* xdisp.c (window_outdated): Remove eassert since it hits

some suspicious corner cases (see Bug#13007 and Bug#13012).
(mode_line_update_needed): New function.
(redisplay_internal, redisplay_window): Use it.
(ensure_selected_frame): New function.
(redisplay_internal, unwind_redisplay): Use it.
(redisplay_internal): Move comment about buffer_shared...
(buffer_shared_and_changed): ...near to its real use.

2 files changed, 49 insertions, 39 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index b1c3b0025e1..b19ecc926d0 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2012-11-29  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	* xdisp.c (window_outdated): Remove eassert since it hits
+	some suspicious corner cases (see Bug#13007 and Bug#13012).
+	(mode_line_update_needed): New function.
+	(redisplay_internal, redisplay_window): Use it.
+	(ensure_selected_frame): New function.
+	(redisplay_internal, unwind_redisplay): Use it.
+	(redisplay_internal): Move comment about buffer_shared...
+	(buffer_shared_and_changed): ...near to its real use.
+
 2012-11-29  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* callproc.c (Fcall_process): Don't misreport vfork failure.
diff --git a/src/xdisp.c b/src/xdisp.c
index 3b19d5d14d4..8cca758c47b 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -10894,16 +10894,18 @@ echo_area_display (int update_frame_p)
 static int
 buffer_shared_and_changed (void)
 {
+  /* The variable buffer_shared is set in redisplay_window and
+     indicates that we redisplay a buffer in different windows. */
   return (buffer_shared > 1 && UNCHANGED_MODIFIED < MODIFF);
 }
 
-/* Nonzero if W doesn't reflect the actual state of
-   current buffer due to its text or overlays change.  */
+/* Nonzero if W doesn't reflect the actual state of current buffer due
+   to its text or overlays change.  FIXME: this may be called when
+   XBUFFER (w->buffer) != current_buffer, which looks suspicious.  */
 
 static int
 window_outdated (struct window *w)
 {
-  eassert (XBUFFER (w->buffer) == current_buffer);
   return (w->last_modified < MODIFF 
 	  || w->last_overlay_modified < OVERLAY_MODIFF);
 }
@@ -10923,6 +10925,16 @@ window_buffer_changed (struct window *w)
 	      != !NILP (w->region_showing)));
 }
 
+/* Nonzero if W has %c in its mode line and mode line should be updated.  */
+
+static int
+mode_line_update_needed (struct window *w)
+{
+  return (!NILP (w->column_number_displayed)
+	  && !(PT == w->last_point && !window_outdated (w))
+	  && (XFASTINT (w->column_number_displayed) != current_column ()));
+}
+
 /***********************************************************************
 		     Mode Lines and Frame Titles
  ***********************************************************************/
@@ -12967,6 +12979,15 @@ select_frame_for_redisplay (Lisp_Object frame)
   } while (!EQ (frame, old) && (frame = old, 1));
 }
 
+/* Make sure that previously selected OLD_FRAME is selected unless it has been
+   deleted (by an X connection failure during redisplay, for example).  */
+
+static void
+ensure_selected_frame (Lisp_Object old_frame)
+{
+  if (!EQ (old_frame, selected_frame) && FRAME_LIVE_P (XFRAME (old_frame)))
+    select_frame_for_redisplay (old_frame);
+}
 
 #define STOP_POLLING					\
 do { if (! polling_stopped_here) stop_polling ();	\
@@ -13052,13 +13073,11 @@ redisplay_internal (void)
   /* Remember the currently selected window.  */
   sw = w;
 
-  if (!EQ (old_frame, selected_frame)
-      && FRAME_LIVE_P (XFRAME (old_frame)))
-    /* When running redisplay, we play a bit fast-and-loose and allow e.g.
-       selected_frame and selected_window to be temporarily out-of-sync so
-       when we come back here via `goto retry', we need to resync because we
-       may need to run Elisp code (via prepare_menu_bars).  */
-    select_frame_for_redisplay (old_frame);
+  /* When running redisplay, we play a bit fast-and-loose and allow e.g.
+     selected_frame and selected_window to be temporarily out-of-sync so
+     when we come back here via `goto retry', we need to resync because we
+     may need to run Elisp code (via prepare_menu_bars).  */
+  ensure_selected_frame (old_frame);
 
   pending = 0;
   reconsider_clip_changes (w, current_buffer);
@@ -13144,21 +13163,13 @@ redisplay_internal (void)
   count1 = SPECPDL_INDEX ();
   specbind (Qinhibit_point_motion_hooks, Qt);
 
-  /* If %c is in the mode line, update it if needed.  */
-  if (!NILP (w->column_number_displayed)
-      /* This alternative quickly identifies a common case
-	 where no change is needed.  */
-      && !(PT == w->last_point && !window_outdated (w))
-      && (XFASTINT (w->column_number_displayed) != current_column ()))
+  if (mode_line_update_needed (w))
     w->update_mode_line = 1;
 
   unbind_to (count1, Qnil);
 
   FRAME_SCROLL_BOTTOM_VPOS (XFRAME (w->frame)) = -1;
 
-  /* 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_and_changed ()
 			    || cursor_type_changed);
@@ -13533,14 +13544,11 @@ redisplay_internal (void)
 	    }
 	}
 
-      if (!EQ (old_frame, selected_frame)
-	  && FRAME_LIVE_P (XFRAME (old_frame)))
-	/* We played a bit fast-and-loose above and allowed selected_frame
-	   and selected_window to be temporarily out-of-sync but let's make
-	   sure this stays contained.  */
-	select_frame_for_redisplay (old_frame);
-      eassert (EQ (XFRAME (selected_frame)->selected_window,
-		   selected_window));
+      /* We played a bit fast-and-loose above and allowed selected_frame
+	 and selected_window to be temporarily out-of-sync but let's make
+	 sure this stays contained.  */
+      ensure_selected_frame (old_frame);
+      eassert (EQ (XFRAME (selected_frame)->selected_window, selected_window));
 
       if (!pending)
 	{
@@ -13759,17 +13767,13 @@ redisplay_preserve_echo_area (int from_where)
 
 
 /* Function registered with record_unwind_protect in redisplay_internal.
-   Clear redisplaying_p.  Also, select the previously
-   selected frame, unless it has been deleted (by an X connection
-   failure during redisplay, for example).  */
+   Clear redisplaying_p.  Also select the previously selected frame.  */
 
 static Lisp_Object
 unwind_redisplay (Lisp_Object old_frame)
 {
   redisplaying_p = 0;
-  if (! EQ (old_frame, selected_frame)
-      && FRAME_LIVE_P (XFRAME (old_frame)))
-    select_frame_for_redisplay (old_frame);
+  ensure_selected_frame (old_frame);
   return Qnil;
 }
 
@@ -15565,12 +15569,7 @@ redisplay_window (Lisp_Object window, int just_this_one_p)
   if (BYTEPOS (opoint) < CHARPOS (opoint))
     emacs_abort ();
 
-  /* If %c is in mode line, update it if needed.  */
-  if (!NILP (w->column_number_displayed)
-      /* This alternative quickly identifies a common case
-	 where no change is needed.  */
-      && !(PT == w->last_point && !window_outdated (w))
-      && (XFASTINT (w->column_number_displayed) != current_column ()))
+  if (mode_line_update_needed (w))
     update_mode_line = 1;
 
   /* Count number of windows showing the selected buffer.  An indirect