Bug 514957

On launching a game using PROTON_ENABLE_WAYLAND=1 and PROTON_ENABLE_HDR=1, HDR works as intended *unless* your KDE color settings are set to "Prefer Color Accuracy." When using "Prefer Efficiency," the game produces HDR content correctly to the screen, but upon entering a menu (I.E. Elden Ring inventory screen and settings menus), the game reverts the highlights to being clamped. Disabling Tonemapping using KWIN_DISABLE_TONEMAPPING=1 in environment settings fixes the issue by disabling the tonemapper entirely.


STEPS TO REPRODUCE
1. Open Display Configuration system settings
2. Set "Color Accuracy" to "Prefer Color Accuracy"
3. Open a game that supports HDR output (Elden Ring: Nightreign was a good testing example for me due to the giant Grace in the middle of the starting room being a large highlight that pushes peak brightness)

OBSERVED RESULT:
The highlights are washed out, not pushing peak brightness, as they do when using Efficiency mode.

EXPECTED RESULT
Highlights and other peak-brightness-pushing elements push the peak brightness set by the monitor's config regardless of color accuracy mode

SOFTWARE/OS VERSIONS:
CachyOS using KDE Plasma: 
KDE Plasma Version: 6.5.5
KDE Frameworks Version: 6.22.0
Qt Version: 6.10.1

ADDITIONAL INFORMATION
Efficiency mode incorrectly raises black levels by a noticeable amount on my OLED monitor, regardless of brightness settings. The only fix to this for me is to set Prefer Color Accuracy as the setting for color accuracy, but doing so breaks the HDR output in-game. Additionally, using Efficiency and then trying to enable HDR through gamescope results in the same brightness issues, whereas PROTON_ENABLE_WAYLAND=1 and PROTON_ENABLE_HDR=1 work fine.