Guile SDL2 demo; https://telegra.ph/ARPG-na-Scheme-02-01

demo.scm

(use-modules (ice-9 threads)
             (sdl2)
             (sdl2 events)
             (sdl2 rect)
             (sdl2 render)
             (sdl2 video))

(define window-width  640)
(define window-height 480)

(define (draw ren)
  "Draws the window"
  (clear-renderer ren)
  (set-renderer-draw-color! ren 0 255 0 0)
  (render-fill-rect ren (make-rect 0 0 window-width window-height))
  (present-renderer ren))

(define (need-quit?)
  "#t if main window was closed, #f otherwise"
  (let ([event (poll-event)])
    (if event
        (quit-event? event)
        #f)))

(define (main-loop ren)
  "Main application loop"
  (draw ren)
  (unless (need-quit?)
    (main-loop ren)))

(define (main)
  "Application entry point"
  (sdl-init)
  (call-with-window (make-window #:title "Test"
                                 #:size (list window-width window-height))
                    (lambda (window)
                      (call-with-renderer (make-renderer window)
                                          main-loop)))
  (sdl-quit))


(call-with-new-thread main)