#include <GL/glut.h>
#include <string.h>

int width = 640;
int height = 480;

void init(int argc, char** argv)
{
    glutInit(&argc, argv); // Initialisierung der GLUT Bibliothek
    glutInitDisplayMode(GLUT_SINGLE); // Initialisierung des Single Buffer Modes
    glutInitWindowSize(width, height); // Fenstergröße in Pixel (Breite, Hoehe)
    glutInitWindowPosition(
        100, 100); // Fensterposition in Pixel, ausgehend vom Ursprung des Window Systems
    glViewport(0, 0, width, height);
    glutCreateWindow("Hello world"); // Erstellen des Fensters
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0, width, 0, height);
    glMatrixMode(GL_MODELVIEW);
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
}

void display(void)
{
    const char* myText = "Hello World!";
    int j;

    glClear(GL_COLOR);
    glColor3f(1.0, 0.0, 0.0);

    glBegin(GL_POLYGON);
    glVertex3f((width / 2) - (width / 4), (height / 2) - (height / 4), 0.0);
    glVertex3f((width / 2) + (width / 4), (height / 2) - (height / 4), 0.0);
    glVertex3f((width / 2) + (width / 4), (height / 2) + (height / 4), 0.0);
    glVertex3f((width / 2) - (width / 4), (height / 2) + (height / 4), 0.0);
    glEnd();

    glColor3f(1.0, 1.0, 1.0);
    glRasterPos2i((width / 2) - (width / 4) + 10, (height / 2) - (height / 4) + 10);
    for (j = 0; j < strlen(myText); j++) {
        glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, myText[j]);
    }

    glFlush();
}

int main(int argc, char** argv)
{
    init(argc, argv);
    glutDisplayFunc(display); // Callback-Funktion für das Fenster
    glutMainLoop(); // Abgabe der Kontrolle an GLUT-Bibliothek
    return 0;
}