I would like to test changes to my window manager’s package without logging out of my user session. Currently I’ve been deploying to a second computer, but it would be nice if I could do it with one computer. Can anybody suggest a good way to run multiple X displays for testing window-manager changes, or do you have another strategy for testing?
You can just use
nixos-rebuild build-vm -I nixpkgs=path-to-your-nixpkgs -I nixos-config=test-crd.nix to build a virtual machine image with your configuration.
You can use Xephyr to run a nested X server. Then run the window manager with the
DISPLAY environment variable set such that it connects to Xephyr.
Those are helpful, thank you both.