#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <sys/time.h>

#include <GL/glut.h>

int gfxsizex = 1000, gfxsizey = 800;
int len = 3000, clear = 1, continuous = 1;
struct timeval lastt;
int count = 0;

void draw (void) {
    int i;
    static int s = 0;
    float scale = gfxsizey / 2;
    fprintf (stderr, "draw s %d\n", s);
    if (clear)
	glClear (GL_COLOR_BUFFER_BIT);
    glBegin (GL_LINE_LOOP);
    for (i = 0; i < len; i++) {
	glColor3ub (127 + 128 * ((i+s) & 0x01),
		    127 + 64  * ((i+s) & 0x02),
		    127 + 32  * ((i+s) & 0x04));
	glVertex3f (scale * (1+ sin (i*2*M_PI/len)), scale * (1+ cos (i*2*M_PI/len)), 0);
    }
    glEnd();
    glFlush           ();
    glutSwapBuffers   ();
    s = (s+1)%len;
    if (continuous)
	glutPostRedisplay ();
}


void reshape (int width, int height) {
    fprintf (stderr, "reshape %d %d\n", width, height);
    gfxsizex = width;
    gfxsizey = height;
    glViewport     (0, 0, width, height);
    glMatrixMode   (GL_PROJECTION);
    glLoadIdentity ();
    glOrtho        (0, width, 0, height, 0, 1);
    glMatrixMode   (GL_MODELVIEW);
    glLoadIdentity ();
    glutPostRedisplay ();
}


void keyboard (unsigned char key, int x, int y) {
    exit (0);
}


int main (int argc, char *argv[]) {
    int db = 1;
    glutInitWindowSize  (gfxsizex, gfxsizey);
    glutInit            (&argc, argv);
    if (argc > 1) {
	len = atoi  (argv[1]);
	if (argc > 2) {
		if (argv[2][0] == 's')
		    db = 0;
		if (argc > 3) {
		    if (argv[3][0] == 'c')
			clear = 1;
		    if (argc > 4) {
			if (argv[4][0] == 'e')
			    continuous = 0;
		    }
		}
	}
    } else
	fprintf (stderr, "Usage: %s [<num_of_lines> [s|d (buffering) [c|- (clear) [e (run on expose only)]]]\n", argv[0]);
    fprintf (stderr, "Using %s buffer, lineloop of length %d\n",
	     db ? "double":"single", len);
    if (db)
	glutInitDisplayMode (GLUT_RGB|GLUT_DOUBLE);
    else
	glutInitDisplayMode (GLUT_RGB);
    glutCreateWindow    (argv[0]);
    glutReshapeFunc     (reshape);
    glutDisplayFunc     (draw);
    glutKeyboardFunc    (keyboard);

    gettimeofday (&lastt, NULL);
    glutMainLoop        ();

    exit (0);
}