appkit:timer

(appkit:timer seconds fn)

Starts a repeating NSTimer that calls fn with no arguments every seconds until it answers nil, which invalidates the timer; answers the timer, which (objc:send timer "invalidate") also stops. fn runs on the main thread, inside AppKit's event loop, so it may repaint the window directly. 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 *ticks* 0)
CL-USER> (appkit:timer 1
    (lambda ()
      (setq *ticks* (+ *ticks* 1))
      (appkit:set-text *label* (format nil "~a s" *ticks*))
      (< *ticks* 10)))
#<objc __NSCFTimer>