Impossible layer-shell surface caused segfault

[CicadaSeventeen]

Describe the bug
On the Wayland compositor, applications can request a layer shell surface. However, when the user switches to another TTY, wayfire registers a new placeholder virtual output and closes the real output. Since the placeholder virtual output has a size of 0, it's impossible to register certain fixed-size layer shell surfaces on it. This causes wayfire to crash due to a segmentation fault.
In my example, the program causing this crash is xfce4-panel, which has recently added Wayland support but is still not reliable enough. Although xfce4-panel itself exhibits bad behavior and should be considered buggy, wayfire should not crash due to an application's bug, but should instead handle the situation differently, for example, by killing the process that requests an impossible layer shell surface.

To Reproduce
Steps to reproduce the behavior:

1. Run wayfire and Run xfce4-panel
2. Switch to tty with like ctrl+alt+F3
3. wayfire segfault and crasg

Expected behavior
Wayfire should kill problematic process and continue to run on NOOP-1

Screenshots or stacktrace
Logs here:

II 2026-01-05 11:48:48.854 - [libseat] [libseat/backend/logind.c:382] Disabling seat
II 2026-01-05 11:48:48.854 - [backend/drm/backend.c:112] DRM FD paused
II 2026-01-05 11:48:48.854 - [src/core/output-layout.cpp:1323] remove output: eDP-1
II 2026-01-05 11:48:48.854 - [src/core/output-layout.cpp:1204] new output: NOOP-1
II 2026-01-05 11:48:48.854 - [src/core/output-layout.cpp:702] Couldn't find matching mode 1280x720@0 for output NOOP-1. Trying to use custom mode(might not work)
EE 2026-01-05 11:48:48.862 - [src/core/output-layout.cpp:601] disabling output: eDP-1
II 2026-01-05 11:48:48.862 - [src/core/output-layout.cpp:232] transfer views from eDP-1 -> NOOP-1
EE 2026-01-05 11:48:48.864 - [backend/drm/drm.c:1349] connector eDP-1: Failed to disable CRTC 88
qt.qpa.wayland: There are no outputs - creating placeholder screen
EE 2026-01-05 11:48:48.884 - [src/view/layer-shell/layer-shell.cpp:631] layer-surface has calculated width and height < 0
EE 2026-01-05 11:48:48.885 - [src/main.cpp:144] Fatal error: Segmentation fault

Wayfire version
0.10.0

[ammen99]

We have a related fix in the master branch, could you try compiling it from source?

[CicadaSeventeen]

We have a related fix in the master branch, could you try compiling it from source?

Thank you. The build of the master branch did indeed fix this bug, although I found new related bugs, but they are less serious in comparison.

BTW, I think the new bug is more likely to be related to xfce4-panel rather than wayfire, but I still want to show you what happens.

The newly discovered bug is that xfce4-panel starts flickering continuously after switching tty. I've provided a screen recording. Note that this was recorded directly using OBS, so it's likely not a graphics card driver error, but rather an error in the actual content of the screen. Restarting xfce4-panel resolves this issue.

I've attached the video here.

2026-01-05.19-22-56.mp4

[ammen99]

We have a related fix in the master branch, could you try compiling it from source?

Thank you. The build of the master branch did indeed fix this bug, although I found new related bugs, but they are less serious in comparison.

BTW, I think the new bug is more likely to be related to xfce4-panel rather than wayfire, but I still want to show you what happens.

The newly discovered bug is that xfce4-panel starts flickering continuously after switching tty. I've provided a screen recording. Note that this was recorded directly using OBS, so it's likely not a graphics card driver error, but rather an error in the actual content of the screen. Restarting xfce4-panel resolves this issue.

I've attached the video here.

2026-01-05.19-22-56.mp4

Does the bug go away if you move a window over the flickering area? If yes could be a damage tracking related bug in Wayfire, otherwise most certainly in the panel.

[CicadaSeventeen]

Does the bug go away if you move a window over the flickering area? If yes could be a damage tracking related bug in Wayfire, otherwise most certainly in the panel.

No. It is very likely to be a xfce4-panel bug.

Thanks for your reply.

[Tamaranch]

No. It is very likely to be a xfce4-panel bug.

As for the flickering, I don't think so. In the video shown (and in the configuration given in the xfce issue), we can see that there are two panels on the left, with free space between them. However, this free space also flickers, so it is not xfce4-panel that is causing this, but the compositor.

[ammen99]

Yeah flickering which disappears when you move a view over it means a compositor bug in 99.999999% of the cases :)

[CicadaSeventeen]

Yeah flickering which disappears when you move a view over it means a compositor bug in 99.999999% of the cases :)

But flickering will not disappear in my case. Sorry that I have not managed to clarify that.

[CicadaSeventeen]

The conditions under which flickering occurs are difficult to ascertain. I haven't identified sufficient conditions for reproduction; I've only found some necessary ones.

For example, whether flickering occurs is related to the xfce4-panel settings. A panel the same length as the screen never flickers, while a panel shorter than half the screen length is very likely to flicker. It seems the panel is repeatedly registered in different locations.

Some flickering only lasts a few seconds, but others flicker indefinitely, as shown in the video. I can't figure out what factors determine this difference.

I'm sorry, I'm unable to provide more information and may have to stop here for now.