;; this file:
;;   https://dataswamp.org/~incal/common-lisp/general-base/gl-incal.lisp

(defun init-gl (context win &optional (w 640) (h 480))
  (glut:init)
  (glut:init-display-mode :single :rgb :depth)
  (gl:enable :depth-test)

  (sdl2:hide-cursor)
  (sdl2:gl-make-current win context)

  (gl:viewport 0 0 w h)

  (gl:matrix-mode :projection)
  (let*((near 2)
        (far (* -1 near)) )
    (gl:ortho near far near far near far) )

  (gl:matrix-mode :modelview)
  (gl:load-identity)

  (gl:clear-color 0.0 0.0 0.0 1.0)
  (gl:clear :color-buffer :depth-buffer) )