Fix current-line hscrolling when overlays change

* src/xdisp.c (redisplay_internal): Disable "optimization 1" when
auto-hscrolling current line and we're redisplaying the selected
window.  (Bug#43835)

1 files changed, 6 insertions, 1 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 05f69b0321f..6c401d0abb9 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -15581,7 +15581,12 @@ redisplay_internal (void)
               && CHARPOS (this_line_end_pos) == CHARPOS (tlendpos)
               /* Line has same height as before.  Otherwise other lines
                  would have to be shifted up or down.  */
-              && this_line_pixel_height == line_height_before)
+              && this_line_pixel_height == line_height_before
+              /* Cannot use this optimization if hscrolling current
+                 line and this line is the current one, because
+                 display_line above is not informed about the
+                 current-line's vpos, and cannot DTRT in that case.  */
+              && !hscrolling_current_line_p (w))
             {
               /* If this is not the window's last line, we must adjust
                  the charstarts of the lines below.  */