program ogl_p1;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes, gl, glut;

var ScreenWidth, ScreenHeight: Integer;
const
  AppWidth = 640;
  AppHeight = 480;

procedure resize(width, height: LongInt); cdecl;
var
  ar: Real;
begin
     ar := width div height;

     glViewport(0, 0, width, height);
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity;
     glFrustum(-ar,ar,-1.0,1.0,2.0,100.0);

     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity;
end;

procedure display; cdecl;
begin
     glutSwapBuffers();
end;

procedure key(key: Byte; x,y: Integer); cdecl;
var
   mode: Integer;
begin
     WriteLn('Key = ', key);
     case key of
          ord('q'), 27:
            begin
                 Halt(0);
                 Exit;
            end;
          ord('r'):
            begin
                 mode:=glutGetModifiers();
                 if (mode <> 0) then
                 begin
                      case mode of
                           1:
                             begin
                    WriteLn('SHIFT key ', mode);
                    Exit;
                             end;
                           2:
                             begin
                    WriteLn('CTRL key ', mode);
                    Exit;
                             end;
                           4:
                             begin
                    WriteLn('ALT key ', mode);
                    Exit;
                             end;
                      end;
                      mode:=0;
                 end;
                 Exit;
            end;
     end;
     glutPostRedisplay();
end;

procedure skey(key: Integer; x,y: Integer); cdecl;
begin
     case key of
          GLUT_KEY_F1: Halt(0);
          GLUT_KEY_LEFT: WriteLn('GLUT_KEY_LEFT ', key);
          GLUT_KEY_RIGHT: WriteLn('GLUT_KEY_RIGHT ', key);
          GLUT_KEY_UP: WriteLn('GLUT_KEY_UP ', key);
          GLUT_KEY_DOWN: WriteLn('GLUT_KEY_DOWN ', key);
     end;
     glutPostRedisplay();
end;

procedure idle(); cdecl;
begin
     glutPostRedisplay();
end;

procedure main();
begin
     glutInit(@argc, argv);
     glutInitWindowSize(AppWidth, AppHeight);
     glutInitWindowPosition(10,10);
     glutInitDisplayMode(GLUT_RGB or GLUT_DOUBLE or GLUT_DEPTH);

     glutCreateWindow('TestApp');

     glutReshapeFunc(@resize);
     glutDisplayFunc(@display);

     glutKeyboardFunc(@key);
     glutSpecialFunc(@skey);

     glutMainLoop();
end;

begin
     main();
end.