Further adjustments for restoring killed buffer windows (Bug#68235)

* etc/NEWS: Announce 'window-restore-killed-buffer-windows'.
* src/buffer.h (struct buffer) : New field last_name_.
* src/buffer.c (Fbuffer_last_name): New function to return last
name of buffer before it was killed or renamed.
(bset_last_name, Fget_buffer_create, Fmake_indirect_buffer)
(Frename_buffer, Fkill_buffer, init_buffer_once): Set buffer's
last_name_ field accordingly.
* src/window.c (window_restore_killed_buffer_windows): New
variable replacing Vwindow_kept_windows_functions.
(Fset_window_configuration): Use
window_restore_killed_buffer_windows instead of
Vwindow_kept_windows_functions.
* lisp/window.el (window--state-put-2, window-state-put): Use
'window-restore-killed-buffer-windows' instead of
'window-kept-windows-functions'.
* doc/lispref/windows.texi (Window Configurations): Describe
'window-restore-killed-buffer-windows' which replaces
'window-kept-windows-functions'.

3 files changed, 119 insertions, 65 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 43a9249528c..07d19dfc078 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -327,6 +327,11 @@ bset_name (struct buffer *b, Lisp_Object val)
   b->name_ = val;
 }
 static void
+bset_last_name (struct buffer *b, Lisp_Object val)
+{
+  b->last_name_ = val;
+}
+static void
 bset_overwrite_mode (struct buffer *b, Lisp_Object val)
 {
   b->overwrite_mode_ = val;
@@ -647,6 +652,7 @@ even if it is dead.  The return value is never nil.  */)
   name = Fcopy_sequence (buffer_or_name);
   set_string_intervals (name, NULL);
   bset_name (b, name);
+  bset_last_name (b, name);
 
   b->inhibit_buffer_hooks = !NILP (inhibit_buffer_hooks);
   bset_undo_list (b, SREF (name, 0) != ' ' ? Qnil : Qt);
@@ -866,6 +872,7 @@ Interactively, CLONE and INHIBIT-BUFFER-HOOKS are nil.  */)
   name = Fcopy_sequence (name);
   set_string_intervals (name, NULL);
   bset_name (b, name);
+  bset_last_name (b, name);
 
   /* An indirect buffer shares undo list of its base (Bug#18180).  */
   bset_undo_list (b, BVAR (b->base_buffer, undo_list));
@@ -1282,6 +1289,17 @@ Return nil if BUFFER has been killed.  */)
   return BVAR (decode_buffer (buffer), name);
 }
 
+DEFUN ("buffer-last-name", Fbuffer_last_name, Sbuffer_last_name, 0, 1, 0,
+       doc: /* Return last name of BUFFER, as a string.
+BUFFER defaults to the current buffer.
+
+This is the name BUFFER had before the last time it was renamed or
+immediately before it was killed.  */)
+  (Lisp_Object buffer)
+{
+  return BVAR (decode_buffer (buffer), last_name);
+}
+
 DEFUN ("buffer-file-name", Fbuffer_file_name, Sbuffer_file_name, 0, 1, 0,
        doc: /* Return name of file BUFFER is visiting, or nil if none.
 No argument or nil as argument means use the current buffer.  */)
@@ -1652,6 +1670,7 @@ This does not change the name of the visited file (if any).  */)
   (register Lisp_Object newname, Lisp_Object unique)
 {
   register Lisp_Object tem, buf;
+  Lisp_Object oldname = BVAR (current_buffer, name);
   Lisp_Object requestedname = newname;
 
   CHECK_STRING (newname);
@@ -1669,12 +1688,12 @@ This does not change the name of the visited file (if any).  */)
       if (NILP (unique) && XBUFFER (tem) == current_buffer)
 	return BVAR (current_buffer, name);
       if (!NILP (unique))
-	newname = Fgenerate_new_buffer_name (newname,
-	                                     BVAR (current_buffer, name));
+	newname = Fgenerate_new_buffer_name (newname, oldname);
       else
 	error ("Buffer name `%s' is in use", SDATA (newname));
     }
 
+  bset_last_name (current_buffer, oldname);
   bset_name (current_buffer, newname);
 
   /* Catch redisplay's attention.  Unless we do this, the mode lines for
@@ -2095,6 +2114,7 @@ cleaning up all windows currently displaying the buffer to be killed. */)
      This gets rid of them for certain.  */
   reset_buffer_local_variables (b, 1);
 
+  bset_last_name (b, BVAR (b, name));
   bset_name (b, Qnil);
 
   block_input ();
@@ -4666,6 +4686,7 @@ init_buffer_once (void)
   /* These used to be stuck at 0 by default, but now that the all-zero value
      means Qnil, we have to initialize them explicitly.  */
   bset_name (&buffer_local_flags, make_fixnum (0));
+  bset_last_name (&buffer_local_flags, make_fixnum (0));
   bset_mark (&buffer_local_flags, make_fixnum (0));
   bset_local_var_alist (&buffer_local_flags, make_fixnum (0));
   bset_keymap (&buffer_local_flags, make_fixnum (0));
@@ -6026,6 +6047,7 @@ There is no reason to change that value except for debugging purposes.  */);
   defsubr (&Smake_indirect_buffer);
   defsubr (&Sgenerate_new_buffer_name);
   defsubr (&Sbuffer_name);
+  defsubr (&Sbuffer_last_name);
   defsubr (&Sbuffer_file_name);
   defsubr (&Sbuffer_base_buffer);
   defsubr (&Sbuffer_local_value);
diff --git a/src/buffer.h b/src/buffer.h
index 87ba2802b39..bbe1aeff668 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -309,6 +309,9 @@ struct buffer
   /* The name of this buffer.  */
   Lisp_Object name_;
 
+  /* The last name of this buffer before it was renamed or killed.  */
+  Lisp_Object last_name_;
+
   /* The name of the file visited in this buffer, or nil.  */
   Lisp_Object filename_;
 
diff --git a/src/window.c b/src/window.c
index ea761fad8bc..928c4ae02a8 100644
--- a/src/window.c
+++ b/src/window.c
@@ -7109,23 +7109,9 @@ current at the start of the function.  If DONT-SET-MINIWINDOW is non-nil,
 the mini-window of the frame doesn't get set to the corresponding element
 of CONFIGURATION.
 
-Normally, this function will try to delete any dead window in
-CONFIGURATION whose buffer has been deleted since CONFIGURATION was
-made.  However, if the abnormal hook `window-kept-windows-functions' is
-non-nil, it will preserve such a window in the restored layout and show
-another buffer in it.
-
-After restoring the frame layout, this function runs the abnormal hook
-`window-kept-windows-functions' with two arguments - the frame whose
-layout it has restored and a list of entries for each window whose
-buffer has been found dead when it tried to restore CONFIGURATION: Each
-entry is a list of four elements <window, buffer, start, point> where
-`window' denotes the window whose buffer was found dead, `buffer'
-denotes the dead buffer, and `start' and `point' denote the last known
-positions of `window-start' and `window-point' of the buffer in that
-window.  Any function run by this hook should check such a window for
-liveness because another function run by this hook may have deleted it
-in the meantime."
+This function consults the variable `window-restore-killed-buffer-windows'
+when restoring a window whose buffer was killed after CONFIGURATION was
+recorded.
 
 If CONFIGURATION was made from a frame that is now deleted,
 only frame-independent values can be restored.  In this case,
@@ -7378,10 +7364,12 @@ the return value is nil.  Otherwise the value is t.  */)
 		   BUF_PT (XBUFFER (w->contents)),
 		   BUF_PT_BYTE (XBUFFER (w->contents)));
 	      w->start_at_line_beg = true;
-	      if (!NILP (Vwindow_kept_windows_functions))
-		kept_windows = Fcons (list4 (window, p->buffer,
+	      if (FUNCTIONP (window_restore_killed_buffer_windows)
+		  && !MINI_WINDOW_P (w))
+		kept_windows = Fcons (listn (6, window, p->buffer,
 					     Fmarker_last_position (p->start),
-					     Fmarker_last_position (p->pointm)),
+					     Fmarker_last_position (p->pointm),
+					     p->dedicated, Qt),
 				      kept_windows);
 	    }
 	  else if (!NILP (w->start))
@@ -7398,16 +7386,25 @@ the return value is nil.  Otherwise the value is t.  */)
 	      set_marker_restricted_both (w->pointm, w->contents, 0, 0);
 	      set_marker_restricted_both (w->old_pointm, w->contents, 0, 0);
 	      w->start_at_line_beg = true;
-	      if (!NILP (w->dedicated))
-		/* Record this window as dead.  */
-		dead_windows = Fcons (window, dead_windows);
-	      /* Make sure window is no more dedicated.  */
-	      wset_dedicated (w, Qnil);
-	      if (!NILP (Vwindow_kept_windows_functions))
-		kept_windows = Fcons (list4 (window, p->buffer,
-					     Fmarker_last_position (p->start),
-					     Fmarker_last_position (p->pointm)),
-				      kept_windows);
+	      if (!MINI_WINDOW_P (w))
+		{
+		  if (FUNCTIONP (window_restore_killed_buffer_windows))
+		    kept_windows
+		      = Fcons (listn (6, window, p->buffer,
+				      Fmarker_last_position (p->start),
+				      Fmarker_last_position (p->pointm),
+				      p->dedicated, Qnil),
+			       kept_windows);
+		  else if (EQ (window_restore_killed_buffer_windows, Qdelete)
+			   || (!NILP (p->dedicated)
+			       && (NILP (window_restore_killed_buffer_windows)
+				   || EQ (window_restore_killed_buffer_windows,
+					  Qdedicated))))
+		    /* Try to delete this window later.  */
+		    dead_windows = Fcons (window, dead_windows);
+		  /* Make sure window is no more dedicated.  */
+		  wset_dedicated (w, Qnil);
+		}
 	    }
 	}
 
@@ -7459,13 +7456,12 @@ the return value is nil.  Otherwise the value is t.  */)
       unblock_input ();
 
       /* Scan dead buffer windows.  */
-      if (!NILP (Vwindow_kept_windows_functions))
-	for (; CONSP (dead_windows); dead_windows = XCDR (dead_windows))
-	  {
-	    window = XCAR (dead_windows);
-	    if (WINDOW_LIVE_P (window) && !EQ (window, FRAME_ROOT_WINDOW (f)))
-	      delete_deletable_window (window);
-	  }
+      for (; CONSP (dead_windows); dead_windows = XCDR (dead_windows))
+	{
+	  window = XCAR (dead_windows);
+	  if (WINDOW_LIVE_P (window) && !EQ (window, FRAME_ROOT_WINDOW (f)))
+	    delete_deletable_window (window);
+	}
 
       /* Record the selected window's buffer here.  The window should
 	 already be the selected one from the call above.  */
@@ -7513,9 +7509,9 @@ the return value is nil.  Otherwise the value is t.  */)
 
   SAFE_FREE ();
 
-  if (!NILP (Vrun_hooks) && !NILP (Vwindow_kept_windows_functions))
-    run_hook_with_args_2 (Qwindow_kept_windows_functions, frame,
-			  kept_windows);
+  if (!NILP (Vrun_hooks) && FUNCTIONP (window_restore_killed_buffer_windows))
+    safe_calln (window_restore_killed_buffer_windows,
+		frame, kept_windows, Qconfiguration);
 
   return FRAME_LIVE_P (f) ? Qt : Qnil;
 }
@@ -8514,8 +8510,9 @@ syms_of_window (void)
   DEFSYM (Qheader_line_format, "header-line-format");
   DEFSYM (Qtab_line_format, "tab-line-format");
   DEFSYM (Qno_other_window, "no-other-window");
-  DEFSYM (Qwindow_kept_windows_functions,
-	  "window-kept-windows-functions");
+  DEFSYM (Qconfiguration, "configuration");
+  DEFSYM (Qdelete, "delete");
+  DEFSYM (Qdedicated, "dedicated");
 
   DEFVAR_LISP ("temp-buffer-show-function", Vtemp_buffer_show_function,
 	       doc: /* Non-nil means call as function to display a help buffer.
@@ -8673,27 +8670,59 @@ its buffer or its total or body size since the last redisplay.  Each
 call is performed with the frame temporarily selected.  */);
   Vwindow_configuration_change_hook = Qnil;
 
-  DEFVAR_LISP ("window-kept-windows-functions",
-	       Vwindow_kept_windows_functions,
-	       doc: /* Functions run after restoring a window configuration or state.
-These functions are called by `set-window-configuration' and
-`window-state-put'.  When the value of this variable is non-nil, these
-functions restore any window whose buffer has been deleted since the
-corresponding configuration or state was saved.  Rather than deleting
-such a window, `set-window-configuration' and `window-state-put' show
-some live buffer in it.
-
-The value should be a list of functions that take two arguments.  The
-first argument specifies the frame whose configuration has been
-restored.  The second argument, if non-nil, specifies a list of entries
-for each window whose buffer has been found dead at the time
-'set-window-configuration' or `window-state-put' tried to restore it in
-that window.  Each entry is a list of four values - the window whose
-buffer was found dead, the dead buffer, and the positions of start and
-point of the buffer in that window.  Note that the window may be already
-dead since another function on this list may have deleted it in the
-meantime.  */);
-  Vwindow_kept_windows_functions = Qnil;
+  DEFVAR_LISP ("window-restore-killed-buffer-windows",
+	       window_restore_killed_buffer_windows,
+	       doc: /* Control restoring windows whose buffer was killed.
+This variable specifies how the functions `set-window-configuration' and
+`window-state-put' shall handle a window whose buffer has been killed
+since the corresponding configuration or state was made.  Any such
+window may be live - in which case it shows some other buffer - or dead
+at the time one of these functions is called.
+
+As a rule, `set-window-configuration' leaves the window alone if it is
+live while `window-state-put' deletes it.  The following values can be
+used to override the default behavior for dead windows in the case of
+`set-window-configuration' and for dead and live windows in the case of
+`window-state-put'.
+
+- t means to restore the window and show some other buffer in it.
+
+- `delete' means to try to delete the window.
+
+- `dedicated' means to try to delete the window if and only if it is
+  dedicated to its buffer.
+
+- nil, the default, means that `set-window-configuration' will try to
+  delete the window if and only if it is dedicated to its buffer while
+  `window-state-put' will unconditionally try to delete it.
+
+- a function means to restore the window, show some other buffer in it
+  and add an entry for that window to a list that will be later passed
+  as argument to that function.
+
+If a window cannot be deleted (typically, because it is the last window
+on its frame), show another buffer in it.
+
+If the value is a function, it should take three arguments.  The first
+argument specifies the frame whose windows have been restored.  The
+third argument is the constant `configuration' if the windows are
+restored by `set-window-configuration' and the constant `state' if the
+windows are restored by `window-state-put'.
+
+The second argument specifies a list of entries for @emph{any} window
+whose previous buffer has been encountered dead at the time
+`set-window-configuration' or `window-state-put' tried to restore it in
+that window (minibuffer windows are excluded).  This means that the
+function specified by this variable may also delete windows encountered
+live by `set-window-configuration'.
+
+Each entry is a list of six values - the window whose buffer was found
+dead, the dead buffer or its name, the positions of start and point of
+the buffer in that window, the dedicated status of the window as
+reported by `window-dedicated-p' and a boolean - t if the window was
+live when `set-window-configuration' tried to restore it and nil
+otherwise.  */);
+  window_restore_killed_buffer_windows = Qnil;
 
   DEFVAR_LISP ("recenter-redisplay", Vrecenter_redisplay,
 	       doc: /* Non-nil means `recenter' redraws entire frame.