Function finish_window_open 

pub fn finish_window_open(id: NodeId, raw: RawHandle, size: Size) -> bool

Backend-facing: complete a Pending window open (docs/windows.md). id is the node the backend’s open_window received; raw is the new window’s CONTENT container; size its content size in points. false ⇒ the window was closed before completion — the backend should drop the native window it just created.