pong/pong.c

#include <stdio.h>
#include <stdlib.h>
#include <allegro5/allegro.h>
#include <allegro5/allegro_font.h>
#include <allegro5/allegro_ttf.h>
#include <allegro5/allegro_image.h>
#include <allegro5/allegro_primitives.h>
#include <math.h>

#define WIN_WIDTH 1000
#define WIN_HEIGHT 600

void alleg_init();

void alleg_init() {
	al_init();
	al_install_keyboard();
	al_install_mouse();
	al_init_image_addon();
	al_init_font_addon();
	al_init_ttf_addon();

	return;
}

int main(int argc, char** argv) {
//	Initialization

	alleg_init();
	ALLEGRO_DISPLAY* disp = al_create_display(WIN_WIDTH, WIN_HEIGHT);
	ALLEGRO_EVENT_QUEUE* queue  = al_create_event_queue();
	al_register_event_source(queue,al_get_keyboard_event_source());
	ALLEGRO_COLOR black = al_map_rgba(0,0,0,255);
	ALLEGRO_COLOR white = al_map_rgba(255,255,255,255);
	ALLEGRO_EVENT event;
	ALLEGRO_FONT* main_font = al_load_ttf_font("/usr/share/fonts/cantarell/Cantarell-VF.otf", 30, 0);

	bool running = false;
	srand(time(NULL)); // Seed for RNG

	float width = 25;  // Width and height of paddles
	float height = 150;
	float start_x_1 = 10; // Top-left coordinates of first paddle
	float start_y_1 = 10;
	float start_x_2 = WIN_WIDTH - 10 - width; // Top-left coordinates of second paddle
	float start_y_2 = 10;
	float velocity_1 = 0;  // Vertical velocity of first paddle
	float velocity_2 = 0;  // Vertical velocity of second paddle

	float circ_x = 60; // Center coordinates of ball
	float circ_y = 25;
	float circ_rad = 15;  // Radius of ball
	float ball_speed = sqrt(72); // Pythagorean distance travelled by ball in one main-loop iteration
	float circ_vel_x = (float)(rand())/(float)(RAND_MAX / 3) + 4.0; // Horizontal velocity of ball (Randomly generated, 4 to 7) - borrowed from https://stackoverflow.com/a/13409133
	float circ_vel_y = sqrt(pow(ball_speed,2) - pow(circ_vel_x,2)); // Vertical velocity of ball - Subtract X velocity from hypotenuse / ball_speed

	int score_1 = 0; // Player 1 score
	int score_2 = 0; // Player 2 score

//	I reset the ball position here, so that the ball starts from the same place after I press SPACE
	circ_x = 60;
	circ_y = 25;

	al_clear_to_color(black);
	al_draw_filled_rectangle(start_x_1, start_y_1, start_x_1 + width, start_y_1 + height, white);
	al_draw_filled_rectangle(start_x_2, start_y_2, start_x_2 + width, start_y_2 + height, white);
	al_draw_filled_circle(circ_x, circ_y, circ_rad, white);
	al_draw_text(main_font, white, (WIN_WIDTH / 2), (WIN_HEIGHT / 2), ALLEGRO_ALIGN_CENTRE, "Welcome to Pong!\0");
	al_flip_display();

	do {
		al_wait_for_event(queue, &event);
	} while (!(event.type == ALLEGRO_EVENT_KEY_DOWN && event.keyboard.keycode == ALLEGRO_KEY_SPACE));

	running = true;

	al_clear_to_color(black);
	al_draw_filled_rectangle(start_x_1, start_y_1, start_x_1 + width, start_y_1 + height, white);
	al_draw_filled_rectangle(start_x_2, start_y_2, start_x_2 + width, start_y_2 + height, white);
	al_draw_filled_circle(circ_x, circ_y, circ_rad, white);
	al_flip_display();

	while (running) {
		// Code borrowed from: https://stackoverflow.com/a/30078011

		while (!al_is_event_queue_empty(queue)) {
			al_get_next_event(queue, &event);

			if (event.type == ALLEGRO_EVENT_KEY_DOWN) {
				switch (event.keyboard.keycode) {
					case ALLEGRO_KEY_W:
						velocity_1 -= 5;
						break;
					case ALLEGRO_KEY_S:
						velocity_1 += 5;
						break;
					case ALLEGRO_KEY_UP:
						velocity_2 -= 5;
						break;
					case ALLEGRO_KEY_DOWN:
						velocity_2 += 5;
						break;

					case ALLEGRO_KEY_Q:
						running = false;
						break;
				}

			} else if (event.type == ALLEGRO_EVENT_KEY_UP) {
				switch (event.keyboard.keycode) {
					case ALLEGRO_KEY_W:
						velocity_1 += 5;
						break;
					case ALLEGRO_KEY_S:
						velocity_1 -= 5;
						break;
					case ALLEGRO_KEY_UP:
						velocity_2 += 5;
						break;
					case ALLEGRO_KEY_DOWN:
						velocity_2 -= 5;
						break;

				}
			}
		}

		al_clear_to_color(black);

		// Update positions
		((velocity_1 < 0 && start_y_1  > 0) || (velocity_1 > 0 && start_y_1 + height < WIN_HEIGHT)) && (start_y_1 += velocity_1);
		((velocity_2 < 0 && start_y_2  > 0) || (velocity_2 > 0 && start_y_2 + height < WIN_HEIGHT)) && (start_y_2 += velocity_2);
		circ_x += circ_vel_x;
		circ_y += circ_vel_y;

		if (circ_x + circ_rad >= WIN_WIDTH - 10 - width) { // FOR PADDLE 2: If the circle has reached the point where the paddle would be...
			if (circ_y > start_y_2 && circ_y < start_y_2 + height) { // If the circle is touching the paddle...
				circ_vel_x = -circ_vel_x;
			}
		} else if (circ_x - circ_rad <= 10 + width) { // FOR PADDLE 1
			if (circ_y > start_y_1 && circ_y < start_y_1 + height) {
				circ_vel_x = -circ_vel_x;
			}
		}

		if ((circ_y + circ_rad >= WIN_HEIGHT) || (circ_y - circ_rad <= 0)) {
			circ_vel_y = -circ_vel_y;
		}

		if (circ_x - circ_rad <= 0 || circ_x + circ_rad >= WIN_WIDTH) {
			if (circ_x - circ_rad <= 0) {
				score_2++;
			}
			if (circ_x + circ_rad >= WIN_WIDTH) {
				score_1++;
			}
			printf("Player 1: %d\n",score_1);
			printf("Player 2: %d\n\n", score_2);
			circ_x = 60;
			circ_y = 25;
			circ_vel_x = (float)(rand())/(float)(RAND_MAX / 3) + 4.0;
			circ_vel_y = sqrt(pow(ball_speed,2) - pow(circ_vel_x,2));
			sleep(1);
		}

		//Redraw shapes
		al_draw_filled_rectangle(start_x_1, start_y_1, start_x_1 + width, start_y_1 + height + velocity_1, white);
		al_draw_filled_rectangle(start_x_2, start_y_2, start_x_2 + width, start_y_2 + height + velocity_2, white);
		al_draw_filled_circle(circ_x, circ_y, circ_rad, white);
		al_flip_display();

	printf("Ball x: %.0f y: %.0f\n", circ_x, circ_y);
	}

//	Clean up
	al_destroy_display(disp);
	al_destroy_event_queue(queue);

	return 0;
}