Function layout_vstack_constrained 

pub fn layout_vstack_constrained(
    children: &[StackEntry],
    width: usize,
    height: usize,
    gap: usize,
) -> Vec<(Arc<dyn Component>, usize)>

Constrained layout calculation for VStack.

Given a fixed height, distribute space among children based on their basis, grow, shrink, and min_size options.

Intrinsic heights come from Component::render; callers that already have a render cache should use [layout_vstack_constrained_with] so a component measured here is not rendered a second time when it is painted.