Whether either (or both) Alt keys should be held for the character to activate the shortcut.
It defaults to false, meaning all Alt keys must be released when the event is received in order to activate the shortcut. If it's true, then either one or both Alt keys must be pressed.
On macOS and iOS, the alt flag indicates that the Option key (⌥) is pressed. Because the Option key affects the character generated on these platforms, it can be unintuitive to define CharacterActivators for them.
For instance, if you want the shortcut to trigger when Option+s (⌥-s) is
pressed, and what you intend is to trigger whenever the character 'ß' is
produced, you would use
CharacterActivator('ß', alt: true) instead of
CharacterActivator('s', alt: true). This is because
CharacterActivator('s', alt: true) will
never trigger, since the 's' character can't be produced when the Option
key is held down.
If what is intended is that the shortcut is triggered when Option+s (⌥-s)
is pressed, regardless of which character is produced, it is better to use
SingleActivator, as in
SingleActivator(LogicalKeyboardKey.keyS, alt: true).
final bool alt;