;; Example 7-2  Using a Display list

(use gl)
(use gl.glut)

(define *list-name* 0)

(define (init)
  (set! *list-name* (gl-gen-lists 1))
  (gl-new-list *list-name* GL_COMPILE)
  (gl-color 1.0 0.0 0.0)
  (gl-begin GL_TRIANGLES)
  (gl-vertex 0.0 0.0)
  (gl-vertex 1.0 0.0)
  (gl-vertex 0.0 1.0)
  (gl-end)
  (gl-translate 1.5 0.0 0.0)
  (gl-end-list)
  (gl-shade-model GL_FLAT)
  )

(define (draw-line)
  (gl-begin GL_LINES)
  (gl-vertex 0.0 0.5)
  (gl-vertex 15.0 0.5)
  (gl-end))

(define (disp)
  (gl-clear GL_COLOR_BUFFER_BIT)
  (gl-color 0.0 1.0 0.0)
  (dotimes (i 10) (gl-call-list *list-name*))
  (draw-line)
  (gl-flush)
  )

(define (reshape w h)
  (gl-viewport 0 0 w h)
  (gl-matrix-mode GL_PROJECTION)
  (gl-load-identity)
  (if (<= w h)
      (glu-ortho-2d 0.0 1.0 (* -0.5 (/ h w)) (* 1.5 (/ h w)))
      (glu-ortho-2d 0.0 (* 2.0 (/ w h)) -0.5 1.5))
  (gl-matrix-mode GL_MODELVIEW)
  (gl-load-identity)
  )

(define (keyboard key x y)
  (cond
   ((= key 27)                          ;ESC
    (exit 0)))
  )

(define (main args)
  (glut-init args)
  (glut-init-display-mode (logior GLUT_SINGLE GLUT_RGB))
  (glut-init-window-size 650 50)
  (glut-create-window (car args))
  (init)
  (glut-reshape-func reshape)
  (glut-keyboard-func keyboard)
  (glut-display-func disp)
  (glut-main-loop)
  0)