Event Handling

Event-driven keyboard input mechanism More...

Typedefs
typedef void(*	kbd_event_handler_t) (maple_device_t *dev, kbd_key_t key, key_state_t state, kbd_mods_t mods, kbd_leds_t leds, void *ud)
	Keyboard Event Handler Callback.

Functions
void	kbd_set_event_handler (kbd_event_handler_t callback, void *user_data)
	Registers an Event Handler.
void	kbd_get_event_handler (kbd_event_handler_t *callback, void **user_data)
	Returns the Registered Event Handler.

Detailed Description

Event-driven keyboard input mechanism

One method of checking for key input is to register an event handler, which will be notified every time a key changes state.

We first create a simple handler to print ENTER key events:

static void on_key_event(maple_device_t *dev, kbd_key_t key,
                         key_state_t state, kbd_mods_t mods,
                         kbd_leds_t leds, void *user_data) {

    if(key == KBD_KEY_ENTER) {
        if(state.value == KEY_STATE_CHANGED_DOWN)
            printf("Enter pressed!\n");
        else if(state.value == KEY_STATE_CHANGED_UP)
            printf("Enter released!\n");
    }
}

We then register our callback as the keyboard event handler:

kbd_set_event_handler(on_key_event, NULL);

Typedef Documentation

kbd_event_handler_t

typedef void(* kbd_event_handler_t) (maple_device_t *dev, kbd_key_t key, key_state_t state, kbd_mods_t mods, kbd_leds_t leds, void *ud)

Keyboard Event Handler Callback.

Function type which can be registered to listen to keyboard key events.

Parameters

dev	The maple device the event originated from.
key	The raw key ID whose state change triggered the event.
state	The new (transition) state of the key in question: KEY_STATE_CHANGED_DOWN: key pressed event KEY_STATE_CHANGED_UP: key released event
mods	Flags containing the states of all modifier keys.
leds	Flags containing the states of all LEDs.
ud	Arbitrary user-pointer which was registered with this handler.

See also

kbd_set_event_handler

Function Documentation

kbd_get_event_handler()

void kbd_get_event_handler	(	kbd_event_handler_t *	callback,
		void **	user_data )

Returns the Registered Event Handler.

This function returns the handler that has currently been registered to be notified upon keyboard events. The handler is returned in the form of its callback function and associated userdata.

Parameters

callback	Pointer-to-pointer which will be modifed to point to the address of the currently installed callback.
user_data	Pointer-to-pointer which will be modified to point to the address of the userdata associated with the currently installed callback.

See also

kbd_set_event_handler(), kbd_event_handler_t

kbd_set_event_handler()

void kbd_set_event_handler	(	kbd_event_handler_t	callback,
		void *	user_data )

Registers an Event Handler.

This function registers a function pointer as the keyboard event callback handler, also taking a generic user data pointer which gets passed back to the handler upon invocation.

The callback will be invoked any time a key state transition occurs on any connected keyboard. That is a key has either gone from released to pressed or from pressed to released.

Parameters

callback	Pointer to the function to be called upon key transition events.
user_data	Generic pointer which is stored internally and gets passed back to callback upon an event firing.

See also

kbd_get_event_handler(), kbd_event_handler_t