OnEventView: add note regarding single callback per event
@@ -10,6 +10,9 @@ use view::{View, ViewWrapper};
/// This view registers a set of callbacks tied to specific events, to be run
/// in certain conditions.
///
+/// **Note**: only one callback can be registered per event. Trying to register
+/// a new one will replace any existing one for that event.
+///
/// * Some callbacks are called only for vents ignored by the wrapped view
/// (those registered by [`on_event`] or [`on_event_inner`])
/// * Others are processed first, and can control whether the child view should
