"Return WCONFIG's wtree's `wg-wtree-buf-uids'."

  (wg-wtree-unique-buf-uids (wg-wconfig-wtree wconfig)))

(defun wg-workgroup-base-wconfig-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP's working wconfig."

  (wg-wconfig-buf-uids (wg-workgroup-base-wconfig workgroup)))

(defun wg-workgroup-saved-wconfigs-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP's base wconfig."

  (reduce 'wg-string-list-union

          (wg-workgroup-saved-wconfigs workgroup)

          :key 'wg-wconfig-buf-uids))

(defun wg-workgroup-all-wconfig-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP's wconfigs."

  (union (wg-workgroup-base-wconfig-buf-uids workgroup)

         (wg-workgroup-saved-wconfigs-buf-uids workgroup)

         :test 'string=))

(defun wg-workgroup-all-buf-uids (workgroup)

  "Return a new list of all unique buf uids in WORKGROUP."

  (reduce 'wg-string-list-union

          (list (wg-workgroup-base-wconfig-buf-uids workgroup)

                (wg-workgroup-saved-wconfigs-buf-uids workgroup)

(defun wg-session-all-buf-uids (&optional session)

  "Return a new list of all unique buf uids in SESSION.

SESSION nil defaults to `wg-current-session'."

  (reduce 'wg-string-list-union

          (wg-session-workgroup-list (or session (wg-current-session)))

          :key 'wg-workgroup-all-buf-uids))

(defun wg-buffer-list-all-uids (&optional buffer-list)

  "Return a list of the uids of all buffers in BUFFER-LIST in

which `wg-buffer-uid' is locally bound.

BUFFER-LIST nil defaults to `buffer-list'."

  (delq nil (mapcar 'wg-buffer-uid (or buffer-list (buffer-list)))))

(defun wg-all-buf-uids (&optional session buffer-list)

  "Return the union of `wg-session-all-buf-uids' and `wg-buffer-list-all-uids'."

  (union (wg-session-all-buf-uids session)

         (wg-buffer-list-all-uids buffer-list)

         :test 'string=))

(defun wg-gc-bufs ()

  "gc bufs from `wg-buf-list' that are no longer needed."

  (let ((all-buf-uids (wg-all-buf-uids)))

    (wg-asetf (wg-buf-list)