Function tree 

pub fn tree<R>(state: &Entity<TreeState>, render_item: R) -> Tree
where
    R: Fn(usize, &TreeEntry, bool, &mut Window, &mut App) -> ListItem + 'static,

Create a Tree.

Arguments

• state - The shared state managing the tree items.
• render_item - A closure to render each tree item.

let state = cx.new(|_| {
    TreeState::new().items(vec![
        TreeItem::new("src")
            .child(TreeItem::new("lib.rs"),
        TreeItem::new("Cargo.toml"),
        TreeItem::new("README.md"),
    ])
});

tree(&state, |ix, entry, selected, window, cx| {
    div().px(px(16.) * entry.depth()).child(item.label.clone())
})