KDE HDR makes the effects very dark

[Kevadroz]

Describe the Bug

When HDR is enabled in Plasma 6 the effects are very very dark

Steps to reproduce the behavior:

1. Use one of the effects
2. Enable HDR on KDE display options
3. open/colse a window

System

Please complete the following information:

• Linux distribution: Arch Linux
• Burn-My-Windows version: Hexagon from KDE Store at date 2024-02-29
• KWin / Plasma Version: 6.0.1

[Schneegans]

Hi there! Thanks for the report. However, I have no way to test this on my end. Also, I tried reaching out to the KWin developers on Matrix but didn't get any reply. So I am not sure how to proceed here. I'll try to ask them again.

Since this HDR support is pretty new and still kind of experimental, it's hard to find any documentation about it. Maybe if more people start using Plasma 6 and HDR, more will experience this issue and at some point someone will show up who has the knowledge to fix it :thinking:

[jasonslay]

I have a framework 13 laptop (AMD) with this issue. What's interesting is that it doesn't support HDR. I'm on Arch/KDE as well and I only see this when using Wayland. When using X11 the effects look normal. Maybe this isn't purely an HDR bug?

[jasonslay]

I have a framework 13 laptop (AMD) with this issue. What's interesting is that it doesn't support HDR. I'm on Arch/KDE as well and I only see this when using Wayland. When using X11 the effects look normal. Maybe this isn't purely an HDR bug?

Disabling the color profile applied to the monitor allows the effects to work as expected. I applied the color profile following these directions so others might also have this issue.

[mmcnutt]

further to this bug, it is also triggered with any colour profile, not just HDR. You can trigger it by reading the profile out of your monitor in Plasma 6.1 - so with 6.1 you wont need HDR hardware to fault find this

[Zamundaaa]

If you want to make the effect support HDR, you can

• #include "colormanagement.glsl" in your shader, which adds a whole bunch of uniforms and functions for color management
• use sourceEncodingToNitsInDestinationColorspace(color) to convert from the source color to nits on the output
• assume the source encoding is sRGB (non-sRGB input will be opt in for js effects, once that's supported. If the window uses HDR, KWin will map it to sRGB automatically before the shader gets it), and use sourceEncodingToNitsInDestinationColorspace(color) also for sRGB colors you're using in the shader
• play with the brightness values if you want, you could for example make use of brightness levels up to maxDestinationLuminance for fire or things like that
• use nitsToDestinationEncoding(color) to convert to the value KWin's framebuffer expects at the end of the shader

I also hope to make KWin automatically patch shaders from javascript effects to support color management, but that's going to take at least until Plasma 6.3.

[Schneegans]

@Zamundaaa thanks for this information! I'll see if I find an HDR screen somewhere and then I'll try to implement this.

[Zamundaaa]

You don't need an HDR screen, setting an ICC profile (in 6.1, not anymore in 6.2) makes the difference very obvious too.