1 files changed, 106 insertions, 9 deletions

diff --git a/src/window.c b/src/window.c
index ef61d668499..324689498ae 100644
--- a/src/window.c
+++ b/src/window.c
@@ -1,6 +1,6 @@
 /* Window creation, deletion and examination for GNU Emacs.
    Does not include redisplay.
-   Copyright (C) 1985-1987, 1993-1998, 2000-2011
+   Copyright (C) 1985-1987, 1993-1998, 2000-2012
                  Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -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;
 
 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 +5860,59 @@ 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. */
+              if (CONSP (pers) && !NILP (XCDR (pers)))
+                {
+                  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 ();
@@ -5896,7 +5965,9 @@ and for each displayed buffer, where display starts, and the positions of
 point and mark.  An exception is made for point in the current buffer:
 its value is -not- saved.
 This also records the currently selected frame, and FRAME's focus
-redirection (see `redirect-frame-focus').  */)
+redirection (see `redirect-frame-focus').  The variable
+`window-persistent-parameters' specifies which window parameters are
+saved by this function.  */)
   (Lisp_Object frame)
 {
   register Lisp_Object tem;
@@ -6433,6 +6504,7 @@ syms_of_window (void)
   DEFSYM (Qabove, "above");
   DEFSYM (Qbelow, "below");
   DEFSYM (Qauto_buffer_name, "auto-buffer-name");
+  DEFSYM (Qclone_of, "clone-of");
 
   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.
+This alist specifies which window parameters shall get 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:
+
+nil means the parameter is neither saved by `window-state-get' nor by
+`current-window-configuration'.
+
+t means the parameter is saved by `current-window-configuration' and,
+provided its WRITABLE argument is nil, by `window-state-get'.
+
+The symbol `writable' means the parameter is saved unconditionally by
+both `current-window-configuration' and `window-state-get'.  Do not use
+this value for parameters without read syntax (like windows or frames).
+
+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, Qt));
+
   defsubr (&Sselected_window);
   defsubr (&Sminibuffer_window);
   defsubr (&Swindow_minibuffer_p);