Function range_locus 

pub fn range_locus(
    root: &dyn Widget,
    theme: &Theme,
    key: &PresenceKey,
    range: SelectionRange,
) -> Option<(*const dyn Widget, Rect)>

The widget under root (itself included) that shows the remote caret or selection range at key, and the box it draws it in: what a view following that member reveals, and where their cursor rests.