Big lags when app sub window is occluded with another sub window

[GoranKovac]

Describe the bug
Some apps that have multiple windows and one is occluded with another huge lag starts that last about 2-3 seconds. Some apps like that are Godot, Reaper when ImGui script is running and gets occluded. Its almost impossible to work if even more windows occlude one another.
Gnome also suffers from this problem but KDE has this fixed.

To Reproduce
Steps to reproduce the behavior:
Godot:

1. Create new Script or Scene in FileSystem (Right click / Create new...)
2. Click Browse Path
3. If Browse window occludes Create Script/Scene window lag kicks in

Reaper:

1. Install ReaImgui via ReaPack
2. Start ReaImgui Demo
3. Occlude it with another window

Expected behavior
No Lag

Screenshots
This is recorded with gnome since it has recording tool but exactly same behavior is on Cosmic
Godot
https://github.com/user-attachments/assets/6e12d64c-ff28-49cc-ab9d-02841c40ab1d
Reaper
https://github.com/user-attachments/assets/0b7431c2-aa86-4bc9-a70e-cdc363e48d31

Desktop (please complete the following information):

• OS: Arch, Cosmic Alpha 7

[Drakulix]

This sounds like an application problem. Cosmic (and presumably Gnome) throttle the windows refresh rate, if it isn't visible. An application has to deal with this happening.

[GoranKovac]

This sounds like an application problem. Cosmic (and presumably Gnome) throttle the windows refresh rate, if it isn't visible. An application has to deal with this happening.

Ok, in Cosmic case how would the application know when its window/sub window is occluded? Is there some notification from Cosmic or something? I can forward this to ReaImgui developer to try to fix Reaper part.

[Drakulix]

This sounds like an application problem. Cosmic (and presumably Gnome) throttle the windows refresh rate, if it isn't visible. An application has to deal with this happening.

Ok, in Cosmic case how would the application know when its window/sub window is occluded? Is there some notification from Cosmic or something? I can forward this to ReaImgui developer to try to fix Reaper part.

No, the window in question just gets less frequent frame-callbacks (which is documented behaviour of the wayland core protocol).

[GoranKovac]

I need to ask:
Could there be some mechanism behind to workaround this? Some option in settings or something else?
The issue is there are a lot of apps doing this (to be clear I'm specifically talking about XWayland/X11 apps) and having to contact their devs to fix this does not seem like viable solution.
Those apps are designed for X11 so I would assume (maybe silly of me) that they would work the same via XWayland layer.
KDE has solved this and I've double checked just to be sure and this issue is not present in their Wayland session.

[GoranKovac]

Hyprland , cinnamon wayland, xfce wayland and Niri non of them have this issue @Drakulix