Task: OpenGL

C: #include <stdlib.h>
#include <GL/gl.h>
#include <GL/glut.h>

void paint(void)
{
  glClearColor(0.3,0.3,0.3,0.0);
  glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

  glShadeModel(GL_SMOOTH);

  glLoadIdentity();
  glTranslatef(-15.0, -15.0, 0.0);

  glBegin(GL_TRIANGLES);
  glColor3f(1.0, 0.0, 0.0);
  glVertex2f(0.0, 0.0);
  glColor3f(0.0, 1.0, 0.0);
  glVertex2f(30.0, 0.0);
  glColor3f(0.0, 0.0, 1.0);
  glVertex2f(0.0, 30.0);
  glEnd();

  glFlush();
}

void reshape(int width, int height)
{
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-30.0, 30.0, -30.0, 30.0, -30.0, 30.0);
  glMatrixMode(GL_MODELVIEW);
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitWindowSize(640, 480);
  glutCreateWindow("Triangle");

  glutDisplayFunc(paint);
  glutReshapeFunc(reshape);

  glutMainLoop();

  return EXIT_SUCCESS;
}











Ada: with Lumen.Window;
with Lumen.Events;
with Lumen.Events.Animate;
with GL;
with GLU;

procedure OpenGL is

   The_Window : Lumen.Window.Handle;

   Program_Exit : Exception;

   
   procedure Quit_Handler (Event : in Lumen.Events.Event_Data) is
   begin
      raise Program_Exit;
   end;

   
   procedure Resize_Scene (Width, Height : in Natural) is
      use GL;
      use GLU;
   begin
      
      glViewport (0, 0, GLsizei (Width), GLsizei (Height));

      
      glMatrixMode (GL_PROJECTION);
      glLoadIdentity;

      
      gluPerspective (45.0, GLdouble (Width) / GLdouble (Height), 0.1, 100.0);

      
      glMatrixMode (GL_MODELVIEW);
      glLoadIdentity;
   end Resize_Scene;

   procedure Init_GL is
      use GL;
      use GLU;
   begin
      
      glShadeModel (GL_SMOOTH);

      
      glClearColor (0.0, 0.0, 0.0, 0.0);

      
      glClearDepth (1.0);
      
      glEnable (GL_DEPTH_TEST);
      
      glDepthFunc (GL_LEQUAL);

      glHint (GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
   end Init_GL;

   
   procedure Resize_Handler (Event : in Lumen.Events.Event_Data) is
      Height : Natural := Event.Resize_Data.Height;
      Width  : Natural := Event.Resize_Data.Width;
   begin
      
      if Height = 0 then
         Height := 1;
      end if;

      Resize_Scene (Width, Height);
   end;

   procedure Draw is
      use GL;
   begin
      
      glClear (GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);
      
      glLoadIdentity;

      
      glBegin (GL_TRIANGLES);
      glColor3f (1.0, 0.0, 0.0);
      glVertex3f ( 0.0,  1.0, 0.0);
      glColor3f (0.0, 1.0, 0.0);
      glVertex3f (-1.0, -1.0, 0.0);
      glColor3f (0.0, 0.0, 1.0);
      glVertex3f ( 1.0, -1.0, 0.0);
      glEnd;
   end Draw;

   procedure Frame_Handler (Frame_Delta : in Duration) is
   begin
      Draw;
      Lumen.Window.Swap (The_Window);
   end Frame_Handler;

begin

   Lumen.Window.Create (Win    => The_Window,
                        Name   => "OpenGL Demo",
                        Width  => 640,
                        Height => 480,
                        Events => (Lumen.Window.Want_Key_Press => True,
                                   Lumen.Window.Want_Exposure  => True,
                                   others                      => False));

   Resize_Scene (640, 480);
   Init_GL;

   Lumen.Events.Animate.Select_Events
     (Win   => The_Window,
      FPS   => Lumen.Events.Animate.Flat_Out,
      Frame => Frame_Handler'Unrestricted_Access,
      Calls => (Lumen.Events.Resized       => Resize_Handler'Unrestricted_Access,
                Lumen.Events.Close_Window  => Quit_Handler'Unrestricted_Access,
                others                     => Lumen.Events.No_Callback));

exception
   when Program_Exit =>
      null; 
end OpenGL;