Wouldn't that conflict with Windows application main thread? As I understand it on macOS the main thread is the only one that can drive the GUI application, which pretty much means entering a macOS specific event loop (or calling it often enough), and that doesn't seem to very compatible with sharing execution with Windows main thread. The Windows main thread could also be spawned as a separate thread from it, but wouldn't that be more likely to break some possible assumptions about the TID of the Windows main thread vs its PID? Or is that not an issue for some reason? (Fwiw I think it would be nice to have this and I was investigating some way to implement in-process compositor with a dedicated thread. On wayland and macOS I was trying to merge this thread with their existing thread, and I ended up figuring that on macOS only the main thread can interact with GUI.) -- https://gitlab.winehq.org/wine/wine/-/merge_requests/9579#note_128967