appkit:visible-p

(appkit:visible-p window)

Whether the window is on screen: t after appkit:window, nil after it is closed. Part of the appkit package, a Cocoa widget layer written in rontolisp over objc and loaded on first use: macOS (java -jar, the rontolisp binary, or a compiled .class / .jar; never a .wasm), with a display. See the macOS GUI guide.

CL-USER> (appkit:visible-p *win*)
T