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