From 60185c2fa667fdd8a3900936130895b8a783c127 Mon Sep 17 00:00:00 2001
From: Stefan Kangas <stefankangas@gmail.com>
Date: Mon, 24 Aug 2020 02:46:15 +0200
Subject: [PATCH] Improve frame-title-format and icon-title-format

* src/xdisp.c (decode_mode_spec): Support new '%B'-construct.
(syms_of_xdisp): Change 'Vframe_title_format' and 'Vicon_title_format'
to use the new '%B'-construct.  Replace 'invocation-name' with the
text "GNU Emacs".  (Bug#41147)
* doc/lispref/modes.texi (%-Constructs): Document new '%B'-construct.
* etc/NEWS: Announce the above changes.
---
 doc/lispref/modes.texi |  6 ++++++
 etc/NEWS               | 14 ++++++++++++++
 src/xdisp.c            | 12 +++++++++---
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index 33a07c9fb4..92c660617d 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -2245,6 +2245,12 @@ %-Constructs
 The current buffer name, obtained with the @code{buffer-name} function.
 @xref{Buffer Names}.
 
+@item %B
+The visited file name obtained with the @code{buffer-file-name}
+function, but shortened using @code{abbreviate-file-name}.  If the
+current buffer is not visiting a file, use the current buffer name
+obtained with the @code{buffer-name} function instead.
+
 @item %c
 The current column number of point, counting from zero starting at the
 left margin of the window.
diff --git a/etc/NEWS b/etc/NEWS
index ad63955f7b..9bbcc7896c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -121,6 +121,15 @@ the mouse cursor is on the scroll bars, fringes, margins, header line,
 and mode line.  ('mwheel-mode' is enabled by default on most graphical
 displays.)
 
+---
+** The default 'frame-title-format' has been changed.
+It now includes the file or buffer name even when there is only a
+single frame, but no longer contains 'invocation-name'.  To get the
+old behavior back, add the following to your Init file:
+
+    (setq frame-title-format '(multiple-frames "%b"
+                              ("" invocation-name "@" system-name)))
+
 
 * Editing Changes in Emacs 28.1
 
@@ -1091,6 +1100,11 @@ It was used to allow loading Lisp libraries compiled by XEmacs, a
 modified version of Emacs which is no longer actively maintained.
 This is no longer supported, and setting this variable has no effect.
 
++++
+** The Mode Line Format has a new '%B'-construct.
+The new construct adds the abbreviated file name or name of the
+current buffer.  See the Emacs Lisp Reference Manual for more details.
+
 +++
 ** The macro 'with-displayed-buffer-window' is now obsolete.
 Use macro 'with-current-buffer-window' with action alist entry 'body-function'.
diff --git a/src/xdisp.c b/src/xdisp.c
index dd73758043..4920260406 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -26424,6 +26424,13 @@ decode_mode_spec (struct window *w, register int c, int field_width,
       obj = BVAR (b, name);
       break;
 
+    case 'B':
+      if (!NILP (BVAR (b, filename)))
+	obj = call1 (intern ("abbreviate-file-name"), BVAR (b, filename));
+      else
+	obj = BVAR (b, name);
+      break;
+
     case 'c':
     case 'C':
       /* %c, %C, and %l are ignored in `frame-title-format'.
@@ -34830,13 +34837,12 @@ syms_of_xdisp (void)
      Oracle Developer Studio 12.6.  */
   Lisp_Object icon_title_name_format
     = pure_list (empty_unibyte_string,
-		 intern_c_string ("invocation-name"),
-		 build_pure_c_string ("@"),
+		 build_pure_c_string ("%B - GNU Emacs at "),
 		 intern_c_string ("system-name"));
   Vicon_title_format
     = Vframe_title_format
     = pure_list (intern_c_string ("multiple-frames"),
-		 build_pure_c_string ("%b"),
+		 build_pure_c_string ("%B"),
 		 icon_title_name_format);
 
   DEFVAR_LISP ("message-log-max", Vmessage_log_max,
-- 
2.28.0