/*
 *  single.c
 *
 *  This program animates a square rotating. The square is drawn into the
 *  using "single" buffer mode. As a result the image tears and flickers.
 *
 *  Pat Hanrahan 1/97
 */
#include "glut.h"

static GLfloat spin = 0.0;

void 
Spin(void)
{
    spin = spin + 2.0;
    if (spin > 360.0)
	spin = spin - 360.0;

    glutPostRedisplay();
}

void 
Display(void)
{
    glClearColor (0.0, 0.0, 0.0, 1.0);
    glClear (GL_COLOR_BUFFER_BIT);

    glPushMatrix ();
	glRotatef (spin, 0.0, 0.0, 1.0);
	glColor3f (1.0, 1.0, 1.0);
	glRectf (-25.0, -25.0, 25.0, 25.0);
    glPopMatrix ();

    glFinish();
}

void 
Reshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= h) 
	glOrtho (-50.0, 50.0, -50.0*(GLfloat)h/(GLfloat)w, 
	    50.0*(GLfloat)h/(GLfloat)w, -1.0, 1.0);
    else 
	glOrtho (-50.0*(GLfloat)w/(GLfloat)h, 
	    50.0*(GLfloat)w/(GLfloat)h, -50.0, 50.0, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity ();
}

void
Keyboard( unsigned char key, int x, int y )
{
#define ESCAPE '\033'

    if( key == ESCAPE )
        exit(0);
}

int
main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowSize(512, 512);
    glutCreateWindow("Spinning Square (Single Buffer)");

    glutDisplayFunc(Display);
    glutReshapeFunc(Reshape);
    glutKeyboardFunc(Keyboard);
    glutIdleFunc(Spin);

    glutMainLoop();
}