Provide persistent window parameters.

* window.c (Vwindow_persistent_parameters): New variable.
(Fset_window_configuration, save_window_save): Handle persistent
window parameters.

* window.el (window-state-ignored-parameters): Remove variable.
(window--state-get-1): Rename argument MARKERS to IGNORE.
Handle persistent window parameters.  Make copy of clone-of
parameter only if requested.  (Bug#10348)
(window--state-put-2): Install a window parameter only if it has
a non-nil value or an existing parameter shall be overwritten.

* windows.texi (Window Configurations, Window Parameters):
Describe persistent window parameters.

6 files changed, 241 insertions, 47 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index f69eeeaadd4..8304554ace6 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2012-01-16  Martin Rudalics  <rudalics@gmx.at>
+
+        * windows.texi (Window Configurations, Window Parameters):
+        Describe persistent window parameters.
+
 2011-12-27  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * variables.texi (Creating Buffer-Local): Warn against misuses of
diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi
index 85e1b9340fc..5f4e530089d 100644
--- a/doc/lispref/windows.texi
+++ b/doc/lispref/windows.texi
@@ -3104,7 +3104,9 @@ window configuration; see @ref{Frame Configurations}.
 @defun current-window-configuration &optional frame
 This function returns a new object representing @var{frame}'s current
 window configuration.  The default for @var{frame} is the selected
-frame.
+frame.  This function saves copies of window parameters listed by the
+variable @code{window-persistent-parameters}, see @ref{Window
+Parameters} for details.
 @end defun
 
 @defun set-window-configuration configuration
@@ -3206,24 +3208,30 @@ configurations.
 
   The objects returned by @code{current-window-configuration} die
 together with the Emacs process.  In order to store a window
-configuration on disk and read it back in another Emacs session the
-following two functions can be used.
+configuration on disk and read it back in another Emacs session, the
+functions described next can be used.  These functions are also useful
+to clone the state of a frame into an arbitrary live window
+(@code{set-window-configuration} effectively clones the windows of a
+frame into the root window of that very frame only).
 
-@defun window-state-get &optional window markers
+@defun window-state-get &optional window ignore
 This function returns the state of @var{window} as a Lisp object.  The
 argument @var{window} can be any window and defaults to the root window
 of the selected frame.
 
-The optional argument @var{markers} non-@code{nil} means to use markers
-for sampling positions like @code{window-point} or @code{window-start}.
-This argument should be non-@code{nil} only if the value is used for
-putting the state back in the same session since markers slow down
-processing.
+If the optional argument @var{ignore} is non-@code{nil}, this means to
+not use markers for sampling positions like @code{window-point} or
+@code{window-start}.  This argument should be non-@code{nil} when the
+state shall be written on disk and read back in another session.
+
+The variable @code{window-persistent-parameters} specifies whether and
+which window parameters are saved by this function, see @ref{Window
+Parameters} for details.
 @end defun
 
-The value returned by @code{window-state-get} can be converted by using
+The value returned by @code{window-state-get} can be converted, using
 one of the functions defined by Desktop Save Mode (@pxref{Desktop Save
-Mode}) to an object that can be written to a file.  Such objects can be
+Mode}), to an object that can be written to a file.  Such objects can be
 read back and converted to a Lisp object representing the state of the
 window.  That Lisp object can be used as argument for the following
 function in order to restore the state window in another window.
@@ -3268,6 +3276,51 @@ This function sets @var{window}'s value of @var{parameter} to
 is the selected window.
 @end defun
 
+By default, functions saving and restoring window configurations or the
+states of windows (@xref{Window Configurations}) do not care about
+window parameters.  This means, that when you change the value of a
+parameter within the body of a @code{save-window-excursion}, the
+previous value is not restored upon exit of that macro.  It also means
+that when you clone via @code{window-state-put} a window state saved
+earlier by @code{window-state-get}, the cloned windows come up with no
+parameters at all.  The following variable allows to override the
+standard behavior.
+
+@defvar window-persistent-parameters
+This variable is an alist specifying which parameters get saved by
+@code{current-window-configuration} and @code{window-state-get} and
+subsequently restored by @code{set-window-configuration} and
+@code{window-state-put}, see @ref{Window Configurations}.
+
+The @sc{car} of each entry of this alist is the symbol specifying the
+parameter.  The @sc{cdr} must be one of the following:
+
+@table @asis
+@item @code{state}
+This value means the parameter is saved by @code{window-state-get}
+provided its @var{ignore} argument is @code{nil}.  The function
+@code{current-window-configuration} does not save this parameter.
+
+@item @code{nil}
+This value specifies that the parameter is saved by
+@code{current-window-configuration} and, provided its @var{ignore}
+argument is @code{nil}, by @code{window-state-get}.
+
+@item @code{t}
+This means that the parameter is saved unconditionally by both
+@code{current-window-configuration} and @code{window-state-get}.  This
+value should not be used for parameters whose values do not have a read
+syntax.  Otherwise, invoking @code{window-state-put} in another session
+may fail with an @code{invalid-read-syntax} error.
+@end table
+
+Parameters that have been saved are restored to their previous values by
+@code{set-window-configuration} respectively are installed by
+@code{window-state-put}.  Parameters that have not been saved are left
+alone by @code{set-window-configuration} respectively are not installed
+by @code{window-state-put}.
+@end defvar
+
 Some functions, notably @code{delete-window},
 @code{delete-other-windows} and @code{split-window} may behave specially
 when their @var{window} argument has a parameter set.  You can override
@@ -3287,7 +3340,7 @@ windows when exiting that function.
 @end defvar
 
 The following parameters are currently used by the window management
-code.
+code:
 
 @table @asis
 @item @code{delete-window}
@@ -3309,14 +3362,20 @@ This parameter affects the execution of @code{other-window}
 @item @code{no-other-window}
 This parameter marks the window as not selectable by @code{other-window}
 (@pxref{Cyclic Window Ordering}).
+
+@item @code{clone-of}
+This parameter specifies the window this one has been cloned from and is
+installed by @code{window-state-get}, see @ref{Window Configurations}.
+
+@item @code{quit-restore}
+This parameter tells how to proceed with a window when the buffer it
+shows is no more needed.  It is installed by the buffer display
+functions (@pxref{Choosing Window}) and consulted by the function
+@code{quit-window} (@pxref{Quitting Windows}).
 @end table
 
 In addition, the parameters @code{window-atom} and @code{window-side}
-are reserved and should not be used by applications.  The
-@code{quit-restore} parameter tells how to proceed with a window when
-the buffer it shows is no more needed.  This parameter is installed by
-the buffer display functions (@pxref{Choosing Window}) and consulted by
-the function @code{quit-window} (@pxref{Quitting Windows}).
+are reserved and should not be used by applications.
 
 
 @node Window Hooks
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index e40d43ee8b9..676f767ae42 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,12 @@
+2012-01-16  Martin Rudalics  <rudalics@gmx.at>
+
+        * window.el (window-state-ignored-parameters): Remove variable.
+        (window--state-get-1): Rename argument MARKERS to IGNORE.
+        Handle persistent window parameters.  Make copy of clone-of
+        parameter only if requested.  (Bug#10348)
+        (window--state-put-2): Install a window parameter only if it has
+        a non-nil value or an existing parameter shall be overwritten.
+
 2012-01-15  Michael Albinus  <michael.albinus@gmx.de>
 
         * net/tramp-sh.el (tramp-remote-path): Set tramp-autoload cookie.
diff --git a/lisp/window.el b/lisp/window.el
index 8eb0ac3575b..54e5ec9c74c 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -3568,10 +3568,7 @@ specific buffers."
     ))
 
 ;;; Window states, how to get them and how to put them in a window.
-(defvar window-state-ignored-parameters '(quit-restore)
-  "List of window parameters ignored by `window-state-get'.")
-
-(defun window--state-get-1 (window &optional markers)
+(defun window--state-get-1 (window &optional ignore)
   "Helper function for `window-state-get'."
   (let* ((type
           (cond
@@ -3589,12 +3586,27 @@ specific buffers."
             (normal-width . ,(window-normal-size window t))
             (combination-limit . ,(window-combination-limit window))
             ,@(let (list)
-                (dolist (parameter (window-parameters window))
-                  (unless (memq (car parameter)
-                                window-state-ignored-parameters)
-                    (setq list (cons parameter list))))
-                (unless (window-parameter window 'clone-of)
-                  ;; Make a clone-of parameter.
+                ;; Make copies of persistent window parameters whose cdr
+                ;; is either t or, when IGNORE is non-nil, is either nil
+                ;; or `state'.
+                (dolist (pers window-persistent-parameters)
+                  (when (and (consp pers)
+                             (or (eq (cdr pers) t)
+                                 (and (memq (cdr pers) '(state nil))
+                                      (not ignore))))
+                    (let ((par (assq (car pers) (window-parameters window))))
+                      (setq list (cons (cons (car pers) (when par (cdr par)))
+                                       list)))))
+                ;; Save `clone-of' parameter unless IGNORE or
+                ;; `window-persistent-parameters' prevail.
+                (when (and (not (assq 'clone-of (window-parameters window)))
+                           (let ((clone-of
+                                  (assq 'clone-of
+                                        window-persistent-parameters)))
+                             (when clone-of
+                               (if ignore
+                                   (eq (cdr clone-of) t)
+                                 (memq (cdr clone-of) '(state nil))))))
                   (setq list (cons (cons 'clone-of window) list)))
                 (when list
                   `((parameters . ,list))))
@@ -3616,30 +3628,31 @@ specific buffers."
                        (scroll-bars . ,(window-scroll-bars window))
                        (vscroll . ,(window-vscroll window))
                        (dedicated . ,(window-dedicated-p window))
-                       (point . ,(if markers (copy-marker point) point))
-                       (start . ,(if markers (copy-marker start) start))
+                       (point . ,(if ignore point (copy-marker point)))
+                       (start . ,(if ignore start (copy-marker start)))
                        ,@(when mark
-                           `((mark . ,(if markers
-                                          (copy-marker mark) mark)))))))))))
+                           `((mark . ,(if ignore
+                                          mark (copy-marker mark))))))))))))
          (tail
           (when (memq type '(vc hc))
             (let (list)
               (setq window (window-child window))
               (while window
-                (setq list (cons (window--state-get-1 window markers) list))
+                (setq list (cons (window--state-get-1 window ignore) list))
                 (setq window (window-right window)))
               (nreverse list)))))
     (append head tail)))
 
-(defun window-state-get (&optional window markers)
+(defun window-state-get (&optional window ignore)
   "Return state of WINDOW as a Lisp object.
 WINDOW can be any window and defaults to the root window of the
 selected frame.
 
-Optional argument MARKERS non-nil means use markers for sampling
-positions like `window-point' or `window-start'.  MARKERS should
-be non-nil only if the value is used for putting the state back
-in the same session (note that markers slow down processing).
+Optional argument IGNORE non-nil means do not use markers for
+sampling positions like `window-point' or `window-start' and do
+not record parameters unless `window-persistent-parameters'
+requests it.  IGNORE should be non-nil when the return value
+shall be written to a file and read back in another session.
 
 The return value can be used as argument for `window-state-put'
 to put the state recorded here into an arbitrary window.  The
@@ -3665,7 +3678,7 @@ value can be also stored on disk and read back in a new session."
      ;; These are probably not needed.
      ,@(when (window-size-fixed-p window) `((fixed-height . t)))
      ,@(when (window-size-fixed-p window t) `((fixed-width . t))))
-   (window--state-get-1 window markers)))
+   (window--state-get-1 window ignore)))
 
 (defvar window-state-put-list nil
   "Helper variable for `window-state-put'.")
@@ -3744,10 +3757,15 @@ value can be also stored on disk and read back in a new session."
           (state (cdr (assq 'buffer item))))
       (when combination-limit
         (set-window-combination-limit window combination-limit))
-      ;; Process parameters.
+      ;; Assign saved window parameters.  If a parameter's value is nil,
+      ;; don't assign it unless the new window has it set already (which
+      ;; shouldn't happen unless some `window-configuration-change-hook'
+      ;; function installed it).
       (when parameters
         (dolist (parameter parameters)
-          (set-window-parameter window (car parameter) (cdr parameter))))
+          (when (or (cdr parameter)
+                    (window-parameter window (car parameter)))
+            (set-window-parameter window (car parameter) (cdr parameter)))))
       ;; Process buffer related state.
       (when state
         ;; We don't want to raise an error here so we create a buffer if
diff --git a/src/ChangeLog b/src/ChangeLog
index eb03ef1357f..aa4e92b4134 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2012-01-16  Martin Rudalics  <rudalics@gmx.at>
+
+        * window.c (Vwindow_persistent_parameters): New variable.
+        (Fset_window_configuration, save_window_save): Handle persistent
+        window parameters.
+
 2012-01-14  Eli Zaretskii  <eliz@gnu.org>
 
         * w32fns.c (signal_user_input): Don't do a QUIT, to avoid
diff --git a/src/window.c b/src/window.c
index 39eaa1ec241..3dc6029d24d 100644
--- a/src/window.c
+++ b/src/window.c
@@ -57,7 +57,7 @@ static Lisp_Object Qreplace_buffer_in_windows, Qget_mru_window;
 static Lisp_Object Qwindow_resize_root_window, Qwindow_resize_root_window_vertically;
 static Lisp_Object Qscroll_up, Qscroll_down, Qscroll_command;
 static Lisp_Object Qsafe, Qabove, Qbelow;
-static Lisp_Object Qauto_buffer_name;
+static Lisp_Object Qauto_buffer_name, Qclone_of, Qstate;
 
 static int displayed_window_lines (struct window *);
 static struct window *decode_window (Lisp_Object);
@@ -5410,6 +5410,7 @@ the return value is nil.  Otherwise the value is t.  */)
     {
       Lisp_Object window;
       Lisp_Object dead_windows = Qnil;
+      register Lisp_Object tem, par, pers;
       register struct window *w;
       register struct saved_window *p;
       struct window *root_window;
@@ -5543,7 +5544,28 @@ the return value is nil.  Otherwise the value is t.  */)
           w->vertical_scroll_bar_type = p->vertical_scroll_bar_type;
           w->dedicated = p->dedicated;
           w->combination_limit = p->combination_limit;
-          w->window_parameters = p->window_parameters;
+          /* Restore any window parameters that have been saved.
+             Parameters that have not been saved are left alone.  */
+          for (tem = p->window_parameters; CONSP (tem); tem = XCDR (tem))
+            {
+              pers = XCAR (tem);
+              if (CONSP (pers))
+                {
+                  if (NILP (XCDR (pers)))
+                    {
+                      par = Fassq (XCAR (pers), w->window_parameters);
+                      if (CONSP (par) && !NILP (XCDR (par)))
+                        /* Reset a parameter to nil if and only if it
+                           has a non-nil association.  Don't make new
+                           associations.  */
+                        Fsetcdr (par, Qnil);
+                    }
+                  else
+                    /* Always restore a non-nil value.  */
+                    Fset_window_parameter (window, XCAR (pers), XCDR (pers));
+                }
+            }
+
           XSETFASTINT (w->last_modified, 0);
           XSETFASTINT (w->last_overlay_modified, 0);
 
@@ -5810,7 +5832,7 @@ save_window_save (Lisp_Object window, struct Lisp_Vector *vector, int i)
 {
   register struct saved_window *p;
   register struct window *w;
-  register Lisp_Object tem;
+  register Lisp_Object tem, pers, par;
 
   for (;!NILP (window); window = w->next)
     {
@@ -5838,12 +5860,60 @@ save_window_save (Lisp_Object window, struct Lisp_Vector *vector, int i)
       p->vertical_scroll_bar_type = w->vertical_scroll_bar_type;
       p->dedicated = w->dedicated;
       p->combination_limit = w->combination_limit;
-      p->window_parameters = w->window_parameters;
+      p->window_parameters = Qnil;
+
+      if (!NILP (Vwindow_persistent_parameters))
+        {
+          /* Run cycle detection on Vwindow_persistent_parameters.  */
+          Lisp_Object tortoise, hare;
+
+          hare = tortoise = Vwindow_persistent_parameters;
+          while (CONSP (hare))
+            {
+              hare = XCDR (hare);
+              if (!CONSP (hare))
+                break;
+
+              hare = XCDR (hare);
+              tortoise = XCDR (tortoise);
+
+              if (EQ (hare, tortoise))
+                /* Reset Vwindow_persistent_parameters to Qnil.  */
+                {
+                  Vwindow_persistent_parameters = Qnil;
+                  break;
+                }
+            }
+
+          for (tem = Vwindow_persistent_parameters; CONSP (tem);
+               tem = XCDR (tem))
+            {
+              pers = XCAR (tem);
+              /* Save values for persistent window parameters whose cdr
+                 is either nil or t.  */
+              if (CONSP (pers) && (NILP (XCDR (pers)) || EQ (XCDR (pers), Qt)))
+                {
+                  par = Fassq (XCAR (pers), w->window_parameters);
+                  if (NILP (par))
+                    /* If the window has no value for the parameter,
+                       make one.  */
+                    p->window_parameters = Fcons (Fcons (XCAR (pers), Qnil),
+                                                  p->window_parameters);
+                  else
+                    /* If the window has a value for the parameter,
+                       save it.  */
+                    p->window_parameters = Fcons (Fcons (XCAR (par),
+                                                         XCDR (par)),
+                                                  p->window_parameters);
+                }
+            }
+        }
+
       if (!NILP (w->buffer))
         {
-          /* Save w's value of point in the window configuration.
-             If w is the selected window, then get the value of point
-             from the buffer; pointm is garbage in the selected window.  */
+          /* Save w's value of point in the window configuration.  If w
+             is the selected window, then get the value of point from
+             the buffer; pointm is garbage in the selected window.  */
           if (EQ (window, selected_window))
             {
               p->pointm = Fmake_marker ();
@@ -6433,6 +6503,8 @@ syms_of_window (void)
   DEFSYM (Qabove, "above");
   DEFSYM (Qbelow, "below");
   DEFSYM (Qauto_buffer_name, "auto-buffer-name");
+  DEFSYM (Qclone_of, "clone-of");
+  DEFSYM (Qstate, "state");
 
   staticpro (&Vwindow_list);
 
@@ -6542,6 +6614,31 @@ retrieved via the function `window-combination-limit' and altered by the
 function `set-window-combination-limit'.  */);
   Vwindow_combination_limit = Qnil;
 
+  DEFVAR_LISP ("window-persistent-parameters", Vwindow_persistent_parameters,
+               doc: /* Alist of persistent window parameters.
+Parameters in this list are saved by `current-window-configuration' and
+`window-state-get' and subsequently restored to their previous values by
+`set-window-configuration' and `window-state-put'.
+
+The car of each entry of this alist is the symbol specifying the
+parameter.  The cdr is one of the following:
+
+The symbol `state' means the parameter is saved by `window-state-get'
+provided its IGNORE argument is nil.  `current-window-configuration'
+does not save this parameter.
+
+nil means the parameter is saved by `current-window-configuration' and,
+provided its IGNORE argument is nil, by `window-state-get'.
+
+t means the parameter is saved unconditionally by both
+`current-window-configuration' and `window-state-get'.  Parameters
+without read syntax (like windows or frames) should not use that.
+
+Parameters not saved by `current-window-configuration' or
+`window-state-get' are left alone by `set-window-configuration'
+respectively are not installed by `window-state-put'.  */);
+  Vwindow_persistent_parameters = list1 (Fcons (Qclone_of, Qstate));
+
   defsubr (&Sselected_window);
   defsubr (&Sminibuffer_window);
   defsubr (&Swindow_minibuffer_p);