[NVIDIA + Plasma 6.5 Wayland] HDR path produces grey/washed image (desktop HDR OK)

[steccas]

Is there an existing issue for this?

• [X] I have searched the existing issues

Are you using any gamescope patches or a forked version of gamescope?

• [x] The issue occurs on upstream gamescope without any modifications

Current Behavior

Summary

After updating to Plasma 6.5 on Wayland, HDR via Gamescope or Proton is broken (grey, washed-out). Desktop HDR (MPV HDR playback) works correctly.

Was working flawlessly before. Without gamescope I had already the same problem.

Expected Behavior

HDR tone mapping PQ/Rec.2020 as on desktop HDR.

Actual Behavior

Washed-out SDR-like image under HDR mode.

Workarounds Tried

• ColorManagementMode=0 → ineffective
• VRR toggled, exclusive/borderless → no fix
• Gamescope flags (--hdr-itm-enable, nits) → no fix

Hypothesis

Gamescope HDR handshake fails with new KWin color-management protocol v4. NVIDIA ICD lacks VK_EXT_swapchain_colorspace under Wayland → SDR surface rendered under HDR compositor. Lookign at the changelog the KDE team says that plasma 6.5 "improved HDR" management so i suspect that the update breaks something.

Steps To Reproduce

1. Enable HDR in Plasma.
2. Launch:

gamescope --hdr-enabled -w 3440 -h 1440 -W 3440 -H 1440 -f --adaptive-sync --mangoapp -- gamemoderun DXVK_HDR=1 ENABLE_HDR_WSI=1 %command%

3. Observe grey output, despite HDR mode enabled.

Hardware information

- **Distro:** EndeavourOS (Arch-based)  
- **CPU**: 8-core AMD Ryzen 7 5700X3D
- **Kernel:** 6.17  
- **GPU/Driver:** NVIDIA RTX 4070 Super – 580.95.05 Open

Software information

- Desktop environment: **Plasma/KWin (Wayland)** 6.5.0  
- Session type: wayland
- **Gamescope:** 3.16.17
- **Proton/Proton-GE:** 10.21  (latest)
- Gamescope launch command:

gamescope --hdr-enabled -w 3440 -h 1440 -W 3440 -H 1440 -f --adaptive-sync --mangoapp -- gamemoderun DXVK_HDR=1 ENABLE_HDR_WSI=1 %command%

Which gamescope backends have the issue you are reporting?

• [x] Wayland (default for nested gamescope)
• [x] DRM (default for embedded gamescope, i.e. gamescope-session)
• [ ] SDL
• [ ] OpenVR

Logging, screenshots, or anything else

No response

[matte-schwartz]

Maybe try https://github.com/ValveSoftware/gamescope/pull/1999 ?

[kode54]

Same issue on AMD on KDE 6.5:

[gamescope] [Info]  xdg_backend: uMaxContentLightLevel: 80
[gamescope] [Info]  xdg_backend: HDR INFO
[gamescope] [Info]  xdg_backend:   cv_hdr_enabled: true
[gamescope] [Info]  xdg_backend:   uTF: GAMMA22
[gamescope] [Info]  xdg_backend:   bExposeHDRSupport: false
[gamescope] [Info]  xdg_backend: uMaxContentLightLevel: 486
[gamescope] [Info]  xdg_backend: HDR INFO
[gamescope] [Info]  xdg_backend:   cv_hdr_enabled: true
[gamescope] [Info]  xdg_backend:   uTF: GAMMA22
[gamescope] [Info]  xdg_backend:   bExposeHDRSupport: false

I assume the first set of lines is my SDR monitor, while the second is my HDR400 monitor. I'll try #1999

[skaeight]

Replying to https://github.com/ValveSoftware/gamescope/issues/2000#issuecomment-3448094509

Did that fix it?

[kode54]

Replying to #2000 (comment)

Did that fix it?

Yes. Sorry for not posting last night when I actually tested it.

Edit: And the issue I had with the tonemapping shader function, with mpv, was entirely mpv's fault, and has been fixed upstream. (I had somehow thought this was something that affected other software as well, guess it was just incorrect behavior of one app.)

[brenoprata10]

I am also having the same issue, was working fine before updating to plasma 6.5, look how FF7 looks now (totally washed out), before it worked with HDR and it was beautiful :(

BTW, it looks like this for both hdr enable/disabled

Distro: Arch

[adonisd]

Maybe try #1999 ?

applying this fixed it for me.