Function update 

pub fn update<Message, T>(
    event: &Event,
    layout: Layout<'_>,
    cursor: Cursor,
    shell: &mut Shell<'_, Message>,
    state: &mut State,
    value: &mut T,
    range: &RangeInclusive<T>,
    step: T,
    on_change: &dyn Fn(T) -> Message,
    on_release: &Option<Message>,
)
where
    T: Copy + Into<f64> + FromPrimitive,
    Message: Clone,

Processes an Event and updates the State of a SlideBar accordingly.