Funnily enough, both macOS (and nextstep and iOS, though differently combined) have a "windowserver" that applications are clients of, similarly BeOS, and even

Funnily enough, both macOS (and nextstep and iOS, though differently combined) have a "windowserver" that applications are clients of, similarly BeOS, and even Windows NT pre NT4 and since DWM. It's the MacOS Classic and GDI and similar direct-to-hw toolkits that are now outliers