do_arc(3alleg4)

💖 do_arc 💖

okay bestie, you're in the Allegro manual, the game programming library, and this page is all about do_arc — the lil function that goes "hey, here's every single point on this arc, do whatever you want with them." ✨

✨ SYNOPSIS ✨

#include <allegro.h>

void do_arc(BITMAP *bmp, int x, int y, fixed a1, fixed a2, int r, int d,
void (*proc)(BITMAP *bmp, int x, int y, int d));

🌸 DESCRIPTION 🌸

So basically 💅 — do_arc calculates all the points in a circular arc around the point (x, y) with radius r, and for each one it calls the function you handed it. Obsessed, honestly.

That supplied function gets passed:

• a copy of the bmp parameter
• the x and y position
• a copy of the d parameter

...which means it's literally perfect for pairing with putpixel(). 🫶

The arc gets plotted anticlockwise, starting from the angle a1 and ending when it reaches a2. Those values are in 16.16 fixed point format — where 256 equals a full circle, 64 a right angle, etc. Zero is to the right of the centre point, and larger values rotate anticlockwise from there. slay. 🎀

Example, bestie:

   void draw_explosion_ring(BITMAP *bmp, int x, int y, int d)
   {
      ...
   }
      do_arc(screen, SCREEN_W/2, SCREEN_H/2,
          itofix(-21), itofix(43), 50, flame_color,
          draw_explosion_ring);

🦋 SEE ALSO 🦋

• do_circle(3alleg4)
• do_ellipse(3alleg4)
• do_line(3alleg4)
• arc(3alleg4)

and that's the whole vibe, queen 👑 this page lives in Allegro version 4.4.3, so if you're out here arcing your little heart out, that's the version you're doing it in. mwah 💋✨💖