Example: global key event handler

[jamesdbrock]

Here is an example of how to handle global keyboard events in an Edifice app.

KeyHandler = Callable[[QKeyEvent], None]

_global_key_handlers: set[KeyHandler] = set()


def handle_key_up_global(event: QKeyEvent) -> None:
    """
    Use this as the on_key_up event handler for the root Window component.

    Then children can use the use_key_up_global Hook to register their own global key handlers.
    """
    for handler in _global_key_handlers:
        handler(event)


def use_key_up_global(key: Qt.Key, key_up_handler: KeyHandler) -> None:
    """
    Hook to register a global key handler for key up events.

    Example::

        use_key_up_global(Qt.Key.Key_Escape, lambda _: go_back())

    """

    def handler(event: QKeyEvent) -> None:
        # https://doc.qt.io/qtforpython-6/PySide6/QtCore/Qt.html#PySide6.QtCore.PySide6.QtCore.Qt.Key
        if event.key() == key:
            event.accept()
            key_up_handler(event)

    def setup():
        _global_key_handlers.add(handler)

        def cleanup():
            _global_key_handlers.remove(handler)

        return cleanup

    use_effect(setup, (key, key_up_handler))

@component
def EscKey(self, on_escape: Callable[[], None]):
    """This component, when rendered, will globally handle Esc key events."""
    use_key_up_global(Qt.Key.Key_Escape, lambda _: on_escape())
    Label(text="Esc")

@component
def Main(self):
    with Window(
        title="My Application",
        on_key_up=handle_key_up_global,
    ):
        ...