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 * 
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 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
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 * Unpublished-- rights reserved under the copyright laws of the
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(*  varray.ml
 *  This program demonstrates vertex arrays.
 *)

(* OCaml version by Florent Monnier *)

open GL
open Glu
open Glut
open VertArray

let pointer = 1
let interleaved = 2

let drawarray = 1
let arrayelement = 2
let drawelements = 3

let setupMethod = ref pointer
let derefMethod = ref drawarray


let setupPointers() =
  let vertices =
    Bigarray.Array1.of_array Bigarray.nativeint Bigarray.c_layout
    [|  25n;  25n;
       100n; 325n;
       175n;  25n;
       175n; 325n;
       250n;  25n;
       325n; 325n; |]

  and colors =
    Bigarray.Array1.of_array Bigarray.float32 Bigarray.c_layout
    [| 1.0;  0.2;  0.2;
       0.2;  0.2;  1.0;
       0.8;  1.0;  0.2;
       0.75; 0.75; 0.75;
       0.35; 0.35; 0.35;
       0.5;  0.5;  0.5; |] in

  glEnableClientState GL_VERTEX_ARRAY;
  glEnableClientState GL_COLOR_ARRAY;

  glVertexPointer 2  Coord.GL_INT  0  vertices;
  glColorPointer 3  Color.GL_FLOAT  0  colors;
;;


let setupInterleave() =
  let intertwined =
    Bigarray.Array1.of_array Bigarray.float32 Bigarray.c_layout
    [| 1.0; 0.2; 1.0;  100.0; 100.0; 0.0;
       1.0; 0.2; 0.2;    0.0; 200.0; 0.0;
       1.0; 1.0; 0.2;  100.0; 300.0; 0.0;
       0.2; 1.0; 0.2;  200.0; 300.0; 0.0;
       0.2; 1.0; 1.0;  300.0; 200.0; 0.0;
       0.2; 0.2; 1.0;  200.0; 100.0; 0.0; |] in
  
  glInterleavedArrays GL_C3F_V3F  0  intertwined;
;;


let init() =
  glClearColor 0.0 0.0 0.0 0.0;
  glShadeModel GL_SMOOTH;
  setupPointers();
;;


let display() =
  glClear [GL_COLOR_BUFFER_BIT];

  if (!derefMethod = drawarray) then
    glDrawArrays GL_TRIANGLES  0 6

  else if (!derefMethod = arrayelement) then begin
     glBegin GL_TRIANGLES;
     glArrayElement 2;
     glArrayElement 3;
     glArrayElement 5;
     glEnd();
  end
  else if (!derefMethod = drawelements) then begin
    let indices =
      Bigarray.Array1.of_array Bigarray.nativeint Bigarray.c_layout
      [| 0n; 1n; 3n; 4n |]
    in

    glDrawElements GL_POLYGON  4  Elem.GL_UNSIGNED_INT  indices;
  end;

  glFlush ();
;;


let reshape ~width:w ~height:h =
  glViewport 0 0 w h;
  glMatrixMode GL_PROJECTION;
  glLoadIdentity();
  gluOrtho2D 0.0 (float w) 0.0 (float h);
;;


let mouse ~button ~state ~x ~y =
  match button, state with
  | GLUT_LEFT_BUTTON, GLUT_DOWN ->
      if (!setupMethod = pointer) then begin
        setupMethod := interleaved;
        setupInterleave();
      end
      else if (!setupMethod = interleaved) then begin
        setupMethod := pointer;
        setupPointers();
      end;
      glutPostRedisplay();

  | GLUT_MIDDLE_BUTTON, GLUT_DOWN
  | GLUT_RIGHT_BUTTON, GLUT_DOWN ->
      if (!derefMethod = drawarray) then
        derefMethod := arrayelement
      else if (!derefMethod = arrayelement) then
        derefMethod := drawelements
      else if (!derefMethod = drawelements) then
        derefMethod := drawarray;
      glutPostRedisplay();
  | _ -> ()
;;


let keyboard ~key ~x ~y =
  match key with
  | '\027' -> exit 0;
  | _ -> ()
;;


let () =
  ignore(glutInit Sys.argv);
  glutInitDisplayMode [GLUT_SINGLE; GLUT_RGB];
  glutInitWindowSize 350 350;
  glutInitWindowPosition 100 100;
  ignore(glutCreateWindow Sys.argv.(0));

  let gl_version = glGetString GL_VERSION in
  if gl_version < "1.1" then begin
    Printf.eprintf
        "This program demonstrates a feature which is not in OpenGL Version 1.0.\n\
         If your implementation of OpenGL Version 1.0 has the right extensions,\n\
         you may be able to modify this program to make it run.\n%!";
    exit 1;
  end;

  init ();
  glutDisplayFunc ~display;
  glutReshapeFunc ~reshape;
  glutMouseFunc ~mouse;
  glutKeyboardFunc ~keyboard;
  glutMainLoop();
;;