KDE Wayland - View/Set Color Bit Depth?

I have been working on getting KDE Wayland to display with a resolution of 4K with as high of an fps as possible. From discussions I have had on Reddit (linux_gaming), I have figured out how to get a resolution@fps of 4K@90fps.

It was brought to my attention that the selected setting for bit color depth will influence the maximum achievable frame rate that is achievable (this table seems to attest to this: DisplayPort - Wikipedia).

However, I am not familiar with how to even view what the color bit depth is currently set at in KDE Wayland, nor am I familiar with how to change it. Does anyone know how to view the current color bit depth and potentially change it in KDE Wayland? If it matters, my monitor has for color space options DCI-P3 and sRGB, but I don’t know if this has anything to deal with color bit depth.

Many thanks in advance.

Unfortunately this is one of the things where the driver APIs don’t give us a lot of information or control right now, so finding out the currently used bit depth is not possible.
What we can do is to tell the driver to limit the bit depth to some value. If you put KWIN_DRM_PREFER_COLOR_DEPTH=24 into /etc/environment and reboot, the bit depth will be limited to 8 bits per color (the default is 10)

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Does this still work with plasma 6? I need to lower the color depth from 10 to 8 for nomachine to work properly, but when I set this in etc/environment I’m not sure anything happens, or at least nomachine still doesn’t work

Does this still work with plasma 6?

Yes.

I need to lower the color depth from 10 to 8 for nomachine to work properly

That doesn’t sound right. Applications (currently) always get 8 bits per color buffers with screen casting

@Zamundaaa Thanks for the confirmation. The odd think when I set the env variable nomlachine gives me the same error. Their support are the ones telling me they don’t support color depth of 30. At this point not sure what to do other than wait for them to fix it upstream.