* xdisp.c (buffer_shared): Adjust comment.

(buffer_shared_and_changed): New function.
(prepare_menu_bars, redisplay_internal): Use it to
decide whether all windows or frames should be updated.

2 files changed, 22 insertions, 8 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9e83129e585..c749b12cae8 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2012-11-20  Dmitry Antipov  <dmantipov@yandex.ru>
+
+        * xdisp.c (buffer_shared): Adjust comment.
+        (buffer_shared_and_changed): New function.
+        (prepare_menu_bars, redisplay_internal): Use it to
+        decide whether all windows or frames should be updated.
+
 2012-11-20  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * eval.c (Finteractive_p, Fcalled_interactively_p, interactive_p): Remove.
diff --git a/src/xdisp.c b/src/xdisp.c
index 27d9fff0b7d..618f4dfc585 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -515,9 +515,8 @@ Lisp_Object Qmenu_bar_update_hook;
 
 static int overlay_arrow_seen;
 
-/* Number of windows showing the buffer of the selected window (or
-   another buffer with the same base buffer).  keyboard.c refers to
-   this.  */
+/* Number of windows showing the buffer of the selected
+   window (or another buffer with the same base buffer).  */
 
 int buffer_shared;
 
@@ -10889,8 +10888,15 @@ echo_area_display (int update_frame_p)
   return window_height_changed_p;
 }
 
+/* True if the current buffer is shown in more than
+   one window and was modified since last display.  */
+
+static int
+buffer_shared_and_changed (void)
+{
+  return (buffer_shared > 1 && UNCHANGED_MODIFIED < MODIFF);
+}
 
-
 /***********************************************************************
                      Mode Lines and Frame Titles
  ***********************************************************************/
@@ -11196,7 +11202,7 @@ prepare_menu_bars (void)
   /* Update the menu bar item lists, if appropriate.  This has to be
      done before any actual redisplay or generation of display lines.  */
   all_windows = (update_mode_lines
-                 || buffer_shared > 1
+                 || buffer_shared_and_changed ()
                  || windows_or_buffers_changed);
   if (all_windows)
     {
@@ -13116,7 +13122,7 @@ redisplay_internal (void)
   if ((SAVE_MODIFF < MODIFF) != w->last_had_star)
     {
       w->update_mode_line = 1;
-      if (buffer_shared > 1)
+      if (buffer_shared_and_changed ())
         update_mode_lines++;
     }
 
@@ -13141,7 +13147,8 @@ redisplay_internal (void)
   /* The variable buffer_shared is set in redisplay_window and
      indicates that we redisplay a buffer in different windows.  See
      there.  */
-  consider_all_windows_p = (update_mode_lines || buffer_shared > 1
+  consider_all_windows_p = (update_mode_lines
+                            || buffer_shared_and_changed ()
                             || cursor_type_changed);
 
   /* If specs for an arrow have changed, do thorough redisplay
@@ -13433,7 +13440,7 @@ redisplay_internal (void)
     }
 
   CHARPOS (this_line_start_pos) = 0;
-  consider_all_windows_p |= buffer_shared > 1;
+  consider_all_windows_p |= buffer_shared_and_changed ();
   ++clear_face_cache_count;
 #ifdef HAVE_WINDOW_SYSTEM
   ++clear_image_cache_count;