Steam Deck OLED (Stable, Game Mode / gamescope): The Fruit of Grisaia partial redraw on dialogue transitions — screen splits into top/bottom halves; top half freezes while bottom updates; opening in-game menu (RMB) forces repaint

[SomeWellForever]

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

In Steam Deck Game Mode (gamescope session), during sprite/background changes in dialogue, the frame often updates only partially:

• The display splits into two horizontal halves (upper and lower).
• The lower half continues updating correctly with the new sprite/background.
• The upper half stays static (shows an older frame), so the image becomes out-of-sync.

Input continues to work normally, but visuals are wrong until a repaint is forced.

Important: This is consistently “fixed” temporarily if I open the game’s own menu (triggered via right mouse button / RMB). When the in-game menu appears, the whole screen repaints correctly. After closing the menu and continuing dialogue, the partial redraw eventually returns during later transitions.

This is not observed in Desktop Mode.

Given that this reproduces across many years, across multiple SteamOS Stable versions and across all Proton versions tested, it looks like a gamescope/compositor presentation/dirty-region/redraw issue rather than a Proton-specific regression.

Steps To Reproduce

1. Boot Steam Deck into Game Mode (SteamOS Stable).
2. Launch The Fruit of Grisaia.
3. Progress through dialogue and wait for sprite/background transitions.
4. Observe the screen splitting: bottom half updates, top half remains frozen.
5. Press RMB to open the in-game menu → the whole screen repaints correctly.
6. Close the menu and continue reading → the issue returns during later transitions.

Hardware information

- Distro: SteamOS 3.7.17
- CPU: AMD Custom APU 0932 (Steam Deck OLED)
- GPU: AMD Custom APU 0932 (Steam Deck OLED)
- Driver Version: Mesa 24.3.4

Software information

- Desktop environment: latest
- Session type: 
- Gamescope version: latest
- Gamescope launch command(s):

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