1080p Integer Scaling Produces Distortion on 4K Monitor (GNOME/Wayland) Using Proton

[MikaelPerry]

Description:
When running applications through Proton with the environment variable WINE_FULLSCREEN_INTEGER_SCALING=1, resolutions behave as expected in most cases. However, setting the resolution to 1080p on a 4K monitor causes visible distortions – notably on diagonal lines and curved elements (e.g. the letter “O” and the cursor). Resolutions lower than 1080p (e.g., 720p) display correctly, and resolutions above 1080p produce black boxes for 1:1 pixel mapping without distortion.

System Information:
OS: Fedora Linux 41 (Workstation Edition) x86_64
Kernel: Linux 6.12.13-200.fc41.x86_64
DE: GNOME 47.4 (Wayland)
Display: 3840x2160 @ 144 Hz (LS28AG700N - External)
CPU: AMD Ryzen 9 5950X (32 cores) @ 5.98 GHz
GPU: NVIDIA GeForce RTX 3070 Ti [Discrete]
Memory: 62.71 GiB (5.47 GiB in use)

Steps to Reproduce:
Run a Steam game with the environment variable set:
WINE_FULLSCREEN_INTEGER_SCALING=1
Connect to a 4K monitor running under GNOME on Wayland.
Change the resolution to 1080p.
Observe that diagonal lines, curves (e.g., in the letter “O”), and the cursor show noticeable distortions.
Compare with other resolutions:
720p: Image renders perfectly.
Resolutions higher than 1080p: Black boxes are used for 1:1 mapping, but without distortion.
Expected Behavior:
The application should scale the 1080p resolution image cleanly using integer scaling without any distortions, similar to what is seen with 720p or with higher resolutions using black-box mapping.

Actual Behavior:
At 1080p, the scaled image exhibits visible distortions. The artifacting is noticeable on diagonal elements and rounded objects, leading to a degraded visual quality that is easily perceptible when moving the cursor or rendering text.

Additional Notes:
The issue appears specific to the 1080p resolution setting under these conditions.
The problem is reproducible on a Fedora 41 system running GNOME (Wayland) with an NVIDIA GeForce RTX 3070 Ti.
I suspect the problem might lie in the way Proton handles integer scaling for this specific resolution under these display conditions.