1 files changed, 16 insertions, 3 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 93ca88b4bdb..a00b5293619 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -505,6 +505,8 @@ prepare_menu_bars ()
    See Fcall_process; if you called it from here, it could be
    entered recursively.  */
 
+static int do_verify_charstarts;
+
 void
 redisplay ()
 {
@@ -623,7 +625,10 @@ redisplay ()
           if (cursor_vpos >= 0 && this_line_bufpos
               && this_line_endpos == tlendpos)
             {
-              if (this_line_vpos < XFASTINT (w->top) + window_internal_height (w))
+              /* If this is not the window's last line,
+                 we must adjust the charstarts of the lines below.  */
+              if (this_line_vpos + 1
+                  < XFASTINT (w->top) + window_internal_height (w))
                 {
                   int left = XFASTINT (w->left);
                   int *charstart_next_line
@@ -832,7 +837,8 @@ update:
           w->window_end_valid = Qt;
           last_arrow_position = Voverlay_arrow_position;
           last_arrow_string = Voverlay_arrow_string;
-          verify_charstarts (w);
+          if (do_verify_charstarts)
+            verify_charstarts (w);
           if (frame_up_to_date_hook != 0)
             (*frame_up_to_date_hook) (selected_frame);
         }
@@ -1601,7 +1607,14 @@ try_window_id (window)
           blank_end_of_window = 1;
         }
       else if (!scroll_amount)
-        {}
+        {
+          /* Even if we don't need to scroll, we must adjust the
+             charstarts of subsequent lines (that we won't redisplay)
+             according to the amount of text inserted or deleted.  */
+          int oldpos = FRAME_CURRENT_GLYPHS (f)->charstarts[ep.vpos + top][0];
+          int adjust = ep.bufpos - oldpos;
+          adjust_window_charstarts (w, ep.vpos + top - 1, adjust);
+        }
       else if (bp.bufpos == Z - end_unchanged)
         {
           /* If reprinting everything is nearly as fast as scrolling,