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'.

1 files changed, 76 insertions, 38 deletions

diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi
index fe3dc573df5..45d67ba4946 100644
--- a/doc/lispref/windows.texi
+++ b/doc/lispref/windows.texi
@@ -6264,15 +6264,10 @@ this function does is to restore the value of the variable
 @code{minibuffer-selected-window}.  In this case, the function returns
 @code{nil}.  Otherwise, it returns @code{t}.
 
-If the buffer of a window of @var{configuration} has been killed since
-@var{configuration} was made, that window is, as a rule, removed from
-the restored configuration.  However, if that window is the last window
-remaining in the restored configuration, another live buffer is shown in
-it.  Also, if the variable @var{window-kept-windows-functions} is
-non-@code{nil}, any window whose buffer is now dead is not deleted.
-Rather, this function will show another live buffer in that window and
-include an entry for that window when calling any function in
-@var{window-kept-windows-functions} (@pxref{Window Hooks}).
+This function consults the variable
+@code{window-restore-killed-buffer-windows} (see below) when it tries to
+restore a window whose buffer was killed after @var{configuration} was
+recorded.
 
 Here is a way of using this function to get the same effect as
 @code{save-window-excursion}:
@@ -6361,14 +6356,9 @@ a live window, it is replaced by a new live window created on the same
 frame before putting @var{state} into it.  If @var{window} is @code{nil},
 it puts the window state into a new window.
 
-If the buffer of any window recorded in @var{state} has been killed
-since @var{state} was made, that window is, as a rule, not restored.
-However, if that window is the only window in @var{state}, another live
-buffer will be shown in it.  Also, if the variable
-@var{window-kept-windows-functions} is non-@code{nil}, any window whose
-buffer is now dead is restored.  This function will show another live
-buffer in it and include an entry for that window when calling a
-function in @var{window-kept-windows-functions} (@pxref{Window Hooks}).
+This function consults the variable
+@code{window-restore-killed-buffer-windows} (see below) when it tries to
+restore a window whose buffer was killed after @var{state} was recorded.
 
 If the optional argument @var{ignore} is non-@code{nil}, it means to ignore
 minimum window sizes and fixed-size restrictions.  If @var{ignore}
@@ -6376,6 +6366,75 @@ is @code{safe}, this means windows can get as small as one line
 and/or two columns.
 @end defun
 
+By default, @code{set-window-configuration} and @code{window-state-put}
+may delete a window from the restored configuration when they find out
+that its buffer was killed since the corresponding configuration or
+state has been recorded.  The variable described next can be used to
+fine-tune that behavior.
+
+@cindex restoring windows whose buffers have been killed
+@defvar window-restore-killed-buffer-windows
+This variable specifies how @code{set-window-configuration} and
+@code{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.  Usually,
+@code{set-window-configuration} leaves the window alone if it is live
+while @code{window-state-put} deletes it.
+
+The following values can be used to override the default behavior for
+dead windows in the case of @code{set-window-configuration} and for dead
+and live windows in the case of @code{window-state-put}.
+
+@table @asis
+@item @code{t}
+This value means to unconditionally restore the window and show some
+other buffer in it.
+
+@item @code{delete}
+This means to unconditionally try to delete the window.
+
+@item @code{dedicated}
+This means to try to delete the window if and only if it is dedicated to
+its buffer.
+
+@item @code{nil}
+This is the default and means that @code{set-window-configuration} will
+try to delete the window if and only if it is dedicated to its buffer
+and @code{window-state-put} will unconditionally try to delete it.
+
+@item a function
+This 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.
+@end table
+
+If a window cannot be deleted (typically, because it is the last window
+on its frame), @code{set-window-configuration} and
+@code{window-state-put} will show another buffer in it.
+
+If the value of this variable is a function, that function should take
+three arguments.  The first argument specifies the frame whose windows
+have been restored.  The third argument is either the constant
+@code{configuration} if the windows are restored by
+@code{set-window-configuration} or the constant @code{state} if the
+windows are restored by @code{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
+@code{set-window-configuration} or @code{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 @code{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
+previously reported by @code{window-dedicated-p} and a flag that is
+@code{t} if the window has been encountered live by
+@code{set-window-configuration} and @code{nil} otherwise.
+@end defvar
+
 The functions @code{window-state-get} and @code{window-state-put} also
 allow exchanging the contents of two live windows.  The following
 function does precisely that:
@@ -6636,27 +6695,6 @@ Lock fontification function, which will be called whenever parts of a
 buffer are (re)fontified because a window was scrolled or its size
 changed.  @xref{Other Font Lock Variables}.
 
-@cindex window kept windows functions
-@defvar window-kept-windows-functions
-   This variable holds a list of functions that Emacs will call after
-restoring a window configuration via @code{set-window-configuration} or
-state via @code{window-state-put} (@pxref{Window Configurations}).  When
-the value of this variable is non-@code{nil}, these functions will not
-delete any window whose buffer has been killed since the corresponding
-configuration or state was saved, but 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 windows have been restored.
-The second argument specifies a list of entries for each window whose
-buffer has been found dead at the time @code{set-window-configuration}
-or @code{window-state-put} tried to restore it.  Each entry is a list of
-four values - the window whose buffer was found dead, the dead buffer,
-and the last known positions of start and point of the buffer in that
-window.  Any function run by this hook should check that the window is
-live since another function run by this hook may have deleted it in the
-meantime.
-@end defvar
-
 @cindex window change functions
    The remainder of this section covers six hooks that are called
 during redisplay provided a significant, non-scrolling change of a