I am aware that mono in PI 1 / 2 cannot support WinForm with textbox. And that is the reason why I purchase my PI3B.

I installed my Mono on Raspbian with Pixel, using the command below:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list
sudo apt-get install mono-complete

As usual, I can execute my console application without any problem. But when I try to execute my code for WinForm, I get the error message below:

Xlib:  extension "RANDR" missing on display ":10.0".

Anyone has any idea how can I fix this?

1 Answer 1


I had the same error while working on opencv, cv2.imshow(). Try replacing the host server. I replaced tightvncserver with x11vncserver and things worked like a charm.

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