fli_bmp_dirty_from(3)

📦 version 4.4.3.1, in fedora 43, fedora 44

💖 fli_bmp_dirty_from, fli_bmp_dirty_to 💖

okay bestie, so this is from the Allegro manual (yes, the game programming library, the one that lives in fli_bmp_dirty_from(3)) and it's genuinely such a small page but it's SO useful, i promise 🫶

✨ NAME ✨

fli_bmp_dirty_from, fli_bmp_dirty_to — literally just telling you which parts of the image have changed. that's it. that's the whole job. Allegro game programming library, periodt 💅

🌸 SYNOPSIS 🌸

#include <allegro.h>

extern int fli_bmp_dirty_from;

extern int fli_bmp_dirty_to;

two lil extern int globals, living their best life 🌈

🦋 DESCRIPTION 🦋

okay so listen. these two variables get set by next_fli_frame() and what they do is tell you which part of the fli_bitmap has changed since the last time somebody called reset_fli_variables(). iconic behaviour honestly 👑

here's the vibe check on the logic:

  • if fli_bmp_dirty_from is greater than fli_bmp_dirty_to → the bitmap has not changed. nothing happened. it's giving "no thoughts, head empty" 💀
  • otherwise → lines fli_bmp_dirty_from to fli_bmp_dirty_to (inclusive, bestie, don't forget the inclusive part) have altered.

so when are these actually useful?? when you're copying the fli_bitmap onto the screen!! because why would you move data you don't need to move?? that's just wasted effort and we don't do that here 💅 avoid moving data unnecessarily, slay.

example time, and i mean the exact example, no cap:

if (fli_bmp_dirty_from <= fli_bmp_dirty_to)
   blit(fli_bitmap, screen, 0, fli_bmp_dirty_from,
        0, fli_bmp_dirty_from, fli_bitmap->w,
        fli_bmp_dirty_to - fli_bmp_dirty_from + 1);

look at that guard clause doing its little <= check before it even thinks about blitting. main character energy fr fr ✨

👀 SEE ALSO 👀

go read those too, iykyk 🎀

lowkey this is one of those pages that's short but you WILL come back to it, so maybe bookmark it or whatever 🙈

and that's the whole page!! mwah 💜 this has been the Allegro manual, version 4.4.3, and yeah that's the date it was working with — catch you on the next manpage, bestie 🦋✨💖

📦 where this page comes from