// OpenGL Tutorial
// Hello_World.c
// http://www.eecs.tulane.edu/www/Terry/OpenGL/Introduction.html
/*************************************************************************
This program essentially opens a window, clears it, sets the drawing
color, draws the object, and flushes the drawing buffer.  It then goes
into an infinite loop accepting events and calling the appropriate
functions.
*************************************************************************/

//  gcc -o Hello_World Hello_World.c -lm -L/usr/lib -lGLU  -lGL -lglut  -L/usr/X11R6/lib -lX11 -lXext -lXi -lXmu

//OR USE lgcc scripts

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <GL/glut.h>

void init() {

	// Clear the window
	glClear(GL_COLOR_BUFFER_BIT);
}

void reshape(int width, int height) {

	// Set the new viewport size
	glViewport(0, 0, (GLint)width, (GLint)height);

	// Clear the window
	glClear(GL_COLOR_BUFFER_BIT);
}

void draw(void) {

	// Set the drawing color
	glColor3f(1.0, 1.0, 1.0);

	// Specify which primitive type is to be drawn
	glBegin(GL_POLYGON);
		// Specify verticies in quad
		glVertex2f(-0.5, -0.5);
		glVertex2f(-0.5, 0.5);
		glVertex2f(0.5, 0.5);
		glVertex2f(0.5, -0.5);
	glEnd();

	// Flush the buffer to force drawing of all objects thus far
	glFlush();
}

int main(int argc, char **argv) {

	// Open a window, name it "Hello World"
	glutInit(&argc, argv);  
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
	glutInitWindowSize(400, 400); 
	glutInitWindowPosition(200,200); 
	glutCreateWindow("Hello World");	

	// Set the clear color to black
	glClearColor(0.0, 0.0, 0.0, 0.0);

	// Call an initialization function
	init();

	// Assign reshape() to be the function called whenever 
	// a reshape event occurs
	glutReshapeFunc(reshape);

	// Assign draw() to be the function called whenever a display
	// event occurs, generally after a resize or expose event
	glutDisplayFunc(draw);

	// Pass program control to tk's event handling code
	// In other words, loop forever
	glutMainLoop();

	return 0;
}