"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 (gensym))

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

    (if (not (eq value undefined)) value

      (symbol-value variable))))

;;; buffer object utils

(defun wg-buffer-uid (buffer-or-name)

  "Return BUFFER-OR-NAME's buffer-local value of `wg-buffer-uid'."

  (buffer-local-value 'wg-buffer-uid (wg-get-buffer buffer-or-name)))

(defun wg-bufobj-uid (bufobj)

  "Return BUFOBJ's uid."

  (etypecase bufobj

    (buffer (wg-buffer-uid bufobj))

    (wg-buf (wg-buf-uid bufobj))

    (string (wg-bufobj-uid (wg-get-buffer bufobj)))))

(defun wg-bufobj-name (bufobj)

  "Return BUFOBJ's buffer name."

  (etypecase bufobj

    (buffer (buffer-name bufobj))

    (wg-buf (wg-buf-name bufobj))

    (string (wg-buffer-name bufobj))))

(defun wg-bufobj-file-name (bufobj)

  "Return BUFOBJ's filename."

  (etypecase bufobj

    (buffer (buffer-file-name bufobj))

    (wg-buf (wg-buf-file-name bufobj))

    (string (wg-bufobj-file-name (wg-get-buffer bufobj)))))

(defun wg-buf-major-mode (buf)

  "Return BUF's `major-mode'.

It's stored in BUF's local-vars list, since it's a local variable."

  (wg-aget (wg-buf-local-vars buf) 'major-mode))

(defun wg-bufobj-major-mode (bufobj)

  "Return BUFOBJ's major-mode."

  (etypecase bufobj

    (buffer (wg-buffer-major-mode bufobj))

    (wg-buf (wg-buf-major-mode bufobj))

    (string (wg-buffer-major-mode bufobj))))

;; `wg-equal-bufobjs' and `wg-find-bufobj' may need to be made a lot smarter

(defun wg-equal-bufobjs (bufobj1 bufobj2)

  "Return t if BUFOBJ1 is \"equal\" to BUFOBJ2."

  (let ((fname1 (wg-bufobj-file-name bufobj1))

        (fname2 (wg-bufobj-file-name bufobj2)))

    (cond ((and fname1 fname2) (string= fname1 fname2))

          ((or fname1 fname2) nil)

          ((string= (wg-bufobj-name bufobj1) (wg-bufobj-name bufobj2)) t))))

(defun wg-find-bufobj (bufobj bufobj-list)

  "Find BUFOBJ in BUFOBJ-LIST, testing with `wg-equal-bufobjs'."

  (find bufobj bufobj-list :test 'wg-equal-bufobjs))

(defun wg-find-bufobj-by-uid (uid bufobj-list)

  "Find the bufobj in BUFOBJ-LIST with uid UID."

  (find uid bufobj-list :test 'string= :key 'wg-bufobj-uid))

(defun wg-find-buf-in-buf-list (buf buf-list)

  "Find BUF in BUF-LIST.

This is only here for completeness."

  (find buf buf-list))

(defun wg-find-buffer-in-buffer-list (buffer-or-name buffer-list)

  "Find BUFFER-OR-NAME in BUFFER-LIST."

  (find (wg-get-buffer buffer-or-name) buffer-list :key 'wg-get-buffer))

(defun wg-find-buffer-in-buf-list (buffer-or-name buf-list)

  "Find BUFFER-OR-NAME in BUF-LIST."

  (wg-aif (wg-buffer-uid buffer-or-name)

      (wg-find-bufobj-by-uid it buf-list)

    (wg-find-bufobj buffer-or-name buf-list)))

(defun wg-find-buf-in-buffer-list (buf buffer-list)

  "Find BUF in BUFFER-LIST."

  (or (wg-find-bufobj-by-uid (wg-buf-uid buf) buffer-list)

      (wg-find-bufobj buf buffer-list)))

(defun wg-find-buf-by-uid (uid)

  "Find a buf in `wg-buf-list' by UID."

  (wg-find-bufobj-by-uid uid (wg-buf-list)))

(defun wg-set-buffer-uid-or-error (uid &optional buffer)

  "Set BUFFER's buffer local value of `wg-buffer-uid' to UID.

If BUFFER already has a buffer local value of `wg-buffer-uid',

and it's not equal to UID, error."

  (if wg-buffer-uid

    (setq wg-buffer-uid uid)))

;;; wconfig construction

(defun wg-buffer-special-data (buffer)

  "Return BUFFER's auxiliary serialization, or nil."

  (some (lambda (fn) (funcall fn buffer)) wg-special-buffer-serdes-functions))

(defun wg-window-point (ewin)

  "Return `point' or :max.  See `wg-restore-point-max'.

EWIN should be an Emacs window object."

  (let ((p (window-point ewin)))

    (if (and wg-restore-point-max (= p (point-max))) :max p)))

(defun wg-serialize-buffer-local-variables ()

  "Return an alist of buffer-local variable symbols and their values.

See `wg-buffer-local-variables-alist' for details."

  (wg-docar (entry wg-buffer-local-variables-alist)

    (wg-dbind (var ser des) entry

      (when (local-variable-p var)

        (cons var (if ser (funcall ser) (symbol-value var)))))))

(defun wg-buffer-to-buf (buffer)

  "Return the serialization (a wg-buf) of Emacs buffer BUFFER."

  (with-current-buffer buffer

    (wg-make-buf

     :name           (buffer-name)

     :file-name      (buffer-file-name)

     :point          (point)

     :mark           (mark)

     :local-vars     (wg-serialize-buffer-local-variables)

     :special-data   (wg-buffer-special-data buffer))))

(defun wg-add-buffer-to-buf-list (buffer)

  "Make a buf from BUFFER, and add it to `wg-buf-list' if necessary.

If there isn't already a buf corresponding to BUFFER in

`wg-buf-list', make one and add it.  Return BUFFER's uid

in either case."

  (with-current-buffer buffer

    (setq wg-buffer-uid

          (wg-aif (wg-find-buffer-in-buf-list buffer (wg-buf-list))

              (wg-buf-uid it)

            (let ((buf (wg-buffer-to-buf buffer)))

              (push buf (wg-buf-list))

              (wg-buf-uid buf))))))

(defun wg-buffer-uid-or-add (buffer)

  "If there isn't already a buf corresponding to BUFFER in

`wg-buf-list', make one and add it.  Return BUFFER's uid

in either case."

  (or (wg-buffer-uid buffer) (wg-add-buffer-to-buf-list buffer)))

(defun wg-bufobj-uid-or-add (bufobj)

  "If BUFOBJ is a wg-buf, return its uid.

If BUFOBJ is a buffer or a buffer name, see `wg-buffer-uid-or-add'."

  (etypecase bufobj

    (wg-buf (wg-buf-uid bufobj)) ;; possibly also add to `wg-buf-list'

    (buffer (wg-buffer-uid-or-add bufobj))

    (string (wg-bufobj-uid-or-add (wg-get-buffer bufobj)))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;

;; Notes on buffer and window properties:

;;

;; fringes, margins and scroll-bars are properly properties of buffers, but

;; their settings can be forced ephemerally in a window with the set-window-foo

;; functions.

;;

;; window-point is a property of a buffer/window pair, but won't set properly

;; unless the buffer is current -- i.e. (set-window-buffer some-window

;; some-buffer) (set-window-point some-window 0)) won't set some-buffer's point

;; in some-window unless some-buffer is also current.

;;

;; window-start and window-hscroll are properties of buffer/window pairs.

;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defun wg-window-to-win (window)

  "Return the serialization (a wg-win) of Emacs window WINDOW."

  (let ((selected (eq window (selected-window))))

    (with-selected-window window

      (wg-make-win

       :edges              (window-edges window)

       :point              (wg-window-point window)

       :start              (window-start window)

       :hscroll            (window-hscroll window)

       :selected           selected

       :minibuffer-scroll  (eq window minibuffer-scroll-window)

       :dedicated          (window-dedicated-p window)

       :buf-uid            (wg-buffer-uid-or-add (window-buffer window))))))