keyboard_callback(3)            Allegro manual            keyboard_callback(3)



NAME
       keyboard_callback - User specified keyboard callback handler. Allegro
       game programming library.

SYNOPSIS
       #include <allegro.h>


       extern int (*keyboard_callback)(int key);

DESCRIPTION
       If set, this function is called by the keyboard handler in response to
       every keypress. It is passed a copy of the value that is about to be
       added into the input buffer, and can either return this value
       unchanged, return zero to cause the key to be ignored, or return a
       modified value to change what readkey() will later return. This routine
       executes in an interrupt context, so it must be in locked memory.
       Example:

          int enigma_scrambler(int key)
          {
             /* Add one to both the scancode and ascii values. */
             return (((key >> 8) + 1)
          }
          END_OF_FUNCTION(enigma_scrambler)

          ...

             install_timer();
             LOCK_FUNCTION(enigma_scrambler);
             install_keyboard();
             keyboard_callback = enigma_scrambler;

       Note that this callback will be ignored if you also set the unicode
       keyboard callback.


SEE ALSO
       install_keyboard(3), readkey(3), ureadkey(3), keyboard_ucallback(3),
       keyboard_lowlevel_callback(3)



Allegro                          version 4.2.3            keyboard_callback(3)
