(redisplay_window): When deciding whether or not to recenter, don't

use the reset values of BEG_UNCHANGED and END_UNCHANGED.

1 files changed, 18 insertions, 6 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 90977aa3d7d..9c8f7b6a814 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -12777,6 +12777,8 @@ redisplay_window (window, just_this_one_p)
   int rc;
   int centering_position = -1;
   int last_line_misfit = 0;
+  int save_beg_unchanged = BEG_UNCHANGED;
+  int save_end_unchanged = END_UNCHANGED;
 
   SET_TEXT_POS (lpoint, PT, PT_BYTE);
   opoint = lpoint;
@@ -13145,11 +13147,20 @@ redisplay_window (window, just_this_one_p)
           && NILP (do_mouse_tracking)
           && CHARPOS (startp) > BEGV)
         {
-          /* Make sure beg_unchanged and end_unchanged are up to date.
-             Do it only if buffer has really changed.  This may or may
-             not have been done by try_window_id (see which) already. */
+#if 0
+          /* The following code tried to make BEG_UNCHANGED and
+             END_UNCHANGED up to date (similar to try_window_id).
+             Is it important to do so?
+
+             The trouble is that it's a little too strict when it
+             comes to overlays: modify_overlay can call
+             BUF_COMPUTE_UNCHANGED, which alters BUF_BEG_UNCHANGED and
+             BUF_END_UNCHANGED directly without moving the gap.
+
+             This can result in spurious recentering when overlays are
+             altered in the buffer.  So unless it's proven necessary,
+             let's leave this commented out for now. -- cyd.  */
           if (MODIFF > SAVE_MODIFF
-              /* This seems to happen sometimes after saving a buffer.  */
               || BEG_UNCHANGED + END_UNCHANGED > Z_BYTE)
             {
               if (GPT - BEG < BEG_UNCHANGED)
@@ -13157,9 +13168,10 @@ redisplay_window (window, just_this_one_p)
               if (Z - GPT < END_UNCHANGED)
                 END_UNCHANGED = Z - GPT;
             }
+#endif
 
-          if (CHARPOS (startp) > BEG + BEG_UNCHANGED
-              && CHARPOS (startp) <= Z - END_UNCHANGED)
+          if (CHARPOS (startp) > BEG + save_beg_unchanged
+              && CHARPOS (startp) <= Z - save_end_unchanged)
             {
               /* There doesn't seems to be a simple way to find a new
                  window start that is near the old window start, so