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

static GLfloat spin = 0.0;

void init(void)
{
 glClearColor(0.0, 0.0, 0.0, 0.0);
 glShadeModel(GL_FLAT);
}

void display(void)
{
 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();
 glutSwapBuffers();
}

void spinDisplay(void)
{
 spin = spin + 2.0;
 if(spin > 360.0)
    spin = spin - 360.0;
 glutPostRedisplay();
}

void reshape (int w, int h)
{
 glViewport(0, 0, (GLsizei)w, (GLsizei)h);
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 glOrtho(-50.0, 50.0, -50.0, 50.0, -1.0, 1.0);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
}

void mouse (int button, int state, int x, int y)
{
 switch(button) {
   case GLUT_LEFT_BUTTON:
      if(state == GLUT_DOWN)
         glutIdleFunc(spinDisplay);
      break;
    case GLUT_MIDDLE_BUTTON:
      if(state == GLUT_DOWN) 
         glutIdleFunc(NULL);
      break;
    default:
      break;
  }
}

int main(int argc, char *argv[])
{
 glutInit(&argc,argv);
 glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
 glutInitWindowSize(250, 250);
 glutInitWindowPosition(100, 100);
 glutCreateWindow("test swap buffers");
 init();
 glutDisplayFunc(display);
 glutReshapeFunc(reshape);
 glutMouseFunc(mouse);
 glutMainLoop();
 return 0;
}