Simple Allegro 5 program

#include <cstdio>
#include <allegro5/allegro.h>
#include <allegro5/allegro_primitives.h>

int main(int argc, char **argv)
{
    int screenW(640);
    int screenH(480);
    bool quit(false);

    ALLEGRO_DISPLAY *display = NULL;
    ALLEGRO_KEYBOARD_STATE keyState;
    ALLEGRO_BITMAP* buffer = NULL;

    if(!al_init()) { fprintf(stderr, "failed to initialize allegro!\n"); return -1; }

    display = al_create_display(screenW, screenH);
    if(!display) { fprintf(stderr, "failed to create display!\n"); return -1; }

    buffer = al_create_bitmap(screenW, screenH);
    if(!buffer) { fprintf(stderr, "failed to create buffer!\n"); return -1; }

    al_init_primitives_addon();
    al_install_keyboard();

    while (!quit)
    {
        al_get_keyboard_state(&keyState);
        if (al_key_down(&keyState, ALLEGRO_KEY_ESCAPE)) quit = true;

        al_set_target_bitmap(buffer);
        al_clear_to_color(al_map_rgb(0,50,60));
        al_draw_rectangle(0.5,0.5,640,480, al_map_rgb(250,250,0),0);
        al_draw_rectangle(10.5,10.5,630,470, al_map_rgb(250,250,0),0);

        al_set_target_backbuffer(display);
        al_draw_bitmap(buffer,0,0,0);
        al_flip_display();
    }

    al_destroy_bitmap(buffer);
    al_destroy_display(display);
    return 0;
}