[nvidia / vulkan / explicit sync] completely unplayable explicit sync issues when playing minecraft 1.8.9 with gamescope

[fxzzi]

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

Recording_from_25.0109_11.26.09-scaled.mp4

as you can see from the above video, playing minecraft 1.8.9 with gamescope is unplayable.
The above video was shown using zink, where the issue is at its worst, but the issue also occurs on the native opengl, where the ui and environment flickers very briefly. Nowhere near as bad but its still an issue.

You can see in parts of the video the UI of the game starts disappearing, parts of the environment do not render, my character stops rendering at some point, the game completely freezes, only showing a mess of new frames on the top of the screen.

Steps To Reproduce

1. Using prism launcher, create an instance of minecraft 1.8.9, enabling zink (or leave on default, the issue still occurs on opengl, just less severe).
2. Enable gamescope as a wrapper command, the exact command used here was gamescope -f -W 2560 -H 1440 -w 2560 -h 1440 --force-grab-cursor -r 170 --force-windows-fullscreen --
3. go into any singleplayer, multiplayer etc world and it should exhibit the insane flicker that I am having.

Hardware information

- Distro: "NixOS 25.05 (Warbler)
- CPU: Ryzen 5 5600x
- GPU: NVIDIA Geforce RTX 3070
- Driver Version: 565.77 (both open and closed kernel modules exhibit this issue)

Software information

- Desktop environment: Hyprland v0.46.2
- Session type: wayland
- Gamescope version: gamescope version 3.16.1 (gcc 14.2.1)
- Gamescope launch command(s): `-f -W 2560 -H 1440 -w 2560 -h 1440 --force-grab-cursor -r 170  --force-windows-fullscreen`

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

Video attached above showcases the very apparent issue

[matte-schwartz]

Have you tried #1671?

[fxzzi]

Hi,

just tried it right now. Seems to be no change with that env var set.

edit: that also only seems to change something for vulkan. I mentioned in the original post that a similar but much less severe version of this bug occurs on opengl too. Disabling gamescope and both work perfectly however.

[matte-schwartz]

Yes, it's only for Vulkan, but it was worth checking to make sure it didn't make it match OpenGL behavior.

[fxzzi]

Yes, it's only for Vulkan, but it was worth checking to make sure it didn't make it match OpenGL behavior.

An update:

seems the same issue is also present on CS2 for me. when playing the ui flickers every once in a while, as though explicit sync is not even enabled / working.

My launch options for CS2 are as follows (apologies for it being so long lol):

unset LD_PRELOAD; export OBS_VKCAPTURE=1 MANGOHUD=1; gamescope --scaler stretch -f -w 1920 -h 1440 -W 2560 -H 1440 --force-grab-cursor -r 170 -- gamemoderun %command% -fullscreen +fps_max 0 +fps_max_ui 0 -sdlaudiodriver pipewire -nojoy -vulkan

If I can catch it in a video I'll send it here for evidence.

[fxzzi]

_Recording_from_25.01.18_16_44_58-scaled.mp4

I was able to catch it in a video here. You can see quite easily as I walk out into mid the UI and game flickers slightly. Interestingly, this isn't visible when recording with obs-vkcapture, but is still visible on display. xdg / pipewire screen capture captures it though.

[fxzzi]

After further testing again, it seems it is more apparent the higher the fps is. Usually I play with mangohud locking my refresh rate to 170 (now 167, thanks 570 for VRR), however unlocking it in the below video on a very simple map shows the issue extremely clearly. I've added --immediate-flips --adaptive-sync for vrr and tearing, with no change to the issue.

25.01.25-14.51.09.mp4