emacs-27 4b3085a 2/2: Fix last change

[Eli Zaretskii]

branch: emacs-27
commit 4b3085a7fe8980432aa63ddf614fee2a6fb04e94
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix last change
    
    * src/composite.c (composition_reseat_it): Fix of the commentary,
    and a minor change of the last fix.
---
 src/composite.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/composite.c b/src/composite.c
index 2fbe679..a5288cb 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -1171,7 +1171,9 @@ composition_compute_stop_pos (struct composition_it 
*cmp_it, ptrdiff_t charpos,
    character to check, and CHARPOS and BYTEPOS are indices in the
    string.  In that case, FACE must not be NULL.  BIDI_LEVEL is the bidi
    embedding level of the current paragraph, and is used to calculate the
-   direction argument to pass to the font shaper.
+   direction argument to pass to the font shaper; value of -1 means the
+   caller doesn't know the embedding level (used by callers which didn't
+   invoke the display routines that perform bidi-display-reordering).
 
    If the character is composed, setup members of CMP_IT (id, nglyphs,
    from, to, reversed_p), and return true.  Otherwise, update
@@ -1256,7 +1258,16 @@ composition_reseat_it (struct composition_it *cmp_it, 
ptrdiff_t charpos,
              else
                bpos = CHAR_TO_BYTE (cpos);
            }
-         if ((bidi_level & 1) == 0)
+         /* The bidi_level < 0 case below strictly speaking should
+            never happen, since we get here when bidi scan direction
+            is backward in the buffer, which can only happen if the
+            display routines were called to perform the bidi
+            reordering.  But it doesn't harm to test for that, and
+            avoid someon raising their brows and thinking it's a
+            subtle bug...  */
+         if (bidi_level < 0)
+           direction = Qnil;
+         else if ((bidi_level & 1) == 0)
            direction = QL2R;
          else
            direction = QR2L;