Hello World example for Allegro.

hello.c

/*
 * This program uses the Allegro game library to display a blank window.
 *
 * It initializes the display and starts up the main game loop. The
 * game loop only checks for two events: timer (determined by the FPS)
 * and display close (when the user tries to close the window).
 *
 * http://www.damienradtke.org/building-a-mario-clone-with-allegro
 */

#include <stdio.h>
#include <allegro5/allegro.h>

const float FPS = 60;

int main(int argc, char *argv[])
{
	ALLEGRO_DISPLAY *display = NULL;
	ALLEGRO_EVENT_QUEUE *event_queue = NULL;
	ALLEGRO_TIMER *timer = NULL;

	bool running = true;
	bool redraw = true;

	// Initialize allegro
	if (!al_init()) {
		fprintf(stderr, "Failed to initialize allegro.\n");
		return 1;
	}

	// Initialize the timer
	timer = al_create_timer(1.0 / FPS);
	if (!timer) {
		fprintf(stderr, "Failed to create timer.\n");
		return 1;
	}

	// Create the display
	display = al_create_display(640, 480);
	if (!display) {
		fprintf(stderr, "Failed to create display.\n");
		return 1;
	}

	// Create the event queue
	event_queue = al_create_event_queue();
	if (!event_queue) {
		fprintf(stderr, "Failed to create event queue.");
		return 1;
	}

	// Register event sources
	al_register_event_source(event_queue, al_get_display_event_source(display));
	al_register_event_source(event_queue, al_get_timer_event_source(timer));

	// Display a black screen
	al_clear_to_color(al_map_rgb(0, 0, 0));
	al_flip_display();

	// Start the timer
	al_start_timer(timer);

	// Game loop
	while (running) {
		ALLEGRO_EVENT event;
		ALLEGRO_TIMEOUT timeout;

		// Initialize timeout
		al_init_timeout(&timeout, 0.06);

		// Fetch the event (if one exists)
		bool get_event = al_wait_for_event_until(event_queue, &event, &timeout);

		// Handle the event
		if (get_event) {
			switch (event.type) {
				case ALLEGRO_EVENT_TIMER:
					redraw = true;
					break;
				case ALLEGRO_EVENT_DISPLAY_CLOSE:
					running = false;
					break;
				default:
					fprintf(stderr, "Unsupported event received: %d\n", event.type);
					break;
			}
		}

		// Check if we need to redraw
		if (redraw && al_is_event_queue_empty(event_queue)) {
			// Redraw
			al_clear_to_color(al_map_rgb(0, 0, 0));
			al_flip_display();
			redraw = false;
		}
	} 

	// Clean up
	al_destroy_display(display);
	al_destroy_event_queue(event_queue);

	return 0;
}

Makefile

CC := gcc
CFLAGS := -g -Wall
LIBS := -lallegro
SOURCES := $(shell find src/ -type f -name "*.c")
OBJECTS := $(SOURCES:.c=.o)
TARGET := game
 
all: $(SOURCES) $(TARGET)
 
$(TARGET): $(OBJECTS)
    @echo " Linking..."; $(CC) $^ -o $@ $(LIBS)
 
%.o: %.c
    @echo " CC $<"; $(CC) $(CFLAGS) -c -o $@ $<
 
clean:
    @echo " Cleaning..."; $(RM) src/*.o $(TARGET)
 
.PHONY: all clean

Another simple Makefile I recommend for one source file (Allegro 5.0 on Linux) -

CC = gcc
FLAGS = -Wall `pkg-config --cflags --libs allegro-5.0`
BIN = program
SOURCE = program.c

all:
	$(CC) $(SOURCE) $(FLAGS) -o $(BIN)

That is the newer approach to compile by using a make file. I still compile it by using gcc myfile.c -lallegro (Linux) I could just whip up a bash script to simplify it but if I ever publish code I will have to keep up with the new generation.

Where would I put the game logic? In the past I usually had like 3 basic functions for the game loop

void input(); // Handle keyboard/mouse/etc events
void update(); // Update entities with data from user input
void draw(); // Draw entities

Then I guess after that it would display the new frame with all the new data.

So where might I add this pattern to your template?

*Edit: Also, if you don't mind, could you explain how this code works? I watched an allegro tutorial video already and it explained most of what you have here, but you did things differently. Like you flip the display before the game loop and again inside the game loop. Why? In the tutorial I saw there was only one flip at the end of the game loop. This is the video: https://www.youtube.com/watch?v=27G-2-wn41w and this is his site with the code: http://www.gamefromscratch.com/page/Allegro-Tutorial-Series.aspx

Any information you're willing to share would be very helpful. I'm new to the world of game frameworks, but very interested. Thanks!

This is not a hello world example as it produces a black window.

thanka lot it help to understand the basic