(wg-reset-internal (wg-make-session :file-name filename))

         (wg-fontified-message

           (:cmd "(New Workgroups session file)")))))

(defalias 'wg-open-session 'wg-find-session-file)

(defun wg-write-session-file (filename &optional confirm)

  "Write the current session into file FILENAME.

This makes the session visit that file, and marks it as not modified.

If optional second arg CONFIRM is non-nil, this function asks for

confirmation before overwriting an existing file.  Interactively,

confirmation is required unless you supply a prefix argument.

Think of it as `write-file' for Workgroups sessions."

  (interactive (list (read-file-name "Save session as: ")

                     (not current-prefix-arg)))

  (when (and confirm (file-exists-p filename))

    (unless (y-or-n-p (format "File `%s' exists; overwrite? " filename))

      (error "Cancelled")))

  (unless (file-writable-p filename)

    (error "File %s can't be written to" filename))

  (wg-perform-session-maintenance)

  (setf (wg-session-file-name (wg-current-session)) filename)

  (setf (wg-session-version (wg-current-session)) wg-version)

  (if wg-control-frames

  (wg-write-sexp-to-file

   (wg-pickel-all-session-parameters (wg-current-session))

   filename)

  (wg-mark-everything-unmodified)

  (wg-fontified-message (:cmd "Wrote: ") (:file filename)))

(defalias 'wg-save-session-as 'wg-write-session-file)

(defun wg-determine-session-save-file-name ()

  "Return the filename in which to save the session."

  (or (wg-session-file-name (wg-current-session))

      (and wg-session-load-on-start wg-session-file)))

(defun wg-save-session (&optional force)

  "Save the current Workgroups session if it's been modified.

Think of it as `save-buffer' for Workgroups sessions.  Optional

argument FORCE non-nil, or interactively with a prefix arg, save

the session regardless of whether it's been modified."

  (interactive "P")

  (if (and (not (wg-modified-p)) (not force))

      (wg-message "(The session is unmodified)")

    (wg-write-session-file

     (or (wg-determine-session-save-file-name)

         (read-file-name "Save session as: ")))))

  "Return the value of VARIABLE in SESSION.

SESSION nil defaults to the current session.  If VARIABLE does

not have a session-local binding in SESSION, the value is

resolved by Emacs."

  (let* ((undefined (cl-gensym))

         (value (wg-session-parameter session variable undefined)))

    (if (not (eq value undefined)) value

      (symbol-value variable))))

(defun wg-reset-frame (frame)

  "Reset Workgroups' `frame-parameters' in FRAME to nil."

  (set-frame-parameter frame 'wg-workgroup-state-table nil)

  (set-frame-parameter frame 'wg-current-workgroup-uid nil)

  (set-frame-parameter frame 'wg-previous-workgroup-uid nil))

(defun wg-save-session-on-exit (behavior)

  "Perform session-saving operations based on BEHAVIOR."

  (cl-case behavior

    (ask (wg-query-and-save-if-modified))

    (save

     (if (wg-determine-session-save-file-name)

         (wg-save-session)

       (wg-query-and-save-if-modified)))))

(defun wg-reload-session ()

  "Reload current workgroups session."

  (interactive)

  (let ((file (or (wg-determine-session-save-file-name)

                  wg-session-file)))

    (when (file-exists-p file)

      (condition-case err

          (wg-open-session wg-session-file)

        (progn

          (wg-create-first-wg)

          (error (message "Error finding session-file: %s" err)))))

    (wg-create-first-wg)))

(defun wg-save-session-on-emacs-exit ()

  "Call `wg-save-session-on-exit' with `wg-emacs-exit-save-behavior'.

Added to `kill-emacs-query-functions'."

  (wg-save-session-on-exit wg-emacs-exit-save-behavior) t)

(defun wg-save-session-on-workgroups-mode-exit ()

  "Call `wg-save-session-on-exit' with `wg-workgroups-mode-exit-save-behavior'.

Called when `workgroups-mode' is turned off."

  (wg-save-session-on-exit wg-workgroups-mode-exit-save-behavior) t)