Function zng::event::on_command

pub fn on_command<U, CB, E, EB, H>(
    child: U,
    command_builder: CB,
    enabled_builder: EB,
    handler: H,
) -> impl UiNode
where
    U: UiNode,
    CB: FnMut() -> Command + Send + 'static,
    E: Var<bool>,
    EB: FnMut() -> E + Send + 'static,
    H: WidgetHandler<CommandArgs>,

Helper for declaring command event properties.

This function is used by the command_property! macro.

Command

The command_builder closure is called on init to generate the command, it is a closure to allow creation of widget scoped commands. The event handler will receive events for the command and scope that target the widget where it is set.

If the command is scoped on the root widget and on_command is set on the same root widget a second handle is taken for the window scope too, so callers can target the window using the window ID or the root widget ID.

Enabled

The enabled_builder closure is called on init to generate a boolean variable that defines if the command handle is enabled. Command event handlers track both their existence and the enabled flag, see Command::subscribe for details.

Note that the command handler can be enabled even when the widget is disabled, the widget will receive the event while disabled in this case, you can use this to show feedback explaining why the command cannot run.

Route

The event handler is called after the on_pre_command equivalent at the same context level. If the command event targets more then one widget and one widget contains the other, the handler is called on the inner widget first.

Async

Async event handlers are called like normal, but code after the first .await only runs in subsequent updates. This means that propagation must be stopped before the first .await, otherwise you are only signaling other async tasks handling the same event, if they are monitoring the propagation handle.