Function resolve_selection 

pub fn resolve_selection(
    about: Option<SharedSelection>,
    at: Option<Point>,
    focused: Option<SharedSelection>,
    published: &[ResourceSpec],
) -> (Option<SharedSelection>, Option<[f64; 4]>)

Where in the window a request points, and what it is about: the reference the app runner hands the session, resolved against what the window shows.

What its asker named wins. Otherwise the focused selection, when the person pointed at it (or did not point at all). Otherwise the window itself: the first resource the app published, as one whole item. Its resource is named from published when the reference does not name one.