[kde] [Bug 495219] New: HDR Mode Reverts to SDR When Adjusting Brightness via Plasma's Brightness Slider on Acer Monitor

[James]

https://bugs.kde.org/show_bug.cgi?id=495219

            Bug ID: 495219
           Summary: HDR Mode Reverts to SDR When Adjusting Brightness via
                    Plasma's Brightness Slider on Acer Monitor
    Classification: I don't know
           Product: kde
           Version: unspecified
          Platform: Arch Linux
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: unassigned-bugs at kde.org
          Reporter: jheinem01 at icloud.com
  Target Milestone: ---

Created attachment 175128
  --> https://bugs.kde.org/attachment.cgi?id=175128&action=edit
This is the diff between the output of `drm_info` before and after the
brightness adjustment. Due to file size limitations, the full output is not
included as an attachment.

SUMMARY
HDR Mode Reverts to SDR When Adjusting Brightness via Plasma's Brightness
Slider on Acer Monitor

STEPS TO REPRODUCE
1. Enable HDR on [Acer] Monitor:
   - Connect Acer monitor that supports HDR to your system.
   - Set HDR to "auto" in monitor OSD.
   - Open System Settings → Display and Monitor.
   - Enable HDR for the display and apply setting.
2. Adjust Brightness:
   - Use the Plasma brightness slider located in the system tray.
   - Modify the brightness level using either the individual monitor or global
brightness slider.

3. Observe HDR Mode:
   - After adjusting the brightness, observe that the monitor switches from HDR
to SDR mode.

Note: This issue does not affect my Gigabyte monitor, which allows me to toggle
HDR "On" in the monitor OSD which results in it remaining in HDR upon
brightness adjustments.

OBSERVED RESULT
- Acer Monitor: Adjusting the brightness via Plasma's brightness slider causes
the monitor to switch from HDR to SDR mode. Additionally, after rebooting,
turning the monitor off/on, or logging out/in, HDR mode does not persist and
reverts to SDR.
- Gigabyte Monitor: Remains in HDR mode consistently, even after adjusting
brightness, rebooting, or toggling the monitor's power.

EXPECTED RESULT
Adjusting the brightness via Plasma's brightness slider should modify the
display brightness without altering the HDR/SDR mode of the monitor. HDR mode
should remain active on the Acer monitor regardless of brightness adjustments,
similar to the Gigabyte monitor's behavior.

SOFTWARE/OS VERSIONS
Windows: N/A
macOS: N/A
Linux/KDE Plasma: EndeavourOS (Arch Linux)
KDE Plasma Version: 6.2.1
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0
Kernel Version: 6.11.4-arch2-1 (64-bit)
Graphics Platform: Wayland
Processors: 20 × 12th Gen Intel® Core™ i7-12700
Memory: 31.1 GiB of RAM
Graphics Processor: AMD Radeon RX 6650 XT

ADDITIONAL INFORMATION
- Monitor Models:
  - Gigabyte Monitor: Gigabyte M27U
  - Acer Monitor: Acer Nitro XV275K P3

- Connection Type: DisplayPort 1.4
- Wayland/X11: Wayland

- Clarifications:
  - The issue exclusively affects the Acer monitor, which only allows setting
HDR to "Auto" or "Off". In contrast, the Gigabyte monitor allows forcing HDR
"On" directly through its settings, avoiding the reversion to SDR when
adjusting brightness.

- Related Forum Post:
  - https://discuss.kde.org/t/plasma6-2-super-buggy-hdr-mode/23161

- Video Demonstration:
  - https://youtu.be/iJZ-aviftSQ

- Workarounds Tried:
  - Manually re-enabling HDR after each brightness adjustment. This works,
however is inconvenient.

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