An optional property to provide all the keys that might be the final event to trigger this shortcut.
For example, for
Ctrl-A, LogicalKeyboardKey.keyA is the only trigger,
while LogicalKeyboardKey.control is not, because the shortcut should
only work by pressing KeyA after Ctrl, but not before. For
on the other hand, both KeyA and KeyE should be triggers, since either of
them is allowed to trigger.
If provided, trigger keys can be used as a first-pass filter for incoming events in order to optimize lookups, as Intents are stored in a Map and indexed by trigger keys. It is up to the individual implementors of this interface to decide if they ignore triggers or not.
Subclasses should make sure that the return value of this method does not change throughout the lifespan of this object.
This method might also return null, which means this activator declares all keys as trigger keys. Activators whose triggers return null will be tested with accepts on every event. Since this becomes a linear search, and having too many might impact performance, it is preferred to return non-null triggers whenever possible.
Iterable<LogicalKeyboardKey>? get triggers => null;