comment and ask for a reopen! Thank you!

<!-- gh-comment-id:905380051 --> @waydabber commented on GitHub (Aug 25, 2021): I'll close this one since it should be solved. If there is any issue with this, please feel free to comment and ask for a reopen! Thank you!
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Reference: github-starred/MonitorControl#350
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