bionic (3) keyboard_callback.3alleg4.gz

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(3alleg4),      readkey(3alleg4),     ureadkey(3alleg4),     keyboard_ucallback(3alleg4),
       keyboard_lowlevel_callback(3alleg4)