appkit:window

(appkit:window title &key (width 480) (height 300) background dark)

Creates an NSWindow of that content size, titled, centered, shown and made key, and activates the application. The value is the window; closing it (the red button or appkit:close) hides it and does not end the process. :background is an NSColor for the window itself and :dark asks for the dark appearance, which the title bar follows too -- without it the traffic lights sit on a light strip above a dark window. 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> (defvar *win* (appkit:window "hello" :width 420 :height 200))
CL-USER> (appkit:visible-p *win*)
T
CL-USER> (appkit:window "night" :background (appkit:color 26 29 38) :dark t)
#<objc NSWindow>