recursive-sdl2-event-loop.lisp

(defun outer (renderer)
  (unless sdl2::*event-loop*
    (setf sdl2::*event-loop* t)
    (sdl2:in-main-thread (:background nil)
                         (unwind-protect
                              (inner renderer nil)
                           (setf sdl2::*event-loop* nil)))))

(defun inner (renderer quit?)
  (flet ((idle-function ()
           (sdl2:set-render-draw-color renderer 255 255 255 255)
           (sdl2:render-clear renderer)
           (sdl2:render-present renderer)))
    (sdl2:with-sdl-event (event)
      (cond
        ((not (zerop (sdl2:next-event event :poll nil)))
         (let* ((event-type (sdl2:get-event-type event))
                (event-id (and (sdl2::user-event-type-p event-type) (event :user :code))))
           (case event-type
             (:lisp-message
              (sdl2::get-and-handle-messages))
             (:keydown
              (let ((keysym (plus-c:c-ref event sdl2-ffi:sdl-event :key :keysym)))
                (when (sdl2:scancode= (sdl2:scancode-value keysym) :scancode-q)
                  (sdl2:push-event :quit))))
             (:idle
              (idle-function))
             (:quit
              (setf quit? (funcall (lambda () t)))))
           (when (and event-id (not (eq event-type :lisp-message)))
             (sdl2::free-user-data event-id))))
        (quit?
         (return-from inner))
        (t
         (idle-function)))))
  (inner renderer quit?))