// Last time we looked at rotation the cube looked 'broken' now it 
// looked like this because we had a single buffer running. This 
// means that the program is automatically drawing straight to the
// window. To fix this we add a second buffer, by changing the:
// glutInitDisplayMode (GLUT_SINGLE);
// to:
// glutInitDisplayMode (GLUT_DOUBLE);
// this is giving the program to draw what it has to, then transfer
// what is acctually needed to the screen.
// You may notice that alot of games these days even have a triple
// buffer, this makes the image even better.

// When changing the buffer from Single to Double we also have to
// tell the program to swap the buffers, so we acctually see what
// is on the second, and not just what we saw before.

// To do this, change the line in the 'display' function that says:
// glFlush();
// to:
// glutSwapBuffers();

// And your done, the cube should be rotating perfectly.

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

GLfloat angle = 0.0; //set the angle of rotation

void cube (void) {
	glRotatef(angle, 1.0, 0.0, 0.0); //rotate on the x axis
	glRotatef(angle, 0.0, 1.0, 0.0); //rotate on the y axis
	glRotatef(angle, 0.0, 0.0, 1.0); //rotate on the z axis
	glColor3f(1.0, 0.0, 0.0);
	glutWireCube(2);
}

void display (void) {
	glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glLoadIdentity();  
	gluLookAt (0.0, 0.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
	cube();
	glutSwapBuffers();
	angle ++;
}

void reshape (int w, int h) {
	glViewport (0, 0, (GLsizei)w, (GLsizei)h);
	glMatrixMode (GL_PROJECTION);
	glLoadIdentity ();
	gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
	glMatrixMode (GL_MODELVIEW);
}

int main (int argc, char **argv) {
    glutInit (&argc, argv);
	glutInitDisplayMode (GLUT_DOUBLE); //set up the double buffering
	glutInitWindowSize (500, 500);
	glutInitWindowPosition (100, 100);
    glutCreateWindow ("A basic OpenGL Window");
    glutDisplayFunc (display);
	glutIdleFunc (display);
	glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}