(defmacro restartable (&body body)
  `(restart-case
       (progn ,@body)
     (continue () :report "Continue")))


(defparameter *light-diffuse* (vector 1.0 0.0 0.0 1.0))  ;; red diffuse light
(defparameter *light-position* (vector 1.0 1.0 1.0 0.0)) ;; infinite light position

;;; Normals for the 6 faces of the cube
(defparameter *n* '((-1.0 0.0 0.0) (0.0 1.0 0.0) (1.0 0.0 0.0)
		    (0.0 -1.0 0.0) (0.0 0.0 1.0) (0.0 0.0 -1.0)))

;;; Vertex indices for the 6 faces of the cube
(defparameter *faces* '((0 1 2 3) (2 3 6 7) (7 6 5 4)
		       (4 5 1 0) (5 6 2 1) (7 4 0 3)))

;;; will be filled with the vertexes
(defparameter *v* '((-1 -1 1) (-1 -1 -1) (-1 1 -1) (-1 1 1)
		    (1 -1 1) (1 -1 -1) (1 1 -1) (1 1 1)))

(defmacro 2elt (e x y)
  `(elt (elt ,e ,x) ,y))
  
(defmacro 3delt (e1 x1 e2 x3)
  `(elt (elt ,e2 (elt ,e1 ,x1)) ,x3))

(defun draw-box ()
  (dotimes (i 6)
    (gl:with-primitives :quads
      (gl:normal (2elt *n* i 0) (2elt *n* i 1) (2elt *n* i 2))
      (let ((face (elt *faces* i)))
	(dotimes (x 4)
	  (gl:vertex (3delt face x *v* 0) (3delt face x *v* 1) (3delt face x *v* 1)))))))
	
;(cffi:defcallback display :void ()
(defun display ()
  (gl:clear :color-buffer-bit :depth-buffer-bit)
  (draw-box)
  ;;glut:swap-buffers
  (gl:flush)
  (sdl:update-display)
)

(defun init () 
  (gl:light :light0 :diffuse *light-diffuse*)
  (gl:light :light0 :position *light-position*)
  (gl:enable :light0 :lighting :depth-test)

  (gl:matrix-mode :projection)
  (glu:perspective 40.0 ;; FOV
		   1.0  ;; aspect ratio
		   1.0  ;; z near
		   10.0 ;; z far
		   )
  (gl:matrix-mode :modelview)
  (glu:look-at 0 0 5 ;; eye is at 0,0,5
	       0 0 0 ;; center is at 0,0,0
	       0 1 0 ;;up is in pos Y
	       )

  ;; adjust cube position to be asthetic angle
  (gl:translate 0.0 0.0 -1.0)
  (gl:rotate 60 1.0 0.0 0.0)
  (gl:rotate -20 0.0 0.0 1.0))

(defun cube-main-glut () 
  (glut:init "Cube")
  (glut:init-display-mode :double :rgb :depth)
  (glut:create-window "red 3D lighted cube")
  (glut:display-func (cffi:callback display))
  (init)
  (glut:main-loop)
)
       
(defun cube-main-sdl ()
  (sdl:with-init ()
    (sdl:window 320 240 :flags sdl:sdl-opengl)
    (setf cl-opengl-bindings:*gl-get-proc-address* #'sdl-cffi::sdl-gl-get-proc-address)
    (sdl:with-events ()
      (:quit-event () t)
      (:idle ()
	     (restartable (display))))))