/* spinRectangle.c   */
/*
	Purpose -  demo program to spin a rectangle
	around the z-axis, in idle time
*/


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

#define KEY_ESC 27  /* GLUT doesn't supply this  */


/* Global variables */
GLfloat angle = 0.0;



GLvoid keyboard(GLubyte key, GLint x, GLint y)
{
	switch (key) 
	{
	case KEY_ESC:
		exit(0);   /* exit when ESC pressed */
	break;
	}
}

GLvoid checkError( const char* const label )
{
	GLenum error;
	error = glGetError();
	while (GL_NO_ERROR != error )
	{
		fprintf(stderr,"%s: %s\n", label, gluErrorString(error) );
		error = glGetError();
	}
}

void idle( void )
{
	static GLint lastTime = 0;
	GLint time = glutGet(GLUT_ELAPSED_TIME);

	/* increment angle 20 degrees per second */
	angle += 20.0 * (time - lastTime)/1000;
	lastTime = time;

	glutPostRedisplay();
}


GLvoid display(GLvoid)
{
	/* Do all your OpenGL rendering here  */
	glClear(GL_COLOR_BUFFER_BIT);

	glLoadIdentity();  /* reset modelview  */

	glRotatef(angle, 0.0, 0.0, 1.0);
	glRectf(0.0, 0.0, 1.0, 1.0);

/*	glutSwapBuffers(); */  /* switch pointers to front and back buffers */

	checkError("display");
	glFlush();
}

void init(void)
{
	/* set background color */
	glClearColor(0.4,0.4,0.7,1.0);
	/* set the 2D orthographic projection */
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-2.0,2.0,-2.0,2.0,-2.0,2.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

}

int main(int argc, char* argv[])
{
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );  
/*	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB );  */

	glutCreateWindow(argv[0]);

	init();

	glutDisplayFunc(display);
	glutKeyboardFunc(keyboard);
	glutIdleFunc(idle);
/*	glDrawBuffer( GL_BACK ); */  /* draw to back buffer  */

	glutMainLoop();

	return 0;
}