mouse_x(3)

✨ mouse_x — bestie edition ✨

okay so this is the mouse_x(3) page from the Allegro manual, and it's literally just the global variables that hold your mouse's position and button vibes. iconic. let's get into it 🐭💖

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🌸 NAME 🌸

mouse_x, mouse_y, mouse_z, mouse_w, mouse_b, mouse_pos — global variables with the mouse position / button state. it's giving Allegro game programming library energy, fr fr.

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🦋 SYNOPSIS 🦋

#include <allegro.h>

extern volatile int mouse_x;

extern volatile int mouse_y;

extern volatile int mouse_z;

extern volatile int mouse_w;

extern volatile int mouse_b;

extern volatile int mouse_pos;

like. six little extern volatile int besties. that's the whole vibe check. 💅

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💖 DESCRIPTION 💖

so these are the global variables holding the current mouse position and button state. obsessed.

wherever possible, these values get updated asynchronously — like, they update themselves, main character energy, they don't need you. but (and this is the important part, no cap) if mouse_needs_poll() returns TRUE, you have to manually call poll_mouse() to update them with the current input state. so basically you gotta do the work yourself in that case. 🙈

here's the breakdown, bestie:

• mouse_x and mouse_y — the positions, as integers ranging from zero to the bottom right corner of the screen.
• mouse_z and mouse_w — hold the current vertical and horizontal wheel position, when you're using an input driver that supports wheel mice.
• mouse_b — a bitfield indicating the state of each button:
  • bit 0 = the left button
  • bit 1 = the right button
  • bit 2 = the middle button
  • additional non standard mouse buttons might be available as higher bits in this variable 👑

usage example, because we love a demo:

if (mouse_b & 1)
   printf("Left button is pressed\n");

if (!(mouse_b & 2))
   printf("Right button is not pressed\n");

see how bit 1 in mouse_b & 1 = left pressed, and !(mouse_b & 2) = right not pressed. yes queen, bitwise. 🔥

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🌈 the mouse_pos situation 🌈

the mouse_pos variable has the current X coordinate in the upper 16 bits and the Y in the lower 16 bits. it's giving two-for-one, two slays in one int.

this may be useful in tight polling loops, where a mouse interrupt could occur between your reading of the two separate variables — because you can copy this value into a local variable with a single instruction and then split it up at your leisure. atomic-ish behavior, we stan. ✨

example, and yes you're gonna wanna screenshot this:

int pos, x, y;

pos = mouse_pos;
x = pos >> 16;
y = pos & 0x0000ffff;

x from the top bits, y from the bottom bits, 0x0000ffff doing the masking. periodt. 💅

lowkey important: if you read mouse_x and mouse_y separately in a tight loop, an interrupt could sneak in between them. mouse_pos is the way around that. iykyk.

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👑 SEE ALSO 👑

• install_mouse(3)
• poll_mouse(3)
• mouse_needs_poll(3)
• exalpha(3)
• exlights(3)
• exmouse(3)
• exshade(3)
• exspline(3)
• extrans(3)

go read those too bestie, they're all connected, it's a whole cinematic universe 🎀

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Allegro, version 4.4.3, and this page is mouse_x(3) — mwah, that's a wrap, hope your mouse always knows where it is 🫶💜🌸