Function layout 

pub fn layout(
    content: Rect,
    fields: usize,
    value_need: usize,
    list: ListShape,
) -> Layout

Lay out content for fields listed and a value that needs value_need rows. Below WIDE the list sits above the value and takes the rows it needs, leaving the value what its lines need. The split follows what the panes hold, never where the focus is, so Tab moves nothing. From WIDE the two sit side by side, each at full height, the value as wide as [value_pane_width] says, and fields flow into as many columns of list.min_col cells as fit.