Function v_stack 

pub fn v_stack<H: UiHost, F, I>(children: F) -> UiBuilder<FlexBox<H, F>>
where
    F: FnOnce(&mut ElementContext<'_, H>) -> I,
    I: IntoIterator,
    I::Item: IntoUiElement<H>,

Returns a patchable vertical flex layout builder that does not force width: fill.

Use this when you want the column to shrink-wrap its contents (or to avoid inflating child hit boxes due to a fill-width flex root).