Add support for monitor bit depth configuration

[Gwenodai]

Currently you can set resolution, refresh rate, vrr, scale, transform, etc for each output. However, there's no way to control the bit depth of a display through Niri (Such as running a display in 8 or 10 bit mode).

This seems like a strange thing to not have access to considering all of the other output options available. Maybe it was just forgotten?

[YaLTeR]

Some reasons:

1. I don't have a high bit depth or an HDR monitor.
2. I'm not sure if high bit depth is useful without the Wayland color management stuff that we don't have yet.
3. Sometimes the output defaults to 10 bit which can result in higher bandwidth, meaning less monitors can be enabled at the same time. So I made niri force 8 bit for now to increase the chances that a given monitor configuration will work.

[Gwenodai]

Thanks for the response, that's all totally understandable. It was just something I noticed, not exactly a needed feature imo.

I actually didn't realise point 2 was still going to hold that back anyway, and point 3 is very true as well. Though I could see just defaulting all 10 bit displays to 8 bit (unless otherwise specfied by the user) being the 'fix' to that issue.

[Quackdoc]

I'm not sure if high bit depth is useful without the Wayland color management stuff that we don't have yet.

high bitdepth is indeed useful even without the protocol. At the very least Cosmic, Sway and KDE both have a notable improvement when running with a high bitdepth. on high bit displays it can be verified using https://jursonovicst.github.io/gradient/ IF you have a 10bit capable player mpv is one

Sometimes the output defaults to 10 bit which can result in higher bandwidth, meaning less monitors can be enabled at the same time. So I made niri force 8 bit for now to increase the chances that a given monitor configuration will work.

There are other issues too, kmsgrab on ffmpeg usually breaks.

I think if implemented, 8bit by default would be best.

[quadans]

It feels so bad to use a 1000€ OLED monitor to use 8 bit .... why cant I choose this in niri myself?

[Gwenodai]

It feels so bad to use a 1000€ OLED monitor to use 8 bit .... why cant I choose this in niri myself?

There is a debug flag that prevents Niri from limiting the your monitors bit depth.

https://yalter.github.io/niri/Configuration%3A-Debug-Options.html#keep-max-bpc-unchanged

This doesn't seem to actually allow for 10-bit rendering sadly.

[quadans]

It feels so bad to use a 1000€ OLED monitor to use 8 bit .... why cant I choose this in niri myself?

There is a debug flag that prevents Niri from limiting the your monitors bit depth. I personally am using it to enable 10 bit for my monitor and recommend that you do too.

https://yalter.github.io/niri/Configuration%3A-Debug-Options.html#keep-max-bpc-unchanged

I just pasted this into my config.kdl and nothing happend. So I reboot and xdpyinfo | grep depth still says 24 planes (8 bit) instead of 30. Am I doing this right?

[YaLTeR]

I personally am using it to enable 10 bit for my monitor

Does it actually help btw? Like, can clients draw 10-bit buffers and do they make it to the screen and visually draw as 10-bit, even in our current lack of color management? Because when I added the 8-bit forcing, I was under the impression that this wouldn't work as is.

[Gwenodai]

I personally am using it to enable 10 bit for my monitor

Does it actually help btw? Like, can clients draw 10-bit buffers and do they make it to the screen and visually draw as 10-bit, even in our current lack of color management? Because when I added the 8-bit forcing, I was under the impression that this wouldn't work as is.

Yea upon further inspection, it does not actually allow 10-bit buffers to be visually drawn to the screen. It only makes my monitor report that it's a higher bit rate which fooled me originally. :(

[max-niederman]

What's necessary to make this happen? This is an important feature for me and I otherwise love niri, so I'd likely be willing to do some work on it.

[YaLTeR]

Can you try keep-max-bpc-unchanged + the first patch from here #2629 (comment), then check in drm_info | grep -A4 "= Primary" if you've got a 2101010 format, then tell me if anything actually visually became 10-bit?

[dleyvacastro]

Hi , I also have an HDR capable screen.

drm_info | grep -A4 "= Primary"
    │       ├───"type" (immutable): enum {Overlay, Primary, Cursor} = Primary
    │       ├───"FB_ID" (atomic): object framebuffer = 301
    │       │   ├───Object ID: 301
    │       │   ├───Size: 2880×1620
    │       │   ├───Format: ABGR2101010 (0x30334241)
--
    │       ├───"type" (immutable): enum {Overlay, Primary, Cursor} = Primary
    │       ├───"FB_ID" (atomic): object framebuffer = 0
    │       ├───"IN_FENCE_FD" (atomic): srange [-1, INT32_MAX] = -1
    │       ├───"CRTC_ID" (atomic): object CRTC = 0
    │       ├───"CRTC_X" (atomic): srange [INT32_MIN, INT32_MAX] = 0
--
    │       ├───"type" (immutable): enum {Overlay, Primary, Cursor} = Primary
    │       ├───"FB_ID" (atomic): object framebuffer = 0
    │       ├───"IN_FENCE_FD" (atomic): srange [-1, INT32_MAX] = -1
    │       ├───"CRTC_ID" (atomic): object CRTC = 0
    │       ├───"CRTC_X" (atomic): srange [INT32_MIN, INT32_MAX] = 0
--
    │       ├───"type" (immutable): enum {Overlay, Primary, Cursor} = Primary
    │       ├───"FB_ID" (atomic): object framebuffer = 0
    │       ├───"IN_FENCE_FD" (atomic): srange [-1, INT32_MAX] = -1
    │       ├───"CRTC_ID" (atomic): object CRTC = 0
    │       ├───"CRTC_X" (atomic): srange [INT32_MIN, INT32_MAX] = 0

I've performed the changes you mention

tty.rs:

const SUPPORTED_COLOR_FORMATS: [Fourcc; 6] = [
    Fourcc::Abgr2101010,
    Fourcc::Argb2101010,
    Fourcc::Xrgb8888,
    Fourcc::Xbgr8888,
    Fourcc::Argb8888,
    Fourcc::Abgr8888,
];

config.kdl

debug {
    keep-max-bpc-unchanged
}

however i could not see a significant visual change, it looks pretty much as the default release.

Please let me know if there's anything else that i can try.

[DaemonLife]

Niri is cool but I also really miss 10-bit support and color profiles (custom .icc for monitor) like in Sway.