master 6733f45383b: Fix scrolling when continuation line starts with a display string

[Eli Zaretskii]

branch: master
commit 6733f45383bc1f57860d98803391cda076ed7cbb
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix scrolling when continuation line starts with a display string
    
    * src/xdisp.c (start_display): Compute continuation_lines_width
    for starting display in strings and images as well.  (Bug#67201)
---
 src/xdisp.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 041c7adfc50..2dbe85f0f04 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -3766,18 +3766,25 @@ start_display (struct it *it, struct window *w, struct 
text_pos pos)
 
   /* Don't reseat to previous visible line start if current start
      position is in a string or image.  */
-  if (it->method == GET_FROM_BUFFER && it->line_wrap != TRUNCATE)
+  if (it->line_wrap != TRUNCATE)
     {
-      int first_y = it->current_y;
+      enum it_method method = it->method;
 
-      /* If window start is not at a line start, skip forward to POS to
-        get the correct continuation lines width.  */
+      /* If window start is not at a line start, skip forward to POS
+        from the beginning of physical line to get the correct
+        continuation lines width.  */
       bool start_at_line_beg_p = (CHARPOS (pos) == BEGV
                                  || FETCH_BYTE (BYTEPOS (pos) - 1) == '\n');
       if (!start_at_line_beg_p)
        {
+         int first_y = it->current_y;
+         int continuation_width;
+         void *itdata = NULL;
+         struct it it2;
          int new_x;
 
+         if (method != GET_FROM_BUFFER)
+           SAVE_IT (it2, *it, itdata);
          reseat_at_previous_visible_line_start (it);
          move_it_to (it, CHARPOS (pos), -1, -1, -1, MOVE_TO_POS);
 
@@ -3824,6 +3831,17 @@ start_display (struct it *it, struct window *w, struct 
text_pos pos)
          else if (it->current.dpvec_index >= 0)
            it->current.dpvec_index = 0;
 
+         continuation_width = it->continuation_lines_width;
+         /* If we started from a position in something other than a
+             buffer, restore the original iterator state, keeping only
+             the continuation_lines_width, since we could now be very
+             far from the original position.  */
+         if (method != GET_FROM_BUFFER)
+           {
+             RESTORE_IT (it, &it2, itdata);
+             it->continuation_lines_width = continuation_width;
+           }
+
          /* We're starting a new display line, not affected by the
             height of the continued line, so clear the appropriate
             fields in the iterator structure.  */