Bug Report: Graphical Artifacts When Moving the Mouse on a 4K Display at the Default Desktop Scale

Hardware

• CPU: AMD Ryzen 5 5600
• GPU: AMD Radeon RX 9070
• Steam OS：3.8.14

Description

After reinstalling SteamOS, I noticed graphical artifacts whenever I move the mouse on my 4K TV/monitor.

This first appeared during the SteamOS installation process. After the installation finished and I removed the USB installer, the same issue was still present in Desktop Mode.

I found that changing the desktop display scaling to 300% completely fixes the problem. However, 300% is much larger than I would like to use on a 4K display. Any lower/default scaling causes the graphical artifacts to appear while moving the mouse.

Interestingly, this issue does not occur in Gaming Mode. It only happens in Desktop Mode.

Steps to Reproduce

1. Connect a 4K TV or monitor.
2. Install and boot into SteamOS.
3. Enter Desktop Mode.
4. Leave the display scaling at the default value (or any value lower than 300%).
5. Move the mouse around.

Expected Behavior

• Moving the mouse should not produce any graphical artifacts, regardless of the desktop scaling setting.

Actual Behavior

• Graphical artifacts appear while moving the mouse at the default/lower scaling.
• Setting the desktop scaling to 300% makes the issue disappear.
• Gaming Mode is unaffected.

https://github.com/user-attachments/assets/4dbb28cd-4d20-4225-a983-cc2c4beb3e67

Start by reproducing the artifacts in Desktop Mode on a 4K display at the default and lower scaling settings, then compare with 300% scaling and Gaming Mode. Done means identifying and fixing the cause so mouse movement produces no artifacts at the default or lower scaling.