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How can I define a virtual screen/workspace to extend my desktop to which I can connect using VNC. I know vnc4server allowed you to modify the xorg.conf to define a screen, but this is not available anymore. I tried to use xrandr to define a screen in memory and expose it using x11vnc, but this needed me to plugin a cable into the external VGA adapter and this nullifies the options to have the virtual screen act as a third screen.
I've written a blog post on how to almost achieve want you probably want. Shameless plug: http://fomori.org/blog/?p=530 This setup doesn't allow you to drag windows to the virtual desktop, so I stopped using it myself, but maybe it's some help to you.
– twall – 2013-08-28T17:11:52.950