al_draw_star

/*********************************al_draw_star.h*********************************/
#include <allegro5/allegro_primitives.h>
#include <math.h>
#define PI 3.14159265358979323846264338327950288419716939937510582
int al_draw_star(float x, float y, float r, int s, ALLEGRO_COLOR color, float thickness);
/*********************************al_draw_star.c*********************************/
#include "al_draw_star.h"

int al_draw_star(float x, float y, float r, int s, ALLEGRO_COLOR color, float thickness)
{
    int i = 0;
    do
    {
        float y1=y-(r*cos(i*(PI/180)));
        float x1=x+(r*sin(i*(PI/180)));
        float y2=y-((r/2)*cos((i+360/s/2)*(PI/180)));
        float x2=x+((r/2)*sin((i+360/s/2)*(PI/180)));
        al_draw_line(x1, y1, x2, y2, color, thickness);
        y1=y-((r/2)*cos((i+360/s/2)*(PI/180)));
        x1=x+((r/2)*sin((i+360/s/2)*(PI/180)));
        y2=y-(r*cos((i+360/s)*(PI/180)));
        x2=x+(r*sin((i+360/s)*(PI/180)));
        al_draw_line(x1, y1, x2, y2, color, thickness);
        i+=360/s;
    } while(i<360);
}
/*********************************example.c*********************************/
#include <stdio.h>
#include <allegro5/allegro.h>
#include <stdlib.h>
#include "al_draw_star.h"
const float FPS = 60;
const int SCREEN_W = 640;
const int SCREEN_H = 480;
int main()
{
    ALLEGRO_DISPLAY *display = NULL;
    ALLEGRO_EVENT_QUEUE *event_queue = NULL;
    ALLEGRO_TIMER *timer = NULL;
    bool redraw = true;
    al_init();
    al_init_primitives_addon();
    al_install_mouse();
    timer = al_create_timer(1.0 / FPS);
    display = al_create_display(SCREEN_W, SCREEN_H);
    al_clear_to_color(al_map_rgb(255, 0, 255));
    al_set_target_bitmap(al_get_backbuffer(display));
    event_queue = al_create_event_queue();
    al_register_event_source(event_queue, al_get_display_event_source(display));
    al_register_event_source(event_queue, al_get_timer_event_source(timer));
    al_register_event_source(event_queue, al_get_mouse_event_source());
    al_clear_to_color(al_map_rgb(0,0,0));
    al_flip_display();
    al_start_timer(timer);
    while(1)
    {
        ALLEGRO_EVENT ev;
        al_wait_for_event(event_queue, &ev);
        if(ev.type == ALLEGRO_EVENT_TIMER)
        {
            redraw = true;
        }
        else if(ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
        {
            break;
        }
        if(redraw && al_is_event_queue_empty(event_queue))
        {
            redraw = false;
            al_clear_to_color(al_map_rgb(0,0,0));
            al_draw_star(300, 300, 100, 5,al_map_rgb(255,255,255),3);
            al_flip_display();
        }
    }
    al_destroy_timer(timer);
    al_destroy_display(display);
    al_destroy_event_queue(event_queue);
    return 0;
}