Function with_widget_state 

pub fn with_widget_state<U, I, T>(
    child: U,
    id: impl Into<StateId<T>>,
    default: I,
    value: impl IntoVar<T>,
) -> UiNode
where
    U: IntoUiNode,
    I: Fn() -> T + Send + 'static,
    T: StateValue + VarValue,

Helper for declaring properties that set the widget state.

The state ID is set in WIDGET on init and is kept updated. On deinit it is set to the default value.

Examples

static_id! {
    pub static ref FOO_ID: StateId<u32>;
}

#[property(CONTEXT)]
pub fn foo(child: impl IntoUiNode, value: impl IntoVar<u32>) -> UiNode {
    with_widget_state(child, *FOO_ID, || 0, value)
}

// after the property is used and the widget initializes:

/// Get the value from outside the widget.
fn get_foo_outer(widget: &mut UiNode) -> u32 {
    if let Some(mut wgt) = widget.as_widget() {
        wgt.with_context(WidgetUpdateMode::Ignore, || WIDGET.get_state(*FOO_ID))
            .unwrap_or(0)
    } else {
        0
    }
}

/// Get the value from inside the widget.
fn get_foo_inner() -> u32 {
    WIDGET.get_state(*FOO_ID).unwrap_or_default()
}