/*
   Author: Adam Hewgill (November 2002)

   COSC 3P98 example: pointbounce.c: 
   Three polygons bounce on the screen. Alpha causes their
   colours to interact when they are on top of each other.
*/

#if !defined(Linux)
  #include <windows.h>           //Not Linux must be windows
#endif
#include <GL/gl.h>
#include <GL/glut.h>
#include <stdio.h>


#define X	0
#define Y	1
#define XMAX	500
#define YMAX	500

struct global
{
	int r, vel;
	int p1[2], p2[2], p3[2];
	int m1[2], m2[2], m3[2];
	float c1[4], c2[4], c3[4];
}g = {100, 3, {0, 0}, {XMAX, YMAX}, {123, 452}, {1, 1}, {-1, -1}, {1, 2},
     {1, 1, 0, 0.5}, {0, 1, 1, 0.5}, {0, 0, 1, 0.5}};


void draw(void)
{
	// Draw the particles
	glClear(GL_COLOR_BUFFER_BIT);

	glBegin(GL_QUADS);
		glColor4fv(g.c1);
		glVertex2i(g.p1[X]-g.r, g.p1[Y]-g.r);
		glVertex2i(g.p1[X]+g.r, g.p1[Y]-g.r);
		glVertex2i(g.p1[X]+g.r, g.p1[Y]+g.r);
		glVertex2i(g.p1[X]-g.r, g.p1[Y]+g.r);
		glColor4fv(g.c2);
		glVertex2i(g.p2[X]-g.r, g.p2[Y]-g.r);
		glVertex2i(g.p2[X]+g.r, g.p2[Y]-g.r);
		glVertex2i(g.p2[X]+g.r, g.p2[Y]+g.r);
		glVertex2i(g.p2[X]-g.r, g.p2[Y]+g.r);
		glColor4fv(g.c3);
		glVertex2i(g.p3[X]-g.r, g.p3[Y]-g.r);
		glVertex2i(g.p3[X]+g.r, g.p3[Y]-g.r);
		glVertex2i(g.p3[X]+g.r, g.p3[Y]+g.r);
		glVertex2i(g.p3[X]-g.r, g.p3[Y]+g.r);
	glEnd();

	glutSwapBuffers();
	glFlush();
	
	// Move the particles
	g.p1[X] += g.m1[X] * g.vel;
	g.p1[Y] += g.m1[Y] * g.vel;
	g.p2[X] += g.m2[X] * g.vel;
	g.p2[Y] += g.m2[Y] * g.vel;
	g.p3[X] += g.m3[X] * g.vel;
	g.p3[Y] += g.m3[Y] * g.vel;

	// Bounce point 1
	if (g.p1[X] > XMAX || g.p1[X] < 0)
		g.m1[X] *= -1;
	if (g.p1[Y] > YMAX || g.p1[Y] < 0)
		g.m1[Y] *= -1;

	// Bounce point 2
	if (g.p2[X] > XMAX || g.p2[X] < 0)
		g.m2[X] *= -1;
	if (g.p2[Y] > YMAX || g.p2[Y] < 0)
		g.m2[Y] *= -1;

	// Bounce point 3
	if (g.p3[X] > XMAX || g.p3[X] < 0)
		g.m3[X] *= -1;
	if (g.p3[Y] > YMAX || g.p3[Y] < 0)
		g.m3[Y] *= -1;
}


void keyboard(unsigned char key, int x, int y)
{
	switch (key){
		case 0x1B:
		case 'q':
		case 'Q':
			return;
		break;
	}
}


main(int argc, char **argv)
{
	// Initialize OpenGL
	glutInit(&argc, argv);
	glutInitWindowSize(XMAX, YMAX);
	glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
	glutCreateWindow("Particle Bounce");

	// Register Callbacks
	glutKeyboardFunc(keyboard);
	glutDisplayFunc(draw);
	glutIdleFunc(draw); 

	// Setup view
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0, XMAX, 0, YMAX, 0, 1);

	glClearColor(0.0, 0.0, 0.0, 1.0);
	
	//Enable alpha blending
	glEnable(GL_ALPHA_TEST);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	// Start OpenGL
	glutMainLoop();
}