ALLEGRO_PRIM_QUALITY man page
ALLEGRO_PRIM_QUALITY — Allegro 5 API
#include <allegro5/allegro_primitives.h> #define ALLEGRO_PRIM_QUALITY 10
Controls the quality of the approximation of curved primitives (e.g. circles). Curved primitives are drawn by approximating them with a sequence of line segments. By default, this roughly corresponds to error of less than half of a pixel.