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

GLuint framebuffer, renderbuffer;
#define WIDTH 300
#define HEIGHT 350
int numSamples;

void init()
{
	glGetIntegerv(GL_MAX_SAMPLES_EXT, &numSamples);

	glGenFramebuffersEXT(1, &framebuffer);
	glGenRenderbuffersEXT(1, &renderbuffer);
	glBindFramebufferEXT(GL_FRAMEBUFFER, framebuffer);
	glBindRenderbufferEXT(GL_RENDERBUFFER, renderbuffer);
	glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, numSamples, GL_RGBA, WIDTH, HEIGHT);
	glFramebufferRenderbufferEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);
	glEnable (GL_MULTISAMPLE);
	
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0.0, WIDTH, 0.0, HEIGHT, -1.0, 1.0);
}

void display()
{
	glBindFramebufferEXT(GL_FRAMEBUFFER,framebuffer);

	glClearColor(0.0, 0.0, 0.0, 1.0);
	glClear(GL_COLOR_BUFFER_BIT);

	glEnable(GL_BLEND);
	GLenum src_factor, dst_factor;
	src_factor = GL_SRC_ALPHA;
	dst_factor = GL_ONE_MINUS_SRC_ALPHA;
	glBlendFunc (src_factor, dst_factor);
	glColor4f (0.0, 1.0, 0.0, 0.7);
	glMatrixMode(GL_MODELVIEW);
	glBegin(GL_POLYGON);
		glVertex3f (140, 55, 0.0);
		glVertex3f (220, 55, 0.0);
		glVertex3f (220, 165, 0.0);
		glVertex3f (140, 165, 0.0);
	glEnd();

	glBindFramebufferEXT(GL_READ_FRAMEBUFFER, framebuffer);
	glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER, 0);
	glBlitFramebuffer(0, 0, WIDTH, HEIGHT, 0, 0, WIDTH, HEIGHT, GL_COLOR_BUFFER_BIT, GL_NEAREST);
	glBindFramebuffer(GL_FRAMEBUFFER, 0);

	glutSwapBuffers();
}


void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:  /*  Escape Key  */
         exit(0);
         break;
      default:
         break;
    }
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE| GLUT_RGBA | GLUT_ALPHA);
	glutInitWindowSize(WIDTH, HEIGHT);
	glutInitWindowPosition(100, 100);
	glutCreateWindow("msaa");
	init();
	glutDisplayFunc(display);
	glutKeyboardFunc (keyboard);
	glutMainLoop();
	return 0;
}