* src/xdisp.c (syms_of_xdisp): New vars redisplay--all-windows-cause and

redisplay--mode-lines-cause.
(redisplay_internal): Keep them uptodate.  Remove redundant check of
buffer_shared_and_changed.
* *.[chm]: Number every assignment to update_mode_lines so we
can track why it is set.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/window.c b/src/window.c
index ac6bac42800..bc0adaf459f 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2639,7 +2639,7 @@ window_loop (enum window_loop type, Lisp_Object obj, int mini, Lisp_Object frame
                 mark_window_display_accurate (window, 0);
                 w->update_mode_line = 1;
                 XBUFFER (obj)->prevent_redisplay_optimizations_p = 1;
-                ++update_mode_lines;
+                update_mode_lines = 27;
                 best_window = window;
               }
             break;
@@ -3279,7 +3279,7 @@ displaying that buffer.  */)
   if (NILP (object))
     {
       windows_or_buffers_changed = 29;
-      update_mode_lines++;
+      update_mode_lines = 28;
       return Qt;
     }
 
@@ -3290,7 +3290,7 @@ displaying that buffer.  */)
       w->update_mode_line = 1;
       if (BUFFERP (w->contents))
         XBUFFER (w->contents)->prevent_redisplay_optimizations_p = 1;
-      ++update_mode_lines;
+      update_mode_lines = 29;
       return Qt;
     }