How could that possibly work?
What I want is 2 monitors, each of which shows a different desktop from the same set of desktops. I don't just want the same desktop displayed twice - that is easy. I want two different desktops displayed at the same time. Another thing that is easy is to have 2 desktops from 2 different sets of desktops. I don't want that either.
This is architecturally difficult for reasons that I fully understand. The problem is that the idea of virtual desktops is managed by your window manager which sits between you and X. X knows nothing about virtual desktops. Only the window manager knows about them. No X-level solution can possibly do what I want without assistance from that layer - the window manager has to actively cooperate in the idea of displaying two different virtual desktops when normally it only displays one.
That is why VNC won't cut it. The server component of VNC is a replacement for X that is designed to be shared through a simple client. Being at the level of X, it knows nothing about virtual desktops and therefore cannot do anything more than throw out copies of the one desktop that it sees. Sure, I can have one desktop displayed from X, and another from a VNC session. But those two desktops are not managed by the same running window manager, and therefore are selected from different sets of virtual desktops. Which is not what I wanted.
That is why I said up front that I would be willing to switch window managers to get this feature, because I know that I could only get it by using a window manager that had support for this built in.
Cheers,
Ben
