gamescope: the micro-compositor formerly known as steamcompmgr

Gamescope is a microcompositor from Valve that is used on the Steam Deck. Its goal is to provide an isolated compositor that is tailored towards gaming and supports many gaming-centric features such as:

• Spoofing resolutions.
• Upscaling using AMD FidelityFX™ Super Resolution or NVIDIA Image Scaling.
• Limiting framerates.

As a microcompositor it is designed to run as a nested session on top of your existing desktop environment though it is also possible to use it as an embedded compositor as well. — Gamescope - ArchWiki

I currently use it to “fix” some specific display and perfomance issues with games under my NixOS system, by spoofing resolutions and use custom upscaling mechanisms.

Keyboard shortcuts

To use shortcuts need to enable keyboard passthrough, with D-F1 hotkey (D-S-F1 to disable). TODO: maybe something changed: issue: Super key for shortcuts considered harmful.

• Toggle fullscreen: D-f
• Toggle nearest neighbour filtering: D-n
• Toggle FSR upscaling: D-u
• Toggle NIS upscaling: D-y
• Increase FSR sharpness by 1: D-i
• Decrease FSR sharpness by 1: D-o
• Take screenshot (currently goes to /tmp/gamescope_$DATE.png): D-s
• Toggle keyboard grab: D-g