Sets the workspace on which applications will be launched.
This only works when running under a window manager that
supports multiple workspaces, as described in the
Extended Window Manager Hints.
Specifically this sets the
_NET_WM_DESKTOP property described
in that spec.
This only works when using the X11 backend.
When the workspace is not specified or
desktop is set to -1,
it is up to the window manager to pick one, typically it will
be the current workspace.