;;; session.el --- use variables, registers and buffer places across sessions

;; Copyright 1996, 1997, 1998, 1999, 2001, 2002, 2003, 2010, 2011, 2012, 2015
;; Free Software Foundation, Inc.
;;
;; Author: Christoph Wedler <wedler@users.sourceforge.net>
;; Version: 2.4b (see also `session-version' below)
;; Keywords: session, session management, desktop, data, tools
;; X-URL: http://emacs-session.sourceforge.net/

;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3 of the Licence, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <http://gnu.org/licences/>.

;;; Commentary:

;; When you start Emacs, package Session restores various variables (e.g.,
;; input histories) from your last session.  It also provides a menu
;; containing recently changed/visited files and restores the places (e.g.,
;; point) of such a file when you revisit it.

;; For details, check <http://emacs-session.sourceforge.net/> or, if you prefer
;; the manual style, the documentation of functions \\[session-save-session]
;; and `session-store-buffer-places'.

;; Bug fixes, bug reports, improvements, and suggestions for the newest version
;; are strongly appreciated.

;;; To-do:

;; One could imagine a combination of desktop.el and session.el.  IMHO it is
;; easier to include the remaining features of desktop.el (load some files at
;; startup) into session.el, but desktop.el is already part of Emacs...
;; Anyway, here are some ideas for the combined desktop/session:
;;
;;  * Using contexts for buffer positions (idea from bookmark and vc).
;;  * Define common code with bookmark to restore buffers from a
;;    file-representation (for files, dired, info buffers).
;;  * Saving window-configurations?

;;; Installation, private:

;;  1. Make sure to use Emacs-20.2, XEmacs-20.2 or higher.
;;  2. Put this file into your load-path, i.e. any directory mentioned in the
;;     value of `load-path'.
;;  3. Byte-compile this file.
;;  4. Load this package by M-x load-library RET session RET
;;  5. Start customization with M-x customize-group RET session RET or the
;;     menu [Options][Customize...]...[Data][Session].
;;  6. Toggle the [Session Use Package] option to "in use".
;;  7. Save your customization via [Save for future sessions].
;;  8. If you use both this package and desktop.el, customize the variable
;;     `desktop-globals-to-save' to include only the symbol
;;     `desktop-missing-file-warning'.

;; Remark: adding some code to your ~/.emacs like in previous versions of
;; session.el still works.

;;; Installation, system- or distribution-wide:

;; The idea here should be to offer new defaults to your users (like using this
;; package), while allowing them to choose otherwise.  This is probably best
;; done by defining a custom theme (you probably add other customizations to
;; the custom theme file as well, custom themes might only work with newer
;; Emacsen):

;;  1. Like 1-3 in the private installation instruction.
;;  2. Create the autoloads and custom-loads for session.el and make sure that
;;     they are loaded at Emacs startup.  You can do it manually by adding the
;;     code below to your site.start.el.
;;  3. Define a custom theme like `our-custom' by adding a file called
;;     "our-custom-theme.el" with the code below to a directory in the
;;     load-path.
;;  4. Enable your custom theme by adding the code below to your default.el.
;;  5. Tell your users that they can disable this package by customizing the
;;     user option according to 5-7 in the private installation instruction or
;;     by setting `inhibit-default-init' to t.

;; ;; site-start.el, Emacs:
;; (autoload 'session-jump-to-last-change "session" nil t)
;; (autoload 'session-initialize "session" nil t)
;; (eval-after-load "cus-load"
;;   '(progn (custom-add-load 'data 'session)
;;           (custom-add-load 'session 'session)))

;; ;; site-start.el, XEmacs:
;; (autoload 'session-jump-to-last-change "session" nil t)
;; (autoload 'session-initialize "session" nil t)
;; (custom-add-load 'data 'session)
;; (custom-add-load 'session 'session)

;; ;; our-custom-theme.el, Emacs and XEmacs:
;; (deftheme our-custom "Created 2011-01-15.")
;; (custom-theme-set-variables
;;   'our-custom
;;   '(session-use-package t nil (session)))
;; (provide-theme 'our-custom)

;; ;; default.el, Emacs:
;; (enable-theme 'our-custom)

;; ;; default.el, XEmacs:
;; (require-theme 'our-custom)

;;; Installation, integration of other packages

;;(defun my-org-reveal-session-jump ()
;;  (when (and (eq major-mode 'org-mode)
;;             (outline-invisible-p))
;;    (org-reveal)))
;;(add-hook 'session-after-jump-to-last-change-hook 'my-org-reveal-session-jump)

;;; Code:

(require 'custom)

;; General Emacs/XEmacs-compatibility compile-time macros
(eval-when-compile
  (require 'cl)
  (defmacro cond-emacs-xemacs (&rest args)
    (cond-emacs-xemacs-macfn
     args "`cond-emacs-xemacs' must return exactly one element"))
  (defun cond-emacs-xemacs-macfn (args &optional msg)
    (if (atom args) args
      (and (eq (car args) :@) (null msg) ; (:@ ...spliced...)
	   (setq args (cdr args)
		 msg "(:@ ....) must return exactly one element"))
      (let ((ignore (if (string-match "XEmacs" emacs-version) :EMACS :XEMACS))
	    (mode :BOTH) code)
	(while (consp args)
	  (if (memq (car args) '(:EMACS :XEMACS :BOTH)) (setq mode (pop args)))
	  (if (atom args)
	      (or args (error "Used selector %s without elements" mode))
	    (or (eq ignore mode)
		(push (cond-emacs-xemacs-macfn (car args)) code))
	    (pop args)))
	(cond (msg (if (or args (cdr code)) (error msg) (car code)))
	      ((or (null args) (eq ignore mode)) (nreverse code))
	      (t (nconc (nreverse code) args))))))
  ;; Emacs/XEmacs-compatibility `defun': remove interactive "_" for Emacs, use
  ;; existing functions when they are `fboundp', provide shortcuts if they are
  ;; known to be defined in a specific Emacs branch (for short .elc)
  (defmacro defunx (name arglist &rest definition)
    (let ((xemacsp (string-match "XEmacs" emacs-version)) reuses first)
      (while (memq (setq first (car definition))
		   '(:try :emacs-and-try :xemacs-and-try
			  :emacs-only :xemacs-only))
	(if (memq first (if xemacsp
			    '(:xemacs-and-try :xemacs-only)
			  '(:emacs-and-try :emacs-only)))
	    (setq reuses (cadr definition)
		  definition nil)
	  (unless (memq first '(:emacs-only :xemacs-only))
	    (push (cadr definition) reuses)))
	(setq definition (cddr definition)))
      (if (and reuses (symbolp reuses))
	  `(defalias ',name ',reuses)
	(let* ((docstring (if (stringp (car definition)) (pop definition)))
	       (spec (and (not xemacsp)
			  (eq (car-safe (car definition)) 'interactive)
			  (null (cddar definition))
			  (cadar definition))))
	  (if (and (stringp spec)
		   (not (string-equal spec ""))
		   (eq (aref spec 0) ?_))
	      (setq definition
		    (cons (if (string-equal spec "_")
			      '(interactive)
			    `(interactive ,(substring spec 1)))
			  (cdr definition))))
	  (if (null reuses)
	      `(defun ,name ,arglist ,docstring
		 ,@(cond-emacs-xemacs-macfn definition))
	    ;; no dynamic docstring in this case
	    `(eval-and-compile		; no warnings in Emacs
	       (defalias ',name
		 (cond ,@(mapcar (lambda (func) `((fboundp ',func) ',func))
				 (nreverse reuses))
		       (t ,(if definition
			       `(lambda ,arglist ,docstring
				  ,@(cond-emacs-xemacs-macfn definition))
			     'ignore)))))))))))

(eval-when-compile
  (defvar put-buffer-names-in-file-menu)
  (defvar menu-bar-files-menu)
  (defvar yank-menu)
  (defvar minibuffer-local-ns-map))



;;;;##########################################################################
;;;;  User options, configuration variables
;;;;##########################################################################


(defconst session-version "2.4b"
  "Current version of package session.
Check <http://emacs-session.sourceforge.net/> for the newest.")


;;;===========================================================================
;;;  Customization and initialization
;;;===========================================================================

(defgroup session nil
  "Use variables, registers and buffer places across sessions."
  :group 'data
  :link '(emacs-commentary-link "session.el")
  :link '(url-link "http://emacs-session.sourceforge.net/")
  :prefix "session-")

(defgroup session-globals nil
  "Which variables and registers to save across sessions."
  :group 'session
  :prefix "session-")

(defgroup session-places nil
  "Which places are stored for which buffers."
  :group 'session
  :prefix "session-")

(defgroup session-miscellaneous nil
  "Miscellaneous configurations of package session."
  :group 'session
  :prefix "session-")

(defcustom session-initialize t
  "Whether/what to initialize with function `session-initialize'.
If t, do full initialization.  Otherwise, the value should be a list
with element.  To enable, include

 * `de-saveplace' to de-install package saveplace (is redundant),
 * `session' to load and save the session file,
 * `places' to store and use places for files/buffers,
 * `keys' to setup the default key and mouse bindings,
 * `menus' to setup the menus."
  :group 'session-miscellaneous
  :type '(choice (const :tag "All" t)
		 (set :value (de-saveplace session places keys menus)
		      (const :tag "De-install saveplace" de-saveplace)
		      (const :tag "Load/Save Session" session)
		      (const :tag "Store/Use Places" places)
		      (const :tag "Setup Key/Mouse Bindings" keys)
		      (const :tag "Setup Menus" menus))))


;;;===========================================================================
;;;  User Options and Configuration: Menu
;;;===========================================================================

(defcustom session-menu-max-size 36
  "*Max number of entries which may appear in the session menus."
  :group 'session-miscellaneous
  :type 'integer)

(defcustom session-yank-menu-binding
  (and (string-match "XEmacs" emacs-version) [(control button3)])
  "*Mouse binding where `session-popup-yank-menu' is bound to."
  :group 'session-miscellaneous
  :type 'sexp)				; (choice (nil key-binding))

(defcustom session-file-menu-max-string
  (if (if (boundp 'put-buffer-names-in-file-menu)
	  put-buffer-names-in-file-menu	; XEmacs
	nil)				; Emacs: no buffer names in file menu
      (cons 50 20)
    50)
  "*Max length of strings in submenus of the File menu.
Value has the form MAX or (MAX . NAME-THRESHOLD).  If the second form is
used and the length returned by `buffer-name' is longer than
NAME-THRESHOLD, the maximum length will be shortened accordingly.

Deprecated: a negative number -MAX stands for (MAX . 0)."
  :group 'session-miscellaneous
  :type '(choice (cons (integer :tag "Max. length" 50)
		       (integer :tag "Name threshold" 20))
		 (integer 50)))

(defcustom session-edit-menu-max-string 50
  "*Max length of strings in submenus of the Edit menu.
See also `session-compact-yank-gap-regexp'.

When running under Emacs, customize `yank-menu-length' instead."
  :group 'session-miscellaneous
  :type 'integer)

(defcustom session-compact-yank-gap-regexp "\\(\n\\|[ \t][ \t][ \t]\\)[ \t\n]*"
  "*Regexp used when trying to find a gap in a long compact string.
If non-nil, leading and trailing whitespaces are not shown, and we try
to find a gap consisting matched by this regexp if we have to split the
string according to `session-edit-menu-max-string'.

This variable has no effect when running under Emacs."
  :group 'session-miscellaneous
  :type 'string)

(defcustom session-menu-permanent-string " *"
  "*Marker for permanent files in menu \"File >> Open...recently changed\".
A file can set as permanent with prefix argument 3 for a command in
`session-kill-buffer-commands'.  It can be set as non-permanent with
prefix argument -1."
  :group 'session-miscellaneous
  :type 'string)

;; TODO: not quite sure whehter this is needed anymore - and if whether
;; it is the best way to exclude certain files.  Other options are:
;; based on directory, file name, mode, calling command
(defcustom session-set-file-name-exclude-regexp
  "[/\\]\\.overview\\|[/\\]\\.session\\|News[/\\]"
  "*Regexp matching file names not to be stored in `file-name-history'.
This is used by `session-set-file-name-history'.  Value nil means, do
not exclude any file."
  :group 'session-miscellaneous
  :type '(choice (const nil) regexp))

(defvar session-menu-accelerator-support
  (and (featurep 'menu-accelerator-support)
       (fboundp 'submenu-generate-accelerator-spec)
       'submenu-generate-accelerator-spec)
  "Function to generate menu accelerators, or nil if not supported.")

;; calling `abbrev-file-name' on remote files opens the connection!

(defvar session-abbrev-inhibit-function
;; this will be renamed with the next release (when minimum is
;; Emacs-22.1, jun 2007 and XEmacs 21.4.12, jan 2003) -> only there we have
;; `define-obsolete-variable-alias'
  (cond ((fboundp 'file-remote-p) 'file-remote-p)
        ;;  `file-remote-p' doesn't exist in Emacs < 22.1
        ;; (cond-emacs-xemacs
        ;;  ;; as opposed to the docstring of `file-remote-p',
        ;;  ;; `tramp-handle-file-remote-p' does try to open a connection
        ;;  :EMACS (lambda (file) (find-file-name-handler file 'file-remote-p))
        ;;  :XEMACS 'file-remote-p))
	((fboundp 'efs-ftp-path) 'efs-ftp-path)
	((fboundp 'ange-ftp-ftp-name) 'ange-ftp-ftp-name)
	((fboundp 'ange-ftp-ftp-path) 'ange-ftp-ftp-path))
  "Function used to determine whether to abbreviate file name.
A file name is not abbreviated and no buffer information is shown in the
file menus if this function returns non-nil when called with the file name.
If the value is not a function, it directly determines whether to abbreviate
a file name.")

(defvar session-directory-sep-char    ; directory-sep-char is not set
  (if (memq system-type '(ms-dos windows-nt)) ?\\ ?\/)
  "Directory separator character for session menus.")

(defvar session-save-file-coding-system
  (cond-emacs-xemacs
   :EMACS 'iso-latin-1-with-esc
   ;; used `emacs-mule' but this fails with X-Symbol characters...
   :XEMACS (and (featurep 'mule) 'escape-quoted))
  "Coding system to use when writing `session-save-file' if non-nil.")


;;;===========================================================================
;;;  User Options and Configuration: save global variables between sessions
;;;===========================================================================

(defcustom session-globals-max-size 50
  "*Maximal number of elements in the global variables.
Global variables are only saved if they are non-empty lists.  This value
can be shadowed by some element in `session-globals-include'.  If an
element appears more than once in the list, only the first appearance
will be stored."
  :group 'session-globals
  :type 'integer)

(defcustom session-globals-max-string 1024
  "*Maximal length of string elements in global variables."
  :group 'session-globals
  :type 'integer)

(defcustom session-registers-max-string 1024
  "*Maximal length of string elements in registers."
  :group 'session-globals
  :type 'integer)

(defcustom session-save-file
  (expand-file-name ".session"
		    (cond ((boundp 'user-emacs-directory) user-emacs-directory)
			  ((boundp 'user-init-directory) user-init-directory)
			  (t "~")))
  "File to save global variables and registers into.
It is saved with coding system `session-save-file-coding-system' at the
end of an Emacs session and loaded at the beginning.  Used for variables
which are typically changed by editing operations, e.g., history and
ring variables.  See \\[session-save-session] for details."
  :group 'session-globals
  :type 'file)

(defvar session-old-save-file (expand-file-name ".session" "~")
  "Value of `session-save-file' before Version 2.3 of this package.")

(defvar session-save-print-spec '(t 2 1024)
  ;; only for advanced users -> no custom
  "*Print specification for the values of global variables to save.
The value looks like (CIRCLE LEVEL LENGTH) and is used to bind variables
`print-circle', `print-level' and `print-length' when evaluating
`session-save-session'.")

(defcustom session-save-file-modes 384
  "Mode bits of session save file, as an integer, or nil.
After writing `session-save-file', set mode bits of that file to this
value if it is non-nil."
  :group 'session-globals
  :type '(choice (const :tag "Don't change" nil) integer))
  
(defvar session-before-save-hook nil
  "Hook to be run before `session-save-file' is saved.
The functions are called after the global variables are written,
directly before the file is actually saved.")

(defvar session-after-load-save-file-hook
  (cond-emacs-xemacs
   :EMACS (and (default-boundp 'yank-menu)
	       (fboundp 'menu-bar-update-yank-menu)
	       '(session-refresh-yank-menu)))
  "Hook to be run after `session-save-file' has been loaded.
The functions are called when the file has been successfully loaded.")

(defcustom session-globals-regexp "-\\(ring\\|history\\)\\'"
  "Regexp matching global variables to be saved between sessions.
Variables in `session-globals-exclude' are not saved, but variables in
`session-globals-include' are always saved."
  :group 'session-globals
  :type 'regexp)

(defcustom session-globals-exclude
  '(load-history
    register-alist flyspell-auto-correct-ring org-mark-ring
    planner-browser-file-display-rule-ring
    "\\`anything-c-source-")
  "Global variables not to be saved between sessions.
An Element of this list is either a symbol or a regexp matching all
variable names not to be saved.
It affects `session-globals-regexp' and `session-globals-include'."
  :group 'session-globals
  :type '(repeat '(choice variable (string "Regexp"))))

(defcustom session-globals-include '((kill-ring 10)
				     (session-file-alist 100 t)
				     (file-name-history 200)
				     search-ring regexp-search-ring)
  "Global variables to be saved between sessions.
Each element has one of the following forms:
  NAME,
  (NAME MAX-SIZE), or
  (NAME MAX-SIZE ASSOC-P).
where NAME is the symbol name of the variable, whose value must be a
non-empty list and string elements in this list must be smaller than
`session-globals-max-string'.  MAX-SIZE (default is
`session-globals-max-size') is the maximal number of elements to be
saved for this symbol where only the first of equal elements are saved,
and ASSOC-P (default is nil) non-nil means that the variable is an alist
where the equality of elements is checked on the `car'.

If MAX-SIZE or ASSOC-P is non-nil, it can be useful to include a
variable in this list even if it matches `session-globals-regexp'.
`session-globals-exclude' has no effect on these variables.

Do not use this variable to customize your Emacs.  Package custom is the
appropriate choice for this!"
  :group 'session-globals
  :type '(repeat (choice (variable :tag "List var with standard max size")
			 (list variable
			       (integer :tag "Max size")
			       (boolean :tag "Alist")))))


;;;===========================================================================
;;;  Configuration: registers and local variables
;;;===========================================================================

(defcustom session-registers '((?0 . ?9) ?- ?= ?\\ ?` region (?a . ?z) (?A . ?Z))
  "*Registers to be saved in `session-save-file'.
Valid elements in this list are:
  CHAR or (FROM . TO) or `file' or `region' or t.
CHAR is a register to save, (FROM . TO) represents a list of registers
from FROM to TO.  `file' means, only save the following registers in
this list if they contain file or file-query references.  `region'
means, only save registers if they contain a region which has less then
`session-registers-max-string' characters.  t means, allow both content
types.  Processing of this list starts with type `file'.

Before saving the session files, markers in registers are turned into
file references, see variable `session-register-swap-out'."
  :group 'session-globals
  :type '(repeat (choice (const :tag "File registers:" file)
			 (const :tag "String registers:" region)
			 (const :tag "Any register type:" t)
			 (character :tag "Register")
			 (cons :tag "Registers"
			       (character :tag "From")
			       (character :tag "To")))))

(defcustom session-locals-include '(overwrite-mode)
  "Local variables to be stored for specific buffers.
See also `session-locals-predicate'.

Do not add variables to this list which are more appropriate for local
variables in files, i.e., variables which are related to the contents of
the file, e.g. `major-mode'!"
  :group 'session-places
  :type '(repeat variable))

(defcustom session-locals-predicate 'local-variable-p
  "Function which must return non-nil for a local variable to be stored.
This function is called on all variables in `session-locals-include'
with the variable as the first and the current buffer as the second
argument.  Good values are nil (do not store any variable),
`local-variable-p' for local variables, `local-variable-if-set-p' for
variables which become local when set, and t (store all variables in
`session-locals-include')."
  :group 'session-places
  :type '(choice (const :tag "none" nil)
		 (const :tag "All" t)
		 (function-item local-variable-p)
		 (function-item local-variable-if-set-p)
		 (function :tag "Other function")))

(defvar session-register-swap-out (if (fboundp 'register-swap-out)
				      'register-swap-out
				    'session-register-swap-out)
  "Function processing markers in registers when a buffer is killed.
If non-nil, this function is added to `kill-buffer-hook'.  Good values
are `register-swap-out' and the function `session-register-swap-out'.")


;;;===========================================================================
;;;  User Options and Configuration: buffer check--undo, mode+name
;;;===========================================================================

(defcustom session-jump-undo-threshold 240
  "*Number of character positions the undo position must be different.
Without prefix arg, `session-jump-to-last-change' jumps successively to
change positions which differ by at least `session-jump-undo-threshold'
characters compared to the current position and previously visited
change positions, see `session-jump-undo-remember'."
  :group 'session-places
  :type 'integer)

(defcustom session-jump-undo-remember 2
  "*Number of previously visited change positions checked additionally.
See `session-jump-undo-threshold' and `session-jump-to-last-change'."
  :group 'session-places
  :type 'integer)

(defvar session-after-jump-to-last-change-hook nil
  "Hook to be after `session-jump-to-last-change' has been executed.
The functions are called if `point' has been moved.")

;; Problem if homedir is a symlink (/bar/home -> /net/bar.home) & tmp-mounted
;;   (file-truename "~/foo") => "/tmp_mnt/net/bar.home/foo"
;;   (abbreviate-file-name "/tmp_mnt/net/bar.home/foo") => "/net/bar.home/foo"
;; I.e., there is a bug in `abbreviate-file-name' on both Emacs and XEmacs
;; (with 2nd arg t).  Workaround: use the following in your ~/.emacs:

;;(unless (string= (abbreviate-file-name (file-truename "~") t) "~") ; XEmacs
;;  (setq abbreviated-home-dir
;;	(let ((abbreviated-home-dir "$foo"))
;;	  (concat "\\`\\(?:"
;;		  (regexp-quote (abbreviate-file-name (expand-file-name "~")))
;;		  "\\|"
;;		  (regexp-quote (abbreviate-file-name (file-truename "~")))
;;		  "\\)\\(/\\|\\'\\)"))))

(defconst session-use-truenames-default
  (cond-emacs-xemacs
   :EMACS  (string= (abbreviate-file-name (file-truename "~")) "~")
   :XEMACS (and (string= (abbreviate-file-name (file-truename "~") t) "~")
		(if (eq system-type 'windows-nt)
		    'session-xemacs-buffer-local-mswindows-file-p
		  t))))

(defcustom session-use-truenames session-use-truenames-default
  "*Whether to use the canonical file names when saving/restoring places.
If a function, it is called with no argument and returns whether to use
the canonical names of files.  If non-nil, store and check file names
returned by `file-truename'."
  :group 'session-places
  :type '(choice (const :tag "No" nil)
		 (const :tag "Yes" t)
		 (function-item :tag "If not starting with \\\\"
				session-xemacs-buffer-local-mswindows-file-p)
		 (function :tag "Other function")))

(defcustom session-auto-store t
  "*Determines whether a buffer to be killed passes the mode/name check.
This boolean is used by `session-default-buffer-check-p', see
`session-buffer-check-function'.

A buffer passes the mode/name check, if it passes the mode check, see
below, and its file name is not matched by
`session-name-disable-regexp', or if fails the mode check and its file
name is matched by `session-name-enable-regexp'.

A buffer passes the mode check, if this variable is non-nil and its
major mode is not a member of `session-mode-disable-list', or if this
variable is nil and its major mode is a member of
`session-mode-enable-list'."
  :group 'session-places
  :type 'boolean)

(defcustom session-undo-check 1
  "*Determines how a buffer to be killed passes the undo check.
Its value is MIN or (MIN . LAST) where MIN is a number.  Used by
`session-default-buffer-check-p', see `session-buffer-check-function'.

To pass the undo check
 * the length of `buffer-undo-list', assumed to be -1 if no undo
   information is recorded, must be higher or equal to MIN,
 * the first form is used or LAST is nil: no further requirement
 * LAST is `and': additionally, `session-last-change' must be non-nil,
   i.e., the buffer has been changed previously,
 * LAST is `or': alternatively, `session-last-change' is non-nil."
  :group 'session-places
  :type '(choice (integer :tag "Min no of Changes")
		 (cons (integer :tag "Min no of Changes")
		       (choice :tag "Previous and New Changes"
			       (const :tag "Only consider New Changes" nil)
			       (const :tag "AND previously changed" and)
			       (const :tag "OR previously changed" or)))))

(defcustom session-kill-buffer-commands '(kill-this-buffer)
  "*Commands which kill a buffer.
If a prefix argument was provided to any of these commands, it will
influence the decision whether to store places for the buffer, see
`session-store-buffer-places'.  Using commands which use the minibuffer
for input, is useless."
  :group 'session-places
  :type '(repeat (function :tag "Command")))

(defcustom session-buffer-check-function 'session-default-buffer-check-p
  "Function which return non-nil if buffer places should be stored.
Used by `session-store-buffer-places'.  This function is called with the
buffer to check as argument.  You can also assume that the current
buffer is the buffer to check.

The default value `session-default-buffer-check-p' returns non-nil, if
the buffer
 * visits an existing readable file,
 * passes the mode/name check, see `session-auto-store', and
 * passes the undo check, see `session-undo-check', its default value 1
   means: the buffer must have been changed during the session."
  :group 'session-globals
  :type '(choice (function-item :tag "Default check"
				session-default-buffer-check-p)
		 (function :tag "Other function")))

(defcustom session-mode-disable-list
  '(vm-mode gnus-score-mode message-mode tar-mode)
  "*Major modes of buffers for which no places are stored.
See `session-buffer-check-function'."
  :group 'session-globals
  :type '(repeat (function :tag "Major mode")))

(defcustom session-mode-enable-list nil
  "*Major modes of buffers for which places are stored.
See `session-buffer-check-function'."
  :group 'session-globals
  :type '(repeat (function :tag "Major mode")))

(defcustom session-name-disable-regexp
  (concat "\\`" (regexp-quote
		 (if (fboundp 'temp-directory) (temp-directory) "/tmp")))
  "*File names of buffers for which no places are stored.
See `session-buffer-check-function'."
  :group 'session-places
  :type '(choice (const nil) regexp))

(defcustom session-name-enable-regexp nil
  "*File names of buffers for which places are stored.
See `session-buffer-check-function'."
  :group 'session-places
  :type '(choice (const nil) regexp))




;;;;##########################################################################
;;;;  Store buffer places and local variables, change register contents
;;;;##########################################################################


(defvar session-last-change nil
  "Position of last change in current buffer.
This variable is set by `session-find-file-hook' if the buffer was
changed in a previous session.  It can also be set by providing an
prefix argument to `session-jump-to-last-change'.")
(make-variable-buffer-local 'session-last-change)

(defvar session-file-alist nil
  "Alist for places and local variables for some files.
It has the form
  (NAME POINT MARK POINT-MIN POINT-MAX PERMANENT LAST-CHANGE
   (SYMBOL . VAR) ...)

NAME is the file name, POINT is the point position, MARK is the mark
position, POINT-MIN and POINT-MAX determine the narrow part if non-nil,
PERMANENT is the permanent marker (see `session-buffer-check-function'),
LAST-CHANGE is the position of the last change in the previous session
or was explicitly set with prefix argument 0 for command
\\[session-jump-to-last-change].  Optional pairs (SYMBOL . VAR) are
local variables with their values.")

(defvar session-jump-to-last-change-counter 0
  "Number of repeated invocations of `session-jump-to-last-change'.")

(defvar session-jump-to-last-change-recent nil
  "Current position and previously visited change positions.")


;;;===========================================================================
;;;  Position of last change
;;;===========================================================================

(defun session-undo-position (num pos1 pos2)
  "Return a previous undo-position or set it.
If argument NUM is nil, set `session-last-change' to the recomputed
position given by argument POS1 and return POS1 normalized.

Otherwise, return a previous undo-position or nil, if no such position
can be found.  If `session-jump-to-last-change-counter' is nil, the
position found is the stored last-change position.

If POS1 and POS2 are nil, NUM is the number of undo-boundaries to skip.
The position returned is the last change inside the corresponding undo
step.

Otherwise, NUM is the number of undo entries to skip.  The position
returned is the last change after these entries outside the range from
POS1 to POS2.  Increment `session-jump-to-last-change-counter' by the
number of entries skipped additionally."
  (let ((undo-list (and (consp buffer-undo-list) buffer-undo-list))
	elem      ; element in undo-list, t = not of interest
	back-list ; used position must be recomputed due to processed elems
	len       ; length of deletion/insertion
	pos)      ; interesting position in undo-list
    (while (and undo-list (null (car undo-list)))
      (pop undo-list))			; ignore undo-boundaries at beg
    (while undo-list
      ;; inspect element in undo-list ----------------------------------------
      (setq elem (pop undo-list))
      (cond ((atom elem)		; marker position
	     (when (or elem pos1) ; undo-boundary is of interest if POS1=nil
	       (if (integerp elem)
		   (setq pos elem	; use point position in undo-list
			 back-list (cons nil back-list))
		 (setq elem t))))	; ignore uninteresting elem
	    ((stringp (car elem))	; deletion: (TEXT . POSITION)
	     (setq pos (abs (cdr elem))
		   len (length (car elem)))
	     (push (list* pos (+ pos len) (- len)) back-list)
	     (when pos1			; adopt POS{1,2} if after deletion
	       (if (>  pos1 pos) (incf pos1 len))
	       (if (>= pos2 pos) (incf pos2 len))))
	    ((integerp (car elem))	; insertion: (START . END)
	     (setq pos (car elem)
		   len (- (cdr elem) pos))
	     (push (list* pos pos len) back-list)
	     (when pos1			; adopt POS{1,2} if after/in insertion
	       (if (> pos1 pos)
		   (setq pos1 (if (> pos1 (cdr elem)) (- pos1 len) pos)))
	       (if (> pos2 pos)
		   (setq pos2 (if (> pos2 (cdr elem)) (- pos2 len) pos))))
	     (setq pos (cdr elem)))	; point more likely at end of insertion
	    (t
	     (setq elem t)))
      ;; evaluation element inspection ---------------------------------------
      (cond ((null num))		; set POS1 as `session-last-change'
	    ((null pos1)		; looking for undo-boundaries
	     (when (if elem
		       (and (zerop num) pos)
		     (<= (decf num) 0))
	       (setq undo-list nil)))
	    ((eq elem t)		; uninteresting element
	     (setq pos nil))
	    ((> num 0)			; interesting, but not the NUM's one
	     (decf num)
	     (setq pos nil))
	    ((and (<= pos1 pos) (<= pos pos2)) ; inside start region
	     (incf session-jump-to-last-change-counter)
	     (setq pos nil))
	    (t
	     (setq undo-list nil))))
    ;; finalize: evaluate result and process back-list -----------------------
    (cond ((null num)			; set POS1 as `session-last-change'
	   (setq session-last-change pos1
		 pos session-last-change))
	  ((or (null pos) (> num 0))	; no position found in undo-list
	   (setq session-jump-to-last-change-counter nil)
	   (setq pos session-last-change))
	  (t				; pos in undo-list
	   (if session-jump-to-last-change-counter
	       (incf session-jump-to-last-change-counter))
	   (setq back-list (cdr back-list))))
    (when pos
      (while back-list
	(setq elem (pop back-list))
	(cond ((null elem))		; integer position in undo-list
	      ((> pos (cadr elem))	; position after affected region
	       (incf pos (cddr elem)))	; increment/decrement position
	      ((> pos (car elem))	; position in affected region
	       (setq pos (car elem)))))	; set position to region begin
      pos)))

;;;###autoload
(defun session-jump-to-last-change (&optional arg)
  "Jump to the position of the last change.
Without prefix arg, jump successively to previous change positions which
differ by at least `session-jump-undo-threshold' characters by repeated
invocation of this command.  With prefix argument 0, jump to end of last
change.  With numeric prefix argument, jump to start of first change in
the ARG's undo block in the `buffer-undo-list'.

With non-numeric prefix argument (\\[universal-argument] only), set
point as oldest change position.  It might change slightly if you jump
to it due to intermediate insert/delete elements in the
`buffer-undo-list'."
  ;; note: for compatibility reasons (pre v2.2), we use abs(ARG)
  (interactive "P")
  (if (consp arg)
      (let ((pos (session-undo-position nil (point) (point)))
	    (undo-list (and (consp buffer-undo-list) buffer-undo-list)))
	(setq arg 1)
	(while (and undo-list (null (car undo-list))) (pop undo-list))
	(while undo-list (or (pop undo-list) (incf arg)))
	(message "Store %d as special last-change position (%s %d %s)"
		 pos
		 (substitute-command-keys "\\[universal-argument]")
		 arg
		 (substitute-command-keys "\\[session-jump-to-last-change]")))
    ;; set and restrict previously visited undo positions --------------------
    (push (point) session-jump-to-last-change-recent)
    (if (and (null arg) (eq last-command 'session-jump-to-last-change-seq))
	(let ((recent (nthcdr session-jump-undo-remember
			      session-jump-to-last-change-recent)))
	  (if recent (setcdr recent nil)))
      (setcdr session-jump-to-last-change-recent nil) ; only point
      (setq session-jump-to-last-change-counter 0))
    (let (pos)
      (if arg
	  (setq pos (session-undo-position (abs (prefix-numeric-value arg))
					   nil nil))
	;; compute position, compare it with positions in
	;; `session-jump-to-last-change-recent'
	(let ((recent session-jump-to-last-change-recent) old pos1 pos2)
	  (setq pos (point))
	  (while recent			; at least point is there
	    (setq old (pop recent))
	    (setq pos1 (- pos session-jump-undo-threshold)
		  pos2 (+ pos session-jump-undo-threshold))
	    (when (and (<= pos1 old) (<= old pos2))
	      (setq pos (session-undo-position
			 session-jump-to-last-change-counter pos1 pos2))
	      (setq recent (and pos
				session-jump-to-last-change-counter
				session-jump-to-last-change-recent))))))
      (cond ((null pos)
	     (message (if (or arg (atom buffer-undo-list))
			  "Do not know position of last change"
			"Do not know position of last distant change")))
	    ((< pos (point-min))
	     (goto-char (point-min))
	     (message "Change position outside visible region"))
	    ((> pos (point-max))
	     (goto-char (point-max))
	     (message "Change position outside visible region"))
	    (t
	     (goto-char pos)
	     (cond ((null session-jump-to-last-change-counter)
		    (message "Jumped to stored last-change position"))
		   ((null arg)
		    (setq this-command 'session-jump-to-last-change-seq)))
             (run-hooks 'session-after-jump-to-last-change-hook))))))


;;;===========================================================================
;;;  Yank menu (Emacs: refresh existing menu, XEmacs: do our own)
;;;===========================================================================

;; this function should be defined in menu-bar.el...
(defunx session-refresh-yank-menu ()
  :xemacs-only ignore
  "Refresh `yank-menu' according to `kill-ring'."
  (when (and (default-boundp 'yank-menu)
	     (fboundp 'menu-bar-update-yank-menu))
    (let ((killed (reverse (default-value 'kill-ring))))
      (while killed
	(menu-bar-update-yank-menu (pop killed) nil)))))

(defun session-yank (arg)
  "Reinsert the last stretch of killed text, like \\[yank].
Calls `yank' with argument ARG and with `interprogram-paste-function'
bound to nil."
  (interactive "*p")
  (let ((interprogram-paste-function nil)) ;#dynamic
    (yank arg)))

(defun session-popup-yank-menu (event)
  ;; checkdoc-params: (event)
  "Pop up a menu for inserting items in `kill-ring'."
  (interactive "e")
  (when kill-ring
    (setq this-command last-command)
    (popup-menu '("Select and Paste"
		  :filter session-yank-menu-filter))))

(defun session-yank-menu-filter (menu-items)
  ;; checkdoc-params: (menu-items)
  "Return a menu for inserting items in `kill-ring'."
  (let ((menu nil)
	(ring nil)
	(max session-menu-max-size)
	(len (length kill-ring))
	(half-str-len (/ (- session-edit-menu-max-string 4) 2))
	(i 0)
	(active (not buffer-read-only))
	elem
	(interprogram-paste-function nil)) ;#dynamic
    ;; Traversing (append kill-ring-yank-pointer kill-ring) instead indexing
    ;; (current-kill INDEX) would be probably more efficient, but would be a
    ;; very low-level hack
    (while (and (< i len) (> max 0))
      (setq elem (current-kill i t)
	    i (1+ i))
      (unless (or (assoc elem ring) (string-match "\\`[ \t\n]*\\'" elem))
	(push (cons elem i) ring)
	(setq max (1- max))))
    (while ring
      (setq elem (car ring)
	    ring (cdr ring))
      (push (session-yank-string (car elem) half-str-len
				 (list 'session-yank (cdr elem))
				 active)
	    menu))
    (session-menu-maybe-accelerator menu-items menu)))

(defun session-yank-string (string half-len-str callback active)
  ;; checkdoc-order: nil
  "Return menu item STRING with callback CALLBACK.
If ACTIVE is non-nil, the item is active.  HALF-LEN-STR is the length of
the two parts of a abbreviated menu item name."
  (let ((beg (or (and session-compact-yank-gap-regexp
		      (string-match "\\`[ \t\n]+" string)
		      (match-end 0))
		 0))
	(end (or (and session-compact-yank-gap-regexp
		      (string-match "[ \t\n]+\\'" string))
		 (length string))))
    (vector (if (> (- end beg) session-edit-menu-max-string)
		(let ((gap (and session-compact-yank-gap-regexp
				(string-match session-compact-yank-gap-regexp
					      string (- end half-len-str))
				(match-end 0))))
		  (if (and gap (< gap (- end 3)))
		      (setq half-len-str (- (+ half-len-str half-len-str gap)
					    end))
		    (setq gap (- end half-len-str)))
		  (concat (session-subst-char-in-string
			   ?\t ?\ (substring string beg (+ beg half-len-str)) t)
			  " ... "
			  (session-subst-char-in-string
			   ?\t ?\ (substring string gap end) t)))
	      (session-subst-char-in-string
	       ?\t ?\  (substring string beg end) t))
	    callback
	    active)))

;; from EMACS-20.4/lisp/subr.el:
(defunx session-subst-char-in-string (fromchar tochar string &optional inplace)
  :try subst-char-in-string
  "Replace FROMCHAR with TOCHAR in STRING each time it occurs.
Unless optional argument INPLACE is non-nil, return a new string."
  (let ((i (length string))
	(newstr (if inplace string (copy-sequence string))))
    (while (> i 0)
      (setq i (1- i))
      (if (eq (aref newstr i) fromchar)
	  (aset newstr i tochar)))
    newstr))


;;;===========================================================================
;;;  Menu filters
;;;===========================================================================

(defun session-file-opened-recompute ()
  "Move file name of all live buffers to top of the menu of visited files."
  (interactive)
  (session-file-changed-recompute t))

(defun session-file-changed-recompute (&optional for-opened)
  "Store buffer places for all live buffers.
Works like \\[session-file-opened-recompute] if FOR-OPENED is non-nil."
  (interactive)
  (let ((session-use-package t))	;#dynamic
    (save-excursion
      (dolist (buffer (nreverse (buffer-list)))
	(set-buffer buffer)
	(when buffer-file-name
	  (condition-case nil	; potential errors with remote files
	      (if for-opened
		  (session-set-file-name-history)
		(session-store-buffer-places 1))
	    (error nil)))))))

(defun session-file-opened-menu-filter (menu-items)
  ;; checkdoc-params: (menu-items)
  "This is the menu filter for \"File >> Open...recently visited\".
See `session-file-changed-menu-filter'."
  (session-file-changed-menu-filter menu-items file-name-history))

(defun session-file-changed-menu-filter (menu-items &optional files find-fn)
  ;; checkdoc-params: (menu-items)
  "This is the menu filter for \"File >> Open...recently changed\".
It dynamically creates a list of files to use as the contents of the
menu.  The files are taken from FILES or `session-file-alist'.  It
doesn't show the same name twice and shows `session-menu-max-size' names
at most.  FIND-FN or \\[find-file] is the function to use when selecting
a file in the menu."
  (or files (setq files session-file-alist))
  (or find-fn (setq find-fn 'session-find-file))
  (let ((excl nil)
	(menu nil)
	(i session-menu-max-size)
	(max-string (max (cond ((natnump session-file-menu-max-string)
				session-file-menu-max-string)
			       ((integerp session-file-menu-max-string)
				(- 0 session-file-menu-max-string
				   (length (buffer-name))))
			       ((consp session-file-menu-max-string)
				(- (car session-file-menu-max-string)
				   (max (- (length (buffer-name))
					   (cdr session-file-menu-max-string))
					0)))
			       (t 50))
			 16)))
    (while (and files (> i 0))
      (let ((name (pop files)) desc)
	(when (consp name)
	  (setq desc name
		name (car name)))
	(setq name (session-abbrev-file-name name t))
	(unless (member name excl)
	  (setq i (1- i))
	  (push name excl)
          (let ((buf (if (session-abbrev-inhibit-function name)
                         nil
                       (get-file-buffer name))))
            (push (vector (or (session-file-prune-name name max-string) name)
                          (list find-fn name)
                          :keys (concat (and (sixth desc) "p")
					(when buf
					  (with-current-buffer buf
					    (if (consp buffer-undo-list)
						(if (buffer-modified-p)
						    "c" "s")
					      (if buffer-read-only
						  "r" "v"))))))
                  menu)))))
    (session-menu-maybe-accelerator menu-items (nreverse menu))))

(defun session-file-prune-name (elem max-string)
  "Prune name íf menu entry ELEM to use a miximum string length MAX-STRING."
  (when (> (length elem) max-string)
    (let* ((sep-string (char-to-string session-directory-sep-char))
	   (components (split-string elem (regexp-quote sep-string))))
      (or (cdr components)	; successful split
	  (eq session-directory-sep-char ?\/) ; already Unix separator
	  (setq sep-string "/"
		components (split-string elem (regexp-quote sep-string))))
      (let* ((prefix (if (< (length (car components)) 3) ; e.g. "~" or "C:"
			 (concat (pop components) sep-string
				 (pop components))
		       (pop components)))
	     (len (+ (length prefix) 7)) ; "/ ... /"
	     postfix)
	(when (cdr components)		; more than one remaining dir component
	  (setq components (nreverse components))
	  (incf len (length (car components)))
	  (push (pop components) postfix) ; always use last one
	  (while (<= (incf len (1+ (length (car components)))) max-string)
	    (push (pop components) postfix))
	  (concat prefix sep-string " ... " sep-string
		  (mapconcat 'identity postfix sep-string)))))))

(defun session-menu-maybe-accelerator (menu-items menu)
  "Return menu consisting of items in MENU-ITEMS and MENU.
MENU-ITEMS have the usual format of elements in a menu, except that the
name always starts with a accelerator specification \"%_. \".  Also, a
:keys specification will be evaluated if :keys is the first keyword.

The items in MENU will be modified to add accelerator specifications if
`session-menu-accelerator-support' is non-nil."
  (append menu-items
	  (if session-menu-accelerator-support
	      (funcall session-menu-accelerator-support menu)
	    menu)))

(defun session-abbrev-inhibit-function (name)
  "Call function in variable `session-abbrev-inhibit-function'."
  (and session-abbrev-inhibit-function
       (or (not (functionp session-abbrev-inhibit-function))
           (funcall session-abbrev-inhibit-function name))))

(defun session-abbrev-file-name (name &optional call-dfn)
  "Return a version of NAME shortened using `directory-abbrev-alist'.
This function does not consider remote file names (see
`session-abbrev-inhibit-function') and substitutes \"~\" for the user's
home directory.
If optional argument CALL-DFN is non-nil and the file is not remote,
remove final slash according to function `directory-file-name'."
  (if (session-abbrev-inhibit-function name)
      name
    (cond-emacs-xemacs
     (abbreviate-file-name (if call-dfn (directory-file-name name) name)
                           :XEMACS t))))


;;;===========================================================================
;;;  Functions in hooks
;;;===========================================================================

(defun session-find-file (filename)
  "Call \\[find-file] and add FILENAME to `file-name-history'."
  ;; also sets history when just switching to existing buffer
  (interactive "FFind file: ")
  (find-file filename)
  (let ((session-use-package t))	;#dynamic
    (session-set-file-name-history)))

(defun session-set-file-name-history ()
  ;; TODO later: test `this-command' matching regexo "find-file" or similar
  "Add file-name of current buffer to `file-name-history'.
Don't add the file name if it matches
`session-set-file-name-exclude-regexp', or if it is already at the front
of `file-name-history'.  This function is useful in `find-file-hooks'."
  (and session-use-package
       buffer-file-name
       (not (string= (car file-name-history) buffer-file-name))
       (not (string= (car file-name-history) buffer-file-truename))
;;       (file-exists-p buffer-file-name) (file-readable-p buffer-file-name)
       (let ((name (session-abbrev-file-name buffer-file-name)))
	 (unless (and session-set-file-name-exclude-regexp
		      (string-match session-set-file-name-exclude-regexp name))
	   (push name file-name-history)))))

(defun session-find-file-hook ()
  "Function in `find-file-hooks'.  See `session-file-alist'."
  (unless (or (eq this-command 'session-disable)
	      (null session-use-package))
    (let* ((ass (assoc (session-buffer-file-name) session-file-alist))
	   (point (second ass))
	   (mark (third ass))
	   (min (fourth ass))
	   (max (fifth ass))
	   (alist (nthcdr 7 ass)))
      (condition-case nil
	  (while alist
	    (if (local-variable-if-set-p (caar alist) (current-buffer))
		(set (caar alist) (cdar alist)))
	    (setq alist (cdr alist)))
	(error nil))
      (setq session-last-change (seventh ass))
      (and mark
	   (<= (point-min) mark) (<= mark (point-max))
	   ;; I had `set-mark' but this function activates mark in Emacs, but
	   ;; not in XEmacs.  `push-mark' is also OK and doesn't activate in
	   ;; both Emacsen which is better if we use `pending-delete-mode'.
	   (push-mark mark t))
      (and min max
	   (<= (point-min) min) (<= max (point-max))
	   (narrow-to-region min max))
      (and point
	   (<= (point-min) point) (<= point (point-max))
	   (goto-char point)))))

(defun session-kill-buffer-hook ()
  "Function in `kill-buffer-hook'.
See `session-file-alist' and `session-registers'."
  (if (and session-use-package buffer-file-name)
      (let ((arg (if (memq this-command session-kill-buffer-commands)
		     (prefix-numeric-value current-prefix-arg)
		   1)))
	(condition-case nil
	    (if (> arg -2)
		(session-store-buffer-places arg)
	      (setq file-name-history
		    (delete buffer-file-truename
			    (delete buffer-file-name file-name-history)))
;;;	      (setq session-file-alist
;;;		    (delete* (session-buffer-file-name) session-file-alist
;;;			     :key 'car :test 'string=)))  ; Emacs CL policy...
	      (let ((fname (session-buffer-file-name))
		    (alist (cons nil session-file-alist)))
		(while (cdr alist)
		  (if (string= (cadr alist) fname)
		      (setcdr alist (cddr alist))
		    (setq alist (cdr alist))))
		(setq session-file-alist (cdr alist))))
	  (error nil)))))


;;;===========================================================================
;;;  Change register contents from marker to file
;;;===========================================================================

(defun session-register-swap-out ()
  "Turn markers in registers into file references when a buffer is killed.
See variable `session-register-swap-out'."
  (and buffer-file-name
       (let ((tail register-alist))
	 (while tail
	   (and (markerp (cdr (car tail)))
		(eq (marker-buffer (cdr (car tail))) (current-buffer))
		(setcdr (car tail)
			(cons 'file buffer-file-name)))
	   (setq tail (cdr tail))))))



;;;;##########################################################################
;;;;  Save global variables, add functions to hooks
;;;;##########################################################################


(defvar session-successful-p nil
  "Whether the file `session-save-file' has been loaded successfully.")


;;;===========================================================================
;;;  The buffer file name
;;;===========================================================================

(defun session-xemacs-buffer-local-mswindows-file-p ()
  "Return t if the current buffer visits a local file on MS-Windows.
Also returns t if the current buffer does not visit a file.  Return nil
of the current buffer visits a file starting with \"\\\\\".  Workaround
for XEmacs bug in `file-truename' for file names starting with
\"\\\\\"."
  (or (< (length buffer-file-name) 2)
      (not (string= (substring buffer-file-name 0 2) "\\\\"))))

(defun session-buffer-file-name ()
  "Return the buffer file name according to `session-use-truenames'."
  (if (if (functionp session-use-truenames)
	  (funcall session-use-truenames)
	session-use-truenames)
      buffer-file-truename
    buffer-file-name))


;;;===========================================================================
;;;  Store places and local variables for buffer to be killed
;;;===========================================================================

(defun session-toggle-permanent-flag (arg &optional check)
  "Toggle the permanent flag of the current buffer.
With ARG, set permanent flag if and only if ARG is positive.  If the
permanent flag is set, the places are stored as well.  If CHECK is
non-nil, just return the status of the permanent flag: either nil if it
is unset or `session-menu-permanent-string' if it is set."
  (interactive "P")
  (if buffer-file-name
      (let ((permanent (if arg
			   (> (prefix-numeric-value arg) 0)
			 (not (nth 5 (assoc (session-buffer-file-name)
					    session-file-alist))))))
	(if check
	    (if permanent nil session-menu-permanent-string)
	  (session-store-buffer-places (if permanent 3 -1))
	  (message (if permanent
		       "Permanent flag is set and places are stored"
		     "Permanent flag has been unset"))))
    (if check nil (error "Buffer is not visiting a file"))))

(defun session-store-buffer-places (arg)
  "Store places and local variables in current buffer.
An entry for the current buffer and its places is added to the front of
`session-file-alist' if the buffer is visiting a file and if it is
mentioned in the list below.  ARG is the prefix argument to a command in
`session-kill-buffer-commands' or 1 for any other command.

ARG=-2: delete current buffer from `session-file-alist' (implemented
  in `session-kill-buffer-hook')
ARG=-1: delete PERMANENT flag for buffer,
ARG=0: do nothing,
ARG=1: store buffer places, if the PERMANENT flag is set or the buffer
  passes the function in `session-buffer-check-function',
ARG=2: always store buffer places,
ARG=3: set PERMANENT flag and store buffer places.

See also `session-last-change' and `session-locals-include'.

Note that not storing buffer places does not mean deleting an old entry
for the same file.  It means that there is the danger of the entry
becoming too old to be saved across session.  By default, only the first
100 entries of `session-file-alist' are saved, see
`session-globals-include'."
  (let ((file-name (session-buffer-file-name)))
    (when file-name
      (let ((permanent (nthcdr 5 (assoc file-name session-file-alist))))
	(and (< arg 0) (car permanent)
	     (setcar permanent nil))	; reset permanent in existing entry
	(setq permanent (or (car permanent) (> arg 2)))
	(if (or (and permanent (> arg 0))
		(> arg 1)
		(and (= arg 1)
		     (funcall session-buffer-check-function (current-buffer))))
	    (let ((locals session-locals-include)
		  (store nil))
	      (while locals
		(if (if (functionp session-locals-include)
			(funcall session-locals-predicate
				 (car locals) (current-buffer))
		      session-locals-predicate)
		    (push (cons (car locals)
				(symbol-value (car locals)))
			  store))
		(setq locals (cdr locals)))
	      (setq store
		    (nconc (list file-name
				 (point) (mark t)
				 (point-min)
				 (and (<= (point-max) (buffer-size))
				      (point-max))
				 permanent
				 (session-undo-position 0 nil nil))
			   store))
	      (if (equal (caar session-file-alist) file-name)
		  (setcar session-file-alist store)
		(push store session-file-alist))))))))

(defun session-find-file-not-found-hook ()
  "Query the user to delete the permanent flag for a non-existent file.
Always return nil."
  (when session-use-package
    (let ((file-name (session-buffer-file-name)))
      (when file-name
	(let ((permanent (nthcdr 5 (assoc file-name session-file-alist))))
	  (and (car permanent)
	       (y-or-n-p "Delete permanent flag for non-existent file? ")
	       (setcar permanent nil)))))))


;;;===========================================================================
;;;  Default standard check for buffers to be killed
;;;===========================================================================

(defun session-default-buffer-check-p (buffer)
  "Default function for `session-buffer-check-function'.
Argument BUFFER should be the current buffer."
  (and
   ;; undo check -------------------------------------------------------------
   (or (and (eq (cdr-safe session-undo-check) 'or)
	    session-last-change)
       (and (or (not (eq (cdr-safe session-undo-check) 'and))
		session-last-change)
	    (>= (if (listp buffer-undo-list) (length buffer-undo-list) -1)
		(if (consp session-undo-check)
		    (car session-undo-check)
		  session-undo-check))))
   ;; mode and name check ----------------------------------------------------
   (let ((file (buffer-file-name buffer)))
     (and (or (session-abbrev-inhibit-function file)
	      (and (file-exists-p file) (file-readable-p file)))
	  (if (if session-auto-store
		  (not (memq major-mode session-mode-disable-list))
		(memq major-mode session-mode-enable-list))
	      (not (and session-name-disable-regexp
			(string-match session-name-disable-regexp file)))
	    (and session-name-enable-regexp
		 (string-match session-name-enable-regexp file)))))))


;;;===========================================================================
;;;  Save session file
;;;===========================================================================

(defunx session-true-list-p (object)
  :try true-list-p
  "Return t if OBJECT is an acyclic, nil-terminated (ie, not dotted), list."
  (null (if (consp object)
	    (cdr (last object)) ; in Emacs-24.1: safe against cyclic lists
	  object)))

(defun session-make-ring (size seq)
  ;; similar to `ring-convert-sequence-to-ring'	from Emacs-24.1
  "Return ring of length LENGTH containing the elements of sequence SEQ."
  (let ((ring (make-ring size)))
    (dotimes (count (length seq))
      (when (or (ring-empty-p ring)
		(not (equal (ring-ref ring 0) (elt seq count))))
	(ring-insert-at-beginning ring (elt seq count))))
    ring))

(defun session-save-session (&optional force)
  "Save session: file places, *-ring, *-history, registers.
Save some global variables and registers into file `session-save-file'
with coding system `session-save-file-coding-system'.  Run functions in
`session-before-save-hook' before writing the file.

See also `session-globals-regexp', `session-globals-include' and
`session-registers'.

This function does not save the session if `session-use-package' is nil
and FORCE is nil.  When called interactively, FORCE is non-nil.

This command is automatically executed when exiting Emacs, except when
using \\[save-buffers-kill-emacs] with prefix argument 0."
  (interactive "p")
  (and (or force session-use-package)
       session-save-file
       (not (and (eq this-command 'save-buffers-kill-emacs)
		 (equal current-prefix-arg 0)))
       (or session-successful-p
	   (not (file-exists-p session-save-file))
	   (y-or-n-p "Overwrite old session file (not loaded)? "))
       (save-excursion
	 ;; `kill-emacs' doesn't kill the buffers ----------------------------
	 (dolist (buffer (nreverse (buffer-list)))
	   (set-buffer buffer)
	   (when buffer-file-name
	     (condition-case nil	; potential errors with remote files
		 (session-store-buffer-places 1)
	       (error nil))
	     (if session-register-swap-out
		 (funcall session-register-swap-out))))
	 ;; create header of session file ------------------------------------
	 (set-buffer (get-buffer-create " session "))
	 (erase-buffer)
	 (let ((coding-system-for-write	;#dynamic
		(and session-save-file-coding-system
		     (condition-case nil
			 (check-coding-system session-save-file-coding-system)
		       (error nil)))))
	   (when coding-system-for-write
	     (insert (format ";;; -*- coding: %S; -*-\n"
			     session-save-file-coding-system)))
	   (insert ";;; Automatically generated on " (current-time-string)
		   "\n;;; Invoked by " (user-login-name) "@" (system-name)
		   " using " emacs-version "\n")
	   ;; save global variables and registers ----------------------------
           (let (globals-exclude exclude-regexp)
             (dolist (incl session-globals-include)
               (let ((symbol (if (consp incl) (car incl) incl)))
                 (push symbol globals-exclude)
                 (when (default-boundp symbol)
                   (session-save-insert-variable symbol
                                                 (default-value symbol)
                                                 (cdr-safe incl)))))
             (dolist (excl session-globals-exclude)
               (if (stringp excl)
                   (push excl exclude-regexp)
                 (push excl globals-exclude)))
             (when exclude-regexp
               (setq exclude-regexp
                     (concat "\\(?:"
                             (mapconcat 'identity exclude-regexp "\\)\\|\\(?:")
                             "\\)")))
	     (dolist (symbol (apropos-internal session-globals-regexp 'boundp))
               (unless (or (memq symbol globals-exclude)
                           (and exclude-regexp
                                (string-match exclude-regexp
                                              (symbol-name symbol))))
		   (push symbol globals-exclude)
		   (when (default-boundp symbol)
		     (session-save-insert-variable symbol
						   (default-value symbol))))))
	   (session-save-registers)
	   ;; write session file ---------------------------------------------
	   (run-hooks 'session-before-save-hook)
	   (condition-case var
	       (progn
		 (if (file-exists-p session-save-file)
		     (delete-file session-save-file))
		 (make-directory (file-name-directory session-save-file) t)
		 (write-region (point-min) (point-max) session-save-file)
		 (if session-save-file-modes
		     (set-file-modes session-save-file
				     session-save-file-modes)))
	     (error			; efs would signal `ftp-error'
	      (or (y-or-n-p "Could not write session file.  Exit anyway? ")
		  (cond-emacs-xemacs
		   (:EMACS signal :XEMACS signal-error :BOTH
			   (car var) (cdr var))))))
	   (kill-buffer (current-buffer))))))

(defun session-save-insert-variable (symbol val &optional spec)
  "Print SYMBOL and its value VAL into the current buffer.
Argument SPEC looks like (MAX-SIZE ASSOC-P), see variable
`session-globals-include' for details.

Only true lists are printed which do not have a level-1 recursion.
Elements in the list are not printed if one of the following is true:
 - the element is no cons if ASSO-P is non-nil,
 - strings which are too long, see `session-globals-max-string',
 - non-readable elements, or
 - elements which are not fully represented according to the
   specification in `session-save-print-spec'."
  (when (consp val)
    (let ((print-circle (car session-save-print-spec)) ;#dynamic
	  (print-level  (cadr session-save-print-spec)) ;#dynamic
	  (print-length (caddr session-save-print-spec)) ;#dynamic
	  (len   (or (car spec) session-globals-max-size))
	  (ass-p (cadr spec))
	  (ring-size (and (ring-p val) (ring-size val)))
	  (slist nil) klist clist)
      (when ring-size
	(setq val (ring-elements val)))
      (while (and (consp val) (> len 0))
	(if (memq val clist)
	    (setq val t)	; don't print recursive lists
	  (push val clist)
	  (let* ((elem (pop val))
		 (estr (prin1-to-string (if (stringp elem)
					    (substring-no-properties elem)
					  elem))))
	    ;; some text properties cannot be read, e.g. buffer positions
	    ;; read/load isn't clever: ignore non-readable elements
	    (unless (cond (ass-p
			   (or (atom elem)
			       (member (car elem) klist)
			       (condition-case nil
				   (prog1 nil
				     (read estr)
				     (push (car elem) klist))
				 (error t))))
			  ((member estr slist))
			  ((stringp elem)
			   (> (length elem) session-globals-max-string))
			  ((condition-case nil
			       (prog1 nil
				 (read estr))
			     (error t))))
	      (push estr slist)
	      (decf len)))))
      (when (and slist (session-true-list-p val))
	(insert (if ring-size
		    (format "(setq-default %S (session-make-ring %d '("
			    symbol ring-size)
		  (format "(setq-default %S '(" symbol)))
	(setq slist (nreverse slist))
	(while slist
	  (insert (pop slist)
		  (if slist " " (if ring-size ")))\n" "))\n"))))))))

(defunx session-next-range-char (char)
  ;; XEmacs register functions should handle integers as chars better...
  :emacs-only  1+
  "Return the next char after CHAR."
  (int-to-char (1+ char)))

(defun session-save-registers ()
  "Save registers in `session-registers'."
  (let ((chars session-registers)
	(type 'file)
	register from to)
    (while chars
      (if (symbolp (car chars))
	  (setq type  (car chars)
		chars (cdr chars))
	(setq from (car chars)
	      chars (cdr chars))
	(if (consp from)
	    (setq to   (cdr from)
		  from (car from))
	  (setq to from))
	(while (<= from to)
	  (setq register (get-register from))
	  (cond ((null register))
		((and (memq type '(file t))
		      (consp register)
		      (memq (car register) '(file file-query)))
		 (insert (if (eq (car register) 'file)
			     (format "(set-register %S '(file . %S))\n"
				     from (cdr register))
			   (format "(set-register %S '(file-query %S %d))\n"
				   from (cadr register) (caddr register)))))
		((and (memq type '(region t))
		      (stringp register)
		      (< (length register) session-registers-max-string))
		 (insert (format "(set-register %S %S)\n" from register))))
	  (setq from (session-next-range-char from)))))))


;;;===========================================================================
;;;  Minibuffer history completion, see XEmacs' list-mode
;;;===========================================================================

(defvar session-history-help-string
  '(concat (if (device-on-window-system-p)
	       (substitute-command-keys "Click \\<list-mode-map>\\[list-mode-item-mouse-selected] on a history element to select it.\n") "")
	   (substitute-command-keys "In this buffer, type RET to select the element near point.\n\n"))
  "Form the evaluate to get a help string for history elements.")

(defun session-minibuffer-history-help ()
  "List history of current minibuffer type.
In Emacs, the *History* buffer talks about \"completions\" instead
\"history elements\".  In XEmacs before 21.4.9, selecting an entry might
not work if the minibuffer is non-empty."
  (interactive)
  (let ((history (symbol-value minibuffer-history-variable)))
    (message nil)
    (if history
	(with-output-to-temp-buffer "*History*"
	  (cond-emacs-xemacs
	   (display-completion-list
	    (sort history #'string-lessp)
	    :XEMACS
	    :help-string session-history-help-string
	    :completion-string "Elements in the history are:"))
	  (save-excursion
	    (set-buffer standard-output)
	    (setq completion-base-size 0)))
      (ding)
      (session-minibuffer-message " [Empty history]"))))

(defunx session-minibuffer-message (string)
  :emacs-only  minibuffer-message
  :xemacs-only temp-minibuffer-message)


;;;===========================================================================
;;;  Set hooks, load session file
;;;===========================================================================

;; easymenu.el is for top-level menus only...  both Emacs and XEmacs could
;; profit from a better menu interface...
(defunx session-add-submenu (menu)
  "Add the menu MENU to the beginning of the File menu in the menubar.
If the \"File\" menu does not exist, no submenu is added.  See
`easy-menu-define' for the format of MENU."
  (and menu
       :EMACS
       (>= emacs-major-version 21)
       (boundp 'menu-bar-files-menu)
       (let ((keymap (easy-menu-create-menu (car menu) (cdr menu))))
	 ;; `easy-menu-get-map' doesn't get the right one => use hard-coded
	 (define-key menu-bar-files-menu (vector (intern (car menu)))
	   (cons 'menu-item
		 (cons (car menu)
		       (if (not (symbolp keymap))
			   (list keymap)
			 (cons (symbol-function keymap)
			       (get keymap 'menu-prop)))))))
       :XEMACS
       (featurep 'menubar)
       (let ((current-menubar default-menubar) ;#dynamic
	     (first (cadar (find-menu-item default-menubar '("File")))))
	 (when first
	   ;; XEmacs-20.4 `add-submenu' does not have 4th arg IN-MENU
	   (add-submenu '("File") menu
			;; arg BEFORE cannot be retrieved by any
			;; menubar function -- great...
			(cond ((vectorp first) (aref first 0))
			      ((consp first) (car first))))))))

(defunx session-initialize-keys ()
  "Define some key bindings for package session."
  (define-key ctl-x-map [(undo)] 'session-jump-to-last-change)
  (define-key ctl-x-map [(control ?\/)] 'session-jump-to-last-change)
  (define-key minibuffer-local-map [(meta ?\?)]
    'session-minibuffer-history-help)
  (when session-yank-menu-binding
    ;; C-down-mouse-3 pops up mode menu under Emacs
    (define-key global-map session-yank-menu-binding 'session-popup-yank-menu))
  :EMACS
  ;; Emacs doesn't seem to have keymap inheritance...
  (define-key minibuffer-local-completion-map [(meta ?\?)]
    'session-minibuffer-history-help)
  (define-key minibuffer-local-must-match-map [(meta ?\?)]
    'session-minibuffer-history-help)
  (define-key minibuffer-local-ns-map [(meta ?\?)]
    'session-minibuffer-history-help))

(defunx session-initialize-menus ()
  "Add some submenus for package session."
  (session-add-submenu '("Open...Recently Visited"
			 :included file-name-history
			 :filter session-file-opened-menu-filter
			 ["Move File Names Of All Buffers To Top"
			  session-file-opened-recompute]
			 "---"))
  (session-add-submenu '("Open...Recently Changed"
			 ;;:included session-file-alist
			 :filter session-file-changed-menu-filter
			 ["Perform Evaluation For All Buffers"
			  session-file-changed-recompute]
			 ["Permanently List Current Buffer "
			  session-toggle-permanent-flag
			  ;; :keys must be at third position!
			  ;;:keys (session-toggle-permanent-flag nil t)
			  :active buffer-file-name
			  :style toggle
			  :selected (session-toggle-permanent-flag nil t)]
			 "---"))
  :XEMACS
  (and (featurep 'menubar)
       (find-menu-item default-menubar '("Edit"))
       (let ((current-menubar default-menubar))
	 ;; XEmacs-20.4 `add-submenu' does not have 4th arg IN-MENU
	 (add-submenu '("Edit")
		      '("Select and Paste"
			:included kill-ring
			:filter session-yank-menu-filter)
		      (cond ((find-menu-item default-menubar
					     '("Edit" "Delete"))
			     "Delete")	; why just BEFORE, not AFTER
			    ((find-menu-item default-menubar
					     '("Edit" "Paste"))
			     "Paste")
			    ((find-menu-item default-menubar
					     '("Edit" "Undo"))
			     "Undo"))))))

(defun session-initialize-do ()
  "Initialize package session and read previous session file.
Setup hooks and load `session-save-file', see variable `session-initialize'.  At
best, this function is called at the end of the Emacs startup, i.e., add
this function to `after-init-hook'."
  (when (and session-use-package
	     (null (get 'session-initialize :initilized-with)))
    (when (or (eq session-initialize t)
	      (memq 'de-saveplace session-initialize))
      ;; Features of package saveplace, which has an auto-init, are covered by
      ;; this package.
      (when (functionp 'eval-after-load)
	(eval-after-load "saveplace"
	  '(progn
	     (remove-hook 'find-file-hooks 'save-place-find-file-hook)
	     (remove-hook 'kill-emacs-hook 'save-place-kill-emacs-hook)
	     (remove-hook 'kill-buffer-hook 'save-place-to-alist)))))
    (when (or (eq session-initialize t)
	      (memq 'places session-initialize))
      ;; `session-find-file-hook' should be *very* late in `find-file-hooks',
      ;; esp. if some package, e.g. crypt, iso-cvt, change the buffer contents:
      (add-hook 'find-file-hooks 'session-find-file-hook t)
      (add-hook 'find-file-not-found-hooks 'session-find-file-not-found-hook t)
      (add-hook 'kill-buffer-hook 'session-kill-buffer-hook)
      (if session-register-swap-out
	  (add-hook 'kill-buffer-hook session-register-swap-out)))
    (when (or (eq session-initialize t) (memq 'keys session-initialize))
      (condition-case nil
	  (session-initialize-keys)
	(error nil)))
    (when (or (eq session-initialize t) (memq 'menus session-initialize))
      (unless (memq 'session-set-file-name-history find-file-hooks)
	;; already initialized (probably not a good idea to redo for menus)
	(add-hook 'find-file-hooks 'session-set-file-name-history)
	(session-initialize-menus)))
    (when (or (eq session-initialize t)
	      (memq 'session session-initialize))
      ;; Although desktop and savehist also add its function to
      ;; kill-emacs-hook, it might be better to add this function to
      ;; `kill-emacs-query-functions' instead.  People who want to exit Emacs
      ;; without saving the session file might simply call M-x kill-emacs
      (add-hook 'kill-emacs-hook 'session-save-session)
      (or session-successful-p
	  (setq session-successful-p
		(and session-save-file
		     (condition-case nil
			 (progn
			   ;; load might fail with coding-system = emacs-mule
			   (unless (load session-save-file t nil t)
			     (and session-old-save-file
				  (load session-old-save-file t nil t)))
			   (run-hooks 'session-after-load-save-file-hook)
			   t)
		       (error nil))))))
    (put 'session-initialize :initilized-with session-initialize)))

(defun session-initialize-and-set (symbol value)
  "Custom :set function for `session-use-package'.
It sets the default value of SYMBOL to VALUE and initializes this
package."
  (set-default symbol value)     ; symbol should be `session-use-package'
  (when value
    (if (cond-emacs-xemacs
	 :EMACS  (and (boundp 'after-init-time) (null after-init-time))
	 :XEMACS (null init-file-loaded))
	;; in the meantime,`session-use-package' could have been reset to nil
	;; (e.g. when using custom theme with t, user setting with nil)
	(add-hook 'after-init-hook 'session-initialize-do)
      (session-initialize-do))))

;; This must be late in this file as set function is called during loading.
(defcustom session-use-package nil
  "Non-nil if package session is in use.
If in use,
 - the file name history is updated when visiting a file,
 - buffer places are stored when killing a buffer,
 - the session file is saved when exiting Emacs, and
 - keybindings are menus are added the first time the package is put
   into use, see variable `session-initialize'."
  :group 'session
  :type '(boolean :on "in use" :off "not yet initialized or turned off"
		  :help-echo "Use package Session, initialize if necessary.")
  :require 'session
  :set 'session-initialize-and-set)

;;;###autoload
(defun session-initialize ()
  "Initialize package session and read previous session file.
Setup hooks and load `session-save-file', see variable `session-initialize'.  At
best, this function is called at the end of the Emacs startup, i.e., add
this function to `after-init-hook'."
  (interactive)
  (put 'session-initialize :initilized-with nil)
  (custom-set-variables '(session-use-package t nil (session))))

(provide 'session)

;;; session.el ends here
