X11VNC When open VNC connection my desktop is being kind of duplicated

Question

Pretty new to Linux, so my question might be a dummy one. I have ubuntu 20.10 on raspberry Pi 4 (8GB) with Desktop environment. Installed X11VNC and spent some time configuring it. After few hours fighting with it I got it working. However I have an issue, when I establish a connection(tried several different vnc clients, but results is yet the same), my desktop is being duplicated few many times.

Screenshot: https://ibb.co/vwXm3w9

When I click somewhere in the drawn area, it registers it as if I clicked somewhere on the top screen. Basically they are 8-10 mirrors of the main screen.

I have tried for find the configuration of X11VNC tried to play with the settings (try and error) with no luck, tried to reinstall it - no luck...

I am basically new and trying to understand what is causing the problem(duplication) so I could try to search for some solution.

Can someone help me by explaining what is causing the duplication ?

Service Configuration

[Unit]
Description=x11vnc remote desktop server
Requires=display-manager.service
After=display-manager.service network.target syslog.target


[Service]
Type=simple
ExecStart=/usr/bin/x11vnc -display :0 -auth /var/run/lightdm/root/:0 -forever -loop -noxdamage -repeat -rfbauth /home/user/.vnc/passwd -rfbport 5900 -shared -ncache

Restart=on-failure

[Install]
WantedBy=multi-user.target

Answer 1

As I ran into the same problem and I didn't find the answer anywhere online, I'll share it here. Found by reading the x11vnc man page and checking every single argument I (and you) used.

https://linux.die.net/man/1/x11vnc

-ncache n Client-side caching scheme. Framebuffer memory n (an integer) times that of the full display is allocated below the actual framebuffer to cache screen contents for rapid retrieval. So a W x H frambuffer is expanded to a W x (n+1)H one. Use 0 to disable. The n is actually optional, the default is 10. For this and the other -ncache options below you can abbreviate "-ncache" with "-nc". Also, "-nonc" is the same as "-ncache 0" This is an experimental option, currently implemented in an awkward way in that in the VNC Viewer you can see the pixel cache contents if you scroll down, etc. So you will have to set things up so you can't see that region. If this method is successful, the changes required for clients to do this less awkwardly will be investigated.