(desktop-buffer-mode-handlers): Make

non-customizable. Add autoload cookie.  Change initial value to
nil; add elements in respective modules instead. Fix doc string.
(desktop-load-file): New function.
(desktop-minor-mode-handlers): New autoloaded variable.
(desktop-create-buffer): Call minor mode handlers. Use
desktop-load-file to load major and minor mode modules prior to
checking for a handler.
(desktop-save): Don't add nil to desktop-minor-modes for minor
modes with nil function in desktop-minor-mode-table. Don't delete
desktop file before rewriting it.
(desktop-locals-to-save): Add autoload cookie. Don't make
automatically buffer-local.  Add variables column-number-mode,
size-indication-mode, indent-tabs-mode,
indicate-buffer-boundaries, indicate-empty-lines and
show-trailing-whitespace.
(desktop-clear): Allow desktop-clear-preserve-buffers to contain
regexps. Don't use desktop-clear-preserve-buffers-regexp.
(desktop-clear-preserve-buffers-regexp): Delete.
(desktop-clear-preserve-buffers): Update initial value and
docstring.
(desktop-save-buffer): Fix doc string.

1 files changed, 178 insertions, 54 deletions

diff --git a/lisp/desktop.el b/lisp/desktop.el
index 57065d2f813..f8be1f0685d 100644
--- a/lisp/desktop.el
+++ b/lisp/desktop.el
@@ -51,13 +51,66 @@
 ;; function is added to the `after-init-hook'. This function is
 ;; responsible for loading the desktop when Emacs is started.
 
-;; Some words on minor modes: Most minor modes are controlled by
-;; buffer-local variables, which have a standard save / restore
-;; mechanism.  To handle all minor modes, we take the following
-;; approach: (1) check whether the variable name from
-;; `minor-mode-alist' is also a function; and (2) use translation
-;; table `desktop-minor-mode-table' in the case where the two names
-;; are not the same.
+;; Special handling.
+;; -----------------
+;; Variables `desktop-buffer-mode-handlers' and `desktop-minor-mode-handlers'
+;; are supplied to handle special major and minor modes respectively.
+;; `desktop-buffer-mode-handlers' is an alist of major mode specific functions
+;; to restore a desktop buffer. Elements must have the form
+;; 
+;;    (MAJOR-MODE . RESTORE-BUFFER-FUNCTION).
+;; 
+;; Functions listed are called by `desktop-create-buffer' when `desktop-read'
+;; evaluates the desktop file. Buffers with a major mode not specified here,
+;; are restored by the default handler `desktop-restore-file-buffer'.
+;; `desktop-minor-mode-handlers' is an alist of functions to restore
+;; non-standard minor modes.  Elements must have the form
+;; 
+;;    (MINOR-MODE . RESTORE-FUNCTION).
+;; 
+;; Functions are called by `desktop-create-buffer' to restore minor modes.
+;; Minor modes not specified here, are restored by the standard minor mode
+;; function.  If you write a module that defines a major or minor mode that
+;; needs a special handler, then place code like
+
+;;    (defun foo-restore-desktop-buffer
+;;    ...
+;;    (add-to-list 'desktop-buffer-mode-handlers
+;;                 '(foo-mode . foo-restore-desktop-buffer))
+
+;; or
+
+;;    (defun bar-desktop-restore
+;;    ...
+;;    (add-to-list 'desktop-minor-mode-handlers
+;;                 '(bar-mode . bar-desktop-restore))
+
+;; in the module itself, and make shure that the mode function is
+;; autoloaded. See the docstrings of `desktop-buffer-mode-handlers' and
+;; `desktop-minor-mode-handlers' for more info.
+
+;; Minor modes.
+;; ------------
+;; Conventional minor modes (see node "Minor Mode Conventions" in the elisp
+;; manual) are handled in the following way:
+;; When `desktop-save' saves the state of a buffer to the desktop file, it
+;; saves as `desktop-minor-modes' the list of names of those variables in
+;; `minor-mode-alist' that have a non-nil value.
+;; When `desktop-create' restores the buffer, each of the symbols in
+;; `desktop-minor-modes' is called as function with parameter 1.
+;; The variables `desktop-minor-mode-table' and `desktop-minor-mode-handlers'
+;; are used to handle non-conventional minor modes.  `desktop-save' uses
+;; `desktop-minor-mode-table' to map minor mode variables to minor mode
+;; functions before writing `desktop-minor-modes'. If a minor mode has a
+;; variable name that is different form its function name, an entry
+
+;;    (NAME RESTORE-FUNCTION)
+
+;; should be added to `desktop-minor-mode-table'.  If a minor mode should not
+;; be restored, RESTORE-FUNCTION should be set to nil.  `desktop-create' uses
+;; `desktop-minor-mode-handlers' to lookup minor modes that needs a restore
+;; function different from the usual minor mode function.
+;; ---------------------------------------------------------------------------
 
 ;; By the way: don't use desktop.el to customize Emacs -- the file .emacs
 ;; in your home directory is used for that.  Saving global default values
@@ -207,20 +260,15 @@ to the value obtained by evaluating FORM."
   :group 'desktop
   :version "22.1")
 
-(defcustom desktop-clear-preserve-buffers-regexp
-  "^\\(\\*scratch\\*\\|\\*Messages\\*\\|\\*server\\*\\|\\*tramp/.+\\*\\)$"
-  "Regexp identifying buffers that `desktop-clear' should not delete.
-See also `desktop-clear-preserve-buffers'."
-  :type 'regexp
-  :group 'desktop
-  :version "22.1")
-
-(defcustom desktop-clear-preserve-buffers nil
-  "*List of buffer names that `desktop-clear' should not delete.
-See also `desktop-clear-preserve-buffers-regexp'."
+(defcustom desktop-clear-preserve-buffers
+  '("\\*scratch\\*" "\\*Messages\\*" "\\*server\\*" "\\*tramp/.+\\*")
+  "*List of buffers that `desktop-clear' should not delete.
+Each element is a regular expression.  Buffers with a name matched by any of
+these won't be deleted."
   :type '(repeat string)
   :group 'desktop)
 
+;;;###autoload
 (defcustom desktop-locals-to-save
   '(desktop-locals-to-save  ; Itself!  Think it over.
     truncate-lines
@@ -230,12 +278,18 @@ See also `desktop-clear-preserve-buffers-regexp'."
     overwrite-mode
     change-log-default-name
     line-number-mode
-    buffer-file-coding-system)
+    column-number-mode
+    size-indication-mode
+    buffer-file-coding-system
+    indent-tabs-mode
+    indicate-buffer-boundaries
+    indicate-empty-lines
+    show-trailing-whitespace)
   "List of local variables to save for each buffer.
-The variables are saved only when they really are local."
+The variables are saved only when they really are local.  Conventional minor
+modes are restored automatically; they should not be listed here."
   :type '(repeat symbol)
   :group 'desktop)
-(make-variable-buffer-local 'desktop-locals-to-save)
 
 ;; We skip .log files because they are normally temporary.
 ;;         (ftp) files because they require passwords and whatnot.
@@ -301,23 +355,23 @@ file along with the state of the buffer for which it was called.
 When file names are returned, they should be formatted using the call
 \"(desktop-file-name FILE-NAME DESKTOP-DIRNAME)\".
 
-Later, when `desktop-read' calls a function in `desktop-buffer-mode-handlers'
-to restore the buffer, the auxiliary information is passed as the argument
-DESKTOP-BUFFER-MISC.")
+Later, when `desktop-read' evaluates the desktop file, auxiliary information
+is passed as the argument DESKTOP-BUFFER-MISC to functions in
+`desktop-buffer-mode-handlers'.")
 (make-variable-buffer-local 'desktop-save-buffer)
 (make-obsolete-variable 'desktop-buffer-modes-to-save
                         'desktop-save-buffer "22.1")
 (make-obsolete-variable 'desktop-buffer-misc-functions
                         'desktop-save-buffer "22.1")
 
-(defcustom desktop-buffer-mode-handlers
-  '((dired-mode . dired-restore-desktop-buffer)
-    (rmail-mode . rmail-restore-desktop-buffer)
-    (mh-folder-mode . mh-restore-desktop-buffer)
-    (Info-mode . Info-restore-desktop-buffer))
+;;;###autoload
+(defvar desktop-buffer-mode-handlers
+  nil
   "Alist of major mode specific functions to restore a desktop buffer.
-Functions are called by `desktop-read'.  List elements must have the form
-\(MAJOR-MODE . RESTORE-BUFFER-FUNCTION).
+Functions listed are called by `desktop-create-buffer' when `desktop-read'
+evaluates the desktop file.  List elements must have the form
+
+   (MAJOR-MODE . RESTORE-BUFFER-FUNCTION).
 
 Buffers with a major mode not specified here, are restored by the default
 handler `desktop-restore-file-buffer'.
@@ -337,9 +391,17 @@ Furthermore, they may use the following variables:
    desktop-buffer-locals
 
 If a handler returns a buffer, then the saved mode settings
-and variable values for that buffer are copied into it."
-  :type 'alist
-  :group 'desktop)
+and variable values for that buffer are copied into it.
+
+Modules that define a major mode that needs a special handler should contain
+code like
+
+   (defun foo-restore-desktop-buffer
+   ...
+   (add-to-list 'desktop-buffer-mode-handlers
+                '(foo-mode . foo-restore-desktop-buffer))
+
+Furthermore the major mode function must be autoloaded.")
 
 (put 'desktop-buffer-mode-handlers 'risky-local-variable t)
 (make-obsolete-variable 'desktop-buffer-handlers
@@ -355,10 +417,56 @@ mode is active.  RESTORE-FUNCTION is the function to activate the minor mode.
 called.  RESTORE-FUNCTION nil means don't try to restore the minor mode.
 Only minor modes for which the name of the buffer-local variable
 and the name of the minor mode function are different have to be added to
-this table."
+this table.  See also `desktop-minor-mode-handlers'."
   :type 'sexp
   :group 'desktop)
 
+;;;###autoload
+(defvar desktop-minor-mode-handlers
+  nil
+  "Alist of functions to restore non-standard minor modes.
+Functions are called by `desktop-create-buffer' to restore minor modes.
+List elements must have the form
+
+   (MINOR-MODE . RESTORE-FUNCTION).
+
+Minor modes not specified here, are restored by the standard minor mode
+function.
+
+Handlers are called with argument list
+
+   (DESKTOP-BUFFER-LOCALS)
+
+Furthermore, they may use the following variables:
+
+   desktop-file-version
+   desktop-buffer-file-name
+   desktop-buffer-name
+   desktop-buffer-major-mode
+   desktop-buffer-minor-modes
+   desktop-buffer-point
+   desktop-buffer-mark
+   desktop-buffer-read-only
+   desktop-buffer-misc
+
+When a handler is called, the buffer has been created and the major mode has
+been set, but local variables listed in desktop-buffer-locals has not yet been
+created and set.
+
+Modules that define a minor mode that needs a special handler should contain
+code like
+
+   (defun foo-desktop-restore
+   ...
+   (add-to-list 'desktop-minor-mode-handlers
+                '(foo-mode . foo-desktop-restore))
+
+Furthermore the minor mode function must be autoloaded.
+
+See also `desktop-minor-mode-table'.")
+
+(put 'desktop-minor-mode-handlers 'risky-local-variable t)
+
 ;; ----------------------------------------------------------------------------
 (defvar desktop-dirname nil
   "The directory in which the desktop file should be saved.")
@@ -382,23 +490,27 @@ this table."
 ;; ----------------------------------------------------------------------------
 (defun desktop-clear ()
   "Empty the Desktop.
-This kills all buffers except for internal ones and those matching
-`desktop-clear-preserve-buffers-regexp' or listed in
-`desktop-clear-preserve-buffers'.  Furthermore, it clears the
-variables listed in `desktop-globals-to-clear'."
+This kills all buffers except for internal ones and those with names matched by
+a regular expression in the list `desktop-clear-preserve-buffers'.
+Furthermore, it clears the variables listed in `desktop-globals-to-clear'."
   (interactive)
   (desktop-lazy-abort)
   (dolist (var desktop-globals-to-clear)
     (if (symbolp var)
       (eval `(setq-default ,var nil))
       (eval `(setq-default ,(car var) ,(cdr var)))))
-  (let ((buffers (buffer-list)))
+  (let ((buffers (buffer-list))
+        (preserve-regexp (concat "^\\("
+                                 (mapconcat (lambda (regexp)
+                                              (concat "\\(" regexp "\\)"))
+                                            desktop-clear-preserve-buffers
+                                            "\\|")
+                                 "\\)$")))
     (while buffers
       (let ((bufname (buffer-name (car buffers))))
          (or
            (null bufname)
-           (string-match desktop-clear-preserve-buffers-regexp bufname)
-           (member bufname desktop-clear-preserve-buffers)
+           (string-match preserve-regexp bufname)
            ;; Don't kill buffers made for internal purposes.
            (and (not (equal bufname "")) (eq (aref bufname 0) ?\s))
            (kill-buffer (car buffers))))
@@ -622,12 +734,10 @@ See also `desktop-base-file-name'."
                           (and
                             (boundp minor-mode)
                             (symbol-value minor-mode)
-                            (let ((special (assq minor-mode desktop-minor-mode-table)))
-                              (when (or special (functionp minor-mode))
-                                (setq ret
-                                  (cons
-                                    (if special (cadr special) minor-mode)
-                                    ret))))))
+                            (let* ((special (assq minor-mode desktop-minor-mode-table))
+                                   (value (cond (special (cadr special))
+                                                ((functionp minor-mode) minor-mode))))
+                              (when value (add-to-list 'ret value)))))
                         (mapcar #'car minor-mode-alist))
                       ret)
                     (point)
@@ -685,7 +795,6 @@ See also `desktop-base-file-name'."
                   (insert ")\n\n")))
             info)
       (setq default-directory dirname)
-      (when (file-exists-p filename) (delete-file filename))
       (let ((coding-system-for-write 'emacs-mule))
         (write-region (point-min) (point-max) filename nil 'nomessage))))
   (setq desktop-dirname dirname))
@@ -850,13 +959,20 @@ directory DIRNAME."
             buf)
         nil)))
 
+(defun desktop-load-file (function)
+  "Load the file where auto loaded FUNCTION is defined."
+  (let ((fcell (symbol-function function)))
+    (when (and (listp fcell)
+               (eq 'autoload (car fcell)))
+      (load (cadr fcell)))))
+
 ;; ----------------------------------------------------------------------------
 ;; Create a buffer, load its file, set its mode, ...;
 ;; called from Desktop file only.
 
-(eval-when-compile ; Just to silence the byte compiler
-   (defvar desktop-first-buffer) ;; Dynamically bound in `desktop-read'
-)
+;; Just to silence the byte compiler.
+(eval-when-compile
+  (defvar desktop-first-buffer)) ; Dynamically bound in `desktop-read'
 
 (defun desktop-create-buffer
   (desktop-file-version
@@ -877,6 +993,8 @@ directory DIRNAME."
   ;; To make desktop files with relative file names possible, we cannot
   ;; allow `default-directory' to change. Therefore we save current buffer.
   (save-current-buffer
+    ;; Give major mode module a chance to add a handler.
+    (desktop-load-file desktop-buffer-major-mode)
     (let ((buffer-list (buffer-list))
           (result
            (condition-case err
@@ -914,9 +1032,15 @@ directory DIRNAME."
                (auto-fill-mode 0))
               (t
                (mapc #'(lambda (minor-mode)
-                         (when (functionp minor-mode) (funcall minor-mode 1)))
+                         ;; Give minor mode module a chance to add a handler.
+                         (desktop-load-file minor-mode)
+                         (let ((handler (cdr (assq minor-mode desktop-minor-mode-handlers))))
+                           (if handler
+                               (funcall handler desktop-buffer-locals)
+                             (when (functionp minor-mode)
+                               (funcall minor-mode 1)))))
                      desktop-buffer-minor-modes)))
-        ;; Even though point and mark are non-nil when written by `desktop-save'
+        ;; Even though point and mark are non-nil when written by `desktop-save',
         ;; they may be modified by handlers wanting to set point or mark themselves.
         (when desktop-buffer-point
           (goto-char