Constant TREE_INDENT 

pub const TREE_INDENT: f64 = _; // 22f64

One step of a tree’s nesting (VirtualList::with_tree): the disclosure gutter a row’s content stands in by from the depth above it, where the chevron that folds the row in front of it hangs. A list leads every row’s depth’s column by one step, so the top level stands the one step its chevron takes in from the list’s own leading edge.