gregl

[gregl]

Hello,

I have now found a solution.

The issue was related to the monitor being connected through the hardware KVM switch. When the KVM was switched to the other computer, the Linux machine apparently lost or changed the monitor EDID, even though the X11 session itself remained active. In that state, NoMachine displayed application windows correctly, but the Plasma desktop background and panel were missing or black.

I connected a DisplayPort dummy plug / EDID emulator to the second DisplayPort output of the NVIDIA GPU and left it enabled as a separate 1920×1080 display, without screen mirroring.

Current setup:

• DisplayPort 1 → KVM switch and physical monitor
• DisplayPort 2 → dummy DisplayPort EDID emulator

After switching the physical monitor to the Windows computer, NoMachine now continues to show the complete Plasma desktop, including the wallpaper and bottom panel.

I also tested connections from another Windows 11 computer and the full desktop is rendered correctly. Disabling client-side hardware decoding and changing EnableEGLCapture were not necessary for the final solution.

Therefore, the problem appears to have been caused by loss of EDID / active display information when the KVM switched away from the Linux computer, rather than by Plasma rendering or NoMachine video encoding.

Regarding the requested xwd test: the issue no longer occurs with the dummy plug connected. I can still perform the test without the dummy plug if it would be useful for further diagnosis.

Thank you for your help.

[gregl]

Thank you for your reply.

To clarify the setup:
Both the Windows 11 client and the openSUSE Tumbleweed server are connected to a single physical monitor through a hardware KVM switch (Unitek V1310AGY01‑EU, DisplayPort). The Linux machine is not headless — I am connecting to the physical X11 display.

Yes, I am connecting to the physical desktop.
Locally, the KDE Plasma desktop renders correctly.
In NoMachine, only application windows are visible, while the Plasma background and panel appear black.

The desktop shown in NoMachine is therefore not the same as the one displayed on the monitor.

I also tested disabling client‑side hardware decoding as suggested, but this did not change the behavior.

If helpful, I can provide logs or EDID information from both KVM ports.

Thank you for your assistance.

[Author]

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