Issue when starting gamescope with --prefer-ouput parameter

[yrk06]

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

Hi,

I have added gamescope as a session by using the following script:

#!/bin/bash

MANGOAPP_OPT=""

if command -v mangoapp &>/dev/null; then
  MANGOAPP_OPT="--mangoapp"
fi

gamescope -O DP-1 $MANGOAPP_OPT -e -- steam -steamdeck -steamos3

When I launch the session without any output preference, gamescope will show up on my left monitor (DP-2).

If I set -O DP-2 then gamescope will correctly show on my left monitor. Journalctl reports no relevant errors

If I set -O DP-1 then all screens will freeze as soon as the session is started. If a physically disconnect the monitor from the GPU, the screens turn black and gamescope shows up on my left monitor. Journalctl reports no relevant errors

If I set -O HDMI-A-1 gamescope will crash and return to SDDM. I haven't stored these logs just yet, since my main concern is getting it working on DP-1

Steps To Reproduce

1. Have Arch Linux updated
2. Install gamescope-git from AUR
3. Add the session launch script to /usr/bin/
4. Add the .desktop entry under wayland sessions (this entry will call the session launch script)
5. Change the -O parameter in the session launch script
6. Attempt to log in using the gamescope session in SDDM

Hardware information

- Distro: Arch Linux (udpated today)
- CPU: AMD Ryzen 7 5700X 8-Core Processor
- GPU: NVIDIA GeForce RTX 5070
- Driver Version: 575.64
- Monitors:
    - left monitor DP-2
    - central monitor DP-1
    - right monitor HDMI-A-1

Software information

- Desktop environment: Not Applicable
- Session type: DRM
- Gamescope version: gamescope version 3.16.14-2-g81e40911 (gcc 15.1.1)
- Gamescope launch command(s): gamescope -O DP-1 -e -- steam -steamdeck -steamos3

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