Function constraints 

pub fn constraints<'a, R>(
    columns: &[Column<'a>],
    rows: &[R],
    sizing: &Sizing<'_>,
    style: &TableStyle,
    cutoff: Priority,
) -> Vec<Constraint>
where
    R: AsRef<[Cell<'a>]>,

The tracks for the columns kept at cutoff.

Only the surviving tracks, which is what keeps the track list and the hiding in agreement. A caller that dropped a cell but left its track would get a column of empty space, which is the other half of the goingson bug the webview renderer’s grid_template_columns names.