In the context of this script, a special procedure (install-handler key proc) is available, which can be used to install handlers to certain events. Check the man page for more information.

Here is an example layout.scm file replicating rivertiles behavior of having a main window and a stack of windows aside while also automatically locking the screen after five minutes of inactivity.

(install-handler 'idle:300 (lambda (event)
                             (cond ((eq? event 'idle) (system "swaylock &")
                                                      (system "backlight.sh set-to 40"))
                                   ((eq? event 'resume) (system "backlight.sh set-to 100")))))

(define split 0.55)

(define (layout:rows n x y w h)
        (letrec ((height (/ h n))
                 (rows (lambda (n)
                               (if (eq? n 0)
                                   '()
                                   (let ((Y (- (+ y h) (* n height))))
                                        (append (list (list x Y w height))
                                                (rows (- n 1))))))))
                (rows n)))

(define (layout:split n x y w h)
        (if (eq? n 1)
            (list (list x y w h))
            (letrec* ((left (* split w))
                      (right (- w left)))
                     (append (list (list x y left h))
                             (layout:rows (- n 1) (+ x left) y right h)))))

(install-handler 'layout-demand (lambda (view-count width height tags output)
                                  (layout:split view-count 0 0 width height)))