Fix bug in displaying header line with a box face

* src/xdisp.c (get_next_display_element): Handle the case when a
display string acquires the box face from an underlying string,
not from the buffer.  (Bug#23091)

diff --git a/src/xdisp.c b/src/xdisp.c
index d68244e6c9d1b8405bde0c5c7d62f891c799f174..d6ee2de8f39f3e812588596f757322bd36a1e285 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -7229,18 +7229,21 @@ get_next_display_element (struct it *it)
                {
                  ptrdiff_t ignore;
                  int next_face_id;
+                 bool text_from_string = false;
+                 /* Normally, the next buffer location is stored in
+                    IT->current.pos...  */
                  struct text_pos pos = it->current.pos;
 
-                 /* For a string from a display property, the next
-                    buffer position is stored in the 'position'
+                 /* ...but for a string from a display property, the
+                    next buffer position is stored in the 'position'
                     member of the iteration stack slot below the
                     current one, see handle_single_display_spec.  By
-                    contrast, it->current.pos was not yet updated
-                    to point to that buffer position; that will
-                    happen in pop_it, after we finish displaying the
-                    current string.  Note that we already checked
-                    above that it->sp is positive, so subtracting one
-                    from it is safe.  */
+                    contrast, it->current.pos was not yet updated to
+                    point to that buffer position; that will happen
+                    in pop_it, after we finish displaying the current
+                    string.  Note that we already checked above that
+                    it->sp is positive, so subtracting one from it is
+                    safe.  */
                  if (it->from_disp_prop_p)
                    {
                      int stackp = it->sp - 1;
@@ -7249,19 +7252,49 @@ get_next_display_element (struct it *it)
                      while (stackp >= 0
                             && STRINGP ((it->stack + stackp)->string))
                        stackp--;
-                     eassert (stackp >= 0);
-                     pos = (it->stack + stackp)->position;
+                     if (stackp < 0)
+                       {
+                         /* If no stack slot was found for iterating
+                            a buffer, we are displaying text from a
+                            string, most probably the mode line or
+                            the header line, and that string has a
+                            display string on some of its
+                            characters.  */
+                         text_from_string = true;
+                         pos = it->stack[it->sp - 1].position;
+                       }
+                     else
+                       pos = (it->stack + stackp)->position;
                    }
                  else
                    INC_TEXT_POS (pos, it->multibyte_p);
 
-                 if (CHARPOS (pos) >= ZV)
+                 if (text_from_string)
+                   {
+                     Lisp_Object base_string = it->stack[it->sp - 1].string;
+
+                     if (CHARPOS (pos) >= SCHARS (base_string) - 1)
+                       it->end_of_box_run_p = true;
+                     else
+                       {
+                         next_face_id
+                           = face_at_string_position (it->w, base_string,
+                                                      CHARPOS (pos), 0,
+                                                      &ignore, face_id, false);
+                         it->end_of_box_run_p
+                           = (FACE_FROM_ID (it->f, next_face_id)->box
+                              == FACE_NO_BOX);
+                       }
+                   }
+                 else if (CHARPOS (pos) >= ZV)
                    it->end_of_box_run_p = true;
                  else
                    {
-                     next_face_id = face_at_buffer_position
-                       (it->w, CHARPOS (pos), &ignore,
-                        CHARPOS (pos) + TEXT_PROP_DISTANCE_LIMIT, false, -1);
+                     next_face_id =
+                       face_at_buffer_position (it->w, CHARPOS (pos), &ignore,
+                                                CHARPOS (pos)
+                                                + TEXT_PROP_DISTANCE_LIMIT,
+                                                false, -1);
                      it->end_of_box_run_p
                        = (FACE_FROM_ID (it->f, next_face_id)->box
                           == FACE_NO_BOX);