HDR not exposed on Plasma 6.7 / KWin

[2ramiro]

Is there an existing issue for this?

• I have searched the existing issues

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

• The issue occurs on upstream gamescope without any modifications

Current Behavior

After updating to Plasma 6.7, gamescope --hdr-enabled no longer exposes HDR to clients (bExposeHDRSupport: false), while desktop HDR (e.g. browser video) works fine. HDR worked before the 6.7
The issue seems to be
CWaylandBackend::SupportsColorManagement() returns false because the feature gate at src/Backends/WaylandBackend.cpp requires WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_SRGB:
I removed
if ( !Algorithm::Contains( m_WPColorManagerFeatures.eTransferFunctions, WP_COLOR_MANAGER_V1_TRANSFER_FUNCTION_SRGB ) ) return false;
from src/Backends/WaylandBackend.cpp line 2031 and after that hdr was working

Steps To Reproduce

Launch any game with gamescope and hdr enabled and kde 6.7

Hardware information

Fedora 44
Ryzen 5950x
AMD Radeon RX 7900 XTX
Mesa 26.0.8 (LLVM 22.1.5)

Software information

gamescope version 3.16.24-20-ga563226+ (gcc 16.1.1)
KDE Plasma 6.7 / KWin, Wayland session
Wayland backend (nested)

Which gamescope backends have the issue you are reporting?

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

Logging, screenshots, or anything else

No response