Changeable

Changeable<T> is a static builder capability for requesting the next value of a controlled component. It neither commits internal business state nor publishes runtime events.

pub trait Changeable<T>: Sized {
    fn on_change(self, handler: impl Fn(T, &mut Window, &mut App) + 'static) -> Self;
    fn on_change_in<U: 'static>(
        self,
        cx: &Context<U>,
        handler: impl Fn(&mut U, T, &mut Window, &mut Context<U>) + 'static,
    ) -> Self;
}

Checkbox and Switch implement Changeable<bool>, RadioGroup implements Changeable<T>, and Input implements Changeable<SharedString>. Input calls on_change only when a user edit actually changes the value; programmatic InputState::set_value, clear, and reset do not call it. Changes may originate in keyboard, pointer, or platform text-input paths, so the callback carries no ClickEvent.

Each component keeps inherent builders with the same names, delegating to the same implementation as the trait.