Function request_dynamic_surface 

pub fn request_dynamic_surface(
    config: WindowConfig,
    handler: Box<dyn EventHandler<WinitWindow>>,
) -> Arc<AtomicBool> 

Requests a new top-level window rendering handler, created on the next event-loop iteration by the running multi-surface runner (which shares this thread and the one reactive runtime). Returns a flag the caller flips to close the surface. rsx’s winit SurfaceHost uses this to implement open_surface without a per-surface thread. If no multi-surface runner is running, the request simply sits undrained.