Key is actuated.

Receiving this event type means that a key has been actuated
at the timestamp when the event is received, and while the event
recipient is focused.

For example, if the key is a keyboard key, then it was just
pressed.

Key is no longer actuated.

Receiving this event type means that a key has been de-actuated
at the timestamp when the event is received, and while the event
recipient is focused.

For example, if the key is a keyboard key, then it was just
released.

Key was actuated while the client wasn't able to receive it,
and is still actuated now that the client is able to receive
key events.

This may happen in a few ways:

- A new device was connected while its key was actuated.
- The key was actuated while the event recipient did not
have focus.

Therefore, this is not a "regular" key actuation. It reports
now that the key has been actuated in the unknown past. Some
event recipients may therefore decide that this is not an
actionable key event, while some others may decide that it is.

For example, recipients that trigger some user action may
decide to ignore `SYNC` events, to avoid spurious actions. In
contrast, recipients that keep track of the keyboard
state may want to consider a `SYNC` event as a signal
to update the key's state to actuated.

Key may have been actuated, but its actuation has
become invalid due to an event other than a key
de-actuation.

This may happen in a few ways:

- A device was disconnected while its key was actuated.
- The event recipient just lost focus.

Therefore, this is not a "regular" key de-actuation. It reports
the key is no longer validly actuated due to an event other than
a key release. Some event recipients may therefore decide that
this is not an actionable key event, while some others may
decide that it is.

For example, recipients which trigger some user action may
decide to ignore `CANCEL` events, to avoid spurious actions. In
contrast, recipients that keep track of the keyboard
state may want to consider a `CANCEL` event as a signal to update
the key's state to being de-actuated.

The key event was handled and its further propagation should be stopped.

The key event wasn't handled and should be delivered to other clients or listeners.