#include <GL/glut.h>


static const float black[4]    = { 0, 0, 0, 1 };
static const float white[4]    = { 1, 1, 1, 1 };
static const float diffuse[4]  = { 1, 0, 0, 1 };
static const float diffuseb[4] = { 0, 1, 0, 1 };
static const float specular[4] = { 0.5, 0.5, 0.5, 1 };
static const float ambient[4]  = { 0.2, 0.2, 0.2, 1 };
static const float lightpos[4] = { 0, 0, 10, 0 };
static const float shininess = 50;

static double angle = 0.0;

static int autorotate = 1;
static double angle_delta = 1.0;
static int timeout = 10;


static void
display (void)
{
	glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glPushMatrix ();
	glRotated (angle, 0.0, 1.0, 0.0);

	glBegin (GL_QUADS);
	glColor3f (1, 1, 1);
	glNormal3d (0, 0, 1);
	glVertex3d (-1, -1, 0);
	glVertex3d (+1, -1, 0);
	glVertex3d (+1, +1, 0);
	glVertex3d (-1, +1, 0);
	glEnd ();

	glPopMatrix ();

	glutSwapBuffers ();
}

static void
timer (int value)
{
	angle += angle_delta;
	glutTimerFunc (timeout, timer, 0);
	glutPostRedisplay ();
}

int
main (int argc, char **argv)
{
	/* init glut */
	glutInit (&argc, argv);
	glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
	glutCreateWindow ("Backface specular test");
	glutDisplayFunc (display);
	if (autorotate) glutTimerFunc (timeout, timer, 0);

	/* setup lighting */
	glMaterialfv (GL_FRONT, GL_DIFFUSE, diffuse);
	glMaterialfv (GL_BACK,  GL_DIFFUSE, diffuseb);

	glMaterialfv (GL_FRONT_AND_BACK, GL_EMISSION,  black);
	glMaterialfv (GL_FRONT_AND_BACK, GL_SPECULAR,  specular);
	glMaterialfv (GL_FRONT_AND_BACK, GL_AMBIENT,   ambient);
	glMaterialf  (GL_FRONT_AND_BACK, GL_SHININESS, shininess);

	glLightModeli (GL_LIGHT_MODEL_LOCAL_VIEWER, GL_FALSE);
	glLightModeli (GL_LIGHT_MODEL_COLOR_CONTROL, GL_SEPARATE_SPECULAR_COLOR);
	glLightModeli (GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE);

	glLightfv (GL_LIGHT0, GL_AMBIENT,  black);
	glLightfv (GL_LIGHT0, GL_DIFFUSE,  white);
	glLightfv (GL_LIGHT0, GL_POSITION, lightpos);
	glLightfv (GL_LIGHT0, GL_SPECULAR, white);

	glDisable (GL_CULL_FACE);
	glEnable (GL_LIGHTING);
	glEnable (GL_LIGHT0);

	/* setup camera */
	glMatrixMode (GL_PROJECTION);
	gluPerspective (30.0, 1.0, 1.0, 10.0);
	glMatrixMode (GL_MODELVIEW);
	gluLookAt (0.0, 0.0, 5.0,
			   0.0, 0.0, 0.0,
			   0.0, 1.0, 0.0);

	/* setup misc */
	glEnable (GL_DEPTH_TEST);
	glClearColor (0, 0, 1, 1);

	/* run */
	glutMainLoop ();

	return 0;
}