(try_window_id) [!GLYPH_DEBUG]: Give up if

first_unchanged_at_end_row is in front of
last_unchanged_at_beg_row.  This code should be removed after the
release of 21.1.

2 files changed, 22 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 7258c8cce89..f6891ec274b 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2001-09-18  Gerd Moellmann  <gerd@gnu.org>
+
+        * xdisp.c (try_window_id) [!GLYPH_DEBUG]: Give up if
+        first_unchanged_at_end_row is in front of
+        last_unchanged_at_beg_row.  This code should be removed after the
+        release of 21.1.
+
 2001-09-17  Gerd Moellmann  <gerd@gnu.org>
 
         * buffer.h (BUF_COMPUTE_UNCHANGED): Use BUF_MODIFF and
diff --git a/src/xdisp.c b/src/xdisp.c
index a3ac927f785..df8720ee0e8 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -11491,8 +11491,23 @@ try_window_id (w)
   stop_pos = 0;
   if (first_unchanged_at_end_row)
     {
+#if GLYPH_DEBUG
       xassert (last_unchanged_at_beg_row == NULL
                || first_unchanged_at_end_row >= last_unchanged_at_beg_row);
+#else
+      /* This is for the release of 21.1 only, and should be removed
+         after the release.
+
+         This case means that unchanged information is probably bogus,
+         which leads to being unable to compute a correct
+         first_unchanged_at_end_row.  At least that was the case in
+         one debugging session.  I've fixed a bug that can lead to
+         wrong unchanged info, but didn't find a way to reproduce this
+         case.  2001-09-18 gerd.  */
+      if (last_unchanged_at_beg_row 
+          && first_unchanged_at_end_row < last_unchanged_at_beg_row)
+        GIVE_UP (20);
+#endif
       
       /* If this is a continuation line, move forward to the next one
          that isn't.  Changes in lines above affect this line.