Sets the workspace on which applications will be launched when
using this context when running under a window manager that
supports multiple workspaces, as described in the
Extended
Window Manager Hints (http://www.freedesktop.org/Standards/wm-spec).
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.
Since 2.14