Function sortRef

docs/app/js/sanddance-app.js:149627–149634

(sort)

        }))) : keyRef(fields, flat);
    },
    sortRef (sort) {
        if (!sort) return sort; // including id ensures stable sorting
        const a = aggrField(sort.op, sort.field), o = sort.order || Ascending;
        return o.signal ? ref(this.add(Compare({
            fields: a,
            orders: this.signalRef(o.signal)
        }))) : compareRef(a, o);
    },
    // ----
    event (source, type) {
        const key = source + ":" + type;