Function ensure_wayland_display 

pub fn ensure_wayland_display(
    width: i32,
    height: i32,
    render_node: String,
    auto_gpu: String,
    cursor_size: i32,
) -> Result<String, Error>

Bring up the process-wide compositor (ensure_compositor) and return its socket name, so a consumer can place WAYLAND_DISPLAY for the clients it starts; empty where the compositor published no socket within five seconds.