Function ui_layout_system 

pub fn ui_layout_system(
    ui_surface: ResMut<'_, UiSurface>,
    ui_root_node_query: Query<'_, '_, Entity, (With<Node>, Without<ChildOf>)>,
    ui_children: UiChildren<'_, '_>,
    node_query: Query<'_, '_, (Entity, Ref<'_, Node>, Option<&mut ContentSize>, Ref<'_, ComputedUiRenderTargetInfo>)>,
    added_node_query: Query<'_, '_, (), Added<Node>>,
    node_update_query: Query<'_, '_, (&mut ComputedNode, &UiTransform, &mut UiGlobalTransform, &Node, Option<&LayoutConfig>, Option<&BorderRadius>, Option<&Outline>, Option<&ScrollPosition>)>,
    buffer_query: Query<'_, '_, &mut ComputedTextBlock>,
    font_system: ResMut<'_, CosmicFontSystem>,
    removed_children: RemovedComponents<'_, '_, Children>,
    removed_content_sizes: RemovedComponents<'_, '_, ContentSize>,
    removed_nodes: RemovedComponents<'_, '_, Node>,
)

Updates the UI’s layout tree, computes the new layout geometry and then updates the sizes and transforms of all the UI nodes.