debian man page for keyboard_lowlevel_callback

keyboard_lowlevel_callback(3alleg4)				  Allegro manual			       keyboard_lowlevel_callback(3alleg4)

NAME
       keyboard_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 interrupt 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 ALSO
       install_keyboard(3alleg4), keyboard_callback(3alleg4), keyboard_ucallback(3alleg4), exkeys(3alleg4)

Allegro 							   version 4.4.2			       keyboard_lowlevel_callback(3alleg4)