// list-based.  Construct regular expression depending on mode.
      let re = regexpActive
          ? search.value
          : Array.from(getSelection().keys()).map(key => pprofQuoteMeta(nodes[key])).join('|');

      setHrefParams(elem, function (params) {
        if (re != '') {
          // For focus/show/show-from, forget old parameter. For others, add to re.

    const params = url.searchParams;
    for (const p of new URLSearchParams(window.location.search)) {
      params.set(p[0], p[1]);
    }

    // Update params to include src.
    let v = pprofQuoteMeta(stacks.Sources[src].FullName);
    if (param != 'f' && param != 'sf') { // old f,sf values are overwritten
      // Add new source to current parameter value.
      const old = params.get(param);