1.99 class keyboard

The keyboard is the input_device @keyboard_device. Keyboard events refer to it as their event<-device. The window system combines all keyboards, so there is a single keyboard object.

Besides delivering events, the keyboard can be polled using keyboard<-key_down. This is useful for applications such as games that act on keys being held. Such an application may also follow the key events and the key_up events that release them (see class key_data). A game typically reads the keys on each tick of a timer:

tick(Ship) :-
    (   get(@keyboard_device, key_down, cursor_left, @on)
    ->  send(Ship, rotate, -5)
    ;   true
    ),
    ...

See also

- class input_device
- class gamepad

1.99.1 Get methods

keyboard <-key_down: key=name -> bool

@on if the key is held down. key is the name of a key event, e.g., cursor_left, RET, ESC or f1, a single character, space, or the name SDL uses for the key, e.g., Left Shift. A character refers to the key that produces it in the current keyboard layout. Fails with a report if the key is unknown.