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--  US Government Users Restricted Rights
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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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--  OpenGL(TM) is a trademark of Silicon Graphics, Inc.
--

with GL; use GL;
with Glut; use Glut;

package body Texgen_Procs is
   stripeImage : array (0 .. 95) of aliased GLubyte;

   procedure makeStripeImage is
   begin
      for j in 0 .. 31 loop
         if j <= 4 then stripeImage (3*j) := 255;
         else stripeImage (3*j) := 0;
         end if;

         if j > 4 then stripeImage (3*j+1) := 255;
         else stripeImage (3*j+1) := 0;
         end if;

         stripeImage (3*j+2) := 0;
      end loop;
   end makeStripeImage;

   sgenparams : array (0 .. 3) of aliased GLfloat :=
      (1.0, 1.0, 1.0, 0.0);

   procedure DoInit is
   begin
      glClearColor (0.0, 0.0, 0.0, 0.0);

      makeStripeImage;
      glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
      glTexEnvi (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
      glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_REPEAT);
      glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
      glTexParameteri (GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
      glTexImage1D (GL_TEXTURE_1D, 0, 3, 32, 0,
         GL_RGB, GL_UNSIGNED_BYTE, stripeImage(0)'Access);

      glTexGeni (GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);
      glTexGenfv (GL_S, GL_OBJECT_PLANE, sgenparams (0)'ACCESS);

      glEnable (GL_DEPTH_TEST);
      glDepthFunc (GL_LESS);
      glEnable (GL_TEXTURE_GEN_S);
      glEnable (GL_TEXTURE_1D);
      glEnable (GL_CULL_FACE);
      glEnable (GL_LIGHTING);
      glEnable (GL_LIGHT0);
      glEnable (GL_AUTO_NORMAL);
      glEnable (GL_NORMALIZE);
      glFrontFace (GL_CW);
      glCullFace (GL_BACK);
      glMaterialf (GL_FRONT, GL_SHININESS, 64.0);
   end DoInit;

   procedure DoDisplay is
   begin
      glClear (GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);
      glPushMatrix;
      glRotatef (45.0, 0.0, 0.0, 1.0);
      glutSolidTeapot (2.0);
      glPopMatrix;
      glFlush;
   end DoDisplay;


   procedure ReshapeCallback (w : Integer; h : Integer) is
   begin
      glViewport (0, 0, GLsizei(w), GLsizei(h));

      glMatrixMode (GL_PROJECTION);
      glLoadIdentity;

      if w <= h then
         glOrtho (-3.5, 3.5, GLdouble (-3.5*GLdouble (h)/GLdouble (w)),
            GLdouble (3.5*GLdouble (h)/GLdouble (w)), -3.5, 3.5);
      else
         glOrtho ((-3.5*GLdouble (w)/GLdouble (h)),
            GLdouble (3.5*GLdouble (w)/GLdouble (h)), -3.5, 3.5, -3.5, 3.5);
      end if;

      glMatrixMode (GL_MODELVIEW);
      glLoadIdentity;
   end ReshapeCallback;
end Texgen_Procs;