Is it at all possible to have separate X screens when using gnome?

I am trying to set up my secondary monitor as a separate X screen but I cannot seem to get it to work.

I ran nvidia-settings to do the configuration an all seemed to get well. However, after a reboot, gnome gives me a secondary monitor that remains black and that shows my cursor as simply a crosshair. Clicking has no visible effect and trying to launch an application on it from the terminal (with the DISPLAY variable) puts it on the primary screen instead.

I do not think nvidia is to blame (using the closed source driver, btw). When I start fluxbox, I do get two properly working screens…

Gnome settings, by contrast, lists only the main screen and xrand-q lists a disconnected DVI-1-0 port but it is not the one I am looking for (DVI-1-1).

According to a post I have read on the nvidia forums, separate X screens is something that gnome 3 simply does not support. Would that be correct? And might there be a way around it?

What exactly do you mean by this?

Here are some related articles:

Gnome typically “joins” screens: it turns them into a single visual space so that you can seamlessly drag applications back and forth between windows. A separate X screen, by contrast, is independent from other screens. It forms a separate visual space which can have settings (depth, DPI, …) that are different from those of other X screens connected to the same system (something that is impossible when screens are joined).

The reason I would like to configure my system this way is that I am using two monitors that are vastly different. One is 4K, the other not even FullHD. The effect is that windows appearing on the smaller monitor look HUGE relative to the other one (and I mean HUUUUUUGE). Of course, I could reduce the impact by scaling the larger monitor up but it seems like such a waste of space to use a 4K screen as it were only 1920x1080.

Thanks, hui. Those articles essentially describe the sort of xorg.conf that nvidia-settings automatically generates when you configure your second screen as a “new X screen”. The trouble is that such a custom xorg.conf only works in combination with less sophisticated desktop/window managers like fluxbox. If you run gnome instead, the xorg.conf gets bypassed and you end up worse, with just a single monitor (the second one is completely ignored).