Refactor tutorial 03

03/tutorial-03.lisp

@@ -1,8 +1,8 @@
-(defpackage #:sdl2-tutorial-3
+(defpackage #:sdl2-tutorial-03
   (:use :common-lisp)
   (:export :main))
 
-(in-package :sdl2-tutorial-3)
+(in-package :sdl2-tutorial-03)
 
 (defparameter *screen-width* 640)
 (defparameter *screen-height* 480)
@@ -17,12 +17,20 @@
        (let ((,surface (sdl2:get-window-surface ,window)))
          ,@body))))
 
-(defun main()
+(defun load-image (pathname)
+  (let* ((fullpath (merge-pathnames pathname (asdf:system-source-directory :sdl2-tutorial)))
+         (image (sdl2:load-bmp fullpath)))
+    (if (autowrap:wrapper-null-p image)
+        (error "cannot load image ~a (check that file exists)" fullpath)
+        image)))
+
+(defun run ()
   (with-window-surface (window screen-surface)
-    (let ((image (sdl2:load-bmp "3/exit.bmp")))
+    (let ((image (load-image "./03/exit.bmp")))
       (sdl2:with-event-loop (:method :poll)
         (:quit () t)
         (:idle ()
                (sdl2:blit-surface image nil screen-surface nil)
                (sdl2:update-window window)
-               (sdl2:delay 100))))))    ;reduce cpu usage
+               ;; reduce cpu usage
+               (sdl2:delay 100))))))