keyboard_lowlevel_callback(3) Allegro manual keyboard_lowlevel_callback(3)NAMEkeyboard_lowlevel_callback - User specified low level keyboard event
handler. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
extern void (*keyboard_lowlevel_callback)(int scancode);
DESCRIPTION
If set, this function is called by the keyboard handler in response to
every keyboard event, both presses (including keyboard repeat rate) and
releases. It will be passed a raw keyboard scancode byte (scancodes are
7 bits long), with the top bit (8th bit) clear if the key has been
pressed or set if it was released. This routine executes in an inter‐
rupt context, so it must be in locked memory. Example:
volatile int key_down, key_up;
void keypress_watcher(int scancode)
{
if (scancode & 0x80) {
key_up = 1;
} else {
key_down = 1;
}
} END_OF_FUNCTION(keypress_watcher)
...
install_timer();
LOCK_FUNCTION(silence_g_key);
LOCK_VARIABLE(key_down);
LOCK_VARIABLE(key_up);
install_keyboard();
keyboard_lowlevel_callback = keypress_watcher;
/* Disable keyboard repeat to get typewriter effect. */
set_keyboard_rate(0, 0);
...
while (game_loop) {
if (key_down) {
key_down = 0;
/* Play sample of typewriter key press. */
}
if (key_up) {
key_up = 0;
/* Play sample of typewriter key release. */
}
}
SEE ALSOinstall_keyboard(3), keyboard_callback(3), keyboard_ucallback(3),
exkeys(3)Allegro version 4.4.2 keyboard_lowlevel_callback(3)
