/* prac1b.c  */

/*
   Purpose: Allow keyboard input to change background colour of screen.
*/

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

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

int myrandom(int m)
{
	return rand()%m;
}

GLvoid keyboard(GLubyte key, GLint x, GLint y)
{
	switch (key) {
	case ' ':
		glClearColor(myrandom(10)/10.0, myrandom(10)/10.0, myrandom(10)/10.0,1.0);
		glutPostRedisplay();
		break;
	case KEY_ESC:
		exit(0);   /* exit when ESC pressed */
	}
}

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

void init( void )
{
	/* set background color */
	glClearColor(1.0,1.0,0.0,1.0);
}

int main(int argc, char* argv[])
{
	GLint width;
	GLint height;

	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

	width = glutGet(GLUT_SCREEN_WIDTH);
	height = glutGet(GLUT_SCREEN_HEIGHT);

	glutInitWindowPosition(width/4, height/4);
	glutInitWindowSize(width/2, height/2);
	glutCreateWindow(argv[0]);

	glutDisplayFunc(display);
	glutKeyboardFunc(keyboard);

	init();

	glutMainLoop();

	return 0;
}