Allegro 在尝试画线时抛出错误

Question

For some reason allegro (C++ Game Engine), throws errors when i try to run... So first this code works fine ! :

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

int main(void)
{
    int width = 640, height = 480;
       ALLEGRO_DISPLAY *display = NULL;

    if (!al_init()) 
       return -1;


       display = al_create_display(width, height);


   if (!display) 
       return -1;


        al_flip_display();

        //al_draw_line(100, 100, width - 100, 100, al_map_rgb(255, 0, 0), 1);
        al_rest(3);


           al_destroy_display(display);
       return 0;
    }

But all the sudden when i try to uncomment that line above i get this "error".

More Closer Up:

As you can see above this is some type of assertion failling... Im Confused?! Help would be appreciated!

Answer 1

Before you can use the primitives add-on you need to initialize it by calling al_init_primitives_addon .

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

int main(void)
{
    int width = 640, height = 480;
    ALLEGRO_DISPLAY *display = NULL;

    if (!al_init())
        return -1;


    display = al_create_display(width, height);

    if (!display)
        return -1;

    al_init_primitives_addon();

    if (!al_init_primitives_addon())
        return -1;

    al_draw_line(0, 50, 300, 100, al_map_rgb(255, 0, 4), 1.0f);

    al_flip_display();


    al_rest(13);


    al_shutdown_primitives_addon();

    al_destroy_display(display);
    return 0;
}

The full documentation can be found here: https://www.allegro.cc/manual/5/al_init_primitives_addon .

Don't forget to call al_shutdown_primitives_addon when you're done.