(redisplay_window): If current window start is not at the

beginning of a line, select a new window start if buffer is modified
and window start is in the modified region, but the first change is
before window start.

diff --git a/src/xdisp.c b/src/xdisp.c
index 075e05b0e132f28f47223903b61469e44989afb9..db987ad5a90bef00a1aea1745e32fc6f3158dc37 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -12860,6 +12860,33 @@ redisplay_window (window, just_this_one_p)
               || (XFASTINT (w->last_modified) >= MODIFF
                   && XFASTINT (w->last_overlay_modified) >= OVERLAY_MODIFF)))
     {
+
+      /* If first window line is a continuation line, and window start
+        is inside the modified region, but the first change is before
+        current window start, we must select a new window start.*/
+      if (NILP (w->start_at_line_beg))
+       {
+         /* 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 (MODIFF > SAVE_MODIFF
+             /* This seems to happen sometimes after saving a buffer.  */
+             || BEG_UNCHANGED + END_UNCHANGED > Z_BYTE)
+           {
+             if (GPT - BEG < BEG_UNCHANGED)
+               BEG_UNCHANGED = GPT - BEG;
+             if (Z - GPT < END_UNCHANGED)
+               END_UNCHANGED = Z - GPT;
+           }
+
+         if (CHARPOS (startp) > BEG + BEG_UNCHANGED
+             && CHARPOS (startp) <= Z - END_UNCHANGED)
+           {
+             centering_position = 0;
+             goto recenter;
+           }
+       }
+
 #if GLYPH_DEBUG
       debug_method_add (w, "same window start");
 #endif